Variation of Attenuation Value of Pancreas at Dual Phase MDCT: Comparison of the Bolus-tracking Technique vs. the Fixed Scan Delay Protocol

ABSTRACT

PURPOSE: To clarify the difference between the bolus-tracking technique and a fixed scan delay protocol in the achievement of the optimal pancreatic phase of the pancreas with MDCT. MATERIALS AND METHODS: 526 patients underwent pancreatic and portal venous phase imaging of the pancreas using 16-channel MDCT. All the examinations were randomized into either scanning using a bolus-tracking technique with a scan delay of 20s after the aorta was enhanced > 100 HU (groups 1 and 2) or scanning with a scan delay of 38 s from the beginning of the injection (groups 3 and 4). A contrast material of 300 mgI/mL (groups 1 and 3) or 370 mgI/mL (groups 2 and 4) at an injection speed of 3 mL/sec was injected at 2 mL/kg body weight. The pancreatic CT attenuation values were compared. RESULTS: The scan delay times of the pancreatic phase in groups 1 and 2 were 38+/-3.8s and 37.4+/-3.4s, respectively. At the pancreatic phase, the pancreatic attenuation values of groups 1 and 2 were slightly higher than those of groups 3 and 4 (115.5+/-15.4 vs 111.7+/-15.1HU; p=0.093, 128.3+/-17.1 vs 119+/-17.1HU; p=0.003). There was no significant difference between groups at the portal venous phase. CONCLUSION: The use of a bolus-tracking technique in the optimal pancreatic phase of pancreatic CT does not significantly improve the pancreatic enhancement but does at higher iodine concentrations.