Applications Of Multidetector Row Helical CT In Liver Scans

Part 1 Multidetector row helical CT angiography of hepatic vessels PurposeTo optimize the scan time of the early arterial phase of hepatic CT scan for multidetector row helical CT angiography by comparing the traditional protocol and two automatic bolus tracking protocols through randomized, control and blind trial. To assess the relationship between hepatic vessels enhancement and the grade of CTA images.Materials and MethodsSixty-six patients were divided into three groups, and examined with multiphase enhanced abdominal CT scans (early hepatic arterial, late hepatic arterial and liver parenchyma phase). The delay time of the early arterial phase was determined by following three protocols: 20 seconds after the beginning of contrast agent injection, 3 seconds after triggering at a threshold of 100 HU and 6 seconds after triggering at a threshold of 75 HU measured in the aorta at 10cm below the dome of diaphragm after injection of contrast agent. The late arterial phase began at 5.5 seconds after the early arterial phase. The data of early and late arterial phase were reconstructed with maximum intensity projection (MIP) and volume rendering technique (VRT) to obtain the CT angiography (CTA) images of hepatic artery and portal vein, respectively. The CTA images were reviewed by two radiologists and recorded the degree of visualization of the intrahepatic branches of the hepatic artery and portal vein by A, B, C and D to describe the grade from excellent to poor. Quantitative evaluation of the delay time and the attenuation value of the abdominal aorta, portal vein and hepatic parenchyma were performed by another radiologist. ResultsIn hepatic artery CTA images there are 34 cases of grade A, 17 cases of grade B, 6 cases of grade C and 9 cases of grade D. In portal vein CTA images there are 60 cases of grade A and 6cases of grade B. No grade C and D was revealed.There was no statistically significant difference in the visual evaluation of CTA images of both hepatic artery and portal vein among three groups. The three groups confirm statistically significant differences in the delay time of early arterial phase (P=0.000). Both delay times determined by the two bolus tracking protocols are much longer than that of traditional protocol. The delay time of the early and late arterial phase for the best CTA image of hepatic artery and portal vein is 23.74±4.32s and 41.78±3.68s, respectively.The attenuation values of the aorta in the early arterial phase confirmed significant difference between the grade A and B of hepatic arterial CTA (P=0.009). The aorta-portal vein contrast (difference of attenuation value between aorta and portal vein) of grade A confirmed significant difference with other grades of hepatic CTA (P=0.002, 0.016 and 0.009) . The aorta-liver contrast of grade A was much higher than grade B (P=0.009). And there was no statistical difference among other grades.The attenuation value of portal vein in late arterial phase and the portal vein-liver contrast confirmed significant difference between grade A and B of portal vein CTA (P=0.000 and 0.007). Both values of grade A are much higher than grade B.ConclusionThe automatic bolus tracking protocols showed no significant advantage over the traditional protocol, and the latter is still a simple and useful method for CTA. The delay times for early and late arterial phase should be 20s-25s and 41s-43s, respectively. Both the grades of hepatic artery and portal vein CTA are markedly affected by enhancement of the vessels and the liver parenchyma. And the hepatic artery CTA is also affected by the enhancement of portal vein. Part 2 Perfusion study of primary hepatic tumors: use of multidetector row helical CT and liver perfusion softwarePurposeTo compare and assess computed tomography (CT) perfusion changes between hepatocellular carcinoma (HCC) and hypervascular benign hepatic tumor (HBHT) and between liver neoplasm and tumor-free hepatic parenchyma by using multidetector row helical CT (MDCT) and liver perfusion software. To evaluate the usefulness of the liver perfusion software and the importance of the liver perfusion scans.Materials and MethodsHepatic perfusion scans were performed in 59 patients with HCC (male, 53; female, 6; aged 34-70), and 33patients with HBHT (male, 16; female, 17; aged 29-70) that were proven pathologically or clinically. According to complicating with cirrhosis or not, patients with HCC were divided into two groups: 30 cases with and 29 cases without liver cirrhosis. The scans were performed with cine mode (1s per rotation) on a MDCT scanner. Dynamic scan started at 10 seconds after intravenous injection of nonionic contrast agent (0.5ml/kg, 300mgI/ml) at a flow rate of 4ml/s with a power injector. And data was acquired for 50 seconds. The dynamic data was analyzed by use of the liver perfusion software. Then the values of blood flow (BF), blood volume (BV), mean transit time (MTT), permeability surface area product (PS), hepatic arterial fraction (HAF) and time of arrival in the hepatic lesions and tumor-free liver parenchyma were calculated and analyzed. And the colored perfusion maps for each parameter were created.Results From the values calculated following results were obtained.The BF, BV and HAF of HCC lesions were higher than those of the tumor-free hepatic parenchyma no matter with or without liver cirrhosis (P=0.000), whereas the MTT of HCC lesions were shorter than the tumor-free hepatic parenchyma (P=0.000 and 0.012 for with and without cirrhosis). The BF, BV and HAF of HBHT lesions were also higher than those of the tumor-free hepatic parenchyma (P=0.001, 0.040 and 0.000). No significant difference was seen in other perfusion parameters between both kinds of lesions and tumor-free parenchyma.The MTT of HCC lesions were shorter than HBHT lesions (P=0.012 and 0.030 for with and without cirrhosis). The HAF of HCC lesions were higher than HBHT lesions (P=0.049 and 0.008 for with and without cirrhosis). The BF and HAF of the tumor-free hepatic cirrhosis parenchyma were higher than tumor-free hepatic parenchyma of HBHT (P=0.033 and 0.032).Totally the MTT of HCC lesions (both with and without cirrhosis) were shorter than that of HBHT lesions (P=0.006). The HAF of HCC lesions and tumor-free hepatic parenchyma were both higher than HBHT (P=0.007 and 0.016). Areas under the ROC curve drawn from lesion MTT, HAF and hepatic parenchyma HAF were 0.668, 0.578 and 0.628 (P=0.008, 0.005 and 0.040), respectively.ConclusionBy use of liver perfusion software, significant differences in hepatic perfusion parameters were noted, not only between hepatic tumor lesions and tumor-free hepatic parenchyma, but also between malignant and benign hepatic tumors.Hepatic perfusion CT scans has potential to differentiate between malignant and benign tumor.