Multidetector CT of pancreas: effects of contrast material flow rate and individualized scan delay on enhancement of pancreas and tumor contrast.

Abstract

To prospectively assess whether high contrast material flow rate (8 mL/sec) and individualized scan delay improve enhancement of normal pancreas with multidetector computed tomography (CT) and, as a result, tumor-to-pancreas contrast of pancreatic adenocarcinoma. Informed consent was obtained in 40 patients (21 women, 19 men; mean age, 67.1 years); the institutional review board approved this protocol. Patients were referred for multidetector CT because they were suspected of having a pancreatic tumor and were randomized to receive 150 mL of nonionic contrast material (300 mg of iodine per milliliter) at a flow rate of 4 mL/sec (n = 21) or 8 mL/sec (n = 19). Patients underwent dynamic scanning at one level every 2 seconds for 66 seconds after intravenous administration of contrast material. Contrast enhancement of pancreas and tumors was measured with circular regions of interest (analysis of variance and Bonferroni-Holm corrected post hoc t tests). Peak contrast enhancement in pancreas was observed significantly earlier (mean +/- standard deviation, 28.7 seconds +/- 3.5 vs 48.2 seconds +/- 5.3; P < .05) and was significantly higher (129.0 HU +/- 25.7 vs 106.2 HU +/- 35.4, P < .05) with a flow rate of 8 mL/sec than with a flow rate of 4 mL/sec. Tumor-to-pancreas contrast greater than 40 HU lasted significantly longer with a flow rate of 8 mL/sec than with a flow rate of 4 mL/sec (26.4 seconds +/- 11.9 vs 8.6 seconds +/- 8.3, P < .05). With a flow rate of 8 mL/sec, an individualized scan delay of 19 seconds after aortic transit time revealed higher tumor-to-pancreas contrast than did a fixed scan delay, and tumor conspicuity was better. With 16-section CT, increased contrast material flow rate of 8 mL/sec and individualized scan delay were associated with improved pancreatic enhancement and tumor-to-pancreas contrast compared with flow rate of 4 mL/sec and fixed scan delay.