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Routine pre-contrast CT for liver lesion detection a re-examination
ELSEVIER
ROUTINE PRE-CONTRAST CT FOR LIVER LESION DETECTION A IKE-EXAMINATION NABIL A. YASSA, MD, TULIA T. AGOSTINI, AND MATTHEW s. TAN, MD
Objective: Re-examination of routine pre-contrast computed tomography (CT) through liver. Materials and Methods: 852 abdominal CTs including pre- and post-contrast images were retrospectively reviewed regarding detection of hepatic lesions. Results: 103 cases demonstrated hepatic abnormalities. More liver lesions were identified post-contrast in 89; equal numbers were seen pre- and post-contrast in 10; more lesions were seen pre-contrast in one case. Tiny calcifications were detected only pre-contrast in three cases. Conclusions: Routine pre-contrast scanning through liver is not cost-effective. 0 Elsevier Science Inc., 1997 KEY WORDS:
CT; Liver;
Pre-contrast;
Lesions;
Utility
INTRODUCTION for abdominal computed tomography (CT) vary from one institution to another. Some institutions tailor exams for each clinical condition. Others use a standard protocol aimed at demonstrating most of the pathology likely to occur in a specific population of patients. In this era of managed care it is important to institute methods which optimize effectiveness in demonstrating pathology as well as time- and cost-effectiveness. Pre-contrast imaging of the liver has been recommended in a limited number of settings, including Protocols
From the Department of Radiology, University of Southern California, Los Angeles, California. Address reprint requests to: Nabil A. Yassa, MD, USC University Hospital, 1500 San Pablo St., Los Angeles, CA 90033. Received March 20, 1996; accepted June 2, 1996. CLINICAL IMAGING 1997;21:346-349 0 Elsevier Science Inc., 1997 655 Avenue of the Americas, New York, NY 10010
MD,
the presence of extra-hepatic tumors with a high incidence of hypervascular metastases or the suspicion of a hypervascular primary hepatic tumor (l-4).
Hypervascular metastases include those from endocrine tumors of the pancreas and adrenal, carcinoid tumors, thyroid carcincoma, renal cell carcinoma, melanoma, and breast cancer. Although metastases from breast cancer are more often hypovascular, DuBrow et al. (2) showed that 28% of patients with hepatic metastases from breast cancer had lesions which became isodense after contrast administration, presumably due to hypervascularity. Hypervascular primary malignant tumors of the liver include hepatocellular carcinoma and sarcoma, especially angiosarcoma. (Benign hepatic lesions which demonstrate hypervascularity include focal nodular hyperplasia and hepatocellular adenoma.) Because of altered portal venous flow in cirrhotic livers, non-contrast scanning has been recommended in presence of cirrhosis (5, 6). Preliminary non-contrast scanning has also been advocated in cases of blunt abdominal trauma (7). However, the inclusion of non-enhanced scans through the liver in the routine protocol for abdominal CTs remains a common practice. We examined the utility of this practice over a 3’/,-year period and reviewed the recent literature on non-enhanced CT of the liver. METHODS AND MATERIALS 1109 consecutive abdominal CT examinations performed over a Y/,-year period were retrospectively reviewed. In 109 cases IV contrast medium was not
administered because of a history of renal failure, allergy, or patient refusal of IV contrast. In 148 cases exams were performed only post-IV contrast at the
0899-7071/97/$17.00 PII SO899-7071(96)00083-6
SEPTEMBER/OCTOBER
1997
PRE-CONTRAST CT FOR LIVER LESION DETECTION
TABLE 1. Indications for Abdominal CT Examinations Symptoms/clinical
concern
Upper GI malignancy Rule out abscess Rule out metastatic disease Rule out liver mass Rule out pancreatic mass Rule out renal mass Pain/Weight loss Rule out abdominal mass Rule out retroperitoneal bleed Rule out bowel obstruction Lymphoma Adrenal mass Gynecological malignancy Trauma Total
No. of cases 274 263 149 103
82 81
76 24 16
14 9 8
6 4 1109
347
103 cases both pre-and post-contrast images demonstrated hepatic abnormalities with more abnormalities evident post-contrast, (In four of these 80 cases chemoembolic material was detected in the liver only on pre-contrast studies.) In nine cases liver lesions were detected only post-contrast, the pre-contrast images demonstrating no hepatic abnormality. In 10 of the 103 cases an equal number of hepatic lesions was seen on both pre- and post-contrast images. Tiny liver calcifications were detected only on pre-contrast images in three cases. In one case, where scanner error occurred causing a delay in post-contrast imaging, both pre- and post-contrast images demonstrated hepatic abnormalities, but more lesions were seen on the pre-contrast images.
DISCUSSION radiologist’s request. In the remaining 852 cases the CT examination consisted of lo-mm axial scans at ZO-mm increments through the liver before IV contrast consisted of IO-mm axial scans at IO-mm increments through the entire abdomen with IV contrast enhancement. These 852 cases were included in this study. All CT examinations were performed on a conventional Philips Tomoscan SR 6000 (Philips Medical Systems, Shelton, CT). Post-contrast imaging was initiated 45 seconds after the start of injection of 140 ml of ionic 30% organically bound iodine, iopamido1 (Isovue 300, Squibb Diagnostics, Princeton, NJ). Contrast material was administered at a rate of 2 ml/ set with an automated power injector (Medrad, Pittsburgh, PA). In all cases the scans were photographed using both abdominal (width = 450 HU) and unenhanced liver (width := 150 HU) window settings. Interpretation of the CT examinations with respect to detection of hepatic abnormalities was performed independently by two radiologists (N.A.Y. and M.S.T.) experienced in cross-sectional imaging. Pre-contrast images were interpreted before post-contrast images in half of the cases, and images were interpreted in the opposite order in the other half. Differences in opinion were resolved by consensus. The indications for the abdominal CT examinations are listed in Table 1.
RESULTS In 852 cases both pre- and post-IV contrast scans were available for interpretation. These cases were reviewed with respect to abnormalities involving the liver. In 749 cases the liver appeared normal on both pre- and post-contrast images, whereas a hepatic abnormality was identified in 103 cases. In 80 of these
Institutions differ in their protocols for CT examinations of the abdomen. Although not routinely employed in most academic institutions, the inclusion of routine preliminary non-contrast CT through the liver in standard protocols in prevalent in private practice. There are several possible reasons for this. There may be a continued perception in the community that the risk is high of missing a hypervascular primary or metastatic lesion in the liver. The routine pre-contrast liver scan may be employed in some institutions because of a lack of relevant clinical information afforded the radiologist at the time of scanning. Another issue is the additional reimbursement for the pre-contrast portion of the study. The noncontrast portion of the abdominal CT examination at our institution is roughly equal in cost to the contrast-enhanced portion, excluding the cost of the IV contrast medium. We evaluated this protocol over a 3l/,-year period and found that the pre-contrast portion of the exam was of little utility in our patient population. In only one case, in which scanner error resulted in a delay in post-contrast imaging, were more metastatic lesions identified pre-contrast than post-contrast. In no cases would the presence of metastatic disease, primary liver disease, or post-traumatic liver lesions have been missed by eliminating the pre-contrast portion of the study. In the 1980s it became apparent that hypervascular metastases could become less evident or isodense with normal parenchyma after IV contrast enhancement (8). Hypervascular lesions are hyperdense relative to liver during maximal hepatic arterial opacification, which occurs in the first 20 to 30 seconds of contrast injection. Limitations of conventional CT scanners result in the acquisition of images during the phase of portal venous enhancement, at which time
348
YASSA
ET AL.
CLINICAL IMAGING VOL. 21, NO. 5
1. Pre-contrast image of liver (A) demonstrates small calcification in the left lobe (arrow) which was not detected on the contrast-enhanced scan (B).
FIGURE
there is maximal enhancement of normal liver parenchyma, which is predominantly supplied by the portal venous circulation. As enhancement within a given hypervascular lesion declines, it eventually becomes equal to the enhancement within normal parenchyma. Metastases demonstrate variable rates of enhancement, however, even within one patient. Patten et al. (9) found that although some lesions may become isodense on post-contrast scans, rarely would the presence of metastatic disease be missed altogether on post-contrast images. In 1987 Bressler et al. (1)recommended preliminary non-contrast CT in patients with suspected hypervascular hepatic metastases. This was a retrospective study of 28 patients with hypervascular hepatic metastases, 27 of whom had endocrine tumors of the pancreas or adrenal gland or carcinoid. In 1990 DuBrow et al. (2) studied 88 patients with hepatic metastases from breast cancer and recommended that both non-enhanced and enhanced scans be performed in screening these patients. They found that without the pre-contrast images the presence of metastatic disease would have been missed in one case, and two more cases would have required additional work-up to confirm the presence of metastases. In all three cases the pre-contrast images demonstrated so many lesions that the presence of metastases was not in question. Chomyn et al. (10) in 1992 studied 55 patients with hypervascular metastases from malignant melanoma and concluded that non-enhanced scans were not useful, finding no additional lesions on pre-contrast images. In the 1993 study by Patten et al. (9)101 cases of hypervascular primary hepatic
malignancy or suspected hypervascular hepatic metastases were prospectively studied. In this study, out of 34 patients with hypervascular liver lesions, the presence of hepatic disease would have been missed in only one case without the addition of the non-contrast study, and it was concluded that routine non-enhanced CT even for hypervascular hepatic neoplasms was not necessary. However, as pointed out by Bressler et al. in a subsequent letter (3), few of the patients in the Patten study had primary endocrine tumors. Interestingly, as pointed out by Tomiak et al. (ll), the biphasic contrast CT technique, in which helical scanning is performed both during the earlier hepatic arterial phase and then during the portal venous phase, may obviate the use of pre-contrast scanning for hypervascular metastases. With this new technique hypervascular liver lesions are imaged while they are maximally evident during the hepatic arterial phase. Further studies need to be performed to compare the efficacy of non-contrast CT and arterial phase contrast-enhanced CT in the detection of such lesions. One must also be aware of the possible false positive results with arterial phase scanning due to the phenomenon termed “transient hepatic attenuation differences” (THAD), due to foci of normal liver parenchyma which receive predominantly hepatic arterial supply (5, 12). In our study there was no case in which the presence of significant hepatic lesions would have been missed without the addition of the non-contrast portion of the study. Although tiny liver calcifications were obscured on post-contrast scanning, these were
SEPTEMBER/OCTOBER1997
PRE-CONTRASTCT FOR LIVER LESION DETECTION
349
FIGURE 2. Pre-contrast image (A) better depicts size of hypervascular lesion in left lobe of liver. although lesion is clearly evident post-contrast as well (B). generally felt to be of little clinical significance, as they likely represented old granulomatous disease (Figure 1). Chemoembolic material was also obscured on post-contrast scanning. In these cases non-contrast exams are more useful clinically in excluding the presence of chemoembolic material in the stomach and proximal small bowel than in identifying the chemoembolic material in the liver. In our post-traumatic cases the pre-contrast images were of no additional benefit. In several cases in our series the detection of greater numbers of lesions post-contrast than precontrast could be attributed to the use of the smaller lo-mm scanning increments used post-contrast. A fair comparison of CT with and without IV contrast would involve comparison of scans of equal thickness at equal intervals. This study, however, was a retrospective analysis of the protocol employed in this institution, and our protocol is not unique. Many private practices routinely obtain pre-contrast scans through the liver at wider intervals than the post-contrast scans. See Figure 2. In summary, performing unenhanced scans through the liver in every abdominal CT prior to scanning with IV contrast enhancement increases exam time and technician time, nearly doubles the cost to the patient, and exposes the patient to additional radiation. The routine inclusion of this pre-contrast portion of the CT was of no significant benefit in our study of 852 cases. The utility of non-contrast CT in the detection of hypervascular liver lesions remains controversial, Abdominal CT should be tailored to answer the specific clinical problem. This requires
more involvement from the radiologist and effective communication with the referring physician,
REFERENCES 1. Bressler EL, Alpern MB, Blazer GM, Francis IR, Ensminger WD. Hypervascular hepatic ology 1987;162:49-51.
metastases:
CT evaluation.
Radi-
2. DuBrow RA, David CL, Libshitz HI, Lorigan JG. Detection of hepatic metastases in breast cancer: the role of nonenhanced and enhanced CT scanning. J Comput Assist Tomogr 1990: 14(3):366-369. 3. Bressler EL, Alpern MB. Hypervascular hepatic metastases: reevaluation of unenhanced CT scans. Letter, AJR 1995;164: 512-513. 4. White PG, Adams H. Smith PM. The computed tomographic appearances of angiosarcoma of the iiver. Clinical Radiology 1993;48:321-325. 5. Baron RL. Understanding and optimizing use of contrast terial for CT of the liver. AJR 1994;163:323-331. 6. Nelson RC, Small 163:988. 7. Kelly J, Raptopoulos value of non-contrast AJR 1989:152:41-46.
WC. Questions
and answers.
ma-
AJR 1994;
V. Davidoff A, Waite R. Norton P. The enhanced CT in blunt abdominal trauma.
8. Marchal GJ, Baert AL, Wilms GE. CT of noncystic sions: bolus enhancement. AJR 1980;135:57-65.
liver le-
9. Patten RM, Byun J, Freeny PC. CT of hypervascular hepatic tumors: are unenhanced scans necessary for diagnosis? AJR 1993:161:979-984. 10. Chomyn JJ, Stamm ER, Thickman D. CT of melanoma liver metastases: is the examination without contrast media superfluous? J Comput Assist Tomogr 1992;16:568-571. 11. Tomiak MM, Foley WD, Jacobson DR. Variable-mode CT: imaging protocols. AJR 1995;164:1525-1531.
helical
12. Itai Y, Hachiya K, Ohtomo K, Kokubo T, Yamauchi T. Transient hepatic attenuation differences on dynamic computed tomography. J Comput Assist Tomogr 1987:11:461-465.
ROUTINE PRE-CONTRAST CT FOR LIVER LESION DETECTION A IKE-EXAMINATION NABIL A. YASSA, MD, TULIA T. AGOSTINI, AND MATTHEW s. TAN, MD
Objective: Re-examination of routine pre-contrast computed tomography (CT) through liver. Materials and Methods: 852 abdominal CTs including pre- and post-contrast images were retrospectively reviewed regarding detection of hepatic lesions. Results: 103 cases demonstrated hepatic abnormalities. More liver lesions were identified post-contrast in 89; equal numbers were seen pre- and post-contrast in 10; more lesions were seen pre-contrast in one case. Tiny calcifications were detected only pre-contrast in three cases. Conclusions: Routine pre-contrast scanning through liver is not cost-effective. 0 Elsevier Science Inc., 1997 KEY WORDS:
CT; Liver;
Pre-contrast;
Lesions;
Utility
INTRODUCTION for abdominal computed tomography (CT) vary from one institution to another. Some institutions tailor exams for each clinical condition. Others use a standard protocol aimed at demonstrating most of the pathology likely to occur in a specific population of patients. In this era of managed care it is important to institute methods which optimize effectiveness in demonstrating pathology as well as time- and cost-effectiveness. Pre-contrast imaging of the liver has been recommended in a limited number of settings, including Protocols
From the Department of Radiology, University of Southern California, Los Angeles, California. Address reprint requests to: Nabil A. Yassa, MD, USC University Hospital, 1500 San Pablo St., Los Angeles, CA 90033. Received March 20, 1996; accepted June 2, 1996. CLINICAL IMAGING 1997;21:346-349 0 Elsevier Science Inc., 1997 655 Avenue of the Americas, New York, NY 10010
MD,
the presence of extra-hepatic tumors with a high incidence of hypervascular metastases or the suspicion of a hypervascular primary hepatic tumor (l-4).
Hypervascular metastases include those from endocrine tumors of the pancreas and adrenal, carcinoid tumors, thyroid carcincoma, renal cell carcinoma, melanoma, and breast cancer. Although metastases from breast cancer are more often hypovascular, DuBrow et al. (2) showed that 28% of patients with hepatic metastases from breast cancer had lesions which became isodense after contrast administration, presumably due to hypervascularity. Hypervascular primary malignant tumors of the liver include hepatocellular carcinoma and sarcoma, especially angiosarcoma. (Benign hepatic lesions which demonstrate hypervascularity include focal nodular hyperplasia and hepatocellular adenoma.) Because of altered portal venous flow in cirrhotic livers, non-contrast scanning has been recommended in presence of cirrhosis (5, 6). Preliminary non-contrast scanning has also been advocated in cases of blunt abdominal trauma (7). However, the inclusion of non-enhanced scans through the liver in the routine protocol for abdominal CTs remains a common practice. We examined the utility of this practice over a 3’/,-year period and reviewed the recent literature on non-enhanced CT of the liver. METHODS AND MATERIALS 1109 consecutive abdominal CT examinations performed over a Y/,-year period were retrospectively reviewed. In 109 cases IV contrast medium was not
administered because of a history of renal failure, allergy, or patient refusal of IV contrast. In 148 cases exams were performed only post-IV contrast at the
0899-7071/97/$17.00 PII SO899-7071(96)00083-6
SEPTEMBER/OCTOBER
1997
PRE-CONTRAST CT FOR LIVER LESION DETECTION
TABLE 1. Indications for Abdominal CT Examinations Symptoms/clinical
concern
Upper GI malignancy Rule out abscess Rule out metastatic disease Rule out liver mass Rule out pancreatic mass Rule out renal mass Pain/Weight loss Rule out abdominal mass Rule out retroperitoneal bleed Rule out bowel obstruction Lymphoma Adrenal mass Gynecological malignancy Trauma Total
No. of cases 274 263 149 103
82 81
76 24 16
14 9 8
6 4 1109
347
103 cases both pre-and post-contrast images demonstrated hepatic abnormalities with more abnormalities evident post-contrast, (In four of these 80 cases chemoembolic material was detected in the liver only on pre-contrast studies.) In nine cases liver lesions were detected only post-contrast, the pre-contrast images demonstrating no hepatic abnormality. In 10 of the 103 cases an equal number of hepatic lesions was seen on both pre- and post-contrast images. Tiny liver calcifications were detected only on pre-contrast images in three cases. In one case, where scanner error occurred causing a delay in post-contrast imaging, both pre- and post-contrast images demonstrated hepatic abnormalities, but more lesions were seen on the pre-contrast images.
DISCUSSION radiologist’s request. In the remaining 852 cases the CT examination consisted of lo-mm axial scans at ZO-mm increments through the liver before IV contrast consisted of IO-mm axial scans at IO-mm increments through the entire abdomen with IV contrast enhancement. These 852 cases were included in this study. All CT examinations were performed on a conventional Philips Tomoscan SR 6000 (Philips Medical Systems, Shelton, CT). Post-contrast imaging was initiated 45 seconds after the start of injection of 140 ml of ionic 30% organically bound iodine, iopamido1 (Isovue 300, Squibb Diagnostics, Princeton, NJ). Contrast material was administered at a rate of 2 ml/ set with an automated power injector (Medrad, Pittsburgh, PA). In all cases the scans were photographed using both abdominal (width = 450 HU) and unenhanced liver (width := 150 HU) window settings. Interpretation of the CT examinations with respect to detection of hepatic abnormalities was performed independently by two radiologists (N.A.Y. and M.S.T.) experienced in cross-sectional imaging. Pre-contrast images were interpreted before post-contrast images in half of the cases, and images were interpreted in the opposite order in the other half. Differences in opinion were resolved by consensus. The indications for the abdominal CT examinations are listed in Table 1.
RESULTS In 852 cases both pre- and post-IV contrast scans were available for interpretation. These cases were reviewed with respect to abnormalities involving the liver. In 749 cases the liver appeared normal on both pre- and post-contrast images, whereas a hepatic abnormality was identified in 103 cases. In 80 of these
Institutions differ in their protocols for CT examinations of the abdomen. Although not routinely employed in most academic institutions, the inclusion of routine preliminary non-contrast CT through the liver in standard protocols in prevalent in private practice. There are several possible reasons for this. There may be a continued perception in the community that the risk is high of missing a hypervascular primary or metastatic lesion in the liver. The routine pre-contrast liver scan may be employed in some institutions because of a lack of relevant clinical information afforded the radiologist at the time of scanning. Another issue is the additional reimbursement for the pre-contrast portion of the study. The noncontrast portion of the abdominal CT examination at our institution is roughly equal in cost to the contrast-enhanced portion, excluding the cost of the IV contrast medium. We evaluated this protocol over a 3l/,-year period and found that the pre-contrast portion of the exam was of little utility in our patient population. In only one case, in which scanner error resulted in a delay in post-contrast imaging, were more metastatic lesions identified pre-contrast than post-contrast. In no cases would the presence of metastatic disease, primary liver disease, or post-traumatic liver lesions have been missed by eliminating the pre-contrast portion of the study. In the 1980s it became apparent that hypervascular metastases could become less evident or isodense with normal parenchyma after IV contrast enhancement (8). Hypervascular lesions are hyperdense relative to liver during maximal hepatic arterial opacification, which occurs in the first 20 to 30 seconds of contrast injection. Limitations of conventional CT scanners result in the acquisition of images during the phase of portal venous enhancement, at which time
348
YASSA
ET AL.
CLINICAL IMAGING VOL. 21, NO. 5
1. Pre-contrast image of liver (A) demonstrates small calcification in the left lobe (arrow) which was not detected on the contrast-enhanced scan (B).
FIGURE
there is maximal enhancement of normal liver parenchyma, which is predominantly supplied by the portal venous circulation. As enhancement within a given hypervascular lesion declines, it eventually becomes equal to the enhancement within normal parenchyma. Metastases demonstrate variable rates of enhancement, however, even within one patient. Patten et al. (9) found that although some lesions may become isodense on post-contrast scans, rarely would the presence of metastatic disease be missed altogether on post-contrast images. In 1987 Bressler et al. (1)recommended preliminary non-contrast CT in patients with suspected hypervascular hepatic metastases. This was a retrospective study of 28 patients with hypervascular hepatic metastases, 27 of whom had endocrine tumors of the pancreas or adrenal gland or carcinoid. In 1990 DuBrow et al. (2) studied 88 patients with hepatic metastases from breast cancer and recommended that both non-enhanced and enhanced scans be performed in screening these patients. They found that without the pre-contrast images the presence of metastatic disease would have been missed in one case, and two more cases would have required additional work-up to confirm the presence of metastases. In all three cases the pre-contrast images demonstrated so many lesions that the presence of metastases was not in question. Chomyn et al. (10) in 1992 studied 55 patients with hypervascular metastases from malignant melanoma and concluded that non-enhanced scans were not useful, finding no additional lesions on pre-contrast images. In the 1993 study by Patten et al. (9)101 cases of hypervascular primary hepatic
malignancy or suspected hypervascular hepatic metastases were prospectively studied. In this study, out of 34 patients with hypervascular liver lesions, the presence of hepatic disease would have been missed in only one case without the addition of the non-contrast study, and it was concluded that routine non-enhanced CT even for hypervascular hepatic neoplasms was not necessary. However, as pointed out by Bressler et al. in a subsequent letter (3), few of the patients in the Patten study had primary endocrine tumors. Interestingly, as pointed out by Tomiak et al. (ll), the biphasic contrast CT technique, in which helical scanning is performed both during the earlier hepatic arterial phase and then during the portal venous phase, may obviate the use of pre-contrast scanning for hypervascular metastases. With this new technique hypervascular liver lesions are imaged while they are maximally evident during the hepatic arterial phase. Further studies need to be performed to compare the efficacy of non-contrast CT and arterial phase contrast-enhanced CT in the detection of such lesions. One must also be aware of the possible false positive results with arterial phase scanning due to the phenomenon termed “transient hepatic attenuation differences” (THAD), due to foci of normal liver parenchyma which receive predominantly hepatic arterial supply (5, 12). In our study there was no case in which the presence of significant hepatic lesions would have been missed without the addition of the non-contrast portion of the study. Although tiny liver calcifications were obscured on post-contrast scanning, these were
SEPTEMBER/OCTOBER1997
PRE-CONTRASTCT FOR LIVER LESION DETECTION
349
FIGURE 2. Pre-contrast image (A) better depicts size of hypervascular lesion in left lobe of liver. although lesion is clearly evident post-contrast as well (B). generally felt to be of little clinical significance, as they likely represented old granulomatous disease (Figure 1). Chemoembolic material was also obscured on post-contrast scanning. In these cases non-contrast exams are more useful clinically in excluding the presence of chemoembolic material in the stomach and proximal small bowel than in identifying the chemoembolic material in the liver. In our post-traumatic cases the pre-contrast images were of no additional benefit. In several cases in our series the detection of greater numbers of lesions post-contrast than precontrast could be attributed to the use of the smaller lo-mm scanning increments used post-contrast. A fair comparison of CT with and without IV contrast would involve comparison of scans of equal thickness at equal intervals. This study, however, was a retrospective analysis of the protocol employed in this institution, and our protocol is not unique. Many private practices routinely obtain pre-contrast scans through the liver at wider intervals than the post-contrast scans. See Figure 2. In summary, performing unenhanced scans through the liver in every abdominal CT prior to scanning with IV contrast enhancement increases exam time and technician time, nearly doubles the cost to the patient, and exposes the patient to additional radiation. The routine inclusion of this pre-contrast portion of the CT was of no significant benefit in our study of 852 cases. The utility of non-contrast CT in the detection of hypervascular liver lesions remains controversial, Abdominal CT should be tailored to answer the specific clinical problem. This requires
more involvement from the radiologist and effective communication with the referring physician,
REFERENCES 1. Bressler EL, Alpern MB, Blazer GM, Francis IR, Ensminger WD. Hypervascular hepatic ology 1987;162:49-51.
metastases:
CT evaluation.
Radi-
2. DuBrow RA, David CL, Libshitz HI, Lorigan JG. Detection of hepatic metastases in breast cancer: the role of nonenhanced and enhanced CT scanning. J Comput Assist Tomogr 1990: 14(3):366-369. 3. Bressler EL, Alpern MB. Hypervascular hepatic metastases: reevaluation of unenhanced CT scans. Letter, AJR 1995;164: 512-513. 4. White PG, Adams H. Smith PM. The computed tomographic appearances of angiosarcoma of the iiver. Clinical Radiology 1993;48:321-325. 5. Baron RL. Understanding and optimizing use of contrast terial for CT of the liver. AJR 1994;163:323-331. 6. Nelson RC, Small 163:988. 7. Kelly J, Raptopoulos value of non-contrast AJR 1989:152:41-46.
WC. Questions
and answers.
ma-
AJR 1994;
V. Davidoff A, Waite R. Norton P. The enhanced CT in blunt abdominal trauma.
8. Marchal GJ, Baert AL, Wilms GE. CT of noncystic sions: bolus enhancement. AJR 1980;135:57-65.
liver le-
9. Patten RM, Byun J, Freeny PC. CT of hypervascular hepatic tumors: are unenhanced scans necessary for diagnosis? AJR 1993:161:979-984. 10. Chomyn JJ, Stamm ER, Thickman D. CT of melanoma liver metastases: is the examination without contrast media superfluous? J Comput Assist Tomogr 1992;16:568-571. 11. Tomiak MM, Foley WD, Jacobson DR. Variable-mode CT: imaging protocols. AJR 1995;164:1525-1531.
helical
12. Itai Y, Hachiya K, Ohtomo K, Kokubo T, Yamauchi T. Transient hepatic attenuation differences on dynamic computed tomography. J Comput Assist Tomogr 1987:11:461-465.