Detection of gallstone-related disease using dual-energy CT and effective atomic number analysis

Introduction: This audit aims to evaluate the utility of dual-energy computed tomography (DECT) in accurately identifying gallstone-related disease. Preferred imaging modalities such as ultrasound (US) and magnetic resonance cholangiopancreatography (MRCP) have high sensitivity for identifying cholesterol stones which are radiolucent on conventional CT, however, are limited by their availability. This audit seeks to assess whether the analysis of post-processed dual energy datasets may be able to provide more thorough analysis of the biliary system and enhance gallstone visibility. Methods: Retrospective audit series of dual energy contrast-enhanced CT abdomen examinations performed for acute abdominal pain at our hospital over 6 months. All CT studies were evaluated by two Radiology registrars for the presence of gallstone-related disease using conventional DECT and post processing material decomposition images. This was correlated with complementary modalities (US, MRCP and ERCP), to assess their effect in improving radiolucent gallstone visualisation. Results: The final data set included 69 patients with gallstone related disease. Stone composition analysis identified 36 patients with poorly seen gallstone-related disease on DECT before post-processing; which included 28 patients with predominantly cholesterol-containing stones, 6 patients with sludge, and 2 patients with pigmented stones. Post-processing increased conspicuity in 50% of the examined patients (n=18). Conclusion: DECT is underutilised at many Australian hospitals, including our own. Our findings demonstrate that post-processed DECT atomic number maps have the potential to enhance conspicuity of cholesterol gallstones in a subset of patients.