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1121
Letters
1 Perception
of Radiologic
Fig. 1.-Radiograph subtle fractures of ribs
Images
shows (arrows)
are seen best when fracture line Radiographs of the pelvis almost invariably are interpreted with the image in the “anatomic” position, that is, transversely. This causes one view box to be occupied and another partly overlapped, which is often a nuisance. One day when faced with a pile of radiographs, I
placed a pelvic radiograph in my perception
vertically,
of the image.
for views
of the spine
apparent
increase
and
interrupts
plane.
and I was struck by the increase
I found that this effect also was useful ribs. I was struck particularly with the
Fig. 2.-Horizontaland
processes in the lumbar region, and with how well fractures and other bony lesions could be detected. I wondered if this effect occurs, in part, because the eye makes more horizontal movements than vertical ones, all of which are outside voluntary control [1]. Kundel and Wright [2] studied the eye motions in visual search strategies. They described three patterns of eye movement: circumferential, localized, and complex. A disproportionate amount of time also is spent sampling strong edges. Kundel, in another paper [3], discussed the perception of form, which is not yet well understood at a fundamental level. However, if perception is based, in part, on connecting boundaries to define objects and structures, this is more probable in the horizontal mode because of the scanning along this preferred plane. Also, placing radiographs at an unusual angle may increase the “interest” [4]. It is tempting to speculate that our primordial water-dwelling ancestors had to protect themselves against enemies from all directions of a surrounding sphere. As these ancestors evolved and climbed onto land surfaces, the range of danger became hemispherical, but mainly from a horizontal level, and, because of natural selection, those who
to protect themselves
in this plane were able to
survive. The ability to protect oneself depends on the ability to react to a change in the horizontal plane, which may be caused by an enemy. The greater the deformation, the greater is the stimulus, which poses a threat accompanied by “fear.” Even a small vertical line interrupting a horizontal line is seen easily, as exemplified by a view of rib lesions (Fig. 1). To bring the idea into a life situation, consider the example of the two snakes (Fig. 2). The rearing (vertical) snake appears to be more threatening than the horizontal one.
Cross Edmonton,
Alberta,
Frank I. Jackson Cancer Institute Canada T6G 1Z2
vertical
snakes are same size, but verti-
in my perception of, for example, the spinous of the vertebrae in the lateral views of the spine, especially
were best adapted
horizontal
cal snake
appears
more
sive and threatening companion.
aggresits
than
1
2
REFERENCES 1 . Thomas EL. Search behaviour. Radiol Clin North Am 1969;7 :403-416 2. Kundel HL, Wright DJ. The influence of prior knowledge on visual search strategies
during
the viewing
5-320 3. Kundel HL. Visual perception
of chest
radiographs.
Radiology
1969;93:
31
North
Am
4. Thomas EL. Movements
Please
and
image
display
terminals.
Radiol
Clin
1986;24:69-78
of the eye. Sci Am 1968;279:88-95
Be Specific
Dr. Hams [1] has pointed out that incorrect use of statistical terminology has become frequent in the radiologic literature. We note that this trend is continued in recent articles by Hann et al. [2] and
Brenner [3], both of which state that mammography has low specificity, whereas in fact it is the positive predictive value of mammography
1122
LETTERS
CANCER PRESENT
ABSENT
[
MAMMOGRAM
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TP
v
FP
TP+FP1
+
AJA:154, May 1990
Target values for positive predictive value as a barometer of a mammographic practice are not uniformly agreed on, but Hall et al. [9] have argued that 40% is a reasonable goal when a positive mammogram is defined as one that results in a recommendation of biopsy. Although this is far from controversial [1 0], even higher predictive values have been achieved routinely in screening centers in Sweden
(Falun,
of patients
[11].
Uppsala,
Vesteros)
that deal with large numbers Robert
MAMMOGRAM FN
L; TP+FN
TN
TP
SPE
E
TN1 TN+FPJ
I
A. Schmidt
Charles E. Metz
[)TNj
The University of Chicago Chicago, IL 60637
_____
lPRTP.FP+TN.FN
REFERENCES 1.-Two-by-two table used to calculate statistical results of a mammographic audit. MAMMOGRAM + = biopsy recommended, TP = true positive, FP = false positive, PV (+) = predictive value of a positive test, FN = false negative, TN = true negative, PV (-) = predictive value of a negative test, SENS sensitivity, SPEC = specificity, and PR = prevalence. Fig.
that the data show is low. Unfortunately, such misuse of terminology is likely to cause misunderstanding about the success of mammography screening programs. Primarily because breast cancer is rare in a screened population, screening mammograms are interpreted with high specificity, but their positive predictive value is relatively low [4]. Several recent papers [5-7] have described the procedures that should be used in a mammographic audit. Calculation of results is performed most easily in terms of a two-by-two table that summarizes data obtained from follow-up of the screened population (Fig. 1). With a prevalence offive cancers per 1 000 patients examined, a hypothetical mammographer who recommends biopsies in 5% of patients and fails to detect a single cancer would have a specificity of 95% but a positive predictive value of 0% (true positive [TP] = 0, false positive [FP] = 50, true negative [TN] = 945, false negative [FN] = 5 in Fig. 1). As a contrasting extreme example, an ideal mammographer whose sensitivity is 1 00% and who does biopsies on only 0.5% of patients would have a specificity of 100% and a positive predictive value of 1 00% (TP = 5, FP 0, TN 995, FN 0). More realistically, a good mammographer with a sensitivity of 80% who does biopsies on 1% of patients would have a specificity of 99.4% and a positive predictive value of 40% (TP = 4, FP = 6, TN = 989, FN = 1). Because few patients have cancer in screening mammography, the specificity associated with a particular biopsy rate is determined primarily by the overwhelming predominance of actually negative cases and will vary little from 100%, regardless of the ability of the mammographer, as long as biopsy rates are kept small. In comparing published sensitivities, specificities, and predictive values, it is important to note that all of these calculated results depend on the criterion used for a “positive” mammogram. Because the chief decision in breast imaging is whether to perform a biopsy to determine if cancer is present, we and most other authors take a positive mammogram to be one that resulted in a recommendation of biopsy. Alternatively, a positive mammogram might be taken as one in which the initial interpretation suggested any abnormality. These two definitions of a “positive” mammogram produce different combinations of sensitivity and specificity, which correspond to different points on a single receiver-operating-characteristic curve [8] and different predictive values. The specificity calculated from any given data set is generally high with either definition, however. Using the second definition of a positive mammogram, Sickles [7] found that the specificity of screening mammography was 94.2%, with a positive predictive value of 10%, for example.
1 . Harris AD. Diagnostic specificity: proper use (letter). AJR 1989;153:653 2. Hann L, Ducatman BS, Wang HH, Fein V. Mclntire JM. Nonpalpable breast lesions: evaluation by means of fine-needle aspiration cytology. Radiology
1989;171 :373-376 3. Brenner AJ. Medicolegal aspects of screening mammography. AJR 1989; 153: 53-56 4. Moskowitz M. Screening for breast cancer: how effective are our tests? A critical review. CA 1983;33:26-39 5. Spring DB, Kimbrell-Wilmot K. Evaluating the success of mammography at the local level: how to conduct an audit of your practice. Radiol Clin North Am
1987;25:983-992
6. Bird RE. Low-cost screening mammography: report on finances and review of 21 716 consecutive cases. Radiology 1989;171 :87-90 7. Sickles E, Ominsky SH, Sollitto RA, Galvin HB, Monticciolo DL. Medical audit of a rapid -throughput mammography ology and results of 27,1 14 examinations.
screening program; methodRadiology (in press) in radiologic imaging. Invest Radiol 1986;
8. Metz CE. ROC methodology 21 :720-733 9. Hall FM, Storella JM, Silverstone DZ, Wyshak G. Nonpalpable breast lesions: recommendations for biopsy based on suspicion of carcinoma at mammography. Radiology 1988;1 67:353-358 10. Moskowitz M. Predictive value, sensitivity, and specificity in breast cancer screening. Radiology 1988;1 67 : 576-578 11 . Tabar L. Intemational Teaching Seminar in Mammography. Presented in Falun, Sweden, June 3-10, 1989 Reply I thank
Drs.
Schmidt
and Metz
for their
thoughtful
confirms my premise that there is a significant use of statistical
terminology
in the
letter,
problem
radiologic
which
with incorrect
literature.
Mammo-
graphic screening, in particular, is an area in which proper use of statistics is meaningful and appropriate for both radiologists and referring
physicians.
Robert D. Harris Dartmouth-Hitchcock
Medical
Hanover,
Tracheal
Center
NH 03756
Rupture
I read with
interest
the paper
by Unger
et al. [1],
“Tears
of the
Trachea and Main Bronchi Caused by Blunt Trauma: Radiologic Findings,” in the December 1989 AJR. Although I realize that space limitations references,
preclude authors from I find it an oversight
quoting and including all possible on the part of the authors and
reviewers to omit pertinent and current references in a review article. In particular, the authors failed to refer to the April 1987 AJR article [2] by Rollins and Tocino, “Early Radiographic Signs of Tracheal Rupture,” in which new signs of tracheal 6 in the paper by Unger et al. illustrates
1987 paper.
rupture are described. findings first reported
Figure in the
AJA:154,
Tracheal rupture is not a common ture
is not overwhelming
and
entity, and thus available litera-
1 987
not such
a distant
date
as to
neglect such a reference. Irena M. Tocino LDS Hospital
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1123
LETTERS
May 1990
Salt Lake City, UT 84143 REFERENCES 1 . lk)ger JM, Schuchmann GG, Grossman JE, Pellett JR. Tears of the trachea and main bronchi caused by blunt trauma: radiologic findings. AiR
have reported the occurrence of any deaths associated with surgery for perforation caused by hydrostatic reduction, which is the main source of differences in mortality for surgery vs. hydrostatic reduction as the primary treatment. Because mortality is extremely low for either mode of treatment, I looked at other aspects of each option, such as overall complication rates and costs. The latter value progressively is assuming a cardinal role in the thinking of health care planners, administrators, insurers, the govemment, and, eventually, our own. Sensitivity analysis indicates a break-even point for reducibility rates as low as 1 0-1 5%.
In conclusion,
1989;153:1 175-1180
2. Rollins RJ, Tocino I. Early radiographic
signs of tracheal rupture. AiR
1987;148:695-698
Reply
My colleagues the excellent
and I sincerely
paper by Rollins
regret the inadvertent
and Tocino
[1 ]from
thelist
omission
of
of references
of our paper [2]. Despite what we had considered an exhaustive search of the literature, including a Medline search, we somehow missed this important addition, as it contains
contribution. information
It would have been a valuable on the importance of the appear-
ance of the endotracheal tube and balloon cuff and a discussion of tracheal damage as a function wall pressure, rather than absolute cuff Drs. Rollins and Tocino for this oversight. University
volume.
as I indicated
in the article [2], establishing
more aggressively, will have to use their experience regarding their rate of success when small-bowel obstruction is present. This figure is essential in using my estimates. My article simply provided some guidelines so that those who attempt hydrostatic reduction will have rational data to fit their own experience. John C. Leonidas Schneider
tracheal rupture of cuff-to-tracheal
in
Our
apologies
a policy
of always operating or always attempting hydrostatic reduction when small-bowel obstruction is present is difficult, and it may be necessary to tailor the treatment for the patient; estimates are not always sound. This applies to my estimates as well as those of others, including Franken et al. Radiologists, if they attempt hydrostatic reduction
Children’s
Hospital
New Hyde Park, NY 11042
to
REFERENCES
of Wisconsin,
June M. Unger Clinical Science Center Madison, WI 53792
1 . Franken EA Jr, Kao SCS, Smith WL, Sato Y. Imaging of the acute abdomen in infants and children. AiR 1989;153:921-928 2. Leonidas JC. Treatment of intussusception with small bowel obstruction: application of decision analysis. AiR 1985;145:665-669
REFERENCES 1 . Rollins RJ, Tocino I. Early radiographic
signs of tracheal
rupture.
AJR
Reply
1987;148:695-698 2. Unger JM, Schuchmann GG, Grossman JE, Pellett JR. Tears of the trachea and main bronchi caused by blunt trauma: radiologic findings. AJR 1989;153:1175-1
Hydrostatic
discussed
180
Reduction
of Intussusception
I would like to clarify certain points on the advisability of attempting hydrostatic reduction of intussusception, a topic recently discussed in the excellent article by Franken et al. [1]. The subject controversial, as the available information is incomplete.
is, indeed, The diag-
nosis of gangrenous intussusception cannot be made preoperatively. When evidence of small-bowel obstruction is present on radiographs, the probability
of gangrenous
intussusception
increases,
and that of
hydrostatic reducibility decreases. In the article quoted by Franken et al. “Treatment of Intussusception with Small Bowel Obstruction: Application of Decision Analysis [2], I used pooled data to arrive at some numerical conclusions. Published articles indicate that the reducibility of intussusception in the presence of small-bowel obstruction is only about 40%. This figure is obviously not a “hard” statistic. Nevertheless, the 95% confidence interval indicates that with existing data, the projected reducibility in a theoretically infinite number of attempts should range from 33% to 49% (i.e., much higher than the estimate
of 10-20%
quoted
by Franken
et al).
Moreover,
experience. is indeed
obstruction should be able to be reduced rate. This figure is higher than anyone’s
Franken et al. are, therefore, a prime
consideration.
to achieve published
correct about survival, which
No recent
publications,
however,
reduction
in our review article,
Infants
and Children”
a
to individualize
need
for his astute comments
hydrostatic
on the advisability
of intussusception,
“Imaging
[1]. We have no argument
each decision.
which
was
of the Acute Abdomen
in
with his emphasizing
His points on minimizing
mor-
bidity are equally valid. The situation is one in which we are all looking at the same elephant from different aspects and with incomplete information.
One of our reasons for quoting
Leonidas’s
article [2] on the use of
decision making in the treatment of intussusception was to introduce the reader to that important technique of diagnostic radiology by citing such a well-done study. Our own anecdotal experience is that successful hydrostatic reduction of intussusception in the presence of bowel obstructions occurs in about only 1 0% of cases. Using this
figure as our own individual
result and applying
Leonidas’s
decision
tree indicates increased mortality and morbidity with hydrostatic reduction compared with surgery. Thus, our recommendation to the radiologist who is not particularly expert at this procedure is to be
conservative. E. A. Franken, Jr. Simon C. S. Kao Wilbur
L. Smith
Yutaka Sato
my esti-
mates were subjected to sensitivity analysis so that room could be left for variation of the data. The cutoff point regarding the lowest possible mortality from treatment of intussusception was a 50-60% rate of reduction. In other words, at least 50-60% of intussusceptions with small-bowel the best survival
We thank Dr. Leonidas of attempting
The University of Iowa Iowa City, IA 52242
REFERENCES 1 . Franken EA Jr, Kao SCS, Smith WL, Sato Y. Imaging of the acute abdomen in infants and children. AiR 1989:153:921-928 2. Leonidas JC. Treatment of intussusception with small bowel obstruction: application of decision analysis. AiR 1985;145:665-669
LETTERS
1124
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Bile Duct Necrosis After Partial Hepatectomy Transcatheter Hepatic Arterial Embolization
and
In an attempt
to control the remaining
intrahepatic
from the gastroduodenal tree in our patient shows
the gastroduodenal
The effectiveness of transcatheter arterial embolization in the treatment of malignant hepatic tumors has been reported [1]. Side effects are minimal and usually require only conservative treatment. The selective ischemic effect of transcatheter arterial embolization on hepatic tumors compared with normal hepatic parenchyma plays a major role in the success of the treatment. Necrosis of the main bile duct usually does not occur after proximal transcatheter arterial embolization [2] because of the dual blood supply to the biliary tree from the hepatic and gastroduodenal arteries. We came to this conclusion after encountering a case of extensive necrosis of the bile duct in a patient whose blood supply to the intrahepatic bile ducts was totally dependent on a branch of the left hepatic artery because of previous radiologic interventions and surgery. The patient had had transcatheter arterial embolization twice and transcatheter portal embolization and laparotomy for hepatocellular carcinoma. Finally, he had surgery to remove the right lobe containing the main tumor and an intrahepatic metastasis in the lateral segment. During the operation, the liver was skeletonized completely, and the common bile duct in the hepatoduodenal ligament was dissected completely free from adjacent tissue. The right hepatic artery also was ligated. Severe fibrosis of the bile duct in the liver hilus was
observed.
AJA:154,
Gotoh Monden
Masato Sakon Toshio Kanai Koji Umeshita
Wakio Endoh Jun Okamura Kenichi Wakasa Masami Sakurai
Tarou Marukawa Kuroda Takesada Mon Osaka University Medical School Osaka 553, Japan Chikazumi
REFERENCES
1 . Chuang VC, Wallace S. Hepatic artery embolization in the treatment of hepatic neoplasms. Radiology 1981 140:51-58 2. Makuuchi M, Sukigara M, Mori T, et al. Bile duct necrosis: complication of transcatheter hepatic arterial embolization. Radiology 1985;156:331-334 3. Zajko AB, Campbell WL. Logsdon GA, et al. Cholangiographic findings in hepatic artery occlusion after liver transplantation. AJR 1987;1 49: 485-489
Periportal
Lymphedema
in Trauma
Previous reports have described
bolization.
Patients
zones of low attenuation
ascribed
to dilated hepatic lymphatics surrounding portal venous radicles in patients with rejection ofliver transplants, [1 , 2], hepatic or penihepatic hematomas, upper abdominal lymphadenopathy, congestive heart failure [3], and constrictive pericarditis [4].
Over 9 months, we found hepatic perivascular
lymphedema
in five
and 62 years old) of 540 patients who had abdominopelvic CT because of trauma (Fig. 1). None of the five patients with periportal collars had any other CT evidence of abdominal trauma; all (20,
21 , 23,
had extremity
45,
injuries. All five patients
were hypotensive
when they
arrived in the emergency department and received large volumes of IV fluids as part of routine posttrauma resuscitation immediately
before the CT scan was performed. Although we did not review the records to determine
Fig. 1.-Bile duct necrosis after partial hepatectomy and transcatheter hepatic arterial embolization. A, Artenogram shows contrast medium injected through indwelling arterial catheter has extravasated into biliary tree. B, cholangiogram obtained after injection of contrast medium through percutaneous transhepatic biliary drainage tube shows extensive necrosis of bile duct.
artery. Morito
tases, transcatheter arterial embolization on the 1 6th day after surgery by using
An arteriogram performed via the indwelling arterial catheter showed extravasation of contrast medium into the biliary tree (Fig. 1A). CT scan showed a large biloma in the right subphrenic and hilar space of the remaining left lobe. Percutaneous transhepatic biliary drainage was performed. Injection of contrast medium showed extensive necrosis of the bile duct that began just above the fibrotic hilar bile duct recognized at surgery (Fig. 1 B). The capillary network from the gastroduodenal artery was assumed to have ended in this portion, and the intrahepatic biliary tree was completely dependent on the blood flow from the left hepatic artery. This extensive necrosis of the bile duct was comparable with that occurring after hepatic arterial thrombosis in liver allografts in patients who lack blood flow
artery [3]. The condition of the hilar biliary the importance of arterial blood flow from
Mitsukazu
metas-
of the left lobe was done a catheter that had been inserted through the right gastroepiploic artery during the operation. High fever, nausea, and vomiting developed 1 1 days after the em-
May 1990
A
how
much
IV fluid
they
of the other 535 patients
received,
we
suspect
that
B
Fig. 1.-A and B, Contrast-enhanced CT scans of abdomen and pelvis of a trauma patient who had received 2 I of IV fluids show ring lucencies (A) due to periportal lymphedema surrounding portal vein branches and distension of bladder (B). Bladder dome was at level of umbilicus.
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1125
LETTERS
AJR:154, May 1990
vigorous hydration can cause distension of the peniportal lymphatics and peniportal collars even in patients with normal cardiac output. Thus, in patients with hepatic injuries, peniportal collars may be caused by vigorous hydration rather than by the trauma itself. John F. Cox Arnold C. Friedman Paul D. Radecki Anna S. Lev-Toaff Dma F. Caroline Temple
University
Philadelphia,
Hospital PA
19140
REFERENCES 1 . Wechsler AJ, Munoz SJ, Needleman L, et al. The periportal collar: a CT sign of liver transplant rejection. Radiology 1987;165:57-60 2. Marincek B, Barbier PA, Becker CD, Mettler D, Ruchti C. CT appearance of impaired lymphatic drainage in liver transplants. AJR 1986;147: 51 9-523 3. Koslin DB, Stanley AJ, Berland LL, Shin MS, Dalton SC. Hepatic penivascular lymphedema: CT appearance. AJR 1988;150: 111-113. 4. Goldstein L, Mervis SE, Kostrubiak IS, Tumey SZ. CT diagnosis of acute pericardial tamponade after blunt chest trauma. AJR 1989;152:739-741
Confusing Similarities Between Retroperitoneal Lymphangioma
Peripancreatic and Other Lesions
We recently observed a case that not only emphasizes the important similarities between retropenitoneal lymphangioma and other benign cystic or vascular tumors but also illustrates the difficulty of radiologically distinguishing those lesions arising in the pancreas itself from those merely arising in the contiguous extrapancreatic retropenitoneum. A renal sonogram of an asymptomatic 58-year-old woman incidentally showed a well-demarcated cystic mass in the pancreatic head containing multiple internal septa (Fig. 1A). CT of the mass showed that it had a density near that of water, with internal septa less clearly defined than on sonography. Spin-echo MR imaging of the mass showed low signal intensity on Ti -weighted images (300/20) and high signal intensity on T2-weighted images (Fig. 1 B). The initial diagnosis was primary cystic neoplasm of the pancreas. On exploratory laparotomy, however, it was found that the mass arose from the retropenitoneal soft tissues; the pancreas itself was normal. A
frozen section of the mass was interpreted originally as a microcystic (glycogen-nich) adenoma of the pancreas, but final histologic study showed instead a cavernous retropenitoneal lymphangioma. Aetropenitoneal lymphangiomas and microcystic pancreatic adenomas are both benign, often asymptomatic, and found only incidentally. Both lesions also are composed of multiple small cysts lined with a single layer of cells and separated by thin fibrous septa [1 , 2]. On CT, both appear well demarcated and hypodense [3, 4]. On MA, both tumors are hypointense on Ti-weighted images and hyperintense on T2-weighted images; the internal septa usually are visualized better on the latter [4]. Nevertheless, sonography of an adenoma usually shows a hypoechoic, solid-appearing lesion in which individual small cysts cannot be resolved [3]. Lymphangiomas, on the other hand, may have prominent solid components, but their cystic character is usually more evident [5] (Fig. 1). Additionally, the microcystic pancreatic adenoma often contains a distinctive central stellate or partially calcified scar [3]. The clinical, histologic, sonographic, CT, and MR characteristics of hemangiomas and lymphangiomas also may be quite similar. CT of hemangiomas, however, usually shows a distinctive pattern of contrast enhancement different from that observed with lymphangiomas. Also, on sonography, hemangiomas usually are more solid and less cystic than lymphangiomas. In essence, therefore, the differentiation between a retropenitoneal lymphangioma and a comparable cystic or vascular intrapancreatic or extrapancreatic mass may require close scrutiny of subtle radiologic
differences.
necessary
Biopsy
or
for a conclusive
percutaneous
aspiration
might
still
be
diagnosis. H. Richard Parvey Ronald L. Eisenberg Don M. Morris Warren D. Grafton Peter C. Meyers Louisiana
State
University
Medical
Shreveport,
Center LA
71130
REFERENCES
1 . Murao T, Toda K, Tomiyama Y. Lymphangioma of the pancreas: a case report with electron microscopic observations. Acta Pathol Jpn 1987;37: 503-510 2. Compagno J, Oertel JE. Microcystic adenomas of the pancreas (glycogenrich cystadenomas): a clinicopathologic study of 34 cases. Am J Clin Pathol 1978;69:289-298 3. Friedman AC, Lichtenstein JE, Dachman AH. Cystic neoplasms of the pancreas: radiological-pathological correlation. Radiology 1983:149(1): 45-50
4. Minami M, ltai Y, Ohtomo
K, Yoshida
H, Yoshikawa
K, ho M. Cystic
neoplasms of the pancreas: comparison of MR imaging with CT. Radiology 1989;171(1):53-56 5. Blumhagen JO, Wood BJ. Rosenbaum OM. Sonographic evaluation of abdominal lymphangiomas in children. J Ultrasound Med 1987;6(9):
487-495
:_‘
Renal Imaging A Comparison
.t__
..-. .-
in Long-term Dialysis of CT and Sonography
Patients:
.
The significant difference that Taylor et al. [1] found between CT and sonography (1 8%) in the detection of cysts in patients with end-stage kidneys makes me wonder if part or all of the reason for the poorer detection rate with sonography is not related to the equipment used. Thirty-six of the patients were examined on a GE R/T 3600 scanner (General Electric Medical Systems, Milwaukee, WI), whereas only five were examined on an Acuson 1 28 scanner (Acuson, Mt. View, CA). (59%)
Fig. 1.-Cavernous retroperitoneal lymphangioma. A, Oblique transverse real-time sonogram of right upper quadrant shows multiseptated cystic lymphangioma (Ly) sharply demarcated from adjacent pancreatic head (P). Arrow superior mesenteric vein, L = liver, GB = gallbladder. B, Axial T2-weighted MR image, 2000/60 (TR/TE), shows hyperintense peripancreatic lymphangioma (L) with faint internal septation (arrowheads).
LETTERS
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1126
AJR:154,
May 1990
Fig. 1.-A and B, Comparison of images of a phantom (ATS mode 539) obtained on GE 3600 (A) and Acuson 128 (B) 3.5-MHz phased-array scanners with probes. Multizone focus used with both scanners. Lateral resolution in far field of GE unit is much worse than in region of best focus
Fig. 1.-Comparison of sonography with Acuson 128 and contrastenhanced CT with GE CT 8800 in imaging acquired cystic kidney disease. A, Longitudinal sonogram of right kidney (cursors) shows a 1.5-cm cyst
(5 cm depth), whereas lateral resolution in Acuson is uniform and tightly focused from about 5 to 16 cm.
B, Contrast-enhanced CT scan of a slice cysts in lower pole of right kidney (arrows).
The GE R/T 3600 scanner has a significantly poorer beam pattern, especially in the deeper regions ofthe sector image where the kidneys
study shows the inherent greater capacity of CT compared with sonography in defining the diminutive cysts associated with acquired cystic kidney disease (Fig. 1).
usually lie, than the Acuson 128 (compare phantom images of a 3.5MHz phased-array probe scan of GE and Acuson, Fig. 1). Thus,
in interpolar
segment
and no discernible
cysts in lower pole. 1 cm thick
numerous
Andrew J. Taylor
although I agree with the authors that cysts less than 1 cm may be difficult to visualize with the GE scanner, it may be because of the
Eric P. Cohen Scott J. Erickson
that fills in cysts with echoes or cannot
David L. Olson
resolve small ones. I suspect that cysts as small as 0.5 cm could be detected with the Acuson because of its better lateral resolution. It would be helpful if the authors could elaborate on why they think
W. Dennis Foley
poor
lateral beam resolution
shows
even
cysts were missed on sonography. were they echo-free?
between
Were the cysts not seen at all, or
confused with other structures because they How did the detection rate and size of cysts
were not compare
those patients studied with the GE scanner vs the Acuson? Leon Skolnick University
of Pittsburgh,
School Pittsburgh,
Medical
College
of Wisconsin
Milwaukee,
WI
53226
REFERENCE
1 . Taylor AJ, Cohen long-term
dialysis
EP, Erickson SJ, Olson patients: a comparison
WD. Renal imaging in of CT and sonography. AiR
DL, Foley
1989;153:765-767
of Medicine PA
15213
Multiple REFERENCE 1 . Taylor AJ, Cohen EP, Erickson SJ, Olson DL, Foley WO. Renal imaging in long-term dialysis patients: a comparison of CT and sonography. AJR 1989;153:765-767
Hydatid
A 23-year-old man had signs and symptoms that suggested progressive spinal compression at L3. Contrast-enhanced CT of the abdomen
showed
the right kidney,
extending Reply
Dr. Skolnick raises the possibility that our results [1] in the imaging of acquired cystic kidney disease might be skewed because of our available sonographic equipment (i.e. , 36 patients were examined on the GE AfT 3600 scanner [General Electric Medical Systems, Milwaukee, WI], whereas only five were examined on the Acuson 128 [Acuson, Mountain View, CA]). Reviewing the data obtained from the institution that uses the Acuson 1 28 and the GE CT 8800 scanner might be helpful. At that institution, a total of nine kidneys in five patients were imaged. CT showed a greater grade of cystic change in all nine kidneys. With CT, five kidneys in three patients were shown to have changes indicative of acquired cystic kidney disease (i.e., five or more cysts per kidney); sonography showed one patient (or two kidneys) that met the requirements. We certainly agree that the technical considerations for imaging are important. However, we think that the marked difference in our
Cysts
numerous a paraspinal
cysts (Fig. 1). They included a cyst in cyst involving the multifidus muscle and
to the erector spinae muscle, an epidural cyst, a retroper-
itoneal cyst within the pararenal muscle, and a cyst in the innominate
space, a cyst within bone causing marked
the psoas expansion
of the iliac wing. Attenuation values of the cysts ranged from 8 to 25 H. The liver was normal. Chest radiographs and head CT scans showed no abnormalities. Serologic tests for hydatid disease were positive. The lesion in the epidural space was resected, and a germinative
membrane
and scoleces
were
shown.
The diagnosis of histologically.
granulosus infestation was established All the other cysts were left in place, and chemotherapy dazole was started. Echinococcus
Echinococcosis,
caused
or
hydatid
disease,
with meben-
is a parasitic
infestation
by the larval stage
of the tapeworms E. granulosus and Echinococcus multiocularis. The nematode is swallowed in the egg form. In the stomach, the egg dissolves, and the embryo gains access to the body by penetrating the intestinal wall and entering the portal circulation. Most of the embryos lodge in the liver and lung (approximately 60% in the liver and 25% in the lung), and the remainder are
spread
throughout
the rest of the body [1 -4].
Our
case
is unique
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AJR:154,
1127
LETTERS
May 1990
not unite cannot blithely be called a nonunited fracture. Imaging both sides does not avoid this problem if ossicles are unilateral. Resolution of signs and symptoms with therapy directed to the ossicle certainly does not resolve the debate. The natural resolution of signs and symptoms with “a tincture of time” is a long held adage. As indicated by Hindman et al., the significance of findings in light of the patient and the patient’s problems always must be questioned. If doubt exists then in this situation, clinical and radiologic follow-up studies or an isotopic bone scan may be helpful. Mark E. Pierce Canberra
Belconnen
Imaging
Act 261 7, Australia
REFERENCES
1 . Hindman BW, Kulik WJ, Lee G, Avolio RE. Occult fractures of the carpals and metacarpals: demonstration by CT. AiR 1989:153:529-532 2. Kohler A, Zimmer EA. Borderlands of the normal and early pathologic in skeletal roentgenology, 3rd ed. New York: Grune & Stratton, 1968: 79-117 3. Keats TE. Atlas of normal roentgen variants that may simulate disease, 3rd ed. Chicago: Year Book Medical, 1984:399-439
#{149}A;
Reply
Fig. 1.-CT scans show multiple hydatid cysts in a 23-year-old man. A, Cyst in right kidney originating from lateral cortex. Walls are partially calcified. B, Epidural cyst to right of L3 and another cyst originating from right multifidus muscle. Lower part of renal cyst shown in A is seen also. C, Cyst in right pararenal space adjacent to psoas muscle. Cyst affecting erector spinae muscle and a small cyst in right quadratus lumborum muscle
are visible also. D, Cysts originating from right psoas muscle and right iliac wing.
because of the multiple and lung.
sites of involvement
with sparing
of the liver
A. Nun Sener Utku Ozcan Vedat Isik Ali Demirci Private
Hospital Isparta,
of Isparta
We appreciate Dr. Pierce’s interest and constructive comments. We agree that a risk exists of sometimes showing fragments of bone that are normal variants or partial-volumned ridges and prominences and that care must be taken to avoid this possibility. In our study [1], of the 1 6 patients with 21 fractures, 1 1 patients with 1 3 occult fractures showed evidence of fracture healing or marked improvement with surgical removal of the fracture fragment or fusion of the fractured bone to the adjacent carpal bone. Five patients with six fractures, including all of the lunate fractures and one fracture of a metacarpal and one scaphoid fracture, failed to show evidence of fracture healing or clinical improvement, and this type of patient deserves careful clinical, radiologic, and scintigraphic follow-up. Two of these patients had healing of one of their fractures, and two declined to have a recommended surgical procedure. Although the diagnosis of fracture in some of these six instances may be debated, we think the importance of this study is underscored by the diagnosis of the 1 3 fractures that otherwise would have gone unrecognized, and possibly undertreated.
Turkey
B. W. Hindman W. J. Kulik
REFERENCES
G. Lee
1 . Haaga JR. Alfidi AJ. Computed tomography of the brain, head, and neck. St. Louis: Mosby, 1985:128-129 2. Clements A, Bowyer FM. Hydatid disease of the pelvis. C/in Radiol 1986:37:375-377 3. Braithwaite PA, Lees AF. Vertebral hydatid disease: radiological assessment. Radiology
1981;140:763-766
4. Missas 5, Gouliamos A, Kourias E, Kalovidouris A. Primary hydatid disease of the pancreas. Gastrointest Radiol 1987;12:37-38
CT of the Wrist:
What
Is Abnormal?
Hindman et al. [1] concisely underlined the technique of CT of the wrist. They showed the beautiful detail obtained with CT in an area complicated on plain films by overlapping structures. Undoubtedly CT will reveal significant occult fractures in the wrist. However, perspective and a note of caution need to be introduced. It soon becomes obvious that CT also shows the multiple accessory ossicles that may be present normally in the wrist [2, 3]. A clean fracture line that heals is unequivocal. However, a corticated ossicle that does
Flower
A. E. Avolio Imaging Medical Group Los Angeles, CA 90007
REFERENCE
1 . Hindman BW, Kulik WJ, Lee G, Avolio RE. Occult fractures of the carpals and metacarpals: demonstration by CT. AJR 1989;153:529-532
Bone Scan Screening for Occult Carpals and Metacarpals
Fractures
of
Chronic joint pain despite normal radiographs is a frequent occurnence. As the imaging center for a large sports medicine clinic, we encounter many patients with chronic posttraumatic bone pain, particularly about the ankle but also in the wrist. The recent article by Hindman et al. [1 ] on the CT demonstration of occult carpal and metacarpal fractures is most informative. This retrospective review, however, did not mention use of ‘Tc-MDP bone scanning as a
1128
LETTERS
,“,.
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,‘
1
[1 ‘H”
how many standardized aging costs
CT scans
after screening
approach and limited
reviewed
bone scans.
May 1990
by Hindman
et al. [1]
The use of a simple
to chronic joint pain has decreased the imthe number of CT scans performed. W. J. Sisler University Hospital University of British Columbia Vancouver, B.C., Canada
REFERENCES 1 . Hindman BW, Kulik WJ, Lee G, Avolio RE. Occult fractures of the carpals and metacarpals: demonstration by CT. AJR 1989;153:529-532 2. Hopkins SR, Ammann W. Isolated fractures of the capitate: use of nuclear
B
medicine
Fig.1.-Occult fracture ofhamate. A and B, ‘Tc-MDP bone scans show intenseuptakeof radionuclide on frontal (A)and lateral (B)static imagesinregion ofhamate. C, Transaxial thin-slice CT scan throughdistal carpalrow showsanundisplaced fracture of baseofhookofhamate. C
of the 200 wrist
were obtained
AJA:154,
as an aid to diagnosis.
mt
j
Sports
Med
(in press)
3. Young MRA, LowryJH, LairdJD, Ferguson WA. ‘“‘Tc-MDP bone scanning of injuries of the carpal scaphoid. Injury 1988;19: 14-17 4. Sisler WJ. Imaging assessment of post-traumatic tarsal pain. Can J Sports Med (in press)
Reply
We appreciate Dr. Sisler’s comments and agree that technetium bone scanning is an excellent screening technique for patients with chronic posttraumatic joint pain. We also think that his experience of
no abnormal CT scans after normal results on scintigraphy is probably universal and that a fracture diagnosed on the basis of CT findings screening method.The efficacy oftheinitial bone scanafterprelimimay be subject to narynormalradiographs iswellestablished [2,3].At ourinstitution obtained after normal results on scintigraphy atleast, and Isuspectelsewhere, bone scanningtendstobe readily question. We support the position of our hand surgeons that CT, available and ofmuch lowercostthanCT.A simplescanningroutine because of its greater accuracy in detecting fractures, is essential in the management of chronic joint pain. The decision to remove a hasbeenestablished [4],and we havefoundno abnormalCT scans
afterinitial normalbone scans.The following typical case outlines fracture fragment surgically or to allow the fracture to heal with immobilization can be made readily on the basis of CT. This inforthisapproach. useful in fractures of the hamate because A 21-year-old man saw hisfamilyphysician becauseofa 1-year mation is particularly fractures of the tip are treated differently than fractures at the base history ofpainintheulnaraspectofthewristafter fisticuffs. Clinical of the hook. These surgeons go directly to CT when other findings examination showed tendernessoverthepisiform and hamate.Raare highly suggestive of fracture. Few of the 200 patients studied diographswere unremarkable. The tentative clinical diagnosis was a with CT [1 1 had initial screening bone scans. In most of these cases, tearofthefibrocartilage. CT was performed to show a second process or to evaluate a fracture Becausethepainpersisted, arthrography was performed, which of a bone graft. In cases in which the was alsounrevealing. Two months later, a bone scanwas obtained for healing or incorporation thatshowed normaldynamicimageswithimmediatemildincreased process is uncertain, we agree that radionuclide scintigraphy followed and accurate imaging sequence. uptakeofradionuclide attheulnaraspectofthewriston theblood- by CT is a cost-effective B. W. Hindman poolstudy.Staticimages(Fig.i)showed an intenseareaoffocal W. J. Kulik uptakeintheregionofthehamate.The clinical diagnosis inconjuncG. Lee tionwiththebone scanwas therefore probablefracture ofthehook R. E. Avolio of thehamate.Eightdays later, high-resolution thin-slice CT scans Flower Imaging Medical Group were obtained. The transaxial imageswere most revealing, showing Los Angeles, CA 90007 an undisplaced fracture throughthebaseofthehook ofthehamate. Aadionuclide bone scanningisan inexpensive studywitha high capacity fordetection ofoccult fractures. Patients who haveabnormal REFERENCE scansthenhavedirected CT examinations atourinstitution, and the 1. Hindman BW, Kulik WJ, Lee G, Avolio RE. Occult fractures of the carpals rateofdetection offractures ishigh.Itwouldbe interesting toknow and metacarpals: demonstration by CT. AiR 1989;153:529-532
Letters are published at the discretion of the Editor and are subject to editing. Letters to the Editor must not be more than two double-spaced, typewritten pages. One or two figures may be included. Abbreviations should not be used. See Author Guidelines, page A5. Material being submitted or published elsewhere should not be duplicated in letters, and authors of letters must disclose financial associations or other possible conflicts of interest. Letters concerning a paper published in the AJR will be sent to the authors of the paper for a reply to be published in the same issue. Opinions expressed in the Letters to the Editor do not necessarily reflect the opinions of the Editor.
1121
Letters
1 Perception
of Radiologic
Fig. 1.-Radiograph subtle fractures of ribs
Images
shows (arrows)
are seen best when fracture line Radiographs of the pelvis almost invariably are interpreted with the image in the “anatomic” position, that is, transversely. This causes one view box to be occupied and another partly overlapped, which is often a nuisance. One day when faced with a pile of radiographs, I
placed a pelvic radiograph in my perception
vertically,
of the image.
for views
of the spine
apparent
increase
and
interrupts
plane.
and I was struck by the increase
I found that this effect also was useful ribs. I was struck particularly with the
Fig. 2.-Horizontaland
processes in the lumbar region, and with how well fractures and other bony lesions could be detected. I wondered if this effect occurs, in part, because the eye makes more horizontal movements than vertical ones, all of which are outside voluntary control [1]. Kundel and Wright [2] studied the eye motions in visual search strategies. They described three patterns of eye movement: circumferential, localized, and complex. A disproportionate amount of time also is spent sampling strong edges. Kundel, in another paper [3], discussed the perception of form, which is not yet well understood at a fundamental level. However, if perception is based, in part, on connecting boundaries to define objects and structures, this is more probable in the horizontal mode because of the scanning along this preferred plane. Also, placing radiographs at an unusual angle may increase the “interest” [4]. It is tempting to speculate that our primordial water-dwelling ancestors had to protect themselves against enemies from all directions of a surrounding sphere. As these ancestors evolved and climbed onto land surfaces, the range of danger became hemispherical, but mainly from a horizontal level, and, because of natural selection, those who
to protect themselves
in this plane were able to
survive. The ability to protect oneself depends on the ability to react to a change in the horizontal plane, which may be caused by an enemy. The greater the deformation, the greater is the stimulus, which poses a threat accompanied by “fear.” Even a small vertical line interrupting a horizontal line is seen easily, as exemplified by a view of rib lesions (Fig. 1). To bring the idea into a life situation, consider the example of the two snakes (Fig. 2). The rearing (vertical) snake appears to be more threatening than the horizontal one.
Cross Edmonton,
Alberta,
Frank I. Jackson Cancer Institute Canada T6G 1Z2
vertical
snakes are same size, but verti-
in my perception of, for example, the spinous of the vertebrae in the lateral views of the spine, especially
were best adapted
horizontal
cal snake
appears
more
sive and threatening companion.
aggresits
than
1
2
REFERENCES 1 . Thomas EL. Search behaviour. Radiol Clin North Am 1969;7 :403-416 2. Kundel HL, Wright DJ. The influence of prior knowledge on visual search strategies
during
the viewing
5-320 3. Kundel HL. Visual perception
of chest
radiographs.
Radiology
1969;93:
31
North
Am
4. Thomas EL. Movements
Please
and
image
display
terminals.
Radiol
Clin
1986;24:69-78
of the eye. Sci Am 1968;279:88-95
Be Specific
Dr. Hams [1] has pointed out that incorrect use of statistical terminology has become frequent in the radiologic literature. We note that this trend is continued in recent articles by Hann et al. [2] and
Brenner [3], both of which state that mammography has low specificity, whereas in fact it is the positive predictive value of mammography
1122
LETTERS
CANCER PRESENT
ABSENT
[
MAMMOGRAM
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TP
v
FP
TP+FP1
+
AJA:154, May 1990
Target values for positive predictive value as a barometer of a mammographic practice are not uniformly agreed on, but Hall et al. [9] have argued that 40% is a reasonable goal when a positive mammogram is defined as one that results in a recommendation of biopsy. Although this is far from controversial [1 0], even higher predictive values have been achieved routinely in screening centers in Sweden
(Falun,
of patients
[11].
Uppsala,
Vesteros)
that deal with large numbers Robert
MAMMOGRAM FN
L; TP+FN
TN
TP
SPE
E
TN1 TN+FPJ
I
A. Schmidt
Charles E. Metz
[)TNj
The University of Chicago Chicago, IL 60637
_____
lPRTP.FP+TN.FN
REFERENCES 1.-Two-by-two table used to calculate statistical results of a mammographic audit. MAMMOGRAM + = biopsy recommended, TP = true positive, FP = false positive, PV (+) = predictive value of a positive test, FN = false negative, TN = true negative, PV (-) = predictive value of a negative test, SENS sensitivity, SPEC = specificity, and PR = prevalence. Fig.
that the data show is low. Unfortunately, such misuse of terminology is likely to cause misunderstanding about the success of mammography screening programs. Primarily because breast cancer is rare in a screened population, screening mammograms are interpreted with high specificity, but their positive predictive value is relatively low [4]. Several recent papers [5-7] have described the procedures that should be used in a mammographic audit. Calculation of results is performed most easily in terms of a two-by-two table that summarizes data obtained from follow-up of the screened population (Fig. 1). With a prevalence offive cancers per 1 000 patients examined, a hypothetical mammographer who recommends biopsies in 5% of patients and fails to detect a single cancer would have a specificity of 95% but a positive predictive value of 0% (true positive [TP] = 0, false positive [FP] = 50, true negative [TN] = 945, false negative [FN] = 5 in Fig. 1). As a contrasting extreme example, an ideal mammographer whose sensitivity is 1 00% and who does biopsies on only 0.5% of patients would have a specificity of 100% and a positive predictive value of 1 00% (TP = 5, FP 0, TN 995, FN 0). More realistically, a good mammographer with a sensitivity of 80% who does biopsies on 1% of patients would have a specificity of 99.4% and a positive predictive value of 40% (TP = 4, FP = 6, TN = 989, FN = 1). Because few patients have cancer in screening mammography, the specificity associated with a particular biopsy rate is determined primarily by the overwhelming predominance of actually negative cases and will vary little from 100%, regardless of the ability of the mammographer, as long as biopsy rates are kept small. In comparing published sensitivities, specificities, and predictive values, it is important to note that all of these calculated results depend on the criterion used for a “positive” mammogram. Because the chief decision in breast imaging is whether to perform a biopsy to determine if cancer is present, we and most other authors take a positive mammogram to be one that resulted in a recommendation of biopsy. Alternatively, a positive mammogram might be taken as one in which the initial interpretation suggested any abnormality. These two definitions of a “positive” mammogram produce different combinations of sensitivity and specificity, which correspond to different points on a single receiver-operating-characteristic curve [8] and different predictive values. The specificity calculated from any given data set is generally high with either definition, however. Using the second definition of a positive mammogram, Sickles [7] found that the specificity of screening mammography was 94.2%, with a positive predictive value of 10%, for example.
1 . Harris AD. Diagnostic specificity: proper use (letter). AJR 1989;153:653 2. Hann L, Ducatman BS, Wang HH, Fein V. Mclntire JM. Nonpalpable breast lesions: evaluation by means of fine-needle aspiration cytology. Radiology
1989;171 :373-376 3. Brenner AJ. Medicolegal aspects of screening mammography. AJR 1989; 153: 53-56 4. Moskowitz M. Screening for breast cancer: how effective are our tests? A critical review. CA 1983;33:26-39 5. Spring DB, Kimbrell-Wilmot K. Evaluating the success of mammography at the local level: how to conduct an audit of your practice. Radiol Clin North Am
1987;25:983-992
6. Bird RE. Low-cost screening mammography: report on finances and review of 21 716 consecutive cases. Radiology 1989;171 :87-90 7. Sickles E, Ominsky SH, Sollitto RA, Galvin HB, Monticciolo DL. Medical audit of a rapid -throughput mammography ology and results of 27,1 14 examinations.
screening program; methodRadiology (in press) in radiologic imaging. Invest Radiol 1986;
8. Metz CE. ROC methodology 21 :720-733 9. Hall FM, Storella JM, Silverstone DZ, Wyshak G. Nonpalpable breast lesions: recommendations for biopsy based on suspicion of carcinoma at mammography. Radiology 1988;1 67:353-358 10. Moskowitz M. Predictive value, sensitivity, and specificity in breast cancer screening. Radiology 1988;1 67 : 576-578 11 . Tabar L. Intemational Teaching Seminar in Mammography. Presented in Falun, Sweden, June 3-10, 1989 Reply I thank
Drs.
Schmidt
and Metz
for their
thoughtful
confirms my premise that there is a significant use of statistical
terminology
in the
letter,
problem
radiologic
which
with incorrect
literature.
Mammo-
graphic screening, in particular, is an area in which proper use of statistics is meaningful and appropriate for both radiologists and referring
physicians.
Robert D. Harris Dartmouth-Hitchcock
Medical
Hanover,
Tracheal
Center
NH 03756
Rupture
I read with
interest
the paper
by Unger
et al. [1],
“Tears
of the
Trachea and Main Bronchi Caused by Blunt Trauma: Radiologic Findings,” in the December 1989 AJR. Although I realize that space limitations references,
preclude authors from I find it an oversight
quoting and including all possible on the part of the authors and
reviewers to omit pertinent and current references in a review article. In particular, the authors failed to refer to the April 1987 AJR article [2] by Rollins and Tocino, “Early Radiographic Signs of Tracheal Rupture,” in which new signs of tracheal 6 in the paper by Unger et al. illustrates
1987 paper.
rupture are described. findings first reported
Figure in the
AJA:154,
Tracheal rupture is not a common ture
is not overwhelming
and
entity, and thus available litera-
1 987
not such
a distant
date
as to
neglect such a reference. Irena M. Tocino LDS Hospital
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1123
LETTERS
May 1990
Salt Lake City, UT 84143 REFERENCES 1 . lk)ger JM, Schuchmann GG, Grossman JE, Pellett JR. Tears of the trachea and main bronchi caused by blunt trauma: radiologic findings. AiR
have reported the occurrence of any deaths associated with surgery for perforation caused by hydrostatic reduction, which is the main source of differences in mortality for surgery vs. hydrostatic reduction as the primary treatment. Because mortality is extremely low for either mode of treatment, I looked at other aspects of each option, such as overall complication rates and costs. The latter value progressively is assuming a cardinal role in the thinking of health care planners, administrators, insurers, the govemment, and, eventually, our own. Sensitivity analysis indicates a break-even point for reducibility rates as low as 1 0-1 5%.
In conclusion,
1989;153:1 175-1180
2. Rollins RJ, Tocino I. Early radiographic
signs of tracheal rupture. AiR
1987;148:695-698
Reply
My colleagues the excellent
and I sincerely
paper by Rollins
regret the inadvertent
and Tocino
[1 ]from
thelist
omission
of
of references
of our paper [2]. Despite what we had considered an exhaustive search of the literature, including a Medline search, we somehow missed this important addition, as it contains
contribution. information
It would have been a valuable on the importance of the appear-
ance of the endotracheal tube and balloon cuff and a discussion of tracheal damage as a function wall pressure, rather than absolute cuff Drs. Rollins and Tocino for this oversight. University
volume.
as I indicated
in the article [2], establishing
more aggressively, will have to use their experience regarding their rate of success when small-bowel obstruction is present. This figure is essential in using my estimates. My article simply provided some guidelines so that those who attempt hydrostatic reduction will have rational data to fit their own experience. John C. Leonidas Schneider
tracheal rupture of cuff-to-tracheal
in
Our
apologies
a policy
of always operating or always attempting hydrostatic reduction when small-bowel obstruction is present is difficult, and it may be necessary to tailor the treatment for the patient; estimates are not always sound. This applies to my estimates as well as those of others, including Franken et al. Radiologists, if they attempt hydrostatic reduction
Children’s
Hospital
New Hyde Park, NY 11042
to
REFERENCES
of Wisconsin,
June M. Unger Clinical Science Center Madison, WI 53792
1 . Franken EA Jr, Kao SCS, Smith WL, Sato Y. Imaging of the acute abdomen in infants and children. AiR 1989;153:921-928 2. Leonidas JC. Treatment of intussusception with small bowel obstruction: application of decision analysis. AiR 1985;145:665-669
REFERENCES 1 . Rollins RJ, Tocino I. Early radiographic
signs of tracheal
rupture.
AJR
Reply
1987;148:695-698 2. Unger JM, Schuchmann GG, Grossman JE, Pellett JR. Tears of the trachea and main bronchi caused by blunt trauma: radiologic findings. AJR 1989;153:1175-1
Hydrostatic
discussed
180
Reduction
of Intussusception
I would like to clarify certain points on the advisability of attempting hydrostatic reduction of intussusception, a topic recently discussed in the excellent article by Franken et al. [1]. The subject controversial, as the available information is incomplete.
is, indeed, The diag-
nosis of gangrenous intussusception cannot be made preoperatively. When evidence of small-bowel obstruction is present on radiographs, the probability
of gangrenous
intussusception
increases,
and that of
hydrostatic reducibility decreases. In the article quoted by Franken et al. “Treatment of Intussusception with Small Bowel Obstruction: Application of Decision Analysis [2], I used pooled data to arrive at some numerical conclusions. Published articles indicate that the reducibility of intussusception in the presence of small-bowel obstruction is only about 40%. This figure is obviously not a “hard” statistic. Nevertheless, the 95% confidence interval indicates that with existing data, the projected reducibility in a theoretically infinite number of attempts should range from 33% to 49% (i.e., much higher than the estimate
of 10-20%
quoted
by Franken
et al).
Moreover,
experience. is indeed
obstruction should be able to be reduced rate. This figure is higher than anyone’s
Franken et al. are, therefore, a prime
consideration.
to achieve published
correct about survival, which
No recent
publications,
however,
reduction
in our review article,
Infants
and Children”
a
to individualize
need
for his astute comments
hydrostatic
on the advisability
of intussusception,
“Imaging
[1]. We have no argument
each decision.
which
was
of the Acute Abdomen
in
with his emphasizing
His points on minimizing
mor-
bidity are equally valid. The situation is one in which we are all looking at the same elephant from different aspects and with incomplete information.
One of our reasons for quoting
Leonidas’s
article [2] on the use of
decision making in the treatment of intussusception was to introduce the reader to that important technique of diagnostic radiology by citing such a well-done study. Our own anecdotal experience is that successful hydrostatic reduction of intussusception in the presence of bowel obstructions occurs in about only 1 0% of cases. Using this
figure as our own individual
result and applying
Leonidas’s
decision
tree indicates increased mortality and morbidity with hydrostatic reduction compared with surgery. Thus, our recommendation to the radiologist who is not particularly expert at this procedure is to be
conservative. E. A. Franken, Jr. Simon C. S. Kao Wilbur
L. Smith
Yutaka Sato
my esti-
mates were subjected to sensitivity analysis so that room could be left for variation of the data. The cutoff point regarding the lowest possible mortality from treatment of intussusception was a 50-60% rate of reduction. In other words, at least 50-60% of intussusceptions with small-bowel the best survival
We thank Dr. Leonidas of attempting
The University of Iowa Iowa City, IA 52242
REFERENCES 1 . Franken EA Jr, Kao SCS, Smith WL, Sato Y. Imaging of the acute abdomen in infants and children. AiR 1989:153:921-928 2. Leonidas JC. Treatment of intussusception with small bowel obstruction: application of decision analysis. AiR 1985;145:665-669
LETTERS
1124
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Bile Duct Necrosis After Partial Hepatectomy Transcatheter Hepatic Arterial Embolization
and
In an attempt
to control the remaining
intrahepatic
from the gastroduodenal tree in our patient shows
the gastroduodenal
The effectiveness of transcatheter arterial embolization in the treatment of malignant hepatic tumors has been reported [1]. Side effects are minimal and usually require only conservative treatment. The selective ischemic effect of transcatheter arterial embolization on hepatic tumors compared with normal hepatic parenchyma plays a major role in the success of the treatment. Necrosis of the main bile duct usually does not occur after proximal transcatheter arterial embolization [2] because of the dual blood supply to the biliary tree from the hepatic and gastroduodenal arteries. We came to this conclusion after encountering a case of extensive necrosis of the bile duct in a patient whose blood supply to the intrahepatic bile ducts was totally dependent on a branch of the left hepatic artery because of previous radiologic interventions and surgery. The patient had had transcatheter arterial embolization twice and transcatheter portal embolization and laparotomy for hepatocellular carcinoma. Finally, he had surgery to remove the right lobe containing the main tumor and an intrahepatic metastasis in the lateral segment. During the operation, the liver was skeletonized completely, and the common bile duct in the hepatoduodenal ligament was dissected completely free from adjacent tissue. The right hepatic artery also was ligated. Severe fibrosis of the bile duct in the liver hilus was
observed.
AJA:154,
Gotoh Monden
Masato Sakon Toshio Kanai Koji Umeshita
Wakio Endoh Jun Okamura Kenichi Wakasa Masami Sakurai
Tarou Marukawa Kuroda Takesada Mon Osaka University Medical School Osaka 553, Japan Chikazumi
REFERENCES
1 . Chuang VC, Wallace S. Hepatic artery embolization in the treatment of hepatic neoplasms. Radiology 1981 140:51-58 2. Makuuchi M, Sukigara M, Mori T, et al. Bile duct necrosis: complication of transcatheter hepatic arterial embolization. Radiology 1985;156:331-334 3. Zajko AB, Campbell WL. Logsdon GA, et al. Cholangiographic findings in hepatic artery occlusion after liver transplantation. AJR 1987;1 49: 485-489
Periportal
Lymphedema
in Trauma
Previous reports have described
bolization.
Patients
zones of low attenuation
ascribed
to dilated hepatic lymphatics surrounding portal venous radicles in patients with rejection ofliver transplants, [1 , 2], hepatic or penihepatic hematomas, upper abdominal lymphadenopathy, congestive heart failure [3], and constrictive pericarditis [4].
Over 9 months, we found hepatic perivascular
lymphedema
in five
and 62 years old) of 540 patients who had abdominopelvic CT because of trauma (Fig. 1). None of the five patients with periportal collars had any other CT evidence of abdominal trauma; all (20,
21 , 23,
had extremity
45,
injuries. All five patients
were hypotensive
when they
arrived in the emergency department and received large volumes of IV fluids as part of routine posttrauma resuscitation immediately
before the CT scan was performed. Although we did not review the records to determine
Fig. 1.-Bile duct necrosis after partial hepatectomy and transcatheter hepatic arterial embolization. A, Artenogram shows contrast medium injected through indwelling arterial catheter has extravasated into biliary tree. B, cholangiogram obtained after injection of contrast medium through percutaneous transhepatic biliary drainage tube shows extensive necrosis of bile duct.
artery. Morito
tases, transcatheter arterial embolization on the 1 6th day after surgery by using
An arteriogram performed via the indwelling arterial catheter showed extravasation of contrast medium into the biliary tree (Fig. 1A). CT scan showed a large biloma in the right subphrenic and hilar space of the remaining left lobe. Percutaneous transhepatic biliary drainage was performed. Injection of contrast medium showed extensive necrosis of the bile duct that began just above the fibrotic hilar bile duct recognized at surgery (Fig. 1 B). The capillary network from the gastroduodenal artery was assumed to have ended in this portion, and the intrahepatic biliary tree was completely dependent on the blood flow from the left hepatic artery. This extensive necrosis of the bile duct was comparable with that occurring after hepatic arterial thrombosis in liver allografts in patients who lack blood flow
artery [3]. The condition of the hilar biliary the importance of arterial blood flow from
Mitsukazu
metas-
of the left lobe was done a catheter that had been inserted through the right gastroepiploic artery during the operation. High fever, nausea, and vomiting developed 1 1 days after the em-
May 1990
A
how
much
IV fluid
they
of the other 535 patients
received,
we
suspect
that
B
Fig. 1.-A and B, Contrast-enhanced CT scans of abdomen and pelvis of a trauma patient who had received 2 I of IV fluids show ring lucencies (A) due to periportal lymphedema surrounding portal vein branches and distension of bladder (B). Bladder dome was at level of umbilicus.
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1125
LETTERS
AJR:154, May 1990
vigorous hydration can cause distension of the peniportal lymphatics and peniportal collars even in patients with normal cardiac output. Thus, in patients with hepatic injuries, peniportal collars may be caused by vigorous hydration rather than by the trauma itself. John F. Cox Arnold C. Friedman Paul D. Radecki Anna S. Lev-Toaff Dma F. Caroline Temple
University
Philadelphia,
Hospital PA
19140
REFERENCES 1 . Wechsler AJ, Munoz SJ, Needleman L, et al. The periportal collar: a CT sign of liver transplant rejection. Radiology 1987;165:57-60 2. Marincek B, Barbier PA, Becker CD, Mettler D, Ruchti C. CT appearance of impaired lymphatic drainage in liver transplants. AJR 1986;147: 51 9-523 3. Koslin DB, Stanley AJ, Berland LL, Shin MS, Dalton SC. Hepatic penivascular lymphedema: CT appearance. AJR 1988;150: 111-113. 4. Goldstein L, Mervis SE, Kostrubiak IS, Tumey SZ. CT diagnosis of acute pericardial tamponade after blunt chest trauma. AJR 1989;152:739-741
Confusing Similarities Between Retroperitoneal Lymphangioma
Peripancreatic and Other Lesions
We recently observed a case that not only emphasizes the important similarities between retropenitoneal lymphangioma and other benign cystic or vascular tumors but also illustrates the difficulty of radiologically distinguishing those lesions arising in the pancreas itself from those merely arising in the contiguous extrapancreatic retropenitoneum. A renal sonogram of an asymptomatic 58-year-old woman incidentally showed a well-demarcated cystic mass in the pancreatic head containing multiple internal septa (Fig. 1A). CT of the mass showed that it had a density near that of water, with internal septa less clearly defined than on sonography. Spin-echo MR imaging of the mass showed low signal intensity on Ti -weighted images (300/20) and high signal intensity on T2-weighted images (Fig. 1 B). The initial diagnosis was primary cystic neoplasm of the pancreas. On exploratory laparotomy, however, it was found that the mass arose from the retropenitoneal soft tissues; the pancreas itself was normal. A
frozen section of the mass was interpreted originally as a microcystic (glycogen-nich) adenoma of the pancreas, but final histologic study showed instead a cavernous retropenitoneal lymphangioma. Aetropenitoneal lymphangiomas and microcystic pancreatic adenomas are both benign, often asymptomatic, and found only incidentally. Both lesions also are composed of multiple small cysts lined with a single layer of cells and separated by thin fibrous septa [1 , 2]. On CT, both appear well demarcated and hypodense [3, 4]. On MA, both tumors are hypointense on Ti-weighted images and hyperintense on T2-weighted images; the internal septa usually are visualized better on the latter [4]. Nevertheless, sonography of an adenoma usually shows a hypoechoic, solid-appearing lesion in which individual small cysts cannot be resolved [3]. Lymphangiomas, on the other hand, may have prominent solid components, but their cystic character is usually more evident [5] (Fig. 1). Additionally, the microcystic pancreatic adenoma often contains a distinctive central stellate or partially calcified scar [3]. The clinical, histologic, sonographic, CT, and MR characteristics of hemangiomas and lymphangiomas also may be quite similar. CT of hemangiomas, however, usually shows a distinctive pattern of contrast enhancement different from that observed with lymphangiomas. Also, on sonography, hemangiomas usually are more solid and less cystic than lymphangiomas. In essence, therefore, the differentiation between a retropenitoneal lymphangioma and a comparable cystic or vascular intrapancreatic or extrapancreatic mass may require close scrutiny of subtle radiologic
differences.
necessary
Biopsy
or
for a conclusive
percutaneous
aspiration
might
still
be
diagnosis. H. Richard Parvey Ronald L. Eisenberg Don M. Morris Warren D. Grafton Peter C. Meyers Louisiana
State
University
Medical
Shreveport,
Center LA
71130
REFERENCES
1 . Murao T, Toda K, Tomiyama Y. Lymphangioma of the pancreas: a case report with electron microscopic observations. Acta Pathol Jpn 1987;37: 503-510 2. Compagno J, Oertel JE. Microcystic adenomas of the pancreas (glycogenrich cystadenomas): a clinicopathologic study of 34 cases. Am J Clin Pathol 1978;69:289-298 3. Friedman AC, Lichtenstein JE, Dachman AH. Cystic neoplasms of the pancreas: radiological-pathological correlation. Radiology 1983:149(1): 45-50
4. Minami M, ltai Y, Ohtomo
K, Yoshida
H, Yoshikawa
K, ho M. Cystic
neoplasms of the pancreas: comparison of MR imaging with CT. Radiology 1989;171(1):53-56 5. Blumhagen JO, Wood BJ. Rosenbaum OM. Sonographic evaluation of abdominal lymphangiomas in children. J Ultrasound Med 1987;6(9):
487-495
:_‘
Renal Imaging A Comparison
.t__
..-. .-
in Long-term Dialysis of CT and Sonography
Patients:
.
The significant difference that Taylor et al. [1] found between CT and sonography (1 8%) in the detection of cysts in patients with end-stage kidneys makes me wonder if part or all of the reason for the poorer detection rate with sonography is not related to the equipment used. Thirty-six of the patients were examined on a GE R/T 3600 scanner (General Electric Medical Systems, Milwaukee, WI), whereas only five were examined on an Acuson 1 28 scanner (Acuson, Mt. View, CA). (59%)
Fig. 1.-Cavernous retroperitoneal lymphangioma. A, Oblique transverse real-time sonogram of right upper quadrant shows multiseptated cystic lymphangioma (Ly) sharply demarcated from adjacent pancreatic head (P). Arrow superior mesenteric vein, L = liver, GB = gallbladder. B, Axial T2-weighted MR image, 2000/60 (TR/TE), shows hyperintense peripancreatic lymphangioma (L) with faint internal septation (arrowheads).
LETTERS
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1126
AJR:154,
May 1990
Fig. 1.-A and B, Comparison of images of a phantom (ATS mode 539) obtained on GE 3600 (A) and Acuson 128 (B) 3.5-MHz phased-array scanners with probes. Multizone focus used with both scanners. Lateral resolution in far field of GE unit is much worse than in region of best focus
Fig. 1.-Comparison of sonography with Acuson 128 and contrastenhanced CT with GE CT 8800 in imaging acquired cystic kidney disease. A, Longitudinal sonogram of right kidney (cursors) shows a 1.5-cm cyst
(5 cm depth), whereas lateral resolution in Acuson is uniform and tightly focused from about 5 to 16 cm.
B, Contrast-enhanced CT scan of a slice cysts in lower pole of right kidney (arrows).
The GE R/T 3600 scanner has a significantly poorer beam pattern, especially in the deeper regions ofthe sector image where the kidneys
study shows the inherent greater capacity of CT compared with sonography in defining the diminutive cysts associated with acquired cystic kidney disease (Fig. 1).
usually lie, than the Acuson 128 (compare phantom images of a 3.5MHz phased-array probe scan of GE and Acuson, Fig. 1). Thus,
in interpolar
segment
and no discernible
cysts in lower pole. 1 cm thick
numerous
Andrew J. Taylor
although I agree with the authors that cysts less than 1 cm may be difficult to visualize with the GE scanner, it may be because of the
Eric P. Cohen Scott J. Erickson
that fills in cysts with echoes or cannot
David L. Olson
resolve small ones. I suspect that cysts as small as 0.5 cm could be detected with the Acuson because of its better lateral resolution. It would be helpful if the authors could elaborate on why they think
W. Dennis Foley
poor
lateral beam resolution
shows
even
cysts were missed on sonography. were they echo-free?
between
Were the cysts not seen at all, or
confused with other structures because they How did the detection rate and size of cysts
were not compare
those patients studied with the GE scanner vs the Acuson? Leon Skolnick University
of Pittsburgh,
School Pittsburgh,
Medical
College
of Wisconsin
Milwaukee,
WI
53226
REFERENCE
1 . Taylor AJ, Cohen long-term
dialysis
EP, Erickson SJ, Olson patients: a comparison
WD. Renal imaging in of CT and sonography. AiR
DL, Foley
1989;153:765-767
of Medicine PA
15213
Multiple REFERENCE 1 . Taylor AJ, Cohen EP, Erickson SJ, Olson DL, Foley WO. Renal imaging in long-term dialysis patients: a comparison of CT and sonography. AJR 1989;153:765-767
Hydatid
A 23-year-old man had signs and symptoms that suggested progressive spinal compression at L3. Contrast-enhanced CT of the abdomen
showed
the right kidney,
extending Reply
Dr. Skolnick raises the possibility that our results [1] in the imaging of acquired cystic kidney disease might be skewed because of our available sonographic equipment (i.e. , 36 patients were examined on the GE AfT 3600 scanner [General Electric Medical Systems, Milwaukee, WI], whereas only five were examined on the Acuson 128 [Acuson, Mountain View, CA]). Reviewing the data obtained from the institution that uses the Acuson 1 28 and the GE CT 8800 scanner might be helpful. At that institution, a total of nine kidneys in five patients were imaged. CT showed a greater grade of cystic change in all nine kidneys. With CT, five kidneys in three patients were shown to have changes indicative of acquired cystic kidney disease (i.e., five or more cysts per kidney); sonography showed one patient (or two kidneys) that met the requirements. We certainly agree that the technical considerations for imaging are important. However, we think that the marked difference in our
Cysts
numerous a paraspinal
cysts (Fig. 1). They included a cyst in cyst involving the multifidus muscle and
to the erector spinae muscle, an epidural cyst, a retroper-
itoneal cyst within the pararenal muscle, and a cyst in the innominate
space, a cyst within bone causing marked
the psoas expansion
of the iliac wing. Attenuation values of the cysts ranged from 8 to 25 H. The liver was normal. Chest radiographs and head CT scans showed no abnormalities. Serologic tests for hydatid disease were positive. The lesion in the epidural space was resected, and a germinative
membrane
and scoleces
were
shown.
The diagnosis of histologically.
granulosus infestation was established All the other cysts were left in place, and chemotherapy dazole was started. Echinococcus
Echinococcosis,
caused
or
hydatid
disease,
with meben-
is a parasitic
infestation
by the larval stage
of the tapeworms E. granulosus and Echinococcus multiocularis. The nematode is swallowed in the egg form. In the stomach, the egg dissolves, and the embryo gains access to the body by penetrating the intestinal wall and entering the portal circulation. Most of the embryos lodge in the liver and lung (approximately 60% in the liver and 25% in the lung), and the remainder are
spread
throughout
the rest of the body [1 -4].
Our
case
is unique
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AJR:154,
1127
LETTERS
May 1990
not unite cannot blithely be called a nonunited fracture. Imaging both sides does not avoid this problem if ossicles are unilateral. Resolution of signs and symptoms with therapy directed to the ossicle certainly does not resolve the debate. The natural resolution of signs and symptoms with “a tincture of time” is a long held adage. As indicated by Hindman et al., the significance of findings in light of the patient and the patient’s problems always must be questioned. If doubt exists then in this situation, clinical and radiologic follow-up studies or an isotopic bone scan may be helpful. Mark E. Pierce Canberra
Belconnen
Imaging
Act 261 7, Australia
REFERENCES
1 . Hindman BW, Kulik WJ, Lee G, Avolio RE. Occult fractures of the carpals and metacarpals: demonstration by CT. AiR 1989:153:529-532 2. Kohler A, Zimmer EA. Borderlands of the normal and early pathologic in skeletal roentgenology, 3rd ed. New York: Grune & Stratton, 1968: 79-117 3. Keats TE. Atlas of normal roentgen variants that may simulate disease, 3rd ed. Chicago: Year Book Medical, 1984:399-439
#{149}A;
Reply
Fig. 1.-CT scans show multiple hydatid cysts in a 23-year-old man. A, Cyst in right kidney originating from lateral cortex. Walls are partially calcified. B, Epidural cyst to right of L3 and another cyst originating from right multifidus muscle. Lower part of renal cyst shown in A is seen also. C, Cyst in right pararenal space adjacent to psoas muscle. Cyst affecting erector spinae muscle and a small cyst in right quadratus lumborum muscle
are visible also. D, Cysts originating from right psoas muscle and right iliac wing.
because of the multiple and lung.
sites of involvement
with sparing
of the liver
A. Nun Sener Utku Ozcan Vedat Isik Ali Demirci Private
Hospital Isparta,
of Isparta
We appreciate Dr. Pierce’s interest and constructive comments. We agree that a risk exists of sometimes showing fragments of bone that are normal variants or partial-volumned ridges and prominences and that care must be taken to avoid this possibility. In our study [1], of the 1 6 patients with 21 fractures, 1 1 patients with 1 3 occult fractures showed evidence of fracture healing or marked improvement with surgical removal of the fracture fragment or fusion of the fractured bone to the adjacent carpal bone. Five patients with six fractures, including all of the lunate fractures and one fracture of a metacarpal and one scaphoid fracture, failed to show evidence of fracture healing or clinical improvement, and this type of patient deserves careful clinical, radiologic, and scintigraphic follow-up. Two of these patients had healing of one of their fractures, and two declined to have a recommended surgical procedure. Although the diagnosis of fracture in some of these six instances may be debated, we think the importance of this study is underscored by the diagnosis of the 1 3 fractures that otherwise would have gone unrecognized, and possibly undertreated.
Turkey
B. W. Hindman W. J. Kulik
REFERENCES
G. Lee
1 . Haaga JR. Alfidi AJ. Computed tomography of the brain, head, and neck. St. Louis: Mosby, 1985:128-129 2. Clements A, Bowyer FM. Hydatid disease of the pelvis. C/in Radiol 1986:37:375-377 3. Braithwaite PA, Lees AF. Vertebral hydatid disease: radiological assessment. Radiology
1981;140:763-766
4. Missas 5, Gouliamos A, Kourias E, Kalovidouris A. Primary hydatid disease of the pancreas. Gastrointest Radiol 1987;12:37-38
CT of the Wrist:
What
Is Abnormal?
Hindman et al. [1] concisely underlined the technique of CT of the wrist. They showed the beautiful detail obtained with CT in an area complicated on plain films by overlapping structures. Undoubtedly CT will reveal significant occult fractures in the wrist. However, perspective and a note of caution need to be introduced. It soon becomes obvious that CT also shows the multiple accessory ossicles that may be present normally in the wrist [2, 3]. A clean fracture line that heals is unequivocal. However, a corticated ossicle that does
Flower
A. E. Avolio Imaging Medical Group Los Angeles, CA 90007
REFERENCE
1 . Hindman BW, Kulik WJ, Lee G, Avolio RE. Occult fractures of the carpals and metacarpals: demonstration by CT. AJR 1989;153:529-532
Bone Scan Screening for Occult Carpals and Metacarpals
Fractures
of
Chronic joint pain despite normal radiographs is a frequent occurnence. As the imaging center for a large sports medicine clinic, we encounter many patients with chronic posttraumatic bone pain, particularly about the ankle but also in the wrist. The recent article by Hindman et al. [1 ] on the CT demonstration of occult carpal and metacarpal fractures is most informative. This retrospective review, however, did not mention use of ‘Tc-MDP bone scanning as a
1128
LETTERS
,“,.
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,‘
1
[1 ‘H”
how many standardized aging costs
CT scans
after screening
approach and limited
reviewed
bone scans.
May 1990
by Hindman
et al. [1]
The use of a simple
to chronic joint pain has decreased the imthe number of CT scans performed. W. J. Sisler University Hospital University of British Columbia Vancouver, B.C., Canada
REFERENCES 1 . Hindman BW, Kulik WJ, Lee G, Avolio RE. Occult fractures of the carpals and metacarpals: demonstration by CT. AJR 1989;153:529-532 2. Hopkins SR, Ammann W. Isolated fractures of the capitate: use of nuclear
B
medicine
Fig.1.-Occult fracture ofhamate. A and B, ‘Tc-MDP bone scans show intenseuptakeof radionuclide on frontal (A)and lateral (B)static imagesinregion ofhamate. C, Transaxial thin-slice CT scan throughdistal carpalrow showsanundisplaced fracture of baseofhookofhamate. C
of the 200 wrist
were obtained
AJA:154,
as an aid to diagnosis.
mt
j
Sports
Med
(in press)
3. Young MRA, LowryJH, LairdJD, Ferguson WA. ‘“‘Tc-MDP bone scanning of injuries of the carpal scaphoid. Injury 1988;19: 14-17 4. Sisler WJ. Imaging assessment of post-traumatic tarsal pain. Can J Sports Med (in press)
Reply
We appreciate Dr. Sisler’s comments and agree that technetium bone scanning is an excellent screening technique for patients with chronic posttraumatic joint pain. We also think that his experience of
no abnormal CT scans after normal results on scintigraphy is probably universal and that a fracture diagnosed on the basis of CT findings screening method.The efficacy oftheinitial bone scanafterprelimimay be subject to narynormalradiographs iswellestablished [2,3].At ourinstitution obtained after normal results on scintigraphy atleast, and Isuspectelsewhere, bone scanningtendstobe readily question. We support the position of our hand surgeons that CT, available and ofmuch lowercostthanCT.A simplescanningroutine because of its greater accuracy in detecting fractures, is essential in the management of chronic joint pain. The decision to remove a hasbeenestablished [4],and we havefoundno abnormalCT scans
afterinitial normalbone scans.The following typical case outlines fracture fragment surgically or to allow the fracture to heal with immobilization can be made readily on the basis of CT. This inforthisapproach. useful in fractures of the hamate because A 21-year-old man saw hisfamilyphysician becauseofa 1-year mation is particularly fractures of the tip are treated differently than fractures at the base history ofpainintheulnaraspectofthewristafter fisticuffs. Clinical of the hook. These surgeons go directly to CT when other findings examination showed tendernessoverthepisiform and hamate.Raare highly suggestive of fracture. Few of the 200 patients studied diographswere unremarkable. The tentative clinical diagnosis was a with CT [1 1 had initial screening bone scans. In most of these cases, tearofthefibrocartilage. CT was performed to show a second process or to evaluate a fracture Becausethepainpersisted, arthrography was performed, which of a bone graft. In cases in which the was alsounrevealing. Two months later, a bone scanwas obtained for healing or incorporation thatshowed normaldynamicimageswithimmediatemildincreased process is uncertain, we agree that radionuclide scintigraphy followed and accurate imaging sequence. uptakeofradionuclide attheulnaraspectofthewriston theblood- by CT is a cost-effective B. W. Hindman poolstudy.Staticimages(Fig.i)showed an intenseareaoffocal W. J. Kulik uptakeintheregionofthehamate.The clinical diagnosis inconjuncG. Lee tionwiththebone scanwas therefore probablefracture ofthehook R. E. Avolio of thehamate.Eightdays later, high-resolution thin-slice CT scans Flower Imaging Medical Group were obtained. The transaxial imageswere most revealing, showing Los Angeles, CA 90007 an undisplaced fracture throughthebaseofthehook ofthehamate. Aadionuclide bone scanningisan inexpensive studywitha high capacity fordetection ofoccult fractures. Patients who haveabnormal REFERENCE scansthenhavedirected CT examinations atourinstitution, and the 1. Hindman BW, Kulik WJ, Lee G, Avolio RE. Occult fractures of the carpals rateofdetection offractures ishigh.Itwouldbe interesting toknow and metacarpals: demonstration by CT. AiR 1989;153:529-532
Letters are published at the discretion of the Editor and are subject to editing. Letters to the Editor must not be more than two double-spaced, typewritten pages. One or two figures may be included. Abbreviations should not be used. See Author Guidelines, page A5. Material being submitted or published elsewhere should not be duplicated in letters, and authors of letters must disclose financial associations or other possible conflicts of interest. Letters concerning a paper published in the AJR will be sent to the authors of the paper for a reply to be published in the same issue. Opinions expressed in the Letters to the Editor do not necessarily reflect the opinions of the Editor.
