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

Goshima, Satoshi; Kanematsu, Masayuki; Nishibori, Hironori; Sakurai, Kota; Miyazawa, Daisuke; Watanabe, Haruo; Kondo, Hiroshi; Shiratori, Yoshimune; Onozuka, Minoru; Moriyama, Noriyuki; Bae, Kyongtae T

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.