Side-by-side evaluation of virtual non-contrast and post-contrast images improves detection of clinically significant urolithiasis on single-phase split bolus dual-energy CT urography

Objectives: Studies show insufficient sensitivity of virtual non-contrast (VNC) reconstructions for stone detection in dual-energy CT urography (DE-CTU). The aim of this study was to investigate if side-by-side-evaluation of both VNC and post-contrast images could increase the sensitivity of single-phase split bolus DE-CTU. Methods: Consecutive patients with haematuria who underwent split bolus DE-CTU on the same dual-source DE-CT scanner were retrospectively enrolled in the study. Intravenous furosemide and oral hydration were employed. Two readers, independently and then jointly in two separate sessions, recorded the location and the longest axial stone diameter on three randomised sets of images: separate VNC and post-contrast images, and side-by-side-reconstructions. True non-contrast (TNC) images served as the standard of reference. Results: A total of 83 urinary stones were detected on TNC images. Independent reader side-by-side-evaluation of VNC and post-contrast images yielded higher stone detection sensitivity (76 and 84%, respectively) compared to evaluation of only VNC (71 and 81%, respectively) or post-contrast images (64 and 80%, respectively). The sensitivity of joint reader evaluation of side-by-side-images reached almost 86% and was not significantly different from TNC images (p = 0.77). All stones larger than 3 mm were correctly detected by side-by-side-evaluation. Dose reduction of 55% could be achieved by omitting TNC scans. Conclusion: Side-by-side-VNC and post-contrast image evaluation enable detection of clinically significant urolithiasis on single-phase split bolus DE-CTU with significant dose reduction. Advances in knowledge: This study shows that single-phase DE-CTU is feasible if VNC imaging is simultaneously utilised with post-contrast images.

Additional Non-Contrast-Enhanced Computed Tomography (NCECT) of Abdomen to the Routine Magnetic Resonance Cholangiopancreatography (MRCP) Protocol, Increase the Accuracy of Common Bile Duct Stone Detection or Not

Objective: To compare the diagnostic accuracy of magnetic resonance cholangiopancreatography (MRCP) in addition to the non-contrast-enhanced computed tomography (NCECT), with MRCP alone, or NCECT alone for common bile duct (CBD) stone detection using endoscopic retrograde cholangiopancreatography (ERCP) as a gold standard. Materials and Methods: The medical records and image findings were retrospectively reviewed in all consecutive patients that underwent both MRCP and NCECT at Phramongkutklao Hospital between May 2012 and December 2015. The imaging data were reviewed using the consensus of two radiologists who were blind of the final diagnoses from ERCP. The accuracy of each modality in detecting CBD stone was reported as sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). The other associated findings were reported as the presence of gallstones aerobilia, pancreatic calcification, biliary stenting, intrahepatic duct (IHD) dilatation, and CBD dilatation using intermodality agreement and kappa statistics. Results: Two hundred forty-one patients underwent both MRCP and NCECT. The accuracy, sensitivity, specificity, PPV, and NPV of the combined modalities were 98%, 99%, 95%, 98%, and 95%, respectively, which was higher than MRCP alone but it did not reach a statistical significance (accuracy, sensitivity, specificity, PPV, and NPV of MRCP were 97%, 98%, 95%, 99%, and 91%, p=0.77 for accuracy). The other abnormalities found such as aerobilia, presence of gallstone, presence of IHD, and CBD dilatation were similar in both combined MRCP and NCECT as compared with MRCP alone. Conclusion: The accuracy of MRCP alone was good and acceptable for the detection of CBD stone. Adding NCECT to the routine MRCP did not result in a significantly higher accuracy. Thus, routinely adding the NCECT was no longer recommended to avoid unnecessary radiation exposure and increasing the cost of investigation. Keywords: Common bile duct stone, MRCP, NCECT, ERCP, Accuracy