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Multiphase Hepatic CT with a Multirow Detector CT Scanner

¹ Department of Radiology, Medical College of Wisconsin, Froedtert Memorial Lutheran Hospital, 9200 W. Wisconsin Ave., Milwaukee, WI 53226.
² Diagnostic Imaging Associates, Mercy Hospital, 400 University Ave., Des Moines, IA 50314.

View larger version (11K): [in a new window]   Fig. 1. —Graph shows abdominal aortic time—attenuation curve after mini bolus injection of 60% iodinated contrast material at a rate of 5 mL/sec for 4 sec. Injection-to-scan delay is 10 sec. Interscan delay is 2 sec. Zero on time axis corresponds to acquisition time for first contrast-enhanced CT scan obtained after mini bolus administration and is 10 sec postinjection. Injection-to-scan delay for triple-phase study is represented by time interval between beginning of injection and recording of aortic peak. In this 52-year-old man without cirrhosis, injection-to-scan delay was 17 sec.

View larger version (8K): [in a new window]   Fig. 2. —Schematic outline shows injection and acquisition intervals for triple-pass hepatic helical CT techniques used in this study. Injection (black bar) of 60% iodinated contrast material was performed at rate of 5 mL/sec for 30 sec (total volume, 150 mL; iodine load, 42 g). First-pass acquisition (white bar with horizontal lines) was performed using image thickness of 2.5 mm, table speed per rotation of 15 mm, and pitch of 6. Second-pass acquisition (white bar with vertical lines) was performed using image thickness of 5 mm, table speed per rotation of 15 mm, and pitch of 3. Third-pass acquisition (white bar with checkerboard pattern) was performed using image thickness of 5 mm, table speed per rotation of 22.5 mm, and pitch of 6. Pitch values relate to modified definition. In this schematic, injection-to-scan delay was 20 sec.

View larger version (172K): [in a new window]   Fig. 3. —40-year-old man with positive titers for hepatitis virus and normal findings on hepatic CT study. CT scan at level of hepatic hilum during second pass of triple-pass study shows region of interest (ROI) placements in aorta (2), portal vein (5), and hepatic parenchyma (1 = posterior right hepatic lobe, 3 = anterior right hepatic lobe, 4 = left hepatic lobe). ROI measurements in identical locations were obtained during first and third passes.

View larger version (147K): [in a new window]   Fig. 4A. —46-year-old woman with focal nodular hyperplasia. Region-of-interest measurements were obtained from tumor (1) and adjacent hepatic parenchyma (2) at identical anatomic locations during each of three imaging passes. Helical CT scan obtained during first pass shows moderate enhancement of tumor relative to background liver.

View larger version (135K): [in a new window]   Fig. 4B. —46-year-old woman with focal nodular hyperplasia. Region-of-interest measurements were obtained from tumor (1) and adjacent hepatic parenchyma (2) at identical anatomic locations during each of three imaging passes. Helical CT scan obtained at same level as A during second pass shows marked tumor enhancement.

View larger version (117K): [in a new window]   Fig. 4C. —46-year-old woman with focal nodular hyperplasia. Region-of-interest measurements were obtained from tumor (1) and adjacent hepatic parenchyma (2) at identical anatomic locations during each of three imaging passes. Helical CT scan obtained during third pass shows isoattenuation of tumor with background hepatic parenchyma. Note displacement of adjacent right and middle hepatic veins.

View larger version (14K): [in a new window]   Fig. 5A. —Time—attenuation curves of aorta (), portal vein (), and hepatic parenchyma () at midpoints of first, second, and third imaging passes in both patient groups. Zero on time scale corresponds to beginning of first-pass acquisition, which was determined separately in each patient as time from beginning of injection to aortic peak on mini bolus study. Noncirrhotic patients.

View larger version (16K): [in a new window]   Fig. 5B. —Time—attenuation curves of aorta (), portal vein (), and hepatic parenchyma () at midpoints of first, second, and third imaging passes in both patient groups. Zero on time scale corresponds to beginning of first-pass acquisition, which was determined separately in each patient as time from beginning of injection to aortic peak on mini bolus study. Cirrhotic patients.

View larger version (150K): [in a new window]   Fig. 6A. —Representative helical CT scans at midpoints of each of three imaging passes in 40-year-old noncirrhotic man with positive titers for hepatitis virus (same patient as in Figure 3). First-pass acquisition shows isolated enhancement of hepatic artery at hepatic hilum.

View larger version (156K): [in a new window]   Fig. 6B. —Representative helical CT scans at midpoints of each of three imaging passes in 40-year-old noncirrhotic man with positive titers for hepatitis virus (same patient as in Figure 3). Second-pass acquisition shows enhancement of both hepatic artery and portal vein at hepatic hilum.

View larger version (154K): [in a new window]   Fig. 6C. —Representative helical CT scans at midpoints of each of three imaging passes in 40-year-old noncirrhotic man with positive titers for hepatitis virus (same patient as in Figure 3). Third-pass acquisition shows enhancement of main portal vein and its branches in hepatic parenchyma and enhancement of hepatic veins (arrows) not identified on scan obtained during second imaging pass (B). Progressive increase in hepatic enhancement between first and third passes is seen.

View larger version (168K): [in a new window]   Fig. 7A. —Helical CT scans in 50-year-old man with advanced hepatic cirrhosis but no evidence of hepatocellular carcinoma. First-pass acquisition shows enhancement of hepatic artery (arrow) without enhancement of portal vein at hepatic hilum.

View larger version (148K): [in a new window]   Fig. 7B. —Helical CT scans in 50-year-old man with advanced hepatic cirrhosis but no evidence of hepatocellular carcinoma. Second-pass acquisition shows enhancement of hepatic artery (solid arrow) and portal vein (open arrow) at hepatic hilum.

View larger version (153K): [in a new window]   Fig. 7C. —Helical CT scans in 50-year-old man with advanced hepatic cirrhosis but no evidence of hepatocellular carcinoma. Third-pass acquisition shows persistent enhancement of portal vein (arrow) at hepatic hilum. Progressive increase in hepatic enhancement is noted between first and third passes. Hepatic enhancement is inhomogeneous, reflecting underlying cirrhosis.

View larger version (30K): [in a new window]   Fig. 8. —Bar graph shows average tumor-to-liver contrast during each of three imaging passes for both patients with cirrhosis (n = 16) (white bars) and patients without cirrhosis (n = 9) (black bars). For both patient groups, maximum tumor-to-liver contrast occurred during second pass—that is, during late arterial or portal venous inflow phase. Difference in tumor-to-liver contrast between second pass and first and third imaging passes was determined using Student's t test and was significant for both patient groups (cirrhotic patients, p < 0.001; noncirrhotic patients, p < 0.006).

View larger version (186K): [in a new window]   Fig. 9A. —44-year-old man with advanced hepatic cirrhosis and multifocal hepatocellular carcinoma. Triple-pass helical CT study was performed and images at level of largest hepatocellular carcinoma (diameter = 2 cm) are illustrated. Scan obtained during early arterial phase shows moderate tumor enhancement.

View larger version (188K): [in a new window]   Fig. 9B. —44-year-old man with advanced hepatic cirrhosis and multifocal hepatocellular carcinoma. Triple-pass helical CT study was performed and images at level of largest hepatocellular carcinoma (diameter = 2 cm) are illustrated. Scan obtained during late arterial or portal vein inflow phase shows marked tumor enhancement.

View larger version (177K): [in a new window]   Fig. 9C. —44-year-old man with advanced hepatic cirrhosis and multifocal hepatocellular carcinoma. Triple-pass helical CT study was performed and images at level of largest hepatocellular carcinoma (diameter = 2 cm) are illustrated. Scan obtained during hepatic venous phase shows decrease in liver-to-tumor contrast because of relative washout of contrast material from tumor and progressive enhancement of hepatic parenchyma. Marked ascites is noted on all images.

View larger version (159K): [in a new window]   Fig. 10A. —43-year-old man with metastatic pancreatic islet cell neoplasm. Helical CT scan obtained at midpoint of early arterial phase shows moderate rim enhancement of multifocal metastases. Primary pancreatic neoplasm (arrow) can be seen in pancreatic body.

View larger version (154K): [in a new window]   Fig. 10B. —43-year-old man with metastatic pancreatic islet cell neoplasm. Helical CT scan obtained at midpoint of late arterial or portal vein inflow phase shows marked peripheral rim enhancement of multifocal metastatic neoplasm. Note transient hepatic attenuation difference (solid arrows) adjacent to margin of several hepatic metastases. This difference is presumed to result from "sump" effect due to hypervascularity of metastatic neoplasms. Note primary pancreatic neoplasm (open arrow).

View larger version (163K): [in a new window]   Fig. 10C. —43-year-old man with metastatic pancreatic islet cell neoplasm. Helical CT scan obtained at midpoint of hepatic phase shows relative decline in tumor-to-liver contrast because of washout of contrast material from hypervascular neoplasm and progressive enhancement of hepatic parenchyma. Note primary pancreatic neoplasm (arrow).

View larger version (113K): [in a new window]   Fig. 11. —Hepatic and mesenteric CT arteriogram obtained from first pass of triple-pass acquisition in 35-year-old woman with hepatic cirrhosis. Anomalous left hepatic artery (arrow) can be seen arising from left gastric artery, and totally replaced right hepatic artery (REPL RHA) arising from superior mesenteric artery can also be seen. Isolated gastroduodenal artery (GDA) arises from celiac artery (CA). SA = splenic artery.

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