Hitachi Medical Systems America, Inc.

Hitachi

MRI Anatomy and Positioning Series
Module 1: Upper Extremity Orthopedic Imaging

Welcome to the Hitachi Medical Systems America, Inc. MRI Anatomy and Positioning Series. Over the coming months, we will be offering teaching modules to allow users of Hitachi MRI scanners to polish their positioning skills and review the anatomy that should be seen on some common MRI exams. Our intention is to discuss and review the anatomy that is most often seen, and the positioning that is most often used in your MRI studies. Good positioning skills are needed to ensure the best possible image quality for your studies.

In this first module, we will discuss the anatomy and positioning of the bones, joints, ligaments and muscles of the upper extremity. It is not our intention to outline all the anatomy that you may need to know, but rather to inspire you to become more familiar with the common anatomical structures. MRI allows us to be very exact with our work, as we have the ability to align slices exactly parallel or perpendicular to specific anatomic structures. Increased knowledge of cross-sectional anatomy will enable you to perform your job more efficiently and with greater expertise.

initial image
CAUTION: Always route coil cables away from the patient, using pads to eliminate or minimize the chances of contact between the coil cable and the patient. Failure to do so could result in a thermal injury.

Within our modules, we will offer suggestions as to appropriate RF coils to be used for various MRI exams. Your facility may not have all of the coils that are pictured, as some are optional and must be purchased separately. Regardless of the RF coil that is being used, every attempt should be made to route the coil cable(s) in a manner that will avoid contact with the patient.

We will also discuss the use of the various pads that are furnished with our MRI systems (trough pads, table pads, accessory pads, coil cable pads, etc.). It is important to use the various pads that are provided to assist in eliminating, or at least minimizing, the amount of each patient’s skin-to-skin, skin-to-bore, or skin-to-cable contact. Reducing the amount of each of the aforementioned contacts reduces the patient’s chances of thermal injury.

Upper Extremity

Shoulder

MRI may be requested for:

The shoulder “girdle” is comprised of three bones, which are the humerus, the scapula, and the clavicle. The humerus is the long bone that connects the shoulder girdle to the elbow joint. The scapula lies across the posterior and lateral aspect of the chest, where it has muscular protection. The clavicle, on the superior and anterior aspect, transmits weight from the upper limb to the axial skeleton. The shoulder joint is technically the gleno-humeral joint, where the head of the humerus articulates with the glenoid cavity of the scapula. This joint is characterized as a multi-axial ball and socket joint, as its motions include flexion / extension, abduction / adduction, circumduction, and rotation. The shoulder joint has more freedom of movement than any joint in the body, but it is very unstable. It is weak inferiorly, due to a lack of tendinous support, making inferior dislocations of the shoulder fairly common. In addition, only about one third of the humeral head fits into the glenoid fossa of the scapula. The glenoid labrum, a fibrocartilaginous ring around the margin of the glenoid cavity, serves to deepen and enlarge this otherwise shallow fossa. MRI may be ordered to assess a SLAP tear or lesion, which occurs in the glenoid labrum. SLAP is the acronym for Superior Labrum, Anterior to Posterior, which indicates the site and direction of the tear. These tears or lesions may involve the biceps tendon, at the point where it meets the labrum. SLAP tears can result from acute trauma, as well as from activities with repetitive overhead motions (i.e. weightlifting, sports that involve excessive throwing). Common patient complaints with these injuries include pain, a decrease in range of motion, and a catching, grinding, or locking feeling in the shoulder.

Additional shoulder stability is provided by the musculotendinous rotator cuff. The rotator cuff is made up of four muscles (Figure 1): the supraspinatus, infraspinatus, teres minor, and subscapularis (acronym is “sits”). These muscles and their tendons provide a “cuff” over the head of the humerus, then attach anteriorly and laterally at the greater tuberosity of the humerus. The muscles act on the shoulder joint to pull the head of the humerus downward and into the glenoid fossa (Figure 2). The infraspinatus and teres minor provide posterior stabilization, and the subscapularis protects the joint anteriorly. The supraspinatus muscle, which covers the superior aspect of the shoulder, is the most commonly torn rotator cuff muscle. It is used to lift the arm sideways, and is important in “throwing” sports. Rotator cuff tears can result from a single traumatic injury, or years of wear and tear from overuse. Repetitive overhead motions in work or sports (pitchers, swimmers, tennis players) can also cause injuries to the rotator cuff.

Numerous muscles, in addition to those in the rotator cuff, are necessary for the variety of movements involving the shoulder joint (Figure 3). They are required to move and stabilize the scapula, to support the scapula on the thorax, as well as to provide motion of the gleno-humeral joint. Included in the “mover” muscles are the broad deltoid muscle, which covers the anterior, lateral and posterior aspects of the shoulder joint; the large pectoralis major muscle, which lies anteriorly on the upper chest; the teres major, a small muscle that lies posterior and inferiorly across the scapula, but has a tendon of insertion on the anterior humerus; the biceps brachii, along the anterior aspect of the humerus, and the long head of the triceps brachii, a posterior muscle in the humerus.

Ligaments of the shoulder girdle (Figure 4) are a passive source of stability that help keep the shoulder joint from dislocating. They are strong, tough bands that connect bones to bones. However, ligaments have little flexibility. Once stretched, they tend to remain stretched, and can snap if stretched too far. The acromioclavicular ligament connects the acromion of the scapula with the clavicle, and is the site of injury for a “separated shoulder”. The coracoacromial ligament connects the coracoid process of the scapula with the acromion of the scapula. This ligament and two bony parts of the scapula make up the coracoacromial arch, which prevents superior dislocation of the shoulder. The supraspinatus muscle (part of the rotator cuff) travels under this protective arch. The glenohumeral joint is further stabilized by the superior, middle, and inferior ligaments that connect the glenoid area with the humeral head. The inferior glenohumeral ligament can be stretched or torn due to shoulder dislocations. If the ligament pulls the inferior labrum away from the glenoid, the result is a Bankart lesion, which can be diagnosed using MRI.

The muscles of the body move bones by contracting, then pulling on their associated tendons. Tendons are extensions of muscles that attach the muscles to the bones. Unlike the ligaments that were just discussed, tendons are soft, elastic connective tissue. The tendons of the rotator cuff attach the rotator cuff muscles to the humerus, and are important in permitting joint movement without dislocation. MRI may be requested to assess these tendons, especially the supraspinatus tendon. It is particularly vulnerable to tendinitis and impingement problems, as it passes under the acromion and can be pinched when the arm is raised forward or upward. MRI may also be requested to assess injury to the biceps tendon (long head), as this is the sight of more than 90% of biceps ruptures. The long head of the biceps brachii tendon travels through the glenohumeral joint and attaches to the superior aspect of the glenoid, where it becomes part of the glenoid labrum. When injured, the tendon often pulls away from the labrum at this tendon-labral junction.

The shoulder is also the site of numerous bursae, which are tiny sacks that contain a small amount of lubricating fluid (Figure 5). They are located where two body parts move against each other without a joint to reduce friction between them. Shoulder bursae include, but are not limited to, the subscapular, subcoracoid, and subacromial bursae. The subscapular bursa is located between the tendon of the subscapularis muscle and the neck of the scapula. It is continuous with the synovial cavity of the shoulder joint, and contains “physiologic” joint fluid. Fluid seen on MRI in other bursae, such as the subcoracoid, may be a sign of a pathologic process, or communication with a fluid-containing structure. Inflammation of the bursa, or bursitis, is commonly seen in the subacromial bursa.

Open MRI Systems

Introduction

When positioning a patient for a shoulder exam in an open MRI system, it is important to consider the choices you have as far as coil selection and patient setup. Positioning that will result in both the coil and anatomy at isocenter in all three planes will have a positive influence on the image quality of your study.

Components of positioning to consider include coil selection, table pads and accessory pads, table straps, and proper laser light centering. Coil selection will be greatly influenced by the patient’s size and body habitus. The extensive inventory of table and accessory pads should be made use of for proper centering, as well as patient comfort (Figure 6). Table straps can be used to help secure the positions of both the patient and the coil. The straps can remain attached to the table, so they are readily available when needed. On open MRI systems, it is extremely important to have the anatomy of interest centered in the laser localizer beams in all three directions- head-to-foot (axial or transverse plane), right-to-left (sagittal plane), and anterior-to-posterior (coronal plane).

Coils and Positioning

Shoulder Coil

When preparing a patient for a shoulder exam (as well as many other upper extremity studies), position the patient toward the edge of the table away from the affected shoulder. In addition, move the table away from the affected side (Figure 11). This affords you the best opportunity to position the affected shoulder at the exact isocenter of the magnet. Center ON the shoulder joint, NOT ON the midline indicators of the shoulder coil (Figure 12). Due to variations in patient size, many patients' shoulders will not be correctly centered if the midline indicators are used.

The Oasis MRI system offers a specific positioning pad for use with the multiple array shoulder coil (Figures 13 and 14). The table pad was designed with a cut-out area to accomodate the shoulder coil. Specific accessory pads that can be affixed to the outside of the shoulder coil are supplied to assist with coil stability. In addition, thick and thin accessory pads that can be attached inside the coil are provided to aid in patient positioning.

The Altaire, AIRIS Elite, and AIRIS II MRI systems also offer pads designed for use with the shoulder coil (Figures 15 and 16). The pads can help stabilize the shoulder coil on the table, and can be of assistance with positioning, especially for coronal (A-P) centering. The pads are labeled for correct usage with the right or left shoulder. The shoulder coil fits between the two pads for safe storage. The AIRIS II MRI system does not have a designated pad for the Multiple Array shoulder coil; the pad is furnished with the system's Quadrature shoulder coil.

Large Extremity (Solenoid) Coil

Typical positioning of the solenoid coil for a shoulder study involves fitting the coil as snugly as possible along the superior aspect of the shoulder joint (Figures 17 and 18). The coil does not have to be used as a bracelet (fitting around and over the shoulder). Depending on the size and body habitus of the patient, it may be necessary to place the coil and / or the patient on additional table and accessory pads to properly position the shoulder within the coil, as well as for more accurate anterior / posterior centering. The table straps can be used to secure the solenoid coil in a stable position, while keeping it aligned 90 degrees to the table surface.

Table Pads and Accessory Pads

Centering the patient in an open MRI system requires consideration of all three directions: A-P, R-L and H-F. Positioning in the A-P direction requires the selection of table pads and / or accessory pads that will establish the required anatomy at coronal isocenter. As seen below, positioning a patient using insufficient padding does not elevate the shoulder to isocenter, and will typically result in suboptimal images (figures 19 and 20).

Patient not centered A-P

Figure 19. Patient not centered in the A-P direction.

Anatomy not centered at isocenter

Figure 20. Anatomy not at A-P isocenter of magnet.

Table pads and / or accessory pads should be used in an amount sufficient to elevate the patient's shoulder to the point where it is aligned with the laser localizer beam in the A-P direction. When the table is advanced into the magnet, the anatomy will be at the coronal isocenter of the magnet (Figures 21 and 22). Isocenter positioning in all three planes is strongly recommended for optimal images on vertical-field open magnets.

Patient centered in A-P directin

Figure 21. Patient now centered properly in A-P direction.

Anatomy at A-P isocenter

Figure 22. Anatomy now at A-P isocenter of magnet.

Table Straps

The system table straps can be used to help stabilize both the patient and the coil, and are particularly helpful when using the solenoid coil. The straps can remain attached to the table so they are readily accessible.

Laser Localizer Beams

When positioning for the shoulder exam, use the laser localizer beams to ensure A-P, R-L, and H-F centering. Image signal is optimized when the patient's anatomy is at isocenter in all three directions.

For additional information, please refer to the Oasis Patient Positioning and Coils manual, or the Altaire, AIRIS II, or AIRIS Elite Patient Positioning manuals that were supplied with your MRI system.

Echelon MRI System

Introduction

The Echelon MRI system is a horizontal, high-field (1.5T), short-bore magnet. Due to the circular shape of the magnet bore, the width of the table is not as generous as that found on open MRI systems. In addition, the patient table does not have lateral movement capabilities. Isocenter positioning of the shoulder and / or the coil can be challenging, but high signal and outstanding image quality are both easily achieved on the Echelon system.

Coil and Positioning:

Shoulder Coil

The Echelon shoulder coil is the coil of choice for shoulder scanning. Although there are some limitations due to the width of the table, attempts should be made to position the patient near the table edge opposite the affected shoulder. This affords you the best opportunity to position the affected shoulder and shoulder coil as close to isocenter as possible.

Similar to the previously mentioned Oasis shoulder coil, a specific table pad and specific accessory pads are supplied for use with the Echelon shoulder coil (Figure 24). Pads that can be affixed to the top and bottom of the shoulder coil assist with coil stability. Thick and thin accessory pads that can be attached to the inside of the coil are supplied to aid in patient positioning and stabilization of the shoulder (Figure 25).

The system table straps can also be used to help stabilize both the patient and the coil. The straps can remain attached to the table so they are readily accessible.

When positioning for the shoulder exam, use the laser localizer beams to display R-L and H-F centering. Center ON the shoulder joint, NOT ON the midline indicators of the shoulder coil. Due to variations in patient size, many patients' shoulders will not be centered correctly if the midline indicators are used.

For additional information, please refer to the Echelon Patient Positioning and Coils manual that was supplied with your Echelon system.

Scan Setups

The following are HMSA suggestions for routine shoulder imaging. Always check with your radiologist for his / her imaging preferences.

Axial Scans

Our recommendation is to begin a shoulder study with a scan oriented in the transverse or axial plane. Axial slices should cover the area from the AC joint through the glenoid cavity, to include the inferior labrum and fibrous capsule. The slices can be angled in order to align them perpendicular to the orientation of the humerus, as demonstrated in Figure 26.

Axial slice setup

Figure 26. Axial slice setup using coronal images.

Coronal Scans

Slice positioning (and patient positioning) for coronal slice setup can vary from site to site. Many sites align their slices parallel to the supraspinatus tendon or supraspinatus muscle, as shown in Figures 27 and 28. This alignment will be made using one of the more superior slices from the axial series.

Once you have determined the proper angle to use (Figure 29), inferior slices should be viewed to ensure coverage of the entire glenoid cavity (Figures 30 and 31). The images of the humeral head shown below also demonstrate the differences in the position of the bicipital groove with supination of the hand (palm up) versus pronation of the hand (palm down).

Effects of Hand Position on Images of Shoulder Muscles and Tendons

The complex orientations of muscles and tendons will require additional attention to detail when setting up the shoulder studies. The demonstration of specific muscles, in conjunction with the preferences of the radiologist, must be considered when positioning the forearm and hand (Figure 32).

Supination of the hand (palm up) tightens the anterior capsule of the shoulder and separates the Supraspinatus from the Infraspinatus in the coronal orientation (Figure 33). Pronation of the hand (palm down) may be a more comfortable position for the patient, but it allows crossing of the aforementioned tendons, which could mimic a rotator cuff tear (Figure 34). See additional images below (Figures 35 and 36).

Alternate Positioning for Coronal Scans

If slices are not positioned parallel to the supraspinatus muscle, it is common to position the slices across the bowl of the glenoid joint, as shown in Figure 37. However, this joint space is curved, leading to individual interpretations of the proper angulation. It is important to consult the radiologist concerning his / her preferences for slice positioning.

Coronal slice setup using transverse images

Figure 37. Coronal slice setups using transverse images.

Sagittal Scans

The sagittal view representation (Figure 38) and sagittal MR image (Figure 39) may give you a better understanding of the dimension of the shoulder joint. Looking at the sagittal view representation, you can better appreciate the bony support mechanism provided by the scapula.

Sagittal slices should be positioned perpendicular to the plane of the coronal slices, as seen in the transverse image of Figure 40. Sagittal slice coverage should include a few slices medial to the glenoid cavity, and should extend laterally through the humeral head to include a few slices past the biceps tendon.

There are a wide variety of pulse sequences available in your Scan Card Library or Task Library that can be used when creating protocols for shoulder examinations.

ABER (ABduction External Rotation) View

The advantages of MRI in the evaluation of anterior shoulder instability can be appreciated through the use of shoulder positions that stress the stabilizing structures. Routine shoulder views show the rotator cuff and anterior stabilizing structures. The ABER view puts stress on the inferior glenohumeral labral-ligamentous complex, helping to expose pathology of those structures.

The ABER (ABduction External Rotation) position is one that is frequently used as part of an arthrogram study of the shoulder. While the injection of a dilute gadolinium solution is considered off-label use of a contrast medium, it can effectively distend the joint capsule, outline intra-articular structures, and leak into abnormalities (Figure 42).

To perform the ABER view, have the patient raise their arm over their head, keeping their elbow bent and their palm up (Figure 41). Provide support and stabilization for the affected shoulder and arm, as well as generalized patient comfort measures. The shoulder coil should be rotated around the shoulder so that the cable now extends from underneath the shoulder joint. If the solenoid coil is used, it can be positioned around the arm as a bracelet, then centered around the shoulder.

Upper Arm

MRI may be requested for:

The humerus is the long bone in the upper arm that extends from the shoulder to the elbow. At the shoulder, the bony articulation involves the head of the humerus with the glenoid fossa of the scapula. At the elbow, the bony articulations include the capitulum of the humerus with the radial head laterally, and the trochlea of the humerus with the olecranon process of the ulna medially. As the humerus helps to form both the shoulder and elbow joints, it has many muscle insertions along its length.

MRI of the upper arm may be ordered to take advantage of its superior imaging capabilities with regards to the numerous muscles and muscle insertions in this anatomical region (Figure 43). Superiorly, the deltoid and teres major muscles can be imaged, in addition to the four muscles that make up the rotator cuff (supraspinatus, infraspinatus, teres minor, and subscapularis). The subscapularis inserts at the lesser tuberosity of the humerus, while the other three rotator cuff muscles insert at the greater tuberosity. The bicipital groove separates the tuberosities, and is the location of the tendon of the long head of the biceps brachii muscle. The biceps and triceps brachii muscles run the length of the upper arm. An attachment for the brachioradialis muscle is located inferiorly.

The axillary, radial and ulnar nerves that traverse the humerus can also be imaged using MRI. The axillary nerve (and axillary artery) are at risk for injury from anterior or inferior shoulder dislocations, the use of crutches, or a fracture of the humerus. A humerus fracture can also result in injury to the radial nerve, as the path of the nerve closely follows the length of the bone. Striking the ulnar nerve, located at the distal end of the humerus, causes the tingling sensation referred to when you hit your “funny bone” (but striking the humerus is usually not humorous).

Open MRI Systems

Introduction

When positioning a patient for an upper arm exam in an open MRI system, it is important to consider the choices you have as far as coil selection and patient setup, especially in regard to the patient’s size and body habitus. Coverage of the entire upper arm can be challenging, especially if the shoulder and elbow joints are to be included.

Coil selection, table and accessory pads, table straps, and proper laser light centering are all factors to be considered when preparing for an upper arm study. Use of the solenoid coil also involves careful selection of table pads and accessory pads to maintain the anatomy and the coil at isocenter in all three planes. The table straps are helpful when used in conjunction with the solenoid coil to stabilize the coil in a position that is 90° from the tabletop. If a flex coil is used, care must be taken when selecting table pads and when positioning the upper arm to ensure that coronal centering of both the coil and the anatomy is maintained. Regardless of the coil that is selected, every effort must be made to have the anatomy centered in the laser localizer beams in all three directions- head-to-foot (axial or transverse plane), right-to-left (sagittal plane), and anterior-to-posterior (coronal plane).

Coils and Positioning

Solenoid Coil

The coil of choice for a study of the upper arm is the solenoid coil. The coil can be placed alongside the affected arm (Figure 49). Position the patient toward the edge of the table away from the affected arm. In addition, move the table away from the affected side. This affords you the best opportunity to position the affected upper arm at the exact isocenter of the magnet. Using accessory pads, build up the affected arm along its entire length (Figure 50).

The shaft of the humerus should be level, and as close to the center of the solenoid coil as possible. It may be difficult to include both the shoulder and elbow joints in any one coronal or sagittal image. Therefore, it is important to review the patient’s history and doctors order to determine which joint is closest to the anatomy of interest. The coil can then be positioned to include the appropriate joint.

Depending on the size of the patient, the solenoid coil can also be placed around the upper arm like a bracelet, as shown in Figure 51. The solenoid coil’s sizeable coverage area may permit inclusion of both the proximal and distal joints (Figure 52). This will be determined by the patient’s size, as well as the positioning of the coil (Figure 53).

Flexible Body Coil or RAPID Body Coil

When using a flex coil or RAPID body coil to image the upper arm, the patient’s unaffected arm can be positioned outside of the coil and over the patient’s head, in order to give the patient more room in the coil. With the flex coils, it may also be necessary to place padding inside the coil to maintain the anterior portion of the coil in a level position, as well as to put space between the coil and the patient’s face.

The coil should be centered over the upper arm in the Head / Foot direction (Figure 54). The R-L centering should be offset over the affected upper arm (Figure 55).

Note: Scanning any anatomy that is out of isocenter can lead to possible distortion and aliasing. Use the appropriate protocol parameters to minimize these problems. For coronal imaging, we recommend the Head to Foot setting for Phase direction, and the Time / Res mode for Anti-Aliasing.

Table Pads and Accessory Pads

When scanning on an open MRI system, it is especially important to give careful consideration to the centering of both the anatomy and the coil in all three directions- H-F, R-L, and A-P. Proper selection of table pads plays a large role in achieving isocenter positioning, especially in the coronal (A-P) direction. Insufficient padding and non-isocenter scanning typically result in images that are suboptimal. Accessory pads can be used with the solenoid, flex, and RAPID body coils for improved coil stabilization and / or patient comfort. They will also be useful in helping to maintain the entire arm in its required position. The elbow, forearm and hand may require support and stabilization to maintain their positions relative to the upper arm. Consult your radiologist for his / her preferences for alignment and positioning of the upper extremity (pronation or supination of the hand and forearm, flexed or extended position for the elbow, etc.).

Table Straps

The system table straps can be used to help stabilize the patient, as well as the solenoid and / or flex coils. The straps can remain attached to the table so they are readily accessible.

Laser Localizer Beams

When positioning for an upper arm exam, always use the laser localizer beams to ensure A- P, R-L, and H-F centering. Image signal is optimized when the patient’s anatomy is at isocenter in all three directions.

For additional information, please refer to the Oasis Patient Positioning and Coils manual, or the Altaire, AIRIS II, or AIRIS Elite Patient Positioning manuals that were supplied with your MRI system.

Echelon MRI System

Coils and Positioning

Torso / Body Coil

The standard coil used for upper arm scanning is the torso / body coil. The bottom portion of the coil should be placed on the selected table pad. Depending on the patient’s size, you may be able to slightly offset the bottom portion toward the unaffected arm, in order to achieve some degree of R-L centering. Position the patient on the bottom portion of the torso coil with the upper arm centered in the H-F direction. Additional arm positioning, such as pronation or supination of the forearm and hand, is usually determined by the radiologist. Both arms should remain at the patient’s sides while the upper portion of the coil is placed on the patient, and secured with the Velcro® straps.

Accessory pads can be used if needed for patient comfort, as well as to assist with maintaining the forearm and hand in the required position.

The table straps can be used for additional stabilization of the coil, if necessary (Figure 58). Use the laser localizer beams to display H-F and R-L centering. The torso coil, and the upper arm within the coil, should be centered in the H-F direction.

Upper Extremity Coil

The optional upper extremity coil (Figure 59) was designed with anatomic regions such as the upper arm in mind. The coil size and configuration make it a superior fit for various long bone applications. As it is smaller than the torso coil, it is better adapted for some degree of offset centering of the affected upper arm. The upper extremity coil should be centered on the upper arm in the H-F direction, then secured around the arm using the Velcro® strap supplied with the coil (Figure 60).

The pad provided inside the coil makes positioning and scanning more comfortable for the patient. Accessory pads can be used to maintain the forearm in the correct position, as well as to assist in patient comfort. The table straps can be used to further stabilize the long bone coil in its position.

Use the laser localizer to display H-F and R-L centering.

For additional information, please refer to the Echelon Patient Positioning and Coils manual that was supplied with your Echelon system.

Scan Setups

The following are HMSA suggestions for upper arm imaging. Always check with your radiologist for his / her imaging preferences.

Axial Scans

When positioning slices for the upper arm, axial slices are typically positioned only over the area of interest (Figure 61).

Coronal Scans

Coronal slices are typically aligned with the shaft of the humerus, as shown in Figure 62. Be cautious with the field of view that is selected. While it may be possible to visualize both joints, HMSA recommends focusing on the joint closest to the area of interest.

Sagittal Scans

Sagittal slices are also aligned with the shaft of the humerus, as shown in Figure 63. Be cautious with the field of view that is selected. While it may be possible to visualize both joints, HMSA recommends focusing on the joint closest to the area of interest.

There are a wide variety of pulse sequences available in your Scan Card Library or Task Library that can be used when creating protocols for upper arm examinations.

Elbow

MRI may be requested for:

The elbow (Figures 64 and 65) is the joint that connects the distal humerus with the radius and ulna of the forearm. Technically, it is made up of three portions:

  1. Humeroulnar joint; involves the trochlear notch of the ulna and the trochlea of the humerus; simple hinge joint, allowing flexion and extension only.
  2. Radiohumeral joint; involves the head of the radius and the capitulum of the humerus; a pivot-type joint.
  3. Proximal radioulnar joint; involves head of radius and radial notch of ulna; also a pivot-type joint, allowing rotation of radius for pronation and supination of hand.

A common synovial membrane envelopes these articular surfaces. Three fat masses or “fat pads” can be found between the joint capsule and the synovial membrane. The joint capsule is thickened medially and laterally, with these thickened portions usually described as distinct ligaments. The major ligaments are the radial collateral ligament (lateral aspect of joint), the ulnar collateral ligament (medial aspect of joint), and the annular ligament (anterior aspect of joint).

The actions of muscles on the elbow cause flexion or extension of the forearm, as well as a complex articulation of the radius and ulna resulting in pronation or supination of the hand. The majority of the force through the elbow joint is transferred from the humerus to the ulna, with little force being transferred to the radius. Muscles that may be evident in MR images include the Biceps brachii and Brachioradialis anteriorly (Figure 66), and the Triceps brachii and Anconeus posteriorly (Figure 67).

When muscles contract, they pull on the tendons by which they are attached to bones, thereby causing movement of the bones. The biceps tendon attaches the biceps muscle to the radius on the anterior aspect of the elbow, allowing forceful bending of the elbow. The triceps tendon attaches the triceps muscle to the ulna posteriorly, which allows for forceful straightening of the elbow, as seen when performing a push-up. Tendons of the forearm muscles, which flex and extend the wrist, attach at the medial and lateral epicondyles of the humerus. Wrist flexors attach medially, and wrist extensors attach laterally.

MR imaging of the elbow may be ordered to assess injuries to the tendons and ligaments in and around the joint space, to evaluate degenerative disease, or to assess bony abnormalities. Approximately 10 to 25 percent of injuries to the elbow involve dislocations, which are typically diagnosed using x-rays. Tendonitis of the elbow is usually an “overuse” injury, further specified as golfer’s elbow or tennis elbow. Golfer’s elbow, also termed medial epicondylitis, involves the flexor tendon, while tennis elbow, or lateral epicondylitis, involves the extensor tendon. A common ligamentous injury is a sprain or strain of the medial collateral ligament, also known as thrower’s elbow. Constant, repetitive throwing motions result in compression of lateral elbow structures and stretching of medial structures, so pain may be bilateral. The ability to visualize the inflammation, scar tissue, and calcium deposits common to all these elbow injuries makes MRI an invaluable tool for the diagnosis of these conditions.

MRI of the elbow may also be performed to assess nerve injuries. Irritation of the nerves, or pressure on the nerves from constant bending and straightening of the elbow can result in pain, numbness and weakness in the arm or hand. Each of the three main nerves to the forearm crosses the elbow through its own “tunnel, which can contribute to nerve irritation. The ulnar nerve passes through the cubital tunnel on the medial aspect of the elbow. Irritation of the ulnar nerve may be a part of cubital tunnel syndrome. The radial nerve passes through the radial tunnel on the lateral aspect of the elbow. Symptoms of radial tunnel syndrome can mimic tennis elbow, which is a type of tendonitis. The median nerve travels between the heads of the pronator teres muscle, in a medial to lateral direction across the forearm. Problems with the median nerve may be caused by pronator syndrome.

Open MRI Systems

Introduction

When positioning a patient for an elbow exam in an open MRI system, it is important to consider the choices you have as far as coil selection and patient setup, especially in regard to the patient’s size and body habitus, and the extent of their elbow injury or pain. Isocenter positioning in all three planes is the key to optimum image quality.

Coil selection, table and accessory pads, table straps, and proper laser light centering must all be considered when preparing for an elbow examination. The extremity coil may be the coil of choice, but proper anatomical positioning with this coil may be difficult with larger patients. Selection of either the extremity coil or the solenoid coil involves careful selection of table pads and accessory pads to maintain accurate centering in the A-P direction. The table straps are especially helpful in securing the position of both the solenoid coil and the patient. Centering the body part to the laser localizer beams in all three directions is of high importance when scanning on an open MRI system. Consult the radiologist for his / her preferences for positioning of the forearm and hand- i.e. supination vs. pronation.

Coils and Positioning

Knee (Extremity) Coil

The coil of choice for a study of the elbow is the extremity coil. Position the patient toward the edge of the table away from the affected body part. In addition, move the table away from the affected side. This affords you the best opportunity to position the elbow at the exact isocenter of the magnet. Position the elbow in the center of the extremity coil, elevating the elbow as necessary to achieve coronal centering in the coil (Figure 72). Use accessory pads to support the forearm and hand, as well as to aid in proper positioning of the elbow (Figure 73). Center the laser localizer beams to the midline indicators on the extremity coil.

Patients can also be scanned in a prone position, as shown in Figures 74 and 75. Position the patient prone on the table with the affected arm above their head. Position the elbow in the center of the extremity coil. Use pillows and accessory pads to support the patient’s forearm and hand, and to make the patient as comfortable as possible. Accessory pads should also be used inside the coil to help achieve coronal centering of the anatomy, and to maintain the position of the elbow. Center the laser localizer beams to the midline indicators on the extremity coil.

Hint: Because this position may be uncomfortable for the patient, have the exam window open and ready for scanning before positioning the patient.

Large Extremity (Solenoid) Coil

The large extremity or large joint coils, which are solenoid coils, can also be used to provide high quality images for elbow scanning. Position the patient toward the edge of the table away from the affected body part. In addition, move the table away from the affected side. This affords you the best opportunity to position the elbow at the exact isocenter of the magnet. Place the patient’s arm through the solenoid coil, as shown in Figure 76. Use accessory pads or pillows to elevate and support the patient’s forearm, wrist, and hand for comfort, as well as to aid in proper positioning. If necessary, use the table straps to help stabilize both the coil and the patient’s arm. Position the elbow in the center of the solenoid coil. Center the laser localizer beams to the center of the coil.

The solenoid coil may prove to be the coil of choice for elbow imaging on larger patients (Figure 77). This coil allows more flexibility when trying to attain isocenter positioning in all three planes. The solenoid coil also offers impressive signal capabilities for image optimization. The table straps are beneficial for securing the positions of both the solenoid coil and the patient.

Table Pads and Accessory Pads

It is important to give careful consideration to the both the table pads and the accessory pads that will be used to maintain the coil and the anatomy in isocenter. Insufficient table pads can lead to non-isocenter scanning, resulting in sub-optimal images. Correct table pad selection is necessary to place both the extremity coil and the solenoid coil in the coronal (A-P) isocenter position. Accessory pads can be used to help mobilize and stabilize the elbow inside the coil. They can also be used to assist with positioning of the upper arm and forearm, as well as overall patient comfort.

Table Straps

The system table straps can be used to help stabilize both the patient and the coil, especially when using the solenoid coil. The straps can remain attached to the table so they are readily available.

Laser Localizer Beams

When positioning for an elbow exam, always use the laser localizer beams to ensure isocenter positioning in all three directions: A-P, R-L, H-F. Image signal is optimized when the patient’s anatomy is at isocenter in all three directions.

For additional information, please refer to the Oasis Patient Positioning and Coils manual, or the Altaire, AIRIS II, or AIRIS Elite Patient Positioning manuals that were supplied with your MRI system.

Echelon MRI System

Coils and Positioning

General Purpose Coils

The general purpose coils are the standard coils that are best suited for elbow scanning. Depending on the patient’s size and body habitus, attempts should be made to position the patient near the table edge opposite the affected elbow. In addition, positioning the patient slightly obliqued toward the affected elbow may help in achieving a true AP position of the elbow joint. Oblique patient positioning will also aid in moving the anatomy closer to isocenter. The general purpose coils should be positioned on top of and underneath the elbow and facing the same direction, so the open areas of the coils are both centered over the elbow (Figure 80). The joint should then be centered in the coil in the H-F and R-L directions.

Table pads and accessory pads should be used as needed to maintain patient comfort, as well as to maintain the required position of the forearm, wrist and hand. Pads can be used to give extra support to the patient if they are placed in an oblique position. The system table straps can be used for additional stabilization of the patient and the general purpose coils.

Use the laser localizer beams to display H-F and R-L centering. Accurate H-F centering of the elbow joint in the general purpose coils is easily attainable in the Echelon system.

Upper Extremity Coil

The optional upper extremity coil was designed with anatomic regions such as the long bones of the upper extremity in mind. The coil size and configuration also make it a superior fit for use in elbow scanning. The upper extremity coil should be centered on the elbow in the H-F direction. Place the thick pad supplied with the coil on top of the elbow, then secure the coil around the elbow using the Velcro® strap (Figure 81). The thick pad helps to maintain space between opposite sides of the coil, which improves SNR.

Both of the pads provided for use inside the coil make positioning and scanning more comfortable for the patient. Accessory pads can be used to maintain and support the upper arm, forearm and hand as needed. The table straps can be used to further stabilize the upper extremity coil in its position.

Use the laser localizer beams to display H-F and R-L centering. The upper extremity coil should be centered in the H-F direction.

For additional information, please refer to the Echelon Patient Positioning and Coils manual that was supplied with your Echelon system.

Scan Setups

The following are HMSA suggestions for elbow imaging. Always check with your radiologist for his / her imaging preferences.

Axial Scans

Our recommendation is to begin an elbow study with a scan oriented in the transverse or axial plane. It will be to your advantage to align the humerus and forearm parallel to the tabletop when the patient is positioned on the table (Figures 82 and 83). This will help to prevent multiple angulations during slice setup.

Be sure to take into account the axial FOV position prior to angling your slices; this becomes even more important when the FOV is smaller. You will only see your FOV boundaries clearly before the slices are rotated to the desired obliquity. This is demonstrated in Figure 84.

Coronal Scans

Visualize a line connecting the lateral and medial epicondyles of the distal humerus. Coronal slices are typically angled parallel to that line, as seen in the transverse image of Figure 85. The area of coverage will vary, depending on the pathology that may be involved, and the radiologist’s preferences.

Sagittal Scans

Sagittal slices are typically angled perpendicular to a line that would connect the lateral and medial epicondyles of the distal humerus, as seen in the transverse image of Figure 86. Again, the area of coverage will vary, depending on the pathology and the radiologist’s preferences.

There are a wide variety of pulse sequences available in your Scan Card Library or Task Library that can be used when creating protocols for elbow examinations.

Forearm

MRI may be requested for:

The forearm comprises the region between the elbow and the wrist, and includes 2 long bones, the radius and the ulna. Each of these bones has an articulation with the humerus at the elbow joint. In addition, the radius and ulna articulate at proximal and distal radioulnar joints. Rotation of the radius at the proximal radioulnar joint allows for supination and pronation of the hand. The radius crosses the ulna during hand pronation.

Major muscles in the forearm that are involved in flexion of the elbow include the biceps brachii, brachialis, brachioradialis, and the pronator teres. The forearm muscles involved in supination of the forearm and hand are the biceps brachii and the supinator. The main muscles involved in pronation are the pronator teres and pronator quadrates. The forearm is also the origination of multiple flexor and extensor muscles that act on the wrist, hand, and fingers. MRI of the forearm may be ordered to assess strains to any of these muscles resulting from lifting, pushing, pulling, grabbing, or twisting motions. A variety of injuries, categorized as “repetitive stress injuries” might also be the basis for an MRI of the forearm. These types of injuries to muscles, nerves, and tendons result from overuse or improper use of the elbow, wrist, or forearm. Tennis elbow, golfer’s elbow, carpal tunnel syndrome, and cubital tunnel syndrome can all be included under the umbrella of repetitive stress injuries.

The major nerves of the forearm are branches that originate from the brachial plexus. The ulnar nerve (musician’s nerve) supplies forearm muscles, as well as muscles of the hand. This nerve is subject to becoming trapped or pinched on its journey from the brachial plexus to the fingertips. MRI may be ordered to assess cubital tunnel syndrome, which is entrapment of the ulnar nerve in the “tunnel” of tissue under the medial epicondyle of the humerus. The radial nerve also travels from the brachial plexus to the posterior aspect of the hand, but is less likely to be involved in “entrapment” syndromes. The radial nerve innervates many of the hand and wrist extensors. The median nerve is best known for its involvement in carpal tunnel syndrome. However, it is also the entrapped or irritated nerve in pronator (teres) syndrome, which involves finger numbness, elbow pain, and pain on pronation of the forearm. This syndrome can result from repetitive throwing motions. The median nerve innervates the forearm flexor muscles.

Open MRI Systems

Introduction

When positioning a patient for a forearm exam in an open MRI system, one must consider the choices available as far as coil selection and patient setup. The patient’s size and body habitus will influence coil selection, as well as positioning of both the coil and the patient on the table. These choices will also be influenced by the radiologist’s preference for inclusion of one or both joints.

The radiologist should be consulted concerning his / her positioning preferences for the forearm and hand. If the hand is placed in pronation (palm down), the radius crosses over the ulna, placing different stresses and tensions on muscle groups in the forearm. This could impact the radiologist’s interpretation of the images. One must also consider each patient’s pain tolerance, and their ability to maintain a specific position, regardless of whether it is pronation or supination of the hand and forearm.

Coil selection, table and accessory pads, table straps, and proper laser light entering are all factors to be considered when preparing for a forearm study. Careful selection of both table pads and accessory pads is necessary to maintain both the coil and the anatomy at an isocenter position in all three directions- H-F, R-L, and A-P. The table straps are very helpful when using the solenoid coil to maintain the coil in the correct position for forearm imaging, as well as 90° from the tabletop. Every effort should be made to position the forearm in the center of the laser localizer beams in all three directions for optimum image quality.

Coils and Positioning

Extremity Coil

The coil of choice for a study of the forearm is the extremity coil. Position the patient toward the edge of the table away from the affected body part. In addition, move the table away from the affected side. This affords you the best opportunity to position the forearm at the exact isocenter of the magnet. Position the forearm in the center of the extremity coil. Then, center the laser light to the center of the coil. Use accessory pads and sponges for forearm and hand stabilization, patient comfort, and to maintain isocenter positioning in all three directions (Figure 93).

Solenoid Coil

The solenoid coil can also be used to image the forearm. Position the patient toward the edge of the table away from the affected body part. In addition, move the table away from the affected side. This affords you the best opportunity to position the forearm at the exact isocenter of the magnet. Place the solenoid coil alongside the affected forearm. Elevate the entire affected arm with accessory pads to position the anatomy at isocenter of the solenoid coil. Use the table straps to stabilize the coil and the patient’s arm (Figure 94). The solenoid coil should remain at 90 degrees to the tabletop for maximum signal. Center the laser localizer beams to the center of the coil.

Table Pads and Accessory Pads

When scanning on an open MRI system, it is especially important to give careful consideration to the centering of both the anatomy and the coil in all three directions- H-F, R-L, and A-P. Proper selection of table pads plays a large role in achieving isocenter positioning, especially in the coronal (A-P) direction. Insufficient padding and non-isocenter scanning typically result in images that are suboptimal. Accessory pads can be used with both the extremity and solenoid coils for improved coil stabilization and patient comfort. They should be used both inside and outside of the coil to maintain the entire upper extremity in its required position. The upper arm, wrist, and hand should all be on the same plane as the forearm. The radiologist should be consulted for his / her preferences for positioning of the forearm (i.e. supination vs. pronation).

Table Straps

The system table straps can be used to help stabilize both the patient and the coil, especially when using the solenoid coil. The straps can remain attached to the table so they are readily accessible.

Laser Localizer Beams

When positioning for a forearm exam, always use the laser localizer beams to ensure A-P, R-L, and H-F centering. Image signal is optimized when the patient’s anatomy is at isocenter in all three directions.

For additional information, please refer to the Oasis Patient Positioning and Coils manual, or the Altaire, AIRIS II, or AIRIS Elite Patient Positioning manuals that were supplied with your MRI system.

Echelon MRI System

Coils and Positioning

Knee (Extremity) Coil

The extremity coil is one of the coils that may be selected for forearm scanning. The patient will likely be more comfortable if positioned prone on the table, with the affected forearm over their head in a prone position in the coil (Superman position). The knee coil may not allow for optimum imaging of both the elbow and wrist joints. Therefore, the coil should be positioned to include the joint closest to the area of interest on the forearm. This area should be centered in the H-F and R-L directions inside the coil. The extremity coil may be angled slightly on the tabletop for patient comfort, as shown in Figure 98. Excessive angulation will affect image quality by decreasing SNR.

Table pads and accessory pads should be used as needed to maintain patient comfort, as well as to maintain and support the required positions of the elbow, forearm, wrist and hand in relation to each other. Accessory pads can also be used inside the coil to maintain the position of the forearm, and decrease patient motion. Due to the multiple elements located in the bottom portion of the extremity coil, it is not necessary to elevate the forearm to have the anatomy centered in the coronal direction. The system table straps can be used if needed for additional stabilization of the patient and / or extremity coil.

Use the laser localizer beams to display H-F and R-L centering. Depending on the patient’s size and body habitus, the Superman position may allow for fairly accurate centering of the extremity coil in the R-L direction.

Torso / Body Coil

The torso coil is another standard coil that may be used for forearm scanning. Place table pads on the table, then place the bottom portion of the torso coil on the table pads. Position the patient lying prone on the table with the affected forearm over their head. The affected forearm should be pronated, and centered in the bottom portion of the torso coil (Superman position). Place a pillow over the affected forearm, then lay the upper portion of the torso coil on top of the pillow, and secure the upper portion with the Velcro® straps (Figure 99). The pillow serves to increase the distance between the top and bottom portions of the torso coil, which improves SNR.

Additional accessory pads and pillows can be used as needed to maintain patient comfort, and to support the positions of the elbow and forearm in the torso coil. Use of the pillow on top of the forearm will help stabilize the forearm’s position, as well as stabilize the position of the top portion of the coil.

The table straps can be used for additional stabilization of the coil, if necessary. Use the laser localizer beams to display H-F and R-L centering. The torso coil, and the forearm within the coil, should be centered in the H-F and R-L directions.

Upper Extremity Coil

The optional upper extremity coil was designed with anatomic regions such as the forearm in mind. The coil size and configuration make it a superior fit for various long bone applications. As it is smaller than the torso coil, it is better adapted for some degree of offset centering of the affected forearm. The upper extremity coil should be centered on the forearm in the H-F direction. Place the thick pad supplied with the coil on top of the forearm, then secure the coil around the forearm using the Velcro® strap (Figure 100). The thick pad helps to maintain space between opposite sides of the coil, which improves SNR.

Both of the pads provided for use inside the coil make positioning and scanning more comfortable for the patient. Accessory pads can be used to maintain and support the forearm and hand as needed. The table straps can be used to further stabilize the long bone coil in its position.

Use the laser localizer beams to display H-F and R-L centering. The forearm and the upper extremity coil should be centered in the H-F direction.

The upper extremity coil can also be used when the patient is placed in the “Superman position” (Figure 101). The patient will lie prone on the table pads, with the affected forearm over their head. The forearm should be pronated, and positioned in the H-F center of the upper extremity coil. The thick pad supplied with the coil is placed over the affected forearm, and the coil is secured with the Velcro® strap.

Additional accessory pads and pillows should be used as needed for patient comfort, and to support the position of the upper arm.

For additional information, please refer to the Echelon Patient Positioning and Coils manual that was supplied with your Echelon system.

Scan Setups

The following are HMSA suggestions for forearm imaging. Always check with your radiologist for his / her imaging preferences.

Axial Scans

When positioning slices for the forearm, axial slices are typically positioned over the area of interest. If the solenoid coil is being used, be sure that it is positioned to include the area of interest (Figure 102).

Coronal Scans

Coronal slices should be aligned with the shafts of the radius and ulna, as seen in the sagittal image below. Be careful with the field of view that is selected. While it may be possible to visualize both joints, HMSA recommends that you focus on the joint closest to the area of interest.

Sagittal Scans

Sagittal slices should be aligned with the shafts of the radius and ulna, as seen in the coronal image of Figure 104. Be careful with the field of view that is selected. While it may be possible to visualize both joints, HMSA recommends that you focus on the joint closest to the area of interest.

There are a wide variety of pulse sequences available in your Scan Card Library or Task Library that can be used when creating protocols for forearm examinations.

Wrist

MRI may be requested for:

The wrist is the connection between the forearm and hand. It is comprised of two rows of small bones, called carpals (Figure 105). The carpal bones form many different types of joints, with each other, as well as with the radius and the metacarpals. The distal aspect of the ulna is not involved in bony articulation with the carpal bones. Rather, the Triangular Fibrocartilage Complex (TFCC), an articular disc distal to the ulna, is involved in the wrist articulation. The distal surface of the TFCC disc and the distal surface of the radius articulate with the proximal articular surfaces of the scaphoid, lunate, and triquetrum carpal bones.

The variety of injuries and syndromes that may affect the large number of tendons and ligaments associated with the wrist joint make this anatomical region a perfect fit for MRI. The superior imaging capabilities in this modality lend themselves to improved visualization of bones, ligaments, tendons, and nerves.

Forces produced from a fall on the hand typically pass through the radius, scaphoid, and lunate. The most common fractures are seen in the distal radius and scaphoid. Non-displaced fractures of the scaphoid may be more identifiable using MRI, as injury-associated edema is easily seen. Ligaments that help to strengthen the wrist joint capsule include the palmar and dorsal radiocarpal ligaments, and the ulnar and radial collateral ligaments. The transverse carpal ligament (or flexor retinaculum) is the thin, broad ligament on the palmar aspect that creates the “carpal tunnel”. The flexor tendons to the fingers and thumb, as well as the median nerve, pass through this area. A variety of intercarpal ligaments are also found in the wrist joint. The carpal area most commonly affected by ligamentous instability is between the scaphoid and lunate bones.

Flexor and extensor tendons cross the wrist to allow function of the hand and digits. The 12 extensor tendons insert on the dorsal aspect of the hand (posterior aspect), while the 12 flexor tendons insert on the palmar aspect of the hand and wrist (anterior aspect) (Figure 106). Irritated flexor tendons can become thickened or swollen, thereby increasing pressure on the median nerve in the carpal tunnel. Median nerve compression leads to the symptoms associated with carpal tunnel syndrome, including numbness in the thumb, index and middle fingers, and general thumb weakness.

In addition to the previously mentioned median nerve, the radial and ulnar nerves travel through the wrist to innervate various hand muscles. The ulnar nerve, accompanied by the ulnar artery, passes through an area called Guyon’s canal, a “tunnel” between the pisiform and hamate carpal bones (Figure 107). Guyon’s canal syndrome can result from compression of the ulnar nerve. Although not as common as carpal tunnel syndrome, these 2 syndromes can occur together, and may be the specified diagnosis for an MRI exam. Guyon’s canal syndrome typically affects the little finger and half the ring finger, with symptoms of “pins and needles”, then burning pain. It may be seen in cyclists, weight lifters, and people on crutches, who are all placing constant pressure on their palms. Overuse of the wrist by heavy gripping or repeated wrist and hand motions may also lead to ulnar nerve compression. Additional causes of Guyon’s canal syndrome include arthritis, a mass or ganglion in this area, or a traumatic wrist injury, especially one involving the pisiform or hamate carpal bones.

Open MRI Systems

Introduction

It is important to consider the many choices you have as far as coil selection and patient setup when preparing a patient for a wrist exam in an open MRI system. Wrist exams can be performed with the patient lying supine with their wrist by their side, or lying prone with their wrist over their head. The patient’s size and body habitus, as well as the extent of their wrist injury and their pain level, will all influence their position for the exam, as well as your coil selection.

Isocenter positioning in all three planes is the key to optimum image quality for open MRI systems. Coil selection, table and accessory pads, table straps, and proper laser light centering must all be considered when preparing for a wrist examination. Typically, the wrist coil or extremity coil is used for wrist scanning. Table and accessory pads are important in maintaining both the coil and the wrist at an isocenter position, especially in the coronal direction. The table straps may be necessary with the wrist coil to help maintain it in the required position. The laser localizer beams should be centered in all three directions- H-F, R-L, A-P- to optimize image quality.

Coils and Positioning

Wrist Coil

The coil of choice for a wrist study is the wrist coil, which is a purchaseable coil. Position the patient toward the edge of the table away from the affected body part. In addition, move the table away from the affected side. This affords you the best opportunity to position the wrist at the exact isocenter of the magnet. Position the wrist in the center of the coil. Pads that are furnished with the coil should be used to stabilize and cushion the wrist inside the wrist coil. Additional pads supplied with the coil should be used under the elbow, proximal forearm, and hand for proper elevation and patient comfort (Figures 112 and 113). Center the laser localizer beams to the midline indicators on the wrist coil.

Patients can also be scanned in a prone position, as shown in Figure 114. Position the patient prone on the table with the affected wrist above their head. Position the wrist in the center of the wrist coil. Pads that are furnished with the coil should be used to stabilize and cushion the wrist inside the wrist coil. Use pillows and accessory pads to support the patient’s arm and hand, and to make the patient as comfortable as possible. Center the laser localizer beams to the midline indicators on the wrist coil.

Hint: Because this position can be uncomfortable for the patient, have the exam window open and ready for scanning before positioning the patient.

Extremity Coil

The extremity coil may be used for wrist imaging, especially if pain or pathology encompasses a larger area. Wrist pain can be caused by damage to ligaments or tendons in the forearm, so a larger coil and a larger FOV may be required. Position the patient toward the edge of the table away from the affected body part. In addition, move the table away from the affected side. This affords you the best opportunity to position the wrist at the exact isocenter of the magnet. Position the wrist in the center of the extremity coil. Use accessory pads inside the coil to achieve coronal centering of the wrist, and to stabilize the anatomy in the proper position. Pads should also be used under the patient’s forearm, elbow, and upper arm for support and patient comfort (Figure 115). Center the laser localizer beams to the midline indicators on the coil.

The extremity coil can also be used with the patient lying in the prone position, with the affected arm over their head, as shown in Figure 116. Position the wrist in the center of the extremity coil. Use accessory pads inside the coil to achieve coronal centering of the wrist, and to stabilize the anatomy in the proper position. Use pillows and accessory pads to support the patient’s upper arm and forearm, and to make the patient as comfortable as possible. Center the laser localizer beams to the midline indicators on the extremity coil.

Table Pads and Accessory Pads

It is important to give careful consideration to both the table pads and the accessory pads that will be used to position and maintain the coil and the anatomy in isocenter. Insufficient table pads can lead to non-isocenter scanning, resulting in sub-optimal images. Correct table pad selection is necessary to place both the wrist coil and the extremity coil in the coronal (A-P) isocenter position. Accessory pads can be used to help mobilize and stabilize the wrist inside the coil. They should also be used to assist with positioning of the upper arm and forearm, and for overall patient comfort.

Table Straps

The system table straps can be used to help stabilize both the patient and the coil, especially when using the wrist coil. The straps can remain attached to the table so they are readily available.

Laser Localizer Beams

When positioning for a wrist exam, always use the laser localizer beams to ensure isocenter positioning in all three directions: A-P, R-L, H-F. Image signal is optimized when the patient’s anatomy is at isocenter in all three directions.

For additional information, please refer to the Oasis Patient Positioning and Coils manual, or the Altaire, AIRIS II, or AIRIS Elite Patient Positioning manuals that were supplied with your MRI system.

Echelon MRI System

Coils and Positioning

Wrist Coil

The optional wrist coil was designed for easy use with the patient in either the supine or prone position. The coil is affixed to a holder assembly when in use, so both the coil and the patient’s wrist are well stabilized.

Depending on the patient’s size and body habitus, the wrist coil can be used with the patient lying supine on the table, with the affected wrist down at their side. The wrist coil holder assembly should be positioned on the table on the side of the affected wrist. The coil is mounted in the side of the holder in a vertical position, with the patient’s wrist in a decubitus (lateral) position in the coil. Sponges accompany the wrist coil to secure and cushion the wrist inside the coil. Accessory pads can be used to maintain and support the arm in the required position (Figure 121). Use the laser localizer beams to display H-F and R-L centering. The wrist coil should be centered in the H-F direction.

The wrist coil can be easily adapted for use with the patient lying in a prone position (Superman position). The wrist coil holder assembly should be placed in the center of the table. Position the patient lying prone on the table, with the affected wrist over their head. The coil is mounted on the holder assembly in a horizontal position, with the patient’s wrist in a prone position inside the coil. Sponges accompany the wrist coil to secure and cushion the wrist inside the coil. Accessory pads and pillows can be used to maintain patient comfort, and to support the arm in the required position (Figure 122). Use the laser localizer beams to display H-F and R-L centering. The wrist coil should be centered in both the H-F and R-L directions.

Knee (Extremity) Coil

The extremity coil is one of the standard Echelon coils that may be selected for wrist scanning. Depending on the patient’s size and body habitus, the extremity coil can be positioned down at the patient’s side, or above the patient’s head, with the patient in the Superman position (prone on the table, with the affected wrist over their head in a prone position in the coil, Figure 123). The wrist should be centered in the H-F and R-L directions inside the coil.

Table pads and accessory pads should be used as needed to maintain patient comfort, as well as to maintain and support the required position of the upper arm, elbow, forearm and hand. Accessory pads can also be used inside the coil to secure the position of the wrist and reduce patient motion. The wrist does not have to be elevated to the coronal center of the extremity coil, as there are multiple elements in the bottom portion of the coil that provide an abundance of signal. The system table straps can be used if needed for additional stabilization of the patient and / or the extremity coil.

Use the laser localizer beams to display H-F and R-L centering. Depending on the patient’s size and body habitus, the Superman position may allow for fairly accurate centering of the extremity coil in the R-L direction.

For additional information, please refer to the Echelon Patient Positioning and Coils manual that was supplied with your Echelon system.

Patient Orientations

The following sections offer recommendations for patient orientation selections (Figure 124), which are made during patient registration. Included are various patient positioning scenarios for Open MRI systems and the Echelon system. Your radiologist may request a different orientation of the wrist and hand for their viewing and interpretation purposes. A common preference is to have the coronal and sagittal images displaying the anatomy with the fingers pointed upwards, and the axial images displaying the palmar surface pointing downward. In order to display the anatomy in this manner and maintain the accuracy of the orientation markers on the images, it may be necessary to have the radiologist rotate the images after the DICOM transfer process.

initial image
CAUTION: Avoid selecting patient orientations that are different from those recommended in this text. Changing the patient orientation selection in order to have the anatomy display in a different direction will result in images that are labeled incorrectly.

Open MRI Systems

Points to keep in mind concerning the patient orientation selection, the patient’s position, and the position of the wrist that is to be scanned:

  1. Orientation markers are based on the patient being in “true anatomical position”. The palmar surface of the hand is anterior, and the dorsal surface is posterior. The fingers are inferior, or closer to the feet, and the forearm is superior, or closer to the head. On the right hand, the thumb is on the right side, and the little finger is on the left side. On the left hand, the thumb is on the left side, and the little finger is on the right side.

  2. The Patient Orientation that you select should be based on the position of the anatomy that you are scanning, which is not necessarily the position of the patient on the table; i.e., the patient’s body may be supine on the table, but their wrist is prone in the coil.

Patient Prone, Head First, Right or Left Wrist

Positioning the patient in the “Superman” position means that the patient is lying prone on the table, entering the magnet head first, with their affected wrist over their head and positioned prone in the coil.

Patient Orientation was registered as Feet First / Prone (Figure 125).

The result was images with correct orientation markers (the fingers and wrist entered the magnet in the same position they would be in if the patient was feet first; the wrist was prone in the coil)(Figure 126).

Patient Supine, Head First, Right or Left Wrist

When the right or left wrist is to be scanned in a coil at the patient’s side, the patient can be positioned to enter the magnet either head first or feet first. In the example seen here, the patient was positioned supine on the table, and entered the magnet head first. The affected wrist (the right wrist, in this example) was in a prone position in the coil.

Patient Orientation was registered as Head First / Prone (Figure 127).

The result was images with correct orientation markers (the forearm was oriented toward the head, superior to the wrist, and entered the magnet first; the wrist was prone in the coil)(Figure 128).

Patient Supine, Feet First, Right or Left Wrist

In the next example (Figure 129), the patient was again positioned supine on the table, but entered the magnet feet first. The affected wrist (the right wrist, in this example) was in a prone position in the coil.

Patient Orientation was registered as Feet First / Prone.

The result was images with correct orientation markers (the fingers were oriented toward the feet, and entered the magnet first; the wrist was prone in the coil)(Figure 130).

Echelon MRI System

Points to keep in mind concerning the patient orientation selection, the patient’s position, and the position of the anatomy that is to be scanned:

  1. Orientation markers are based on the patient being in “true anatomical position”. The palmar surface of the hand is anterior, and the dorsal surface is posterior. The fingers are inferior, or closer to the feet, and the forearm is superior, or closer to the head. On the right hand, the thumb is on the right side, and the little finger is on the left side. On the left hand, the thumb is on the left side, and the little finger is on the right side.

  2. The Patient Orientation that you select should be based on the position of the anatomy that you are scanning, not necessarily the position of the patient on the table; i.e., the patient’s body may be supine on the table, but their wrist may be in a prone position in the coil.

  3. When using the Echelon wrist coil with the patient’s wrist down at their side, the wrist coil will be in a vertical position in the holder. The patient’s wrist is technically in a decubitus position inside the coil. The Patient Orientation that should be selected is not interchangeable between the right and left wrists as it is on the Open MRI systems.

Patient Prone, Head First, Right or Left Wrist

Positioning the patient in the “Superman” position means that the patient is lying prone on the table, entering the magnet head first, with their affected wrist over their head and positioned prone in the coil.

Patient Orientation was registered as Feet First / Prone (Figure 131).

The result was images with correct orientation markers (the fingers and wrist entered the magnet in the same position they would be in if the patient was feet first; the wrist was prone in the coil) (Figure 132).

Patient Supine, Head First, Right Wrist

When the wrist is to be scanned in the Echelon wrist coil at the patient’s side, the patient can be positioned to enter the magnet either head first or feet first. The wrist coil will be in a vertical position in the holder, and the wrist is technically in a decubitus position in the wrist coil. The Patient Orientation that should be selected will differ between the right and left wrists. In the example shown in Figure 133, the patient was positioned supine on the table, and entered the magnet head first. The right wrist was in a decubitus position in the coil.

Patient Orientation was registered as Head First / Left Decubitus.

The result was images with correct orientation markers (the forearm was oriented toward the head, superior to the wrist, and entered the magnet first; the left side of the right wrist was the side that was down in the coil) (Figure 134).

Patient Supine, Head First, Left Wrist

In the next example (Figure 135), the patient was again positioned supine on the table, and entered the magnet head first. In this case, the left wrist was in a decubitus position in the coil.

Patient Orientation was registered as Head First / Right Decubitus.

The result was images with correct orientation markers (the forearm was oriented toward the head, superior to the wrist, and entered the magnet first; the right side of the left wrist was the side that was down in the coil) (Figure 136).

Patient Supine, Feet First, Right Wrist

The patient can also be positioned to enter the Echelon magnet feet first, with their wrist positioned in the wrist coil at their side. Again, the wrist coil will be in a vertical position in the holder, and the wrist is technically in a decubitus position in the wrist coil. The Patient Orientation that should be selected will again differ between the right and left wrists. In the example shown in Figure 137, the patient was positioned supine on the table, and entered the magnet feet first. The right wrist was in a decubitus position in the coil.

Patient Orientation was registered as Feet First / Left Decubitus.

The result was images with correct orientation markers (the fingers were oriented toward the feet, and entered the magnet first; the left side of the right wrist was the side that was down in the coil) (Figure 138).

Patient Supine, Feet First, Left Wrist

In the next example (Figure 139), the patient was again positioned supine on the table, and entered the magnet feet first. In this case, the left wrist was in a decubitus position in the coil.

Patient Orientation was registered as Feet First / Right Decubitus.

The result was images with correct orientation markers (the fingers were oriented toward the feet, and entered the magnet first; the right side of the left wrist was the side that was down in the coil) (Figure 140).

Scan Setups

The following are HMSA suggestions for routine wrist imaging. Always check with your radiologist for his / her imaging preferences.

Axial Scans

Axial slices should cover the anatomy, from the distal radius and ulna through and including the proximal metacarpals. Slices should be aligned perpendicular to the long axis of the radius and metacarpals, as seen in the coronal and sagittal images below. A slight angulation of the axial slices may be required, depending on the position of the wrist, hand, and forearm, as well as the radiologist’s preferences for the positioning of slices relative to the carpal bones.

Coronal Scans

Coronal slices should be aligned with the long axis of the radius and metacarpals, as seen in the sagittal image of Figure 142. Slice coverage should be adequate to include the soft tissues of the palmar surface, especially for a diagnosis of carpal tunnel syndrome.

Sagittal Scans

Sagittal slices should be aligned with the long axis of the radius and metacarpals, as seen in the coronal image of Figure 143. Slice coverage should expand across the wrist to include required anatomy at both the medial and lateral aspects, as seen in the transverse image of Figure 143.

There are a wide variety of pulse sequences available in your Scan Card Library or Task Library that can be used when creating protocols for wrist examinations.

Scaphoid (Navicular) Fractures

An MR study of the wrist may be requested for the possibility of a scaphoid (or navicular) fracture. The downward force placed upon the wrist during a fall, along with the upward motion of the hand to catch oneself, frequently results in a fracture of the scaphoid bone (Figure 144). Painful palpation of the anatomical “snuffbox” (the hollow created at the base of the thumb when it is extended) may be a strong indicator of a scaphoid fracture.

When a bone abnormality is suspected, it is imperative to perform a sequence that will suppress the yellow marrow of bone, as it is composed of 80 percent fat. STIR, FatSat or FatSep sequences are the usual choices for this imaging requirement. A fracture causes replacement of the yellow fatty marrow with bone marrow edema. This results in images which display bright signal from the edema surrounding the dark or suppressed signal from the intact bone, as seen in Figure 144.

Hand / Fingers

MRI may be requested for:

The hand and fingers comprise the distal portion of the upper extremity. The five metacarpal bones of the hand articulate proximally with the distal row of carpal bones (Figure 145). The distal articulation of the metacarpals involves the five proximal phalanges. These metacarpophalangeal joints are the “knuckles”. The four fingers consist of proximal, middle and distal phalanges, while the thumb has only proximal and distal phalanges. The nine interphalangeal joints (2 in each finger, one in the thumb) are covered by articular cartilage, and are classified as hinge joints.

The numerous small, fragile phalangeal bones are attached to a complex network of flexor and extensor tendons. The phalanges are prone to fractures, and the tendons are prone to tears. Given that MR images can provide detailed information regarding muscles, ligaments, and tendons, it is important to be familiar with the locations and functions of the multiple hand and finger muscles and attachments (Figures 146 and 147). The larger flexor and extensor muscles that control the hands and fingers originate in the forearm. The flexors are found along the anterior aspect of the forearm. Two of the deep flexor muscles that travel through the hand to the fingers include the flexor digitorum profundus, which travels to the four fingers, and the flexor pollicis longus, which travels to the thumb. Flexor tendon injuries can result from lacerations, as well as from forced hyperextension or forced flexion of extended digits. Flexor tendinitis, an irritation of the sheath surrounding a flexor tendon, can result in trigger finger. If the tendon “sticks”, the finger can suddenly shoot out from its bent position, or can remain bent permanently.

The extensor muscles travel through the forearm to the hand along the posterior aspect. Superficial extensors travel to the fingers, while deep extensor muscles furnish the thumb. Extensor tendons are more superficial, and therefore more easily injured from avulsions, crush injuries, burns and minor lacerations. The forced flexion of an extended digit (a finger hit by a baseball, volleyball, etc.) can result in “mallet finger” or “baseball finger” (Figure 148). It is observed as abnormal flexion at the distal interphalangeal joint, resulting from the avulsion or forcible stretching of an extensor tendon. Another extensor tendon injury usually caused by trauma is the “boutonniere deformity” (Figure 149). The tear in the tendon looks like a buttonhole, which translates from the French language as “boutonniere”. The disruption of the extensor mechanism leaves the proximal interphalangeal joint flexed, and the distal interphalangeal joint hyperextended.

Muscles of the thenar eminence (bulge of muscle on palmar surface of first metacarpal) enable the complex movements of the thumb, which include flexion, abduction, adduction, circumduction and opposition. The muscles of opposition are especially important for grasping functions of the hand. The hypothenar eminence (muscles on palmar surface of fifth metacarpal) provides those same movements for the little finger.

Abduction and adduction of the fingers is accomplished by the deep metacarpal muscles- the dorsal interosseous muscles for abduction, and the palmar interosseous muscles for adduction. In addition, the deep lumbrical muscles of the palmar surface serve to flex the fingers at the metacarpal joints, and extend the fingers at the interphalangeal joints. The lumbrical muscles help put the hand in the position necessary for writing.

There are numerous stabilizing ligaments in the joints of the hand and fingers. Collateral ligaments can be found on either side of each finger joint and the thumb joints- metacarpophalangeal joints, proximal interphalangeal joints, and distal interphalangeal joints. These ligaments prevent abnormal sideways bending of these various joints. The strongest ligament, the volar plate, is found close to the palmar surface. It connects the proximal phalanges to the middle phalanges, and prevents hyperextension of the proximal interphalangeal (PIP) joint. The ligaments of the PIP joint are the most commonly injured, especially in sports involving ball handling. “Jammed” fingers are typically sprains of the PIP joints. Chronic disruption or loosening of the volar plate can result in finger deformities, so “jammed” fingers need professional attention for proper diagnosis and treatment.

“Gamekeeper’s thumb” (more commonly referred to as “skier’s thumb”) is another type of ligamentous injury. This diagnosis involves an ulnar collateral ligament injury at the first metacarpophalangeal joint. The term originally described a chronic injury suffered by gamekeepers, who used downward pressure on their thumb and index fingers to break the necks of small animals. Now commonly referred to as “skier’s thumb”, this injury is seen when a skier falls on their outstretched hand while still holding a ski pole, as seen in Figure 150.

The major nerves that supply the hand and fingers include the radial, median, and ulnar nerves, which originate at the brachial plexus. The radial nerve runs along the lateral aspect of the forearm to the dorsal hand surface, where it innervates the posterior aspects of the thumb, index, and middle fingers. The median nerve passes through the carpal tunnel, and is the nerve involved in carpal tunnel syndrome. Compression of the median nerve can lead to numbness in the digits that it innervates, which includes the anterior aspects of the thumb, index finger, middle finger, half of the ring finger, as well as the thenar muscles. The ulnar nerve passes through Guyon’s canal, which is found between the hamate and pisiform carpal bones and their connecting ligament. Compression of the ulnar nerve affects the anterior aspect of the little finger, and half of the ring finger. Heavy gripping and repetitive wrist and hand motions can lead to ulnar nerve compression, which is a symptom of Guyon’s canal syndrome.

Open MRI Systems

Introduction

It is important to consider the many choices you have as far as coil selection and patient setup when preparing a patient for a hand exam in an open MRI system. Hand exams can be performed with the patient lying supine with their hand by their side, or lying prone with their hand over their head. The patient’s size and body habitus, as well as the extent of their hand injury and their pain level, will all influence their position for the exam, as well as your coil selection.

Isocenter positioning in all three planes is the key to optimum image quality for open MRI systems. Coil selection, table and accessory pads, table straps, and proper laser localizer beam centering must all be considered when preparing for a hand or finger(s) examination. Typically, the extremity coil is used when scanning the entire hand. The wrist coil may be used when scanning the fingers, or smaller localized areas of the hand. Table and accessory pads are important in maintaining both the coil and the hand at an isocenter position, especially in the coronal direction. The table straps can be used with either coil to help maintain the coil in its required position. The laser localizer beams should be centered in all three directions- H-F, R-L, A-P- to optimize image quality.

Coils and Positioning

Extremity Coil

The coil of choice for a study of the entire hand is the extremity coil. Position the patient toward the edge of the table away from the affected body part. In addition, move the table away from the affected side. This affords you the best opportunity to position the hand at the exact isocenter of the magnet. Position the hand in the center of the extremity coil. Use accessory pads inside the coil to achieve coronal centering of the hand, and to stabilize the anatomy in the proper position. Pads should also be used under the patient’s forearm, elbow, and upper arm for support and patient comfort. Center the laser localizer beams to the midline indicators on the coil (Figures 155 and 156).

The extremity coil can also be used with the patient lying in the prone position, with the affected arm over their head, as seen in Figure 157. Position the hand in the center of the extremity coil. Use accessory pads inside the coil to achieve coronal centering of the hand, and to stabilize the anatomy in the proper position. Use pillows and accessory pads to support the patient’s upper arm and forearm, and to make the patient as comfortable as possible. Center the laser localizer beams to the midline indicators on the extremity coil.

Wrist Coil

The wrist coil offers outstanding resolution for studies of the fingers, or for smaller, more specific areas of the hand. Position the patient toward the edge of the table away from the affected body part. In addition, move the table away from the affected side. This affords you the best opportunity to position the fingers at the exact isocenter of the magnet. Position the finger(s) in the center of the coil. Pads that are furnished with the coil should be used to stabilize and cushion the fingers inside the wrist coil. Accessory pads and the additional pads supplied with the wrist coil should be used under the elbow, forearm, and hand for proper elevation, support, and patient comfort. Center the laser localizer beams to the midline indicators on the wrist coil.

Note: When scanning the fingers using the wrist coil, the patient can be positioned supine on the table with the arm at the side, or prone with the arm above the head.

Table Pads and Accessory Pads

It is important to give careful consideration to both the table pads and the accessory pads that will be used to position and maintain the coil and the anatomy in isocenter. Insufficient table pads can lead to non-isocenter scanning, resulting in sub-optimal images. Correct table pad selection is necessary to place both the extremity coil and the wrist coil in the coronal (A-P) isocenter position. Accessory pads can be used to help mobilize and stabilize the wrist inside the coil. They should also be used to assist with positioning of the upper arm and forearm, and for overall patient comfort.

Table Straps

The system table straps can be used to help stabilize both the patient and the coil, especially when using the wrist coil. The straps can remain attached to the table so they are readily available.

Laser Localizer Beams

When positioning for a hand or finger exam, always use the laser localizer beams to ensure isocenter positioning in all three directions: A-P, R-L, H-F. Image signal is optimized when the patient’s anatomy is at isocenter in all three directions.

For additional information, please refer to the Oasis Patient Positioning and Coils manual, or the Altaire, AIRIS II, or AIRIS Elite Patient Positioning manuals that were supplied with your MRI system.

Echelon MRI System

Coils and Positioning

Knee (Extremity) Coil

The extremity coil is the Echelon coil best suited for scanning the entire hand. The patient will likely be more comfortable if positioned prone on the table, with the affected hand over their head and positioned prone in the coil (Superman position). The hand should be centered in the H-F and R-L directions inside the coil.

Table pads, accessory pads, and pillows should be used as needed to maintain patient comfort, as well as to maintain and support the required position of the upper arm, elbow, forearm and hand. Accessory pads can be used inside the coil to secure the position of the hand and reduce patient motion. The hand does not have to be elevated to the coronal center of the extremity coil, as there are multiple elements in the bottom portion of the coil that provide an abundance of signal. The system table straps can be used if needed for additional stabilization of the patient and / or the extremity coil.

Use the laser localizer beams to display H-F and R-L centering. Depending on the patient’s size and body habitus, the Superman position may allow for fairly accurate centering of the extremity coil in the R-L direction. The coil can be minimally angled on the table, as seen in Figures 162 and 163. If the coil angle is too steep, both the signal and the images will be sub-optimal.

Wrist Coil

The optional wrist coil offers superior resolution for examinations of the fingers. The coil was designed for easy use with the patient in either the supine or prone position. Because the coil is affixed to a holder assembly when in use, both the coil and the patient’s fingers are well stabilized.

Depending on the patient’s size and body habitus, the wrist coil can be used with the patient lying supine on the table, with the affected fingers down at their side. The wrist coil holder assembly should be positioned on the table on the side of the affected hand / fingers. In order to have the fingers positioned in the center of the coil, the hand should be positioned in the wider end of the coil, with the fingers pointed toward the narrower end, as seen in Figure 164 (this positioning is opposite from normal wrist positioning). It may be easier for the patient to position their hand and fingers when the coil is in a horizontal position. Once the upper portion of the coil is latched to the bottom portion, the patient’s hand and the coil can be rotated to a vertical position, and secured in the holder assembly (Figure 165). The patient’s hand and fingers will be in a decubitus (lateral) position in the coil. Sponges accompany the wrist coil to secure and cushion the hand and fingers inside the coil. Accessory pads can be used to maintain and support the arm in the required position. Use the laser localizer beams to display H-F and R-L centering. The wrist coil should be centered in the H-F direction. Be cautious with the coil cable position and access to table connectors, as the wrist coil is being positioned in a manner different from normal. The coil cable should not come into contact with the patient (Figure 166).

The wrist coil can be easily adapted for use with the patient lying in a prone position (Superman position). The wrist coil holder assembly should be placed in the center of the table. Position the patient lying prone on the table, with the affected hand / fingers over their head. The coil is mounted on the holder assembly in a horizontal position, with the patient’s hand in a prone position inside the coil. Sponges accompany the wrist coil to secure and cushion the fingers inside the coil. Accessory pads and pillows can be used to maintain patient comfort, and to support the arm in the required position. Use the laser localizer beams to display H-F and R-L centering. The wrist coil should be centered in the H-F direction. With the patient lying prone, and the wrist coil affixed to the holder assembly, R-L centering may be possible as well. The coil can be minimally angled on the table, as seen in Figure 167. If the coil angle is too steep, both the signal and the images will be sub-optimal.

As mentioned above, be cautious with the coil cable position and access to table connectors when the wrist coil is used for finger scanning. Pads should be used to prevent the coil cable from coming into contact with the patient.

For additional information, please refer to the Echelon Patient Positioning and Coils manual that was supplied with your Echelon system.

Patient Orientations

Your radiologist may request specific orientations of hand and finger images for their viewing and interpretation purposes. A common preference is to have the coronal and sagittal images displaying the anatomy with the fingers pointed upwards, and the axial images displaying the palmar surface pointing downward. In order to display the anatomy in this manner and maintain the accuracy of the orientation markers on the images, it may be necessary to have the radiologist rotate the images after the DICOM transfer process.

initial image
CAUTION: Avoid selecting patient orientations that are different from those recommended in this text. Changing the patient orientation selection in order to have the anatomy display in a different direction will result in images that are labeled incorrectly.

As discussed earlier in this seminar, specific orientation selections must be made during the Patient Registration process in order to maintain the accuracy of orientation markers on the images. Please refer to the Patient Orientations section in the Wrist portion of this seminar for correct patient orientation selections.

Scan Setups

The following are HMSA suggestions for routine hand / finger imaging. Always check with your radiologist for his / her imaging preferences.

Axial Scans

For a study of the entire hand, axial slices should cover the anatomy to include the distal carpal bones, the metacarpals, and a small portion of the proximal phalanges. Slices should be aligned perpendicular to the long axis of the metacarpals or phalanges, as seen in the coronal and sagittal images in Figure 168.

Axial slices of a finger or fingers should include distal metacarpals, and affected proximal, middle, and distal phalanges. Slices should be aligned perpendicular to the long axis of the metacarpals or phalanges, as seen in the sagittal and coronal images below. When scanning individual fingers, mark the affected area or finger if possible. You may need to include additional anatomy (medial and / or lateral fingers) for orientation and localization purposes for the radiologist. Scans of the thumb will require special attention to slice angles, due to the natural oblique relationship of the first digit to the remainder of the hand. When positioning slices for individual fingers, make sure that the phase encoding direction and the anti-aliasing parameters are sufficient to prevent artifacts in the image.

Coronal Scans

Coronal slices of the hand should be aligned along the long axis of the metacarpals and phalanges, as seen in the sagittal image of Figure 170. Slice coverage should be adequate to include the soft tissues of the palmar surface anteriorly, and the extensor tendons and carpal bones posteriorly.

Coronal slices of a finger or fingers should include distal metacarpals, and affected proximal, middle, and distal phalanges. Slices should be aligned along the long axis of the metacarpals or phalanges, as seen in the sagittal image of Figure 171. When scanning individual fingers, mark the affected area or finger if possible. You may need to include additional anatomy (medial and / or lateral fingers) for orientation and localization purposes for the radiologist. Scans of the thumb will require special attention to slice angles, due to the natural oblique relationship of the first digit to the remainder of the hand. When positioning slices for individual fingers, make sure that the phase encoding direction and the anti-aliasing parameters are sufficient to prevent artifacts in the image.

Sagittal Scans

Sagittal slices of the hand should be aligned along the long axis of the metacarpals and phalanges, as seen in the coronal image of Figure 172. Slice coverage and FOV should be adequate to include the soft tissues of the hand’s medial and lateral aspects, and extend to include the distal carpal bones and the proximal portion of the proximal phalanges.

Sagittal slices of the fingers should be aligned along the long axis of the metacarpals and phalanges, as seen in the coronal image of Figure 173. When scanning individual fingers, confer with the radiologist to determine if only the affected finger should be covered. Scans of the thumb will require special attention to slice angles, due to the natural oblique relationship of the first digit to the remainder of the hand. When positioning slices for individual fingers, make sure that the phase encoding direction and the anti-aliasing parameters are sufficient to prevent artifacts in the image.

There are a wide variety of pulse sequences available in your Scan Card Library or Task Library that can be used when creating protocols for hand / finger examinations.

Alignment with Joints

Due to the numerous joints in the hand and fingers, finding a position that maintains all of the anatomy in the same plane can be difficult. Attempting to force a patient’s hand or fingers into a flat position in a coil may stress already injured tendons and ligaments. This could result in patient discomfort, and ultimately, patient motion during the scan. Slices can be angled to match the angle of the involved joint, as seen in Figure 174. Here, the slices have been angled to align with the distal interphalangeal joint of the second finger. Accessory pads can be used to assist in maintaining the hand and fingers in the appropriate positions.

This concludes the Upper Extremity module of the Hitachi Medical Systems America’s MRI Anatomy and Positioning Series. You must complete the post-test for this activity in order to receive your continuing education credit.

References

  1. Kapit, Wynn, and Lawrence M. Elson. The Anatomy Coloring Book. New York: HarperCollins, 1993.

  2. Brad Walker and The Stretching Institute™. (Copyright 2011). Golfers Elbow, Elbow Tendonitis and Elbow Pain. Retrieved from http://www.thestretchinghandbook.com/archives/golfers-elbow.php

  3. Wikipedia. (Last modified 06April2011). Elbow. Retrieved from http://en.wikipedia.org/wiki/Elbow

  4. Medical Multimedia Group, L.L.C. (n.d.). Elbow Anatomy. Retrieved from http://www.eorthopod.com/content/elbow-anatomy

  5. Shoulder Muscles. (Last updated 02May2011). Retrieved from http://www.shoulderdoc.co.uk/article.asp?article=1178§ion=857

  6. Glenoid Labrum Tear. (Last updated 29October2010). Retrieved from http://www.ucsfhealth.org/conditions/glenoid_labrum_tear/

  7. Rotator Cuff Tears. (Last reviewed October2007). Retrieved from http://orthoinfo.aaos.org/topic.cfm?topic=A00064

  8. The Shoulder Joint. (Last updated 30March2006). Retrieved from http://download.videohelp.com/vitualis/med/shldrjnt.htm

  9. Media Partners, Inc. (28July2010). Shoulder Structure, Function and Common Problems. Retrieved from http://healthpages.org/anatomy-function/shoulder-structure-function-and-problems/

  10. Wikipedia. (Last modified 16April2011). Humerus. Retrieved from http://en.wikipedia.org/wiki/Humerus

  11. Wikipedia. (Last modified 29April2011). Ulnar nerve entrapment. Retrieved from http://en.wikipedia.org/wiki/Ulnar_nerve_entrapment

  12. Boles, Carol A., and Srilatha Kannam, and Anne B. Cardwell. “The Forearm: Anatomy of Muscle Compartments and Nerves.” American Journal of Roentgenology 174(2000): 151-159. Retrieved from http://www.ajronline.rog/cgi/reprint/174/1/151

  13. Wikipedia. (Last modified 4February2011). Radial nerve. Retrieved from http://en.wikipedia.org/wiki/Radial_nerve

  14. Definition of Tennis elbow. (Last Editorial Review 27April2011). Retrieved from http://www.medicinenet.com

  15. Medical Multimedia Group, L.L.C. (n.d.). Guyon’s Canal Syndrome. Retrieved from http://www.eorthopod.com/content/guyons-canal-syndrome

  16. Daniels, James M. II, M.D., and Elvin G. Zook, M.D., and James M. Lynch, M.D. “Hand and Wrist Injuries: Part I. Nonemergent Evaluation.” American Family Physician Vol.69/No.8 (April 15, 2004). Retrieved from http://www.aafp.org/afp/2004/0415/p1941.html

  17. Wikipedia. (Last modified 29April2011). Wrist. Retrieved from http://en.wikipedia.org/wiki/Wrist

  18. Stern, Mark,M.D. (Last update 21September2009). Ulnar Nerve Entrapment. Retrieved from http://emedicine.medscape.com/article/1244885-overview#a0112

References for Anatomy Pictures

  1. Cover picture- http://connect.in.com/human-skeleton/photos-1-1-1-0499c823699210ba6c444b0f47dae74f.html

  2. Figure 1- http://www.blobs.org/science/article.php?article=10#4

  3. Figure 2- http://www.bnphysio.com/main/wp-content/uploads/2009/05/19622.jpg

  4. Figure 3- http://www.thestretchinghandbook.com/archives/rotator-cuff-injury.php

  5. Figure 4- http://www.upperlimbcentre.com/ligaments.htm

  6. Figure 5- http://www.shoulderdoc.co.uk/article.asp?article=1182§ion=857

  7. Figure 26- http://www.nismat.org/orthocor/exam/shoulder.html/?searchterm=pictures of shoulder anatomy (center picture)

  8. Figure 38- http://www.eorthopod.com/content/shoulder-anatomy

  9. Figure 43- http://training.seer.cancer.gov/anatomy/muscular/groups/upper.html

  10. Figure 64- http://en.wikipedia.org/wiki/File:Gray420.png

  11. Figure 66- http://www.innerbody.com/image/musc07.html

  12. Figure 67- http://www.innerbody.com/image/musc07.html

  13. Figure 87- http://www.innerbody.com/image/musc07.html

  14. Figure 105- http://en.wikipedia.org/wiki/File:Carpus.svg (picture on left)

  15. Figure 106- http://www.joint-pain-expert.net/wrist-anatomy.html

  16. Figure 107- http://motionworks.patientsites.com/Injuries-Conditions/Hand/Hand-Issues/Guyon-s-Canal-Syndrome/a~286/article.html

  17. Figure 124- http://emergencymedicaled.com/224The%20Human%20Body.htm

  18. Figure 144- http://www.wrist-guard.com/ (picture on left)

  19. Figure 144- http://www.mlrehabpt.com/?page=library&list=wrist&article=42#article_top (picture on top right)

  20. Figure 144- http://www.knowledgerush.com/kr/encyclopedia/Anatomical_snuff_box/ (picture in center)

  21. Figure 145- http://www.eorthopod.com/content/wrist-anatomy (picture on left)

  22. Figure 145- http://www.eorthopod.com/content/hand-anatomy (picture on right)

  23. Figure 146- http://edge.rit.edu/content/P08027/public/References/testing/Muscle%20Selection

  24. Figure 147- http://en.academic.ru/dic.nsf/enwiki/5853682

  25. Figure 148- http://media.summitmedicalgroup.com/media/db/relayhealth-images/malletfi.jpg

  26. Figure 149- http://www.eorthopod.com/content/boutonniere-deformity-finger

  27. Figure 150- http://www.hughston.com/hha/a_14_1_2.htm

  28. Figure 174- http://www.peakpt.ca/article.php?aid=280 (picture on left)

  29. Figure 174- http://www.aafp.org/afp/2006/0301/p810.html (picture on right)