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MDCT of the Liver and Hypervascular Hepatocellular Carcinomas: Optimizing Scan Delays for Bolus-Tracking Techniques of Hepatic Arterial and Portal Venous Phases

Satoshi Goshima1, Masayuki Kanematsu1, Hiroshi Kondo1, Ryujiro Yokoyama2, Toshiharu Miyoshi2, Hironori Nishibori1, Hiroki Kato1, Hiroaki Hoshi1, Minoru Onozuka3 and Noriyuki Moriyama4

1 Department of Radiology, Gifu University School of Medicine, 1-1 Yanagido, Gifu 501-1194, Japan.
2 Department of Radiology Services, Gifu University School of Medicine, Gifu, Japan.
3 Department of Physiology and Neuroscience, Kanagawa Dental College, Yokosuka, Japan.
4 Department of Diagnostic Radiology, National Cancer Center Hospital, Tokyo, Japan.


Figure 1
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  		Fig. 1 —Diagram illustrating timing scheme. Patients were prospectively randomized into three groups, and scans were initiated at 5, 20, and 45 seconds; 10, 25, and 50 seconds; and 15, 30, and 55 seconds for first (acquisition time, 4.3 seconds), second (acquisition time, 4.3 seconds), and third (acquisition time, 9.1 seconds) phases, respectively, after bolus-tracking program detected increase in CT value of 50 H in aorta just above level of diaphragmatic dome. First- and second-phase images were obtained during single breath-hold, followed by 20-second breathing interval before third-phase scan. Equilibrium phase scan commenced 160 seconds after bolus-tracking trigger.

 

Figure 2
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  		Fig. 2 —Graph showing scan delay after trigger-versus-mean CEI for aorta. Scan delay is amount of time after bolus-tracking program detected threshold enhancement of 50 H in aorta. Mean CEI of aorta in first phase showed peak at 10 seconds after trigger and then began to decrease constantly with time. Mean CEI of aorta was significantly higher at 10 seconds than at 15 seconds (p < 0.001) and higher at 20 seconds than at 25-30 seconds (p < 0.01), respectively. Note that x-axis is indicative not of time course (repeated measurement) but of three different subgroups with different imaging delays, comprising 57 patients each. Error bars = standard errors of means.

 

Figure 3
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  		Fig. 3 —Graph showing scan delay after trigger-versus-mean CEI for spleen, proximal portal veins, liver parenchyma, and hepatic veins. Mean CEI of spleen showed peak at 20 seconds. Mean CEI of spleen was significantly higher at 10-15 seconds than at 5 seconds (p < 0.001) and higher at 20 seconds than at 30 seconds (p < 0.005). Mean CEI of proximal portal veins increased constantly from 5 to 25 seconds, and had peak at 25 seconds. Mean CEI of proximal portal veins was significantly higher at 15 seconds than at 5-10 seconds (p < 0.001) and higher at 25-30 seconds than at 20 seconds (p < 0.005). Mean CEI of liver parenchyma increased constantly from 5 to 30 seconds and then plateaued at 45-55 seconds. Mean CEI of hepatic veins peaked at 45 seconds. Note that x-axis is indicative not of time course (repeated measurement) but of three different subgroups with different imaging delays, comprising 57 patients each. Error bars = standard errors of means.

 

Figure 4
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  		Fig. 4 —Graph showing scan delay after trigger-versus-mean spleen-to-liver contrast curve. Spleen-to-liver contrast in first phase had peak at 10 to 20 seconds and began to reduce at 25 seconds. Mean spleen-to-liver contrast was higher at 10-15 seconds than at 5 seconds (p < 0.001). Note that x-axis is indicative not of time course (repeated measurement) but of three different subgroups with different imaging delays, comprising 57 patients each. Error bars = standard errors of means.

 

Figure 5
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  		Fig. 5 —Graph showing scan delay after trigger-versus-mean hepatocellular carcinoma-to-liver (HCC-to-liver) contrast and CEI of liver with chronic liver damage and HCCs. Mean HCC-to-liver contrast was high (39-44 H) at 10-15 seconds, gradually reduced, and then fell below zero at 45-55 seconds. But there was no significant difference in HCC-to-liver contrast. Mean CEI of liver parenchyma in patients with HCCs increased constantly from 5 to 30 seconds and then plateaued at 45-55 seconds. Note that x-axis is indicative not of time course (repeated measurement) but of three different subgroups with different imaging delays, comprising 57 patients each. Error bars = standard errors of means.

 

Figure 6
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  		Fig. 6A —Graph showing results of prospective qualitative image review. Mean degree of proper hepatic arterial enhancement was constantly high at 5-15 seconds and was higher at 20 seconds than at 25-30 seconds (p < 0.05). Mean degree of proximal portal venous enhancement increased constantly from 5-25 seconds and plateaued at 25-55 seconds. It was higher at 10-15 seconds than at 5 seconds (p < 0.001) and higher at 25-30 seconds than at 20 seconds (p < 0.01).

 

Figure 7
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  		Fig. 6B —Graph showing results of prospective qualitative image review. Mean degree of liver parenchyma increased constantly at 5-30 seconds and peaked at 45 seconds. It was higher at 15 seconds than at 5 seconds (p < 0.05) and higher at 30 seconds than at 20 seconds (p < 0.05). Mean degree of splenic enhancement moiré pattern was high at 5-15 seconds. Mean moiré degree was significantly higher at 20 seconds than at 30 seconds (p < 0.05). Note that x-axis is indicative not of time course (repeated measurement) but of three different subgroups with different imaging delays, comprising 57 patients each. Error bars = standard errors of means.

 

Figure 8
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  		Fig. 7 —Graph showing scan delay after trigger versus qualitative degree of tumor arterial enhancement, washout of hepatocellular carcinoma (HCC), and mean degree of liver with chronic liver damage and HCCs. Mean degree of tumor arterial enhancement was higher at 10-15 seconds than at 5 seconds (p < 0.01) and higher at 20 seconds than at 25-30 seconds (p < 0.01). Mean degree of tumor washout was high at 45-55 seconds, although difference was not significant. Mean degree of liver parenchyma in patients with HCCs constantly increased at images obtained with scan delay of 5-45 seconds and then plateaued. Note that x-axis is indicative not of time course (repeated measurement) but of three different subgroups with different imaging delays, comprising all of 30 patients. Error bars = standard errors of means.

 

Figure 9
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  		Fig. 8A —77-year-old woman with cirrhosis and hypervascular 20-mm-sized hepatocellular carcinoma (HCC) in right hepatic lobe. Amount of contrast material administered was 100 mL. Transverse image at level of right lower segment of liver with scan delay of 10 seconds after trigger showing dense contrast enhancement in abdominal aorta (asterisk), moderate enhancement in HCC (arrow), intense enhancement in spleen (arrowhead), and minimal enhancement in liver parenchyma. Note sufficient enhancement of HCC and preferable spleen-to-liver contrast difference, suggesting that this phase is optimal as hepatic artery phase for detecting hypervascular HCCs.

 

Figure 10
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  		Fig. 8B —77-year-old woman with cirrhosis and hypervascular 20-mm-sized hepatocellular carcinoma (HCC) in right hepatic lobe. Amount of contrast material administered was 100 mL. Transverse image at same level as A with scan delay of 50 seconds after trigger, which shows decreased contrast enhancement in abdominal aorta (asterisk) and spleen (arrowhead), and moderate washout in HCC (large arrow). Note that liver parenchymal enhancement is weak owing to extrahepatic portosystemic shunting (small arrows) caused by portal hypertension.

 

Figure 11
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  		Fig. 9 —69-year-old man with cirrhosis and hypervascular-sized hepatocellular carcinoma (HCC) 25 mm in right hepatic lobe. Amount of contrast material administered was 136 mL. Transverse image at level of porta hepatis with scan delay of 5 seconds after trigger shows dense contrast enhancement in abdominal aorta (asterisk) and proximal hepatic arterial branches (small arrows), moderate enhancement in spleen (arrowhead), mild enhancement of HCC (large arrow), and minimal enhancement in liver parenchyma and portal trunk (curved arrow). Note insufficient HCC and spleen enhancement, suggesting that timing is somewhat premature as hepatic arterial phase for detecting hypervascular HCCs, but that this phase is optimal for 3D CT angiography reconstruction.

 

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