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AJR:159,
MALIGNANT
November1992
Fig. 7.-45-year-old woman with unresectable malignant mesothelioma. CT scan shows lobular tumor rind with direct extension into azygoesophageal recess (R) and invasion of subcarinal space (5). Tumor is adjacent to ascending aorta (A) and pulmonary
artery
(P).
PLEURAL
Fig. 8.-35-year-old woman with unresectable malignant mesothelioma. A, CT scan shows a tumor rind surrounding left hemithorax with a large pleural effusion (E). Tumor (1) was contiguous with and inseparable from descending aorta (D). At surgery, aortic invasion precluded resection. B, MR Image shows tumor (T) extending along descending aorta (D). No fat plane separates mass from mediastinum. Note large effusion (E).
inseparable from adjacent mediastinal structures, without clear signs of invasion. Superficial invasion of the aorta was found in one case (Fig. 8), and tumor invaded the superior
vena cava in the other two patients.
Discussion
Malignant
fatal tumor
mesothelioma
is a locally
that usually
causes
aggressive,
progressive
patients
will be indeterminate,
limited statistical
com-
of the
extrapleural
and aggressive
of the T2-weighted
procedure,
in which
pericardium
if
the pleura, invaded
lung,
dia-
are removed
en
bloc. If the selection of patients is judicious, surgery can increase the length of survival. Although the number of cases in our study was small, and statistical
analysis
for extrapleural
limited,
useful
pneumonectomy
information
was derived.
on resectability
The diaphragm
is a dome-shaped, flexible soft-tissue structure and is well seen by CT and MR. The most reliable findings indicative of resectability were a clear fat plane between the inferior dia-
phragmatic surface and the adjacent abdominal organs and a smooth inferior diaphragmatic contour. Conversely, a softtissue mass encasing the hemidiaphragm was consistently unresectable. Poorly defined margins between abdominal structures and a poorly visualized inferior diaphragmatic surface were indeterminate findings seen more commonly in patients with resectable mesothelioma, but also found in those with unresectable tumors. This was a particular problem with
CT,
as scanning
was
limited
to the
axial
plane.
numbers
of
in our study.
MR findings were slightly better than CT findings for predicting resectability at the chest wall, again in part because MR provides images in multiple planes. Patients with resectable tumors had normal extrapleural fat and muscle with preservation of intercostal spaces and normal signal charac-
Consistent
and visceral
but the small
comparison
teristics in the chest wall on MR images. On CT, findings indicative of invasion and unresectability included infiltration
invariably
pulmonary
MR findings
promise. Treatment options have traditionally been limited to palliative measures, including radiation, chemotherapy, and pleurectomy. Extrapleural pneumonectomy is an extensive phragm,
965
MESOTHELIOMA
MR
provided additional coronal and sagittal images that could help clarify the situation. Understandably then, more CT than
soft
tissues
and
MR findings that indicated
displacement
of ribs.
unresectability
of tumor
in the chest wall included alteration in signal characteristics, best seen as increased signal intensity on the second echo tumor
from
sequence,
the adjacent
due to cicatricial
pleural
changes
and contiguous space.
Signal
extension
of
abnormalities
after biopsy were indistinguishable
from minimal focal tumor invasion, but in any case these patients had resectable disease. Diffuse superficial tumor invasion, however, was almost impossible to detect in a small number of patients, although a diffuse irregular interface between the chest wall and tumor suggested the possibility of invasion.
For all resectable showed morous
tumors
at the mediastinum,
CT and MR
preservation of normal mediastinal fat without tuinfiltration of soft tissues. Tumor was often contig-
uous with and inseparable from mediastinal structures, with displacement, not encasement, of the mediastinum. The most reliable feature of unresectable tumors on either CT or MR was infiltration of soft tissue, with loss of normal fat planes, although tumor surrounding more than 50% of a mediastinal structure without direct evidence of invasion also was suggestive of unresectability. In the two patients with resectable tumors that were thought to be unresectable on the basis of radiologic findings, MR images showed apparent infiltration
PATZ
966
of adjacent mediastinal structures by tumor and subtle changes in signal characteristics on both coronal Ti -weighted and axial T2-weighted images. This was a consequence of
Downloaded from www.ajronline.org by 212.120.195.237 on 11/09/15 from IP address 212.120.195.237. Copyright ARRS. For personal use only; all rights reserved
phase-encoding artifacts and degradation tion. Subtle findings on MR images depend
of the pleural-mediastinal
interface,
of spatial resoluon clear resolution
and proper
gating
is im-
ET AL.
AJR:159,
cases. Correlation of all imaging studies is invaluable in directing exploration to areas of possible invasion, thus limiting the procedure in patients with unresectable tumors. Similarly, the studies are essential in selecting those patients who may benefit
Both MR and CT had high sensitivities in all three regions, but the assessment of specificity was practically impossible because of the small number of patients who had unresectable tumors (Table 2). Because of the small number, we could not compare the two techniques statistically. The rarity of the tumor placed limitations on the study. The only patients were ones seen in the thoracic clinic; thus, the study was confined to a select population of persons whom a diverse group of referring physicians considered candidates for surgery. This
some hope for an otherwise
bias not only distorted
the spectrum
of disease
but
also limited the numbers of patients. CT was the first imaging study because the technique was more readily available and consistently used in the community. This may have biased the extent of disease predicted on the basis of CT vs MR findings, as MR imaging was done closer to the time of surgery,
when
progression
of tumor
may
have
occurred.
In
most patients, however, CT and MR were performed within a short time of each other, and we do not believe that the interval between CT and MR affected the results. The lack of contrast-enhanced CT scans may have limited our ability to detect local invasion; however, we found no difference in the prediction of resectability between findings on enhanced and unenhanced
scans,
and, to our knowledge,
no large controlled
studies have shown a statistically significant advantage in using contrast-enhanced CT scans to detect locally invasive disease. In patients
1992
MR can then be used as the final preoperative radiologic examination to complement CT, particularly in questionable
perative.
selection
November
from
extrapleural
pneumonectomy,
devastating
which
may
offer
disease.
ACKNOWLEDGMENT We thank Philip C. Goodman ration of this manuscript.
for editorial assistance
in the prepa-
REFERENCES 1 . Mossman BT, Gee JB. Asbestos-related diseases. N EngI J Med 1989; 320:1721-1730 2. Legha 55, Muggia F. Pleural mesothelioma: clinical features and therapeutic implications. Ann Intern Med 1977;87:613-621 3. Antman KH, Blum RH, Greenberger JS, Flowerdew G, Shari AT, Canellos GP. Multi-modality therapy for malignant mesothelioma based on a study of natural history. Am J Med 1980;68:356-362 4, Alberts AS, Falkson G, Goedhals L, vorobiof DA, van Der Merwe CA. Malignant
pleural
mesothelioma:
a disease
unaffected
by current
therapeu-
tic maneuvers. J Clin Oncol 1988:6:527-534 5. Sugarbaker DJ, Holier EC, Lee TH, et al. Extrapleural pneumonectomy, chemotherapy, and radiotherapy in the treatment of diffuse malignant pleural
mesothelioma. J Thorac Cardiovasc Surg 1991;102: 10-15 E, Clark RA, Colley DP, Mitchell SE. CT of malignant pleural mesothelioma. AJR 1981;137:287-291 7, Mirvis 5, Dutcher JP, Haney PJ, Whitley NO, Aisner J. CT of malignant pleural mesothelioma. AJR 1983;140:665-670 8. Law MA, Gregor A, Husband JE, Kerr lH. Computed tomography in the assessment of malignant mesothelioma of the pleura. Clin Radiol 1982;
6. Alexander
33:67-70
9. Grant DC, Seltzer SE, Antman KH, Finberg HJ, Koster K. Computed with
ered for resection,
malignant
we suggest
pleural
mesotheliomas
CT as the first imaging
consid-
study.
It is readily available and provides a significant amount of anatomic detail, and the results can be used to exclude from surgery those patients with obviously unresectable tumors.
tomography of malignant 1983;7:626-632
pleural mesothelioma.
J Comput
Assist
Tomogr
10. Kawashima A, Ubshitz HI. Malignant pleural mesothelioma: CT manifestations in 50 cases. AJR 1990;155:965-969 1 1 . Lorigan JG, Libshitz HI. MA imaging of malignant pleural mesothelioma. J ComputAssist Tomogr 1989:13:617-620
Downloaded from www.ajronline.org by 212.120.195.237 on 11/09/15 from IP address 212.120.195.237. Copyright ARRS. For personal use only; all rights reserved
967
Pictorial
Radiographic Paula
Y. George1
Appearance
and
Philip
of Bullet
of Bullet
Bullet
tracks,
Tracks
pulmonary
injury,
by the bullet through
occur
along
lung tissue. Paren-
chymal damage from bullet wounds results from two different effects of injury: formation of a temporary cavity and formation of a permanent cavity [1]. The temporary cavity forms as the bullet passes through lung, causing local stretching and blunt
trauma perpendicular to the porary cavity is not visible on a few milliseconds of passage a fraction of a second. The
I
AJR
Both
February
authors:
159:967-970,
18, 1992;
Department November
accepted of Radiology, 1992
after revision
May 1 5, 1992.
Box 3808,
Duke University
0361-803X/92/1595-0967
The permanent
cavity
is formed
as the advancing
bullet
crushes the tissue it strikes, and it is this cavity that is shown on radiographs as the bullet track [2J. The cylindrical or rounded shape of the bullet track in lung is due to the high
elastic recoil of the lung parenchyma,
which converts
a flat,
linear laceration into a more rounded, elongated cavity. This is similar to what is seen with lung cysts resulting from blunt trauma of the chest. However, because of the continued
forward motion of the bullet, lung cysts due to a missile wound are less spherical and more cylindrical than those resulting
from
uration
blunt trauma. of damage to the lung and the size and configof the parenchymal bullet track are dependent on
several
properties
The degree
Lung tissue
Medical
0 American
permanent
cavity.
of the bullet
type of injury are primarily
path of the projectile. The temradiographs, as it occurs within of the bullet and resolves within temporary cavity injures lung
parenchyma surrounding the bullet path; the damage may be extensive, as the diameter of the temporary cavity is several Received
times larger than the bullet path and subsequent
and of the tissue
through
which it passes. The contributing properties of the bullet that affect its wounding capability include the mass and velocity of the bullet, the shape of the projectile, the yaw or orientation of the bullet as it strikes tissues, and whether the bullet fragments or deforms on impact. The contributing properties of the bullet have recently been well described by Hollerman et al. [1]. The properties of tissue that affect the extent and
in Lung
representing
the course traversed
in the Lung
Goodman
Penetrating missile or bullet wounds to the lung result in a number of abnormalities visible on chest radiographs. One finding that is unique to pulmonary parenchyma is the bullet track, which occurs along the course of a bullet as it traverses the lung. A bullet track may occur in the lung because of this organ’s low specific gravity and high elasticity. In other tissues, such as liver and brain, that have higher specific gravities and lower elastic content, bullet tracks are rarely, if ever, noted because widespread destruction usually occurs. Bullet tracks may have a delayed appearance on chest radiographs, and thus may cause confusion in interpretation if a history of injury is not elicited. With the increase in violet confrontations in the United States, it is more and more likely that radiologists will be asked to interpret chest radiographs of patients who have had penetrating bullet injuries to the thorax. In this pictorial essay, we illustrate the appearance of bullet tracks in lung on chest radiographs.
Formation
Tracks
Essay
its specific
has a low specific
gravity
gravity (0.4-0.5),
and elasticity. as compared
with skeletal muscle (1 .02-1 .04) and rib (1 .1 1), and also has a high elastic content, which resists deformity otherwise caused by the bullet [3]. Both of these properties minimize the effects of the temporary and permanent cavities in the lung.
Center,
Roentgen
Thus,
Durham,
Ray Society
the
lung
is somewhat
NC 2771 0. Address
reprint
requests
resistant
to
to P. Goodman.
gunshot
GEORGE
968
wounds,
which in tissues
of higher specific
gravity
AND
and lower
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elastic content, such as brain and liver, may cause widespread destruction and, in many instances, death.
Appearance
of Bullet
Tracks
on Chest
is visible
in the region
Radiographs
Fig. 1.-Smell-caliber A, Anteroposterlor
superolaterally B, 3 days
gunshot
Injury,
C, Anteroposterlor
In lower anteroposterlor
chest
The size of the parenchymal
abnormality
amount
of tissue
injured
1A, 2A, and 3A).
stage,
the bullet
track
(Figs.
by the missile.
November
depends
is not well visualized
1992
on the
In this initial
because
it is
parenchymal edema, contusion, because the pleura is disrupted,
a pneumothorax or hemothorax may further mask underlying lung abnormalities (Fig. 4A). Within 3-8 days, as the surrounding parenchymal opaciflcation resolves, the bullet track becomes increasingly appar-
wound
chest radiograph
and Is lodged after
of lung struck
AJR:159,
obscured by the surrounding and hemorrhage. In addition,
The appearance of a bullet track on chest radiographs evolves through several stages. Initially, a poorly defined opacity
GOODMAN
radiograph
of right hemithorax. obtaIned on day of Injury shows an opacity representing contusion lobe of right lung. chest radiograph shows partial resolution of contusion; longitudinal obtained
3 weeks
after
gunshot
wound
shows
hematoma
In a well-defined
in middle lobe course
of bullet
and narrower
of right
lung.
track
(arrows)
bullet
Bullet
entered
now can be
track.
1
Fig. 2.-Small-calIber
gunshot wound of left hemithorax. Anteroposterlor chest radIograph taken on day of Injury shows a poorly defined opacity In left lung. Paper clip marks bullet’s entry site, and bullet is seen lateral to this. B, 8 days after Injury, anteroposterior chest radiograph shows partial resolution of contusion in left lung. A tubular opacity, representing hematoma In bullet track (arrows), Is now seen. C, Anteroposterlor chest radiograph obtained 3 weeks afterinjury shows Interval decrease In size of bullet track (arrows). A large loculated posteromedlal empyema (asterIsks) that developed during this time Is noted also. A,
AJR:159,
Fig. 3.-Large-caliber hemithorax.
Bullet
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glon and lodged
BULLET
1992
November
gunshot
entered
TRACKS
969
IN LUNG
wound of left
left supraclavical
just to left of lower
re-
thoracic
spine. A, Anteroposterior chest radiograph taken on day of injury shows consolidation, representing contusion, in upper lobe of left lung. B, 6 days after injury, anteroposterior chest radiograph reveals a decrease In lung contusion. Bullet track (arrows) is filled predominantly with
air. C, Anteroposterior chest radiograph taken 2 weeks after gunshot wound shows a decrease in size of air-filled bullet track. 0, Anteroposterior chest radiograph obtained 6 weeks after injury shows further resolution of bullet track (arrows), which has a parallel, linear, or “tram-track” appearance.
Fig. 4.-Large-caliber
gunshot
wound
of left
hemithorax. A, Anteroposterior chest radiograph taken 2 weeks after gunshot wound to left hemithorax shows air-filled bullet track. An opacity inferior to the bullet track (arrows) represents bullet path
extending
laterally
toward soft tissues of axilla.
There Is a hydropneumothorax. B, Anteroposterior chest radiograph obtained 3 weeks after Injury shows some resolution of
surrounding
contusion.
Air-filled
bullet
track
is
seen en face and is now smaller.
A
ent on the chest radiograph (Figs. 1 B, 2B, and 3B). The bullet track contains mainly blood/hematoma, and on radiographs has either a circular appearance if viewed en face or a tubular appearance if viewed in profile (Fig. 2B).
B
The hematoma in the bullet track resolves over weeks by “shrinking” or slowly diminishing in size from its periphery rather than by dissipating uniformly throughout its substance, and thus, it maintains the same orientation and shape as it
Downloaded from www.ajronline.org by 212.120.195.237 on 11/09/15 from IP address 212.120.195.237. Copyright ARRS. For personal use only; all rights reserved
970
GEORGE
AND
gets smaller (Figs. 1-3). As the hematoma resolves, an airfilled cavity or lung cyst may remain. At this stage, when viewed in profile on chest radiographs, these cavities have a parallel, linear, or “tram-track” appearance(Fig. 3D), and when seen en face, they are round with thin to moderately thick walls (Fig. 4B). The cavity usually resolves completely within a few months by contraction of surrounding scar tissue and compression from adjacent lung. In some cases, air may be seen in the bullet track within a few days of injury, after resolution of the surrounding contusion perhaps a result of direct communication
(Fig.
4A).
This
is
between the bullet direct drainage of blood
track and the bronchial tree, allowing from the site of injury [2]. A delay or failure in resolution of the lung cavity should alert the radiologist to a possible infectious complication [4]. This is a particular problem, as bullet tracks are associated with a considerable amount of tissue destruction, necrosis, and occasionally foreign material, such as bone fragments or cloth-
LIST
942 990 1000 1004 1048 1062 1 082 1086 1 1 06
OF
BOOK
GOODMAN
AJR:159,
November
1992
ing. In addition, bacterial contamination from the cutaneous wound site at the time of injury is always a potential risk [1]. Bullet tracks in the lung may create difficulty and confusion in the
interpretation
of chest
radiographs,
particularly
if a
history of trauma is not elicited or if the potential for this type of abnormal finding on radiographs is not appreciated.
REFERENCES 1 . Hollerman wounds:
JJ,
1.
Fackler Bullets,
ML, CoIdwell DM, Ben-Menachem ballistics, and mechanisms of
V. Gunshot injury. AJR
1990;155:685-690
2. Larose JH. Cavitation of missile tracks in the lung. Radiology 1968;90: 995-998 3. DeMuth WE. High velocity bullet wounds of the thorax. Am J Surg 1968;1 15:616-625 4. Specs EK, Strevey TE. Geiger JP, Aronstam EM. Persistent traumatic lung cavities resulting from Surg 1967;4:133-142
medium-
and
high-velocity
REVIEWS
Basic Doppler Physics. Smith H-J, Zagzebski JA Introduction to Abdominal Ultrasonography. Higashi V. Mizushima A, Matsumoto H Nuclear Medicine Procedure Manual, 2nd ed. Klingensmith WC III, Eshima 0, GoddardJ, eds Gamuts in Ultrasound. Williamson MR, Williamson SL Imaging of the Temporal Bone, 2nd ed. Swartz JO, Harnsberger HR Radioisotopic Methods for Biological and Medical Research. Knoche HW Peripheral Vascular Sonography. A Practical Guide. Polak JF A Radiologic Approach to Diseases of the Chest. Freundlich lM, Bragg OG Outline of Medical Imaging, vols. 1 and 2. Kreel L, Thornton A
missiles.
Ann
Thorac
AJR:159,
MALIGNANT
November1992
Fig. 7.-45-year-old woman with unresectable malignant mesothelioma. CT scan shows lobular tumor rind with direct extension into azygoesophageal recess (R) and invasion of subcarinal space (5). Tumor is adjacent to ascending aorta (A) and pulmonary
artery
(P).
PLEURAL
Fig. 8.-35-year-old woman with unresectable malignant mesothelioma. A, CT scan shows a tumor rind surrounding left hemithorax with a large pleural effusion (E). Tumor (1) was contiguous with and inseparable from descending aorta (D). At surgery, aortic invasion precluded resection. B, MR Image shows tumor (T) extending along descending aorta (D). No fat plane separates mass from mediastinum. Note large effusion (E).
inseparable from adjacent mediastinal structures, without clear signs of invasion. Superficial invasion of the aorta was found in one case (Fig. 8), and tumor invaded the superior
vena cava in the other two patients.
Discussion
Malignant
fatal tumor
mesothelioma
is a locally
that usually
causes
aggressive,
progressive
patients
will be indeterminate,
limited statistical
com-
of the
extrapleural
and aggressive
of the T2-weighted
procedure,
in which
pericardium
if
the pleura, invaded
lung,
dia-
are removed
en
bloc. If the selection of patients is judicious, surgery can increase the length of survival. Although the number of cases in our study was small, and statistical
analysis
for extrapleural
limited,
useful
pneumonectomy
information
was derived.
on resectability
The diaphragm
is a dome-shaped, flexible soft-tissue structure and is well seen by CT and MR. The most reliable findings indicative of resectability were a clear fat plane between the inferior dia-
phragmatic surface and the adjacent abdominal organs and a smooth inferior diaphragmatic contour. Conversely, a softtissue mass encasing the hemidiaphragm was consistently unresectable. Poorly defined margins between abdominal structures and a poorly visualized inferior diaphragmatic surface were indeterminate findings seen more commonly in patients with resectable mesothelioma, but also found in those with unresectable tumors. This was a particular problem with
CT,
as scanning
was
limited
to the
axial
plane.
numbers
of
in our study.
MR findings were slightly better than CT findings for predicting resectability at the chest wall, again in part because MR provides images in multiple planes. Patients with resectable tumors had normal extrapleural fat and muscle with preservation of intercostal spaces and normal signal charac-
Consistent
and visceral
but the small
comparison
teristics in the chest wall on MR images. On CT, findings indicative of invasion and unresectability included infiltration
invariably
pulmonary
MR findings
promise. Treatment options have traditionally been limited to palliative measures, including radiation, chemotherapy, and pleurectomy. Extrapleural pneumonectomy is an extensive phragm,
965
MESOTHELIOMA
MR
provided additional coronal and sagittal images that could help clarify the situation. Understandably then, more CT than
soft
tissues
and
MR findings that indicated
displacement
of ribs.
unresectability
of tumor
in the chest wall included alteration in signal characteristics, best seen as increased signal intensity on the second echo tumor
from
sequence,
the adjacent
due to cicatricial
pleural
changes
and contiguous space.
Signal
extension
of
abnormalities
after biopsy were indistinguishable
from minimal focal tumor invasion, but in any case these patients had resectable disease. Diffuse superficial tumor invasion, however, was almost impossible to detect in a small number of patients, although a diffuse irregular interface between the chest wall and tumor suggested the possibility of invasion.
For all resectable showed morous
tumors
at the mediastinum,
CT and MR
preservation of normal mediastinal fat without tuinfiltration of soft tissues. Tumor was often contig-
uous with and inseparable from mediastinal structures, with displacement, not encasement, of the mediastinum. The most reliable feature of unresectable tumors on either CT or MR was infiltration of soft tissue, with loss of normal fat planes, although tumor surrounding more than 50% of a mediastinal structure without direct evidence of invasion also was suggestive of unresectability. In the two patients with resectable tumors that were thought to be unresectable on the basis of radiologic findings, MR images showed apparent infiltration
PATZ
966
of adjacent mediastinal structures by tumor and subtle changes in signal characteristics on both coronal Ti -weighted and axial T2-weighted images. This was a consequence of
Downloaded from www.ajronline.org by 212.120.195.237 on 11/09/15 from IP address 212.120.195.237. Copyright ARRS. For personal use only; all rights reserved
phase-encoding artifacts and degradation tion. Subtle findings on MR images depend
of the pleural-mediastinal
interface,
of spatial resoluon clear resolution
and proper
gating
is im-
ET AL.
AJR:159,
cases. Correlation of all imaging studies is invaluable in directing exploration to areas of possible invasion, thus limiting the procedure in patients with unresectable tumors. Similarly, the studies are essential in selecting those patients who may benefit
Both MR and CT had high sensitivities in all three regions, but the assessment of specificity was practically impossible because of the small number of patients who had unresectable tumors (Table 2). Because of the small number, we could not compare the two techniques statistically. The rarity of the tumor placed limitations on the study. The only patients were ones seen in the thoracic clinic; thus, the study was confined to a select population of persons whom a diverse group of referring physicians considered candidates for surgery. This
some hope for an otherwise
bias not only distorted
the spectrum
of disease
but
also limited the numbers of patients. CT was the first imaging study because the technique was more readily available and consistently used in the community. This may have biased the extent of disease predicted on the basis of CT vs MR findings, as MR imaging was done closer to the time of surgery,
when
progression
of tumor
may
have
occurred.
In
most patients, however, CT and MR were performed within a short time of each other, and we do not believe that the interval between CT and MR affected the results. The lack of contrast-enhanced CT scans may have limited our ability to detect local invasion; however, we found no difference in the prediction of resectability between findings on enhanced and unenhanced
scans,
and, to our knowledge,
no large controlled
studies have shown a statistically significant advantage in using contrast-enhanced CT scans to detect locally invasive disease. In patients
1992
MR can then be used as the final preoperative radiologic examination to complement CT, particularly in questionable
perative.
selection
November
from
extrapleural
pneumonectomy,
devastating
which
may
offer
disease.
ACKNOWLEDGMENT We thank Philip C. Goodman ration of this manuscript.
for editorial assistance
in the prepa-
REFERENCES 1 . Mossman BT, Gee JB. Asbestos-related diseases. N EngI J Med 1989; 320:1721-1730 2. Legha 55, Muggia F. Pleural mesothelioma: clinical features and therapeutic implications. Ann Intern Med 1977;87:613-621 3. Antman KH, Blum RH, Greenberger JS, Flowerdew G, Shari AT, Canellos GP. Multi-modality therapy for malignant mesothelioma based on a study of natural history. Am J Med 1980;68:356-362 4, Alberts AS, Falkson G, Goedhals L, vorobiof DA, van Der Merwe CA. Malignant
pleural
mesothelioma:
a disease
unaffected
by current
therapeu-
tic maneuvers. J Clin Oncol 1988:6:527-534 5. Sugarbaker DJ, Holier EC, Lee TH, et al. Extrapleural pneumonectomy, chemotherapy, and radiotherapy in the treatment of diffuse malignant pleural
mesothelioma. J Thorac Cardiovasc Surg 1991;102: 10-15 E, Clark RA, Colley DP, Mitchell SE. CT of malignant pleural mesothelioma. AJR 1981;137:287-291 7, Mirvis 5, Dutcher JP, Haney PJ, Whitley NO, Aisner J. CT of malignant pleural mesothelioma. AJR 1983;140:665-670 8. Law MA, Gregor A, Husband JE, Kerr lH. Computed tomography in the assessment of malignant mesothelioma of the pleura. Clin Radiol 1982;
6. Alexander
33:67-70
9. Grant DC, Seltzer SE, Antman KH, Finberg HJ, Koster K. Computed with
ered for resection,
malignant
we suggest
pleural
mesotheliomas
CT as the first imaging
consid-
study.
It is readily available and provides a significant amount of anatomic detail, and the results can be used to exclude from surgery those patients with obviously unresectable tumors.
tomography of malignant 1983;7:626-632
pleural mesothelioma.
J Comput
Assist
Tomogr
10. Kawashima A, Ubshitz HI. Malignant pleural mesothelioma: CT manifestations in 50 cases. AJR 1990;155:965-969 1 1 . Lorigan JG, Libshitz HI. MA imaging of malignant pleural mesothelioma. J ComputAssist Tomogr 1989:13:617-620
Downloaded from www.ajronline.org by 212.120.195.237 on 11/09/15 from IP address 212.120.195.237. Copyright ARRS. For personal use only; all rights reserved
967
Pictorial
Radiographic Paula
Y. George1
Appearance
and
Philip
of Bullet
of Bullet
Bullet
tracks,
Tracks
pulmonary
injury,
by the bullet through
occur
along
lung tissue. Paren-
chymal damage from bullet wounds results from two different effects of injury: formation of a temporary cavity and formation of a permanent cavity [1]. The temporary cavity forms as the bullet passes through lung, causing local stretching and blunt
trauma perpendicular to the porary cavity is not visible on a few milliseconds of passage a fraction of a second. The
I
AJR
Both
February
authors:
159:967-970,
18, 1992;
Department November
accepted of Radiology, 1992
after revision
May 1 5, 1992.
Box 3808,
Duke University
0361-803X/92/1595-0967
The permanent
cavity
is formed
as the advancing
bullet
crushes the tissue it strikes, and it is this cavity that is shown on radiographs as the bullet track [2J. The cylindrical or rounded shape of the bullet track in lung is due to the high
elastic recoil of the lung parenchyma,
which converts
a flat,
linear laceration into a more rounded, elongated cavity. This is similar to what is seen with lung cysts resulting from blunt trauma of the chest. However, because of the continued
forward motion of the bullet, lung cysts due to a missile wound are less spherical and more cylindrical than those resulting
from
uration
blunt trauma. of damage to the lung and the size and configof the parenchymal bullet track are dependent on
several
properties
The degree
Lung tissue
Medical
0 American
permanent
cavity.
of the bullet
type of injury are primarily
path of the projectile. The temradiographs, as it occurs within of the bullet and resolves within temporary cavity injures lung
parenchyma surrounding the bullet path; the damage may be extensive, as the diameter of the temporary cavity is several Received
times larger than the bullet path and subsequent
and of the tissue
through
which it passes. The contributing properties of the bullet that affect its wounding capability include the mass and velocity of the bullet, the shape of the projectile, the yaw or orientation of the bullet as it strikes tissues, and whether the bullet fragments or deforms on impact. The contributing properties of the bullet have recently been well described by Hollerman et al. [1]. The properties of tissue that affect the extent and
in Lung
representing
the course traversed
in the Lung
Goodman
Penetrating missile or bullet wounds to the lung result in a number of abnormalities visible on chest radiographs. One finding that is unique to pulmonary parenchyma is the bullet track, which occurs along the course of a bullet as it traverses the lung. A bullet track may occur in the lung because of this organ’s low specific gravity and high elasticity. In other tissues, such as liver and brain, that have higher specific gravities and lower elastic content, bullet tracks are rarely, if ever, noted because widespread destruction usually occurs. Bullet tracks may have a delayed appearance on chest radiographs, and thus may cause confusion in interpretation if a history of injury is not elicited. With the increase in violet confrontations in the United States, it is more and more likely that radiologists will be asked to interpret chest radiographs of patients who have had penetrating bullet injuries to the thorax. In this pictorial essay, we illustrate the appearance of bullet tracks in lung on chest radiographs.
Formation
Tracks
Essay
its specific
has a low specific
gravity
gravity (0.4-0.5),
and elasticity. as compared
with skeletal muscle (1 .02-1 .04) and rib (1 .1 1), and also has a high elastic content, which resists deformity otherwise caused by the bullet [3]. Both of these properties minimize the effects of the temporary and permanent cavities in the lung.
Center,
Roentgen
Thus,
Durham,
Ray Society
the
lung
is somewhat
NC 2771 0. Address
reprint
requests
resistant
to
to P. Goodman.
gunshot
GEORGE
968
wounds,
which in tissues
of higher specific
gravity
AND
and lower
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elastic content, such as brain and liver, may cause widespread destruction and, in many instances, death.
Appearance
of Bullet
Tracks
on Chest
is visible
in the region
Radiographs
Fig. 1.-Smell-caliber A, Anteroposterlor
superolaterally B, 3 days
gunshot
Injury,
C, Anteroposterlor
In lower anteroposterlor
chest
The size of the parenchymal
abnormality
amount
of tissue
injured
1A, 2A, and 3A).
stage,
the bullet
track
(Figs.
by the missile.
November
depends
is not well visualized
1992
on the
In this initial
because
it is
parenchymal edema, contusion, because the pleura is disrupted,
a pneumothorax or hemothorax may further mask underlying lung abnormalities (Fig. 4A). Within 3-8 days, as the surrounding parenchymal opaciflcation resolves, the bullet track becomes increasingly appar-
wound
chest radiograph
and Is lodged after
of lung struck
AJR:159,
obscured by the surrounding and hemorrhage. In addition,
The appearance of a bullet track on chest radiographs evolves through several stages. Initially, a poorly defined opacity
GOODMAN
radiograph
of right hemithorax. obtaIned on day of Injury shows an opacity representing contusion lobe of right lung. chest radiograph shows partial resolution of contusion; longitudinal obtained
3 weeks
after
gunshot
wound
shows
hematoma
In a well-defined
in middle lobe course
of bullet
and narrower
of right
lung.
track
(arrows)
bullet
Bullet
entered
now can be
track.
1
Fig. 2.-Small-calIber
gunshot wound of left hemithorax. Anteroposterlor chest radIograph taken on day of Injury shows a poorly defined opacity In left lung. Paper clip marks bullet’s entry site, and bullet is seen lateral to this. B, 8 days after Injury, anteroposterior chest radiograph shows partial resolution of contusion in left lung. A tubular opacity, representing hematoma In bullet track (arrows), Is now seen. C, Anteroposterlor chest radiograph obtained 3 weeks afterinjury shows Interval decrease In size of bullet track (arrows). A large loculated posteromedlal empyema (asterIsks) that developed during this time Is noted also. A,
AJR:159,
Fig. 3.-Large-caliber hemithorax.
Bullet
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glon and lodged
BULLET
1992
November
gunshot
entered
TRACKS
969
IN LUNG
wound of left
left supraclavical
just to left of lower
re-
thoracic
spine. A, Anteroposterior chest radiograph taken on day of injury shows consolidation, representing contusion, in upper lobe of left lung. B, 6 days after injury, anteroposterior chest radiograph reveals a decrease In lung contusion. Bullet track (arrows) is filled predominantly with
air. C, Anteroposterior chest radiograph taken 2 weeks after gunshot wound shows a decrease in size of air-filled bullet track. 0, Anteroposterior chest radiograph obtained 6 weeks after injury shows further resolution of bullet track (arrows), which has a parallel, linear, or “tram-track” appearance.
Fig. 4.-Large-caliber
gunshot
wound
of left
hemithorax. A, Anteroposterior chest radiograph taken 2 weeks after gunshot wound to left hemithorax shows air-filled bullet track. An opacity inferior to the bullet track (arrows) represents bullet path
extending
laterally
toward soft tissues of axilla.
There Is a hydropneumothorax. B, Anteroposterior chest radiograph obtained 3 weeks after Injury shows some resolution of
surrounding
contusion.
Air-filled
bullet
track
is
seen en face and is now smaller.
A
ent on the chest radiograph (Figs. 1 B, 2B, and 3B). The bullet track contains mainly blood/hematoma, and on radiographs has either a circular appearance if viewed en face or a tubular appearance if viewed in profile (Fig. 2B).
B
The hematoma in the bullet track resolves over weeks by “shrinking” or slowly diminishing in size from its periphery rather than by dissipating uniformly throughout its substance, and thus, it maintains the same orientation and shape as it
Downloaded from www.ajronline.org by 212.120.195.237 on 11/09/15 from IP address 212.120.195.237. Copyright ARRS. For personal use only; all rights reserved
970
GEORGE
AND
gets smaller (Figs. 1-3). As the hematoma resolves, an airfilled cavity or lung cyst may remain. At this stage, when viewed in profile on chest radiographs, these cavities have a parallel, linear, or “tram-track” appearance(Fig. 3D), and when seen en face, they are round with thin to moderately thick walls (Fig. 4B). The cavity usually resolves completely within a few months by contraction of surrounding scar tissue and compression from adjacent lung. In some cases, air may be seen in the bullet track within a few days of injury, after resolution of the surrounding contusion perhaps a result of direct communication
(Fig.
4A).
This
is
between the bullet direct drainage of blood
track and the bronchial tree, allowing from the site of injury [2]. A delay or failure in resolution of the lung cavity should alert the radiologist to a possible infectious complication [4]. This is a particular problem, as bullet tracks are associated with a considerable amount of tissue destruction, necrosis, and occasionally foreign material, such as bone fragments or cloth-
LIST
942 990 1000 1004 1048 1062 1 082 1086 1 1 06
OF
BOOK
GOODMAN
AJR:159,
November
1992
ing. In addition, bacterial contamination from the cutaneous wound site at the time of injury is always a potential risk [1]. Bullet tracks in the lung may create difficulty and confusion in the
interpretation
of chest
radiographs,
particularly
if a
history of trauma is not elicited or if the potential for this type of abnormal finding on radiographs is not appreciated.
REFERENCES 1 . Hollerman wounds:
JJ,
1.
Fackler Bullets,
ML, CoIdwell DM, Ben-Menachem ballistics, and mechanisms of
V. Gunshot injury. AJR
1990;155:685-690
2. Larose JH. Cavitation of missile tracks in the lung. Radiology 1968;90: 995-998 3. DeMuth WE. High velocity bullet wounds of the thorax. Am J Surg 1968;1 15:616-625 4. Specs EK, Strevey TE. Geiger JP, Aronstam EM. Persistent traumatic lung cavities resulting from Surg 1967;4:133-142
medium-
and
high-velocity
REVIEWS
Basic Doppler Physics. Smith H-J, Zagzebski JA Introduction to Abdominal Ultrasonography. Higashi V. Mizushima A, Matsumoto H Nuclear Medicine Procedure Manual, 2nd ed. Klingensmith WC III, Eshima 0, GoddardJ, eds Gamuts in Ultrasound. Williamson MR, Williamson SL Imaging of the Temporal Bone, 2nd ed. Swartz JO, Harnsberger HR Radioisotopic Methods for Biological and Medical Research. Knoche HW Peripheral Vascular Sonography. A Practical Guide. Polak JF A Radiologic Approach to Diseases of the Chest. Freundlich lM, Bragg OG Outline of Medical Imaging, vols. 1 and 2. Kreel L, Thornton A
missiles.
Ann
Thorac
