CT of the pancreas: Comparison of anatomic structure depiction, image quality, and radiation exposure between 320-detector volumetric images and 64-detector helical images

Abstract

Purpose: To prospectively compare 320-detector volumetric and 64-detector helical computed tomographic (CT) images of the pancreas for depiction of anatomic structures, image noise, and radiation exposure. Materials and Methods: This study was approved by the institutional review board, and written informed consent was obtained. A total of 154 patients (85 men, 69 women; age range, 26-85 years; mean age, 67 years) who underwent biphasic (arterial and pancreatic phase) contrast material - enhanced CT performed with a 320-detector scanner were randomized into two groups: the 320-detector group and the 64-detector group. Biphasic transaxial multiplanar reformatted images and volume-rendered CT angiograms were obtained. CT numbers in the abdominal aorta, pancreas, and abdominal wall fat tissue; signal-to-noise ratio (SNR); and dose-length product (DLP) were compared. In addition, image quality and focal lesion depiction(n = 35) were qualitatively determined in the two groups. Unpaired t and Mann-Whitney tests were used for quantitative and qualitative assessment, respectively. Results: No significant difference in CT numbers of the abdominal aorta and pancreas was noted between the two groups. Mean DLP was 43% lower in the 320-detector group (675.4 mGy•cm) than in the 64-detector group (1187.8 mGy•cm) (P < .001). SNR of the abdominal aorta, pancreas, and abdominal wall fat on biphasic images was significantly lower in the 320-detector group than in the 64-detector group (P < .001). Image quality was acceptable in both groups and was slightly better in the 64-detector group for pancreatic phase axial images (P = .02) and arterial phase multiplanar reformatted images (P < .01). No significant difference was found in the depiction of pancreatic parenchyma, main pancreatic duct, focal pancreatic lesions, splanchnic arteries, or most of the small splanchnic arterial branches. Conclusion: A 320-detector CT scan facilitates fast volumetric contrast-enhanced CT of the entire pancreas with acceptable image quality, even though SNR was significantly lower at 320-detector volumetric scanning. © RSNA, 2011.