Diagnostic Utility of Reduced Radiation Dose Non-Contrast-Enhanced CT with Iterative Reconstruction for Screening in High-Risk Individuals with Pancreatic Cancer: An Anthropomorphic Phantom Study

Abstract

Background: Previous studies showed that the dilated main pancreatic duct (MPD) and pancreatic cysts were the important predictors of the subsequent development of pancreatic cancer. The purpose of this study was to reveal the utility of non-contrast reduced radiation dose CT with iterative reconstruction for screening in high risk pancreatic cancer individuals by assessing the dilated MPD and cysts by using abdominal phantoms. Materials and methods: Two phantoms with normal and abnormal pancreas with dilated MPD (5 mm) and cysts (5 mm, 10 mm and 15 mm) were constructed. Each phantom was scanned by ten images using following three protocols: 120 kVp and 120mA with filtered back projection (FBP) algorithm (120 kVp-FBP), 80 kVp and 168mA with FBP algorithm (80 kVp-FBP), and 80 kVp and 168mA with sinogram affirmed iterative reconstruction (SAFIRE) (80 kVp-SAFIRE). The image noise and contrast-to-noise ratio (CNR) of the 15mm cyst were assessed. The radiation dose was assessed with the volume CT dose index (CTDIvol). Two radiologists scored the image quality and conspicuity of the dilated MPD and cysts. Results: Mean image noise significantly decreased from 80 kVp-FBP images to 80 kVp-SAFIRE and 120 kVp-FBP images (p < 0.001). The CNR significantly increased from 80 kVp-FBP images to 120 kVp-FBP and 80 kVp-SAFIRE images (p < 0.05). Image quality was significantly lower in the 80 kVp-FBP images than in 120 kVp-FBP and 80 kVp- SAFIRE images in both readers (p < 0.05). The conspicuity point for the dilated MPD and three cysts was higher in 80 kVp-SAFIRE images than in 80 kVp-FBP and 120 kVp-FBP images. CTDIvol was reduced by 60 % at 80 kVp protocol. Conclusion: Non-contrast 80 kVp-SAFIRE CT protocol allowed for higher conspicuity of dilated MPD and cysts at a reduced radiation dose compared with 120 kVp-FBP protocols.