Study Of Contrast Material Administration And Scan Protocols For Abdominal Multi-detector Row CT Contrast Enhancement Scan

Part I The optimal scan delay time for abdominal multi-etector row CT contrast enhancement with fixed injection durationPurpose: To determine the optimal scan delay time required for abdominal multi-detector row CT contrast enhancement with fixed injection duration. Materials and methods: Ninety patients were randomized into three groups to receive abdomen MDCT scan with Iopamidol 300(300mg I/mL) 1.7 mL/kg and a fixed 30s injection duration. All the patients were performed abdomen plain CT and contrast enhanced CT including hepatic arterial phase (HAP), hepatic parenchymal phase (HPP) and delayed phase. The HAP and HPP of protocol A, B and C were initiated at 30, 50 seconds; 35, 55 seconds; 40, 60 seconds respectively. The delayed phase of three groups was fixed with 180s. The CT values (Hu) of the aorta, portal vein, liver, pancreas and spleen of each phase were measured and analyzed.Results: In HAP, the enhancement of liver, pancreas, spleen and portal vein were increased with longer scan delay time. In HPP, liver enhancement of group C was better than group A, but there's no significant difference between other groups. The enhancement of the aorta, portal vein, liver, pancreas and spleen in delayed phase has no significant difference among three groups. The peak enhancement time of the aorta and liver was 35s and 60s in time–density curves (TDC).Conclusion: By analyzing the TDC, we concluded that the optimal scan delay time of HAP, HPP and delayed phase for fixed injection duration should be 40s,60s and 180s in abdominal MDCT scan.Part II Comparison of fixed contrast material injection duration with fixed scan delay time and fixed injection rate with bolus- racking technique for abdomen enhancement with multi-detector row CT.Purpose: To observe the impaction of two scan protocols, fixed injection duration with fixed scan delay time and fixed injection rate with bolus-tracking technique, for the abdomen enhancement with multi-detector row CT scan. Materials and methods: One hundred and nine patients were randomized into two groups to receive abdomen MDCT scan with Iopamidol 300(300mg I/mL) 1.7 mL/kg. All the patients were performed abdomen plain CT and contrast enhanced CT including hepatic arterial phase (HAP), hepatic parenchymal phase (HPP) and delayed phase. Protocol of group A was with fixed injection rate of 3.4mL/s, and the scan delay time of HAP was determined by bolus-tracking technique (threshold of 180Hu), and the HPP started 30s after HAP, the delayed phase was fixed with 180s. Protocol of group B was with fixed injection duration of 30s, and the scan delay time of HAP, HPP and delayed phase was 40s, 60s and 180s individually. The CT values (Hu) of the aorta, portal vein, liver, pancreas and spleen of each phase were measured and analyzed. Results: In HAP and HPP, the enhancement of portal vein, liver, pancreas and spleen of group B were significantly better than group A, but there's no significant difference in the aorta. The enhancement of the aorta in HAP and the enhancement of liver in HPP of patients<55kg in group A were significantly better than patients>65kg, but there was no significant difference between two categories in group B.Conclusion: The protocol of fixed injection duration with fixed scan time had significantly better enhancement than protocol of fixed injection rate with bolus-tracking technique mostly, while it also reduced the difference of enhancement amplitude caused by body weight. So the protocol of fixed injection duration with fixed scan time was the optional choice in abdominal MDCT scan.Part III Evaluation of the optimal dose of intravenous contrast material for abdominal multi-detector row CT scan with fixed injection duration.Purpose: To determine the optimal dose of intravenous contrast material for abdominal multi-detector row CT scan with the fixed injection duration on the basis of patient weight.Materials and methods: One hundred and sixty patients were randomized into four groups to receive Iopamidol 300(300mg I/mL) 1.5mL/kg, 1.7 mL/kg, 1.9 mL/kg or 2.1 mL/kg with the fixed duration of 23, 26, 29, 32 seconds respectively. All the patients were performed abdomen plain CT and contrast enhanced CT including hepatic arterial phase (HAP), hepatic parenchymal phase (HPP) and delayed phase. The HAP and HPP started at 10s and 20s after contrast material injection and delayed phase started at a fixed time of 180s. The CT numbers (Hu) of the aorta, portal vein, liver, pancreas and spleen of each phase were measured and analyzed.Results: In HAP, the enhancement of aorta of 1.7 mL/kg, 1.9 mL/kg and 2.1 mL/kg groups was significantly better than the 1.5 mL/kg group, but there's no significant difference among 1.7 mL/kg, 1.9 mL/kg or 2.1 mL/kg groups. The enhancement of pancreas increased with lager doses in HAP. In HPP, the enhancement of portal vein, liver and pancreas of 1.7 mL/kg, 1.9 mL/kg and 2.1 mL/kg groups was significantly better than the 1.5 mL/kg group, but there's no significant difference among 1.7 mL/kg, 1.9 mL/kg or 2.1 mL/kg groups. The enhancement of liver and pancreas of 1.7 mL/kg, 1.9 mL/kg and 2.1 mL/kg groups was significantly better than the 1.5 mL/kg group, while the enhancement of spleen increased with lager doses in delayed phase.Conclusion: The enhancement of aorta in HAP and the enhancement of portal vein, liver, pancreas in HPP of 1.7 mL/kg, 1.9 mL/kg and 2.1 mL/kg groups were significantly better than the 1.5 mL/kg group, but there's no significant difference among 1.7 mL/kg, 1.9 mL/kg or 2.1 mL/kg groups.We concluded that 1.7 mL/kg Iopamidol 300(300mg I/mL) is the optimal dose of intravenous contrast material for abdominal MDCT scan with fixed the injection duration.Part IV Detection of hepatocellular carcinoma with multi- detector row CT by using double-arterial phase enhanced scanning: Effect of iodine concentration of contrast material.Purpose: To evaluate the effect of iodine concentration of contrast material on detection of hepatocellular carcinoma (HCC) with multi-detector row CT by using double-arterial phase and portal venous phase enhanced scanning.Materials and methods: Ninety-five patients with HCC were examined by hepatic plain CT and contrast-enhanced CT including early arterial phase (EAP), late arterial phase (LAP) and hepatic parenchymal phase (HPP) scanning prospectively. Patients were randomized into two groups to receive Iopamidol 370 mg I/mL (48 patients) (1.5 mL/kg body weight) and 300 mg I/mL (47 patients) (1.85 mL/kg body weight) respectively with a fixed injection duration of 30 seconds. The images were interpreted by radiologists and the CT results were compared with the pathological results. The detection sensitivity for tumors of two size categories (?2 or >2 cm) and iodine concentration groups were calculated and analyzed.Results: A total of 259 lesions were detected with 87?2 cm in size and 172 >2 cm. For EAP and LAP, the sensitivity of Iopamidol 370 mg I/mL group was significantly higher than Iopamidol 300 mg I/mL group for tumors?2cm and all tumors. For HPP, there were no significant differences between groups.Conclusion: High iodine concentration contrast material could improve the detection of HCC for EAP and LAP, especially for tumor?2cm.