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Home , Coronal plane, Rhomboid major muscle, Serratus anterior muscle, Spinalis, Subclavius muscle, Thorax

ANATOMY OF THE AND GIRDLE DISPLAYED BY MAGNETIC RESONANCE IMAGING

James D. Collins, MD, Marla L.Shaver, MD, Poonam Batra, MD, and Katheleen Brown, MD Los Angeles, California

In 1971, radiographic of the human Magnetic resonance imaging (MRI) of soft tissues body was added to the gross anatomy course displays normal and abnormal anatomic images of the at UCLA.1 Radiographic contrast studies and surface and connective tissues that cannot be imaged plain anatomical displays were formulated into with conventional radiographic techniques. The advent teaching packages for all systems. Resi- of the cursor lines, depicting the area of tissue selected dents presented each package to first-year for imaging, enables the radiologists at UCLA to offer medical students in the dissection laboratory a new modality for teaching anatomy. Cursor lines may to augment the teaching of anatomy. In Novem- be rotated 180 degrees on the axial, the coronal, and ber 1984, magnetic resonance imaging was sagittal planes of anatomy. The images may be instituted in the radiology department. Imaging magnified and displayed without reconstruction. the chest produced coronal and axial planes When the cursor lines are placed on the lateral chest which displayed the muscles and soft tissues wall of the mid-coronal MR of the chest, the pleural of the thorax. In 1986, the authors presented surface and adjacent muscles of the chest wall are their study of MR anatomy of the chest and demonstrated in the oblique . Applied to to the American Association of the anatomical planes of the thorax, MR imaging Anatomists.2 displays anatomy that assists the teaching of medical The purpose of this presentation is to dem- students, anatomists, and radiologists. David Maxwell onstrate the anatomy of the thorax and shoul- from the UCLA Department of Anatomy prepared a der girdle as displayed by magnetic resonance, template list of anatomical structures to determine if the correlated with regional anatomy, with empha- authors' team could demonstrate the thoracic anatomy sis on soft tissue structures. with MRI. Volunteers were chosen for imaging. The images and prepared list were matched beyond expec- Key Words * gross anatomy * MRI * thorax * chest* tations. shoulder girdle * MRI soft tissues * medical student teaching * chest wall * MRI MATERIALS AND METHODS All images were recorded with a spin echo of TE = 28 and TR = 500, using a 0.3 Tesla Fonar permanent From the Department of Radiological Sciences, UCLA School magnet. Axial (transverse), coronal, and sagittal planes of Medicine, Los Angeles, California. Requests for reprints were selected to image the anatomy for comprehensive should be addressed to Dr James D. Collins, Department of Radiological Sciences, UCLA Medical Center, Los Angeles, CA learning. Anatomical landmarks were maintained for 90024. orientation. Images chosen for display were labeled

26 JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 1 TABLE. ANATOMICAL NOMENCLATURE DIRECTORY CHEST AND SHOULDER GIRDLE F. First of the Series 28. 55. Brachial 1. muscle 29. Pulmonary 56. 2. muscle 30. 57. Median 3. muscle 31. Aorta (descending) 58. posterior humeral circumflex 4. Spine of the 32. artery 5. 33. Vertebral artery 59. Scalenus anterior muscle 6. Supraspinatus muscle 34. 60. Ulnar nerve 7. Deltoid muscle 35. 61. Subracromial bursa 8. 36. thoracis muscle 62. Radial nerve 9. External oblique muscle 37. Brachiocephalic artery 63. Scalenus medius muscle 10. 38. Subcutaneous tissue 64. Biceps muscle 11. Deltoid muscle (posterior) (lymphatics, etc) 65. Right primary 12. Infraspinatus muscle 39. Diaphragm 66. Left primary bronchus 13. 40. Liver 67. Ligamentum arteriosum 14. Acromion process 41. Spleen 68. Bronchial 15. Body of the scapula 42. 69. Axillary nerve 16. 43. Right 70. Inferior vena cava 17. Teres major muscle 44. Left lung 71. Spinal cord 18. Teres minor muscle 45. Vertebral body (thoracic) 72. 19. Coracobrachialis muscle 46. Right 73. Spinalis thoracis and cervicis 20. Triceps muscle (long head) 47. space muscles 21. Triceps muscle (lateral head) 48. Thoracic duct 74. Left ventricle 22. Brachialis muscle 49. Brachial artery 75. Pericardial fat pad (right) 23. 50. Intercostal artery 76. Pericardial fat pad (left) 24. Rhomboid muscle 51. Intercostal muscle 77. 25. 52. 78. Longus collis muscle 26. Humerus (head) 53. Right atrium 79. Biceps muscle (short head) 27. Intertubercular sulcus 54. Left atrium 80. Biceps muscle (long head)

with numbers and assigned to a directory (Table) to assist location of the anatomical structure on each image. Serial images were enlarged to enhance visual association with the gross anatomy prior to dissection. All images were labeled, and mounted on clear transparent plastic panels. The panels were then placed on large radiograph view boxes and backlighted for display. Images selected for presentation are displayed from the mid-coronal and posterior coronal planes. JW-,~~ ~ ~ - ..b Oblique sagittal images were positioned from the left mid-coronal image. RESULTS :~~~~~~~~~~~~~~~~~~~...... The..reader:^should. refer to the nomenclature directory (Table) for Figures 1 through 13 for specific structures. Not every structure is labeled in each figure, and the structures labeled are intended to orient and guide. In general, the , blood vessels, capsules, insertions, and scarred tissues have low signals (black) Figure 1. Thoracic duct (arrows) crosses the in MR Imaging. angle between the internal jugular vein and The vascular supply of nerves are continuous like a the subclavian vein. Aorta (28), subclavian web enveloping the nerve sheaths.6 Small nerves (77). have a relative intermediate high signal in fatty tissue.

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38

(black arrows). Pectoral nerves (white ar- rows). Figure 3. Note the low signals (white arrows) marginating the high signals of the nerves.

Nerves are composed of phospholipids and displayed as a high signal. When the nerves are embedded in fatty crosses the left subclavian artery and internal jugular tissue; the blood supply marginates the nerve from the vein, and the ligamentum arteriosum joins the aorta and fat. pulmonary artery. The is a plexus of Magnetic resonance imaging detects the visual intermediate signals within the high signals of fat display of the nerve and locates the low signal of the surrounding the aorta, left lateral wall of the trachea, left blood supply. Lymph nodes have a relative gray signal carotid artery, and pulmonary artery. and are located in specific anatomical locations. Chyle Serial images two through eight display the muscular (fat) has a high signal and allows location of the structures as they appear from the left medial oblique to thoracic duct. These features are important for under- the lateral oblique position. The spine of the scapula standing the anatomy displayed in the following MR separates the supraspinatus from the infraspinatus muscle images. Figures 1 through 8 demonstrate the surface in Figure 2. The trapezius muscle attaches to the scapula anatomy of the chest wall and shoulder girdle. Figure 1 and clavicle. The low signals of blood vessels and is the first of the series and orients the reader to the intermediate high signals of the nerves overlay the image positions. muscles. The axillary artery, , and brachial The high signals (white) demonstrate deposited fat plexus are positioned in the axillary fat between the and nerve signals.7'8 The low signals (black) demon- subscapularis muscle and the pectoralis muscles. strate a variety of vascular structures coursing through Figure 3 images the teres major and minor muscles. the and muscular tissue. are The subclavius muscle is inferior to the clavicle. The marginated by low signals of the periostium, cortex, anterior deltoid muscle appears superior to the pector- and cartilage. Cartilage may be located when sufficient alis muscle. The triceps muscles are inferior to the fat surrounds the margins. In Figyure 1, the thoracic duct subcutaneous tissue of the chest wall. The axillary

28 JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 1 MRI OF THE THORAX AND SHOULDER GIRDLE l~~~~~

Figure 5. Musculocutaneous nerve (arrow), humerus (25).

Figure 4. Supraspinatus muscle (6), coraco- brachialis muscle (19), humerus (25). Figure 6 demonstrates the posterior humeral circum- flex artery and nerve. The nerve supply to the deltoid muscle lies superior to the axillary artery (56). The nerve is inferior to the supraspinatus muscle and the acromioclavicular joins the acromion process superior body of the scapula. The intermediate signals (14) to the clavicle (5). of the vascular plexus and the lymphatics course within Figures 7 through 13 are posterior coronal views of the subcutaneous tissue (38). the left posterior chest and shoulder girdle. The series Figure 4 displays the coracobrachialis muscle attach- was obtained in the prone position for coronal plane ing to the coracoid process (16). The brachial plexus imaging. The images are displayed from the posterior to parallels the brachial artery and vein. Intermediate high the anterior projection. In Figure 7, the spinalis thoracis signals of the axillary nerve and low signals of the muscle (73) of the erector spinalis group marginates the vascular supply are inferior to the scapula and overlay spinous process of the thoracic spine. The latissimus the subscapularis muscle. The nerve and vascular dorsi muscle (10) is outlined laterally merging with the supply to the deltoid muscle intersects the overlay of the teres major muscle (17) and pectoralis muscle group. (24). In Figure 8, the superior margin of the scapula Figure 5 demonstrates the low signal of the fibrous separates the trapezius muscle and the supraspinatus intermuscular septum between the long and lateral muscles. The deltoid muscle, lungs, and appear. heads of the triceps. The musculocutaneous nerve The signal of the are inferior to the (arrow) is identified between the long and short heads ribs. of the biceps. The last of the pectoralis minor muscle is In Figure 9, the spine of the scapula (4) separates the demonstrated as it attaches to one of the ribs of the chest supraspinatus and the infraspinatus muscle. The long wall. head of the triceps (20) and the teres major (17) and

JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 1 29 MRI OF THE THORAX AND SHOULDER GIRDLE

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Figure 6. Acomo prcs.:.! 4..)., potro Figure 8. Spinal nerves (arrows) communicate with spinal ganglia (bar arrows) and intercos- tal nerves.

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,_ .:...... ' iW64,_il- _t( ^ j - § "g S !!|36 rtFisv. 18 ~ Figure 7 Spinals thoaci muscl merge wit th overlying trpzu mscle ~~~~~~~~~~~~~~~~~~~~~~~...... X

Figure 9. Spinal cord (71), serratus anterior muscle (8), rhomboid muscle (24), right lung (43).

minor muscles (18) intersect. The serratus anterior muscle lies parallel to the latissimus muscle (10). In Figure 10, the arise from the medial aspect of the thoracic aorta and course across the thoracic . The hemiazygous vein (arrow) joins the azygous vein which parallels the aorta. Nerve roots exit to the left of the first thoracic vertebral body. Figure 11 demonstrates the left atrium (54) in the

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30 MRI OF THE THORAX AND SHOULDER GIRDLE

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Figure 10. The intrca ar (

-4 '#!_ _ _ , _ it _ _ .>1 * S_d.g : . . 1 !~4 Figure 12. The coracobrachialis muscle (19) intersects with the teres major muscle. Tho. racic duct (arrow).

The_superiorpulmonaryfromtheaorta The hemiazygosvens enter theleftven(arwatrium jis th ayos vein.

Figur 1. Th vau nev branches (arw ove th let prmr brncus

ofth righ (65 ad letpiay(6)bocu. Th chs In Fiur 1, th thrccdc s h ihlna cirufe scpua nev is ineior to th coaci Fiur I.Th vags nerv brnhsarw pigroesovr the(16).lefTheprmrcotracobrchalirnhs muscle (19) inter-s sects wthteremorajorh hmuscle.oTh reigh pulonryw arteryofthe (46)rih cryosss.65 andtherighnn.lef prmretpimr6brnhshrnhs vau ere(rrw race infriro th umnr Figure 13. The region of the coronary sinus (arrow) and the left coronary artery. set it tee nijr muce.ITh Igh umnr atry ii6crse th rih ndlf riaybrnhs The.suero plmonar ven ene heftim In Figure 13, the left ventricle lies on the bed of the left diaphragm. The convexed left auricle seems to merge with the coronary sinus (arrow) crossing the left ventricle. The coracobrachialis muscle forms a conflu- ence with the teres major and pectoralis major muscles (1). The trapezoid ligament is superior to the coracoid process. The high signal of the pericardial recess lies between the pulmonary artery and aorta (28). Focal high signals of the fat on the left lung represent rib costochondral cartilage. Vertebral arteries are demon- strated as the brachiocephalic and subclavian arteries arch laterally.

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31 MRI OF THE THORAX AND SHOULDER GIRDLE

DISCUSSION AND CONCLUSION imaging is a powerful tool in identifying small tissues Chest and shoulder girdle anatomy as displayed by for teaching and for clinical studies. MRI has allowed the authors' team to prepare exhibits to medical Literature Cited for teaching students, 1. Clemente CD. Anatomy: A regional of the human visiting physicians, and residents in radiology2-57-9 In body. 3rd ed. Baltimore, MD: Urban & Schwartzenberg; 1987. the past, the experienced radiologist interpreted the 2. Collins D, Batra P, Brown K, Shaver M. Anatomy of the plain film by recognizing changes in the normal density thorax and shoulder girdle as displayed by magnetic reso- of the presented anatomy. The displayed abnormal nance. Anat Rec. 1986;214(3):24A. density represented a 3. Collins JD. Shaver ML, Batra P. Brown K. Anatomy of possible differential diagnostic the , and as displayed by MRI: Part One. list. Applying linear tomography to the area of the J Natl Med Assoc. 1989;81(6):680-684. abnormal density usually revealed patterns suggesting a 4. Collins JD, Shaver ML, Batra P, Brown K. Anatomy of diagnosis. the abdomen, back and pelvis as displayed by MRI: Part Two. The correlation' of the radiographic abnormality to J Natl Med Assoc. 1989;81(7):809-813. the clinical was, in most to the 5. Collins JD, Shaver ML, Batra P, Brown K. Anatomy of history cases, convincing the abdomen, back and pelvis as displayed by MRI: Part Three. clinician. However, the fascial planes of anatomy were J NatI Med Assoc. 1989;81 (8);857-861. not always clearly identified by plain radiograph study. 6. Sunderland S. Blood supply of the nerves to the upper Computerized axial tomography (CAT) added an extra In man. Archives of Neurology and Psychology. study demonstrating axial density display of organ 1945;53:91 -106. Reconstruction was often to 7. Collins JD, Shaver ML, Batra P, Brown K. Why can we systems.'I required display see nerves on MRI? Presentation at the American Association the and contrast injections were given to of Anatomists 100th Annual Meeting; 1987 and the 92nd outline vascular structures and the intestinal tract. Annual Convention of the National Medical Association; 1987. Computerized tomography (CT) did not always clearly 8. Collins JD, Shaver ML, Batra P. Brown K. Nerves on display the separation of vasc-ular structures and tumor magnetic resonance imaging. J Natl Med Assoc. masses. Contrast was injected into the to 1989;81 (2):129-134. patients 9. Collins JD, Shaver ML, Batra P, Brown K. Anatomy of separate vascular structures from mass densities. The the upper and lower extremity muscle and tendon insertions as contrast did not entirely distinguish between an displayed by magnetic resonance imaging. Anat Rec. abnormal density and a of the same 1 988;224(4):24A. density. Proton densities separate organ systems. 10. Collins JD, Batra P, Brown RK, Winter J, King W. Magnetic resonance separates proton densities within Computerized chest tomography in asbestos workers sus- pected of having pleural . J Natl Med Assoc. organ systems. 1 987;79(3):273-277. Multiplane imaging of MR does not require recon- 11. Cameron L, Ord VA, Fullerton GD. Characterization of struction. Increasing the signal-to-noise ratio with water proton NMR relaxation times in normal and pathological tissues bags sharpens the details of images and allows by correlation with other tissue parameters. Magn Reson identification of small tissues. 1'12 Positive and negative Imaging. 1984;2:97-106. 12. Collins JD, Shaver ML, Kovacs BJ, et al. Enhancing mode imaging supported by visual display techniques magnetic resonance images using water bags. J Natl Med can be used to image without contrast materials.8"13 Assoc. 1990;3:197-200. These various techniques are possible in many MR 13. Masih S, Bakhda RK, Collins JD. Pelvic fused kidneys: Units. The authors applied these techniques in our Magnetic resonance imaging and intravenous pyelogram corre- studies of disease. Radiological imaging is an important lation. J Natl Med Assoc. 1988;(8):925-927. adjunct to teaching anatomy. Magnetic resonance

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