Purpose: The primary aim of this prospective pilot study was to determine if the administration of intravenous secretin prior to contrast-enhanced computed tomography (CT) improves pancreatic enhancement and pancreatic tumor conspicuity. The second aim was to determine the optimal timing for secretin administration prior to contrast-enhanced CT.
Methods: Local ethics committee approval was obtained. 35 patients (18 men, 17 women; mean age, 67.6 years; age range; 25 to 86 years) with known or suspected pancreatic malignancy or an abdominal malignancy underwent a helical CT of the pancreas. The pancreas was first localised on an unenhanced scan using 10mm sections. Following 120 ml of intravenous 300 mg/ml of non ionic contrast medium (CM), injected at a rate of 5 ml/s, images of the pancreas (3mm slice thickness) and liver (8mm slice thickness) were obtained at 40 and 70 seconds respectively. A second CT was obtained 1-5 days after the first one using the same CT and intravenous contrast medium injection parameters. However 100 IU of secretin was given as an intravenous bolus between 0 and 5 min prior to intravenous contrast medium administration. Each patient acted as their own control. The attenuation in Hounsfield Units (HU) was recorded on non-contrast, pancreatic phase and portal venous phases for both secretin and non-secretin CTs, in the pancreas and pancreatic tumors (where present). Tumor conspicuity was calculated (in the 19 patients with pancreatic adenocarcinomas) by subtracting pancreatic tumor attenuation from pancreatic attenuation. Statistical evaluation comparing pre and post secretin enhancement was performed using matched paired t-tests.
Results: A significant increase in pancreatic enhancement was observed when secretin was injected at 2 to 3 min before contrast material injection (the increase in pancreatic density following secretin at 2 min was 31.5+/-10 HU (29.2%) (p=.035); and at 3 min was 23.2+/-7.8 HU (22.7%) (p=.041). Pancreatic tumor conspicuity in the pancreatic phase was most marked when secretin was injected between 2 to 4 min before contrast medium, with 4 min showing a statistically significant increase in tumor conspicuity, 48.2+/-14.2 HU (p=.04).
Conclusion: Imaging in the pancreatic phase 2 to 4 min after administration of intravenous secretin leads to greater enhancement of the pancreas with greater tumor conspicuity, than imaging without secretin.