ANATOMY OF THE THORAX AND
SHOULDER 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 anatomy of the human
body was added to the gross anatomy course
at UCLA.1 Radiographic contrast studies and
plain anatomical displays were formulated into
teaching packages for all organ systems. Residents presented each package to first-year
medical students in the dissection laboratory
to augment the teaching of anatomy. In November 1984, magnetic resonance imaging was
instituted in the radiology department. Imaging
the chest produced coronal and axial planes
which displayed the muscles and soft tissues
of the thorax. In 1986, the authors presented
their study of MR anatomy of the chest and
shoulder girdle to the American Association of
Anatomists.2
The purpose of this presentation is to demonstrate the anatomy of the thorax and shoulder girdle as displayed by magnetic resonance,
correlated with regional anatomy, with emphasis on soft tissue structures.
Key Words * gross anatomy * MRI * thorax * chest*
shoulder girdle * MRI soft tissues * medical student
teaching * chest wall * MRI nerves
From the Department of Radiological Sciences, UCLA School
of Medicine, Los Angeles, California. Requests for reprints
should be addressed to Dr James D. Collins, Department of
Radiological Sciences, UCLA Medical Center, Los Angeles, CA
90024.
26
Magnetic resonance imaging (MRI) of soft tissues
displays normal and abnormal anatomic images of the
surface and connective tissues that cannot be imaged
with conventional radiographic techniques. The advent
of the cursor lines, depicting the area of tissue selected
for imaging, enables the radiologists at UCLA to offer
a new modality for teaching anatomy. Cursor lines may
be rotated 180 degrees on the axial, the coronal, and
sagittal planes of anatomy. The images may be
magnified and displayed without reconstruction.
When the cursor lines are placed on the lateral chest
wall of the mid-coronal MR of the chest, the pleural
surface and adjacent muscles of the chest wall are
demonstrated in the oblique coronal plane. Applied to
the anatomical planes of the thorax, MR imaging
displays anatomy that assists the teaching of medical
students, anatomists, and radiologists. David Maxwell
from the UCLA Department of Anatomy prepared a
template list of anatomical structures to determine if the
authors' team could demonstrate the thoracic anatomy
with MRI. Volunteers were chosen for imaging. The
images and prepared list were matched beyond expectations.
MATERIALS AND METHODS
All images were recorded with a spin echo of TE = 28
and TR = 500, using a 0.3 Tesla Fonar permanent
magnet. Axial (transverse), coronal, and sagittal planes
were selected to image the anatomy for comprehensive
learning. Anatomical landmarks were maintained for
orientation. Images chosen for display were labeled
JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 1
TABLE. ANATOMICAL NOMENCLATURE DIRECTORY CHEST AND SHOULDER GIRDLE
28. Aorta
55. Brachial vein
F. First of the Series
1. Pectoralis major muscle
29. Pulmonary artery
56. Axillary artery
2. Pectoralis minor muscle
57. Median nerve
30. Trachea
31. Aorta (descending)
3. Trapezius muscle
58. posterior humeral circumflex
32. Subclavian artery
4. Spine of the scapula
artery
33. Vertebral artery
59. Scalenus anterior muscle
5. Clavicle
34. Brachial plexus
60. Ulnar nerve
6. Supraspinatus muscle
35. Mandible
7. Deltoid muscle
61. Subracromial bursa
36. Spinalis thoracis muscle
8. Serratus anterior muscle
62. Radial nerve
9. External oblique muscle
37. Brachiocephalic artery
63. Scalenus medius muscle
10. Latissimus dorsi muscle
38. Subcutaneous tissue
64. Biceps muscle
11. Deltoid muscle (posterior)
(lymphatics, etc)
65. Right primary bronchus
39. Diaphragm
12. Infraspinatus muscle
66. Left primary bronchus
13. Subclavius muscle
40. Liver
67. Ligamentum arteriosum
14. Acromion process
41. Spleen
68. Bronchial arteries
42. Stomach
69. Axillary nerve
15. Body of the scapula
43. Right lung
16. Coracoid process
70. Inferior vena cava
71. Spinal cord
44. Left lung
17. Teres major muscle
72. Rib
45. Vertebral body (thoracic)
18. Teres minor muscle
73. Spinalis thoracis and cervicis
19. Coracobrachialis muscle
46. Right pulmonary artery
47. Intervertebral disc space
muscles
20. Triceps muscle (long head)
74. Left ventricle
21. Triceps muscle (lateral head)
48. Thoracic duct
22. Brachialis muscle
49. Brachial artery
75. Pericardial fat pad (right)
50. Intercostal artery
76. Pericardial fat pad (left)
23. Subscapularis muscle
77. Subclavian vein
24. Rhomboid muscle
51. Intercostal muscle
52. Superior vena cava
78. Longus collis muscle
25. Humerus
79. Biceps muscle (short head)
53. Right atrium
26. Humerus (head)
27. Intertubercular sulcus
54. Left atrium
80. Biceps muscle (long head)
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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.
Oblique sagittal images were positioned from the left
mid-coronal image.
RESULTS
Figure 1. Thoracic duct (arrows) crosses the
angle between the internal jugular vein and
the subclavian vein. Aorta (28), subclavian
(77).
JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 1
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 lungs, blood vessels, joint capsules, tendon
insertions, and scarred tissues have low signals (black)
in MR Imaging.
The vascular supply of nerves are continuous like a
spider web enveloping the nerve sheaths.6 Small nerves
have a relative intermediate high signal in fatty tissue.
27
MRI OF THE THORAX AND SHOULDER GIRDLE
38
(black arrows). Pectoral
rows).
nerves
(white
ar-
Nerves are composed of phospholipids and displayed as
a high signal. When the nerves are embedded in fatty
tissue; the blood supply marginates the nerve from the
fat.
Magnetic resonance imaging detects the visual
display of the nerve and locates the low signal of the
blood supply. Lymph nodes have a relative gray signal
and are located in specific anatomical locations. Chyle
(fat) has a high signal and allows location of the
thoracic duct. These features are important for understanding the anatomy displayed in the following MR
images. Figures 1 through 8 demonstrate the surface
anatomy of the chest wall and shoulder girdle. Figure 1
is the first of the series and orients the reader to the
image positions.
The high signals (white) demonstrate deposited fat
and nerve signals.7'8 The low signals (black) demonstrate a variety of vascular structures coursing through
the mediastinum and muscular tissue. Bones are
marginated by low signals of the periostium, cortex,
and cartilage. Cartilage may be located when sufficient
fat surrounds the margins. In Figyure 1, the thoracic duct
28
Figure 3. Note the low signals (white arrows)
marginating the high signals of the nerves.
subclavian artery and internal jugular
vein, and the ligamentum arteriosum joins the aorta and
pulmonary artery. The vagus nerve is a plexus of
crosses the left
intermediate signals within the high signals of fat
surrounding the aorta, left lateral wall of the trachea, left
carotid artery, and pulmonary artery.
Serial images two through eight display the muscular
structures as they appear from the left medial oblique to
the lateral oblique position. The spine of the scapula
separates the supraspinatus from the infraspinatus muscle
in Figure 2. The trapezius muscle attaches to the scapula
and clavicle. The low signals of blood vessels and
intermediate high signals of the nerves overlay the
muscles. The axillary artery, axillary vein, and brachial
plexus are positioned in the axillary fat between the
subscapularis muscle and the pectoralis muscles.
Figure 3 images the teres major and minor muscles.
The subclavius muscle is inferior to the clavicle. The
anterior deltoid muscle appears superior to the pectoralis muscle. The triceps muscles are inferior to the
subcutaneous tissue of the chest wall. The axillary
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), coracobrachialis muscle (19), humerus (25).
nerve is inferior to the supraspinatus muscle and the
superior body of the scapula. The intermediate signals
of the vascular plexus and the lymphatics course within
the subcutaneous tissue (38).
Figure 4 displays the coracobrachialis muscle attaching to the coracoid process (16). The brachial plexus
parallels the brachial artery and vein. Intermediate high
signals of the axillary nerve and low signals of the
vascular supply are inferior to the scapula and overlay
the subscapularis muscle. The nerve and vascular
supply to the deltoid muscle intersects the overlay of the
pectoralis muscle group.
Figure 5 demonstrates the low signal of the fibrous
intermuscular septum between the long and lateral
heads of the triceps. The musculocutaneous nerve
(arrow) is identified between the long and short heads
of the biceps. The last of the pectoralis minor muscle is
demonstrated as it attaches to one of the ribs of the chest
wall.
JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 1
Figure 6 demonstrates the posterior humeral circumflex artery and nerve. The nerve supply to the deltoid
muscle lies superior to the axillary artery (56). The
acromioclavicular ligament joins the acromion process
(14) to the clavicle (5).
Figures 7 through 13 are posterior coronal views of
the left posterior chest and shoulder girdle. The series
was obtained in the prone position for coronal plane
imaging. The images are displayed from the posterior to
the anterior projection. In Figure 7, the spinalis thoracis
muscle (73) of the erector spinalis group marginates the
spinous process of the thoracic spine. The latissimus
dorsi muscle (10) is outlined laterally merging with the
teres major muscle (17) and rhomboid major muscle
(24). In Figure 8, the superior margin of the scapula
separates the trapezius muscle and the supraspinatus
muscles. The deltoid muscle, lungs, and ribs appear.
The signal of the intercostal nerves are inferior to the
ribs.
In Figure 9, the spine of the scapula (4) separates the
supraspinatus and the infraspinatus muscle. The long
head of the triceps (20) and the teres major (17) and
29
MRI OF THE THORAX AND SHOULDER GIRDLE
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Figure 8. Spinal nerves (arrows) communicate
with spinal ganglia (bar arrows) and intercostal nerves.
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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 intercostal arteries arise from the medial
aspect of the thoracic aorta and course across the
thoracic vertebra. 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 arms
30
JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 1
30
MRI OF THE THORAX AND SHOULDER GIRDLE
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Figure 12. The coracobrachialis muscle (19)
intersects with the teres major muscle. Tho.
racic duct (arrow).
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Figure 13. The region of the coronary sinus
(arrow) and the left coronary artery.
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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 confluence 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 demonstrated as the brachiocephalic and subclavian arteries
arch laterally.
31
JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 1
31
MRI OF THE THORAX AND SHOULDER GIRDLE
DISCUSSION AND CONCLUSION
Chest and shoulder girdle anatomy as displayed by
MRI has allowed the authors' team to prepare exhibits
for teaching surface anatomy to medical students,
visiting physicians, and residents in radiology2-57-9 In
the past, the experienced radiologist interpreted the
plain film by recognizing changes in the normal density
of the presented anatomy. The displayed abnormal
density represented a possible differential diagnostic
list. Applying linear tomography to the area of the
abnormal density usually revealed patterns suggesting a
diagnosis.
The correlation' of the radiographic abnormality to
the clinical history was, in most cases, convincing to the
clinician. However, the fascial planes of anatomy were
not always clearly identified by plain radiograph study.
Computerized axial tomography (CAT) added an extra
study demonstrating axial density display of organ
systems.'I Reconstruction was often required to display
the sagittal plane and contrast injections were given to
outline vascular structures and the intestinal tract.
Computerized tomography (CT) did not always clearly
display the separation of vasc-ular structures and tumor
masses. Contrast was injected into the patients to
separate vascular structures from mass densities. The
contrast did not entirely distinguish between an
abnormal density and a blood vessel of the same
density. Proton densities separate organ systems.
Magnetic resonance separates proton densities within
organ systems.
Multiplane imaging of MR does not require reconstruction. Increasing the signal-to-noise ratio with water
bags sharpens the details of images and allows
identification of small tissues. 1'12 Positive and negative
mode imaging supported by visual display techniques
can be used to image without contrast materials.8"13
These various techniques are possible in many MR
Units. The authors applied these techniques in our
studies of disease. Radiological imaging is an important
adjunct to teaching anatomy. Magnetic resonance
32
imaging is a powerful tool in identifying small tissues
for teaching and for clinical studies.
Literature Cited
1. Clemente CD. Anatomy: A regional atlas of the human
body. 3rd ed. Baltimore, MD: Urban & Schwartzenberg; 1987.
2. Collins D, Batra P, Brown K, Shaver M. Anatomy of the
thorax and shoulder girdle as displayed by magnetic resonance. Anat Rec. 1986;214(3):24A.
3. Collins JD. Shaver ML, Batra P. Brown K. Anatomy of
the abdomen, back and pelvis as displayed by MRI: Part One.
J Natl Med Assoc. 1989;81(6):680-684.
4. Collins JD, Shaver ML, Batra P, Brown K. Anatomy of
the abdomen, back and pelvis as displayed by MRI: Part Two.
J Natl Med Assoc. 1989;81(7):809-813.
5. Collins JD, Shaver ML, Batra P, Brown K. Anatomy of
the abdomen, back and pelvis as displayed by MRI: Part Three.
J NatI Med Assoc. 1989;81 (8);857-861.
6. Sunderland S. Blood supply of the nerves to the upper
limb In man. Archives of Neurology and Psychology.
1945;53:91 -106.
7. Collins JD, Shaver ML, Batra P, Brown K. Why can we
see nerves on MRI? Presentation at the American Association
of Anatomists 100th Annual Meeting; 1987 and the 92nd
Annual Convention of the National Medical Association; 1987.
8. Collins JD, Shaver ML, Batra P. Brown K. Nerves on
magnetic resonance imaging. J Natl Med Assoc.
1989;81 (2):129-134.
9. Collins JD, Shaver ML, Batra P, Brown K. Anatomy of
the upper and lower extremity muscle and tendon insertions as
displayed by magnetic resonance imaging. Anat Rec.
1 988;224(4):24A.
10. Collins JD, Batra P, Brown RK, Winter J, King W.
Computerized chest tomography in asbestos workers suspected of having pleural disease. J Natl Med Assoc.
1 987;79(3):273-277.
11. Cameron L, Ord VA, Fullerton GD. Characterization of
proton NMR relaxation times in normal and pathological tissues
by correlation with other tissue parameters. Magn Reson
Imaging. 1984;2:97-106.
12. Collins JD, Shaver ML, Kovacs BJ, et al. Enhancing
magnetic resonance images using water bags. J Natl Med
Assoc. 1990;3:197-200.
13. Masih S, Bakhda RK, Collins JD. Pelvic fused kidneys:
Magnetic resonance imaging and intravenous pyelogram correlation. J Natl Med Assoc. 1988;(8):925-927.
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