Quantitative Evaluation in Enhancement of Pancreas and Adjacent Vessels during Spiral CT

ABSTRACT

PURPOSE: To determine by quantitative evaluation of pancreatic and adjacent vascular enhancement during spiral CT, the ideal scan delay for examination of the pancreas. MATERIALS AND METHODS: Dual (n=90) and triple (n=90) phase spiral CT scans of patients whose pancreas showed no pathologic condition were retrospectively evaluated. Dual-phase scans were performed at 43 seconds (early), and 5-6 minutes (delayed) after the injection of 120ml of contrast material at an injection rate of 3ml/sec ; triple-phase scans were performed at 25 seconds (arterial), 60-65 seconds (portal) and 5-6 minutes (delayed) after the injection of 120-140ml of contrast material at an injection rate of 2-4ml/sec, and ten patients also underwent precontrast scanning. CT attenuation values (HU) were measured in the head, body and tail of the pancreas, aorta, and main portal vein during each phase of all scans. Triple-phase protocol was used to measure the effect of different total volumes and injection rates on enhancement of the pancreas and adjacent vessels. RESULTS: There was no significant difference in the degree of enhancement of the pancreas head, body and tail during each phase (p>0.05). The pancreas was maximally enhanced on 43 second delayed scan (132+/-20 HU)(p0.05). The main portal vein showed maximum enhancement on 43-second delayed scan (207+/-44 HU)(p<0.05). Different total volume of contrast material did not change the enhancement of the pancreas and adjacent vessels. At an injection rate of 2ml/sec, peak enhancement of the pancreas, aorta and portal vein was obtained on 60-65 second delayed scan, and at 4ml/sec, peak enhancement was obtained on 25 second delayed scan(p<0.05). CONCLUSION: Observing the usual protocols for abdominal spiral CT scanning, the pancreas was most effectively evaluated using a 43-second delayed scan. An increased injection rate resulted in earlier enhancement of the pancreas, aorta and portal vein.