Background: Dual-energy computed tomography (DECT) utilises the technique of simultaneous image acquisition of a body part at two different energy levels of the X-ray tubes. We used the DECT in this project to study its accuracy in non-invasive in vivo differentiation of uric acid (UA) calculi from non-UA calculi using the 3rd generation dual-source computed tomography (CT) scanner.
Materials and methods: The DECT ratios of the various stones were noted and compared with the postextraction analysis of stones for composition. Sixty stones from 53 patients were included in the study, and their DECT results were compared with the post-extraction analysis (by infrared spectroscopy as the standard comparative method).
Results: DECT was highly sensitive and specific in the diagnosis of various types of calculi based on their dual-energy ratio. It was found to be 100% sensitive and specific for differentiating UA stones from the non-UA stones. The DE ratio for the UA stones was found to be 0.98-1.13. Most of the stones belonged to non-UA category (85%), and only 15% were UA calculi. The sensitivity and specificity in differentiating a calcium oxalate from non-calcium oxalate calculus was 97.8% and 92.3%, respectively.
Conclusion: DECT using the 3rd generation CT scanners is highly sensitive in the determination of urinary calculi composition which will be very helpful to the treating surgeon in selecting the optimal modality of treatment as UA stones are amenable to medical therapy while most of the non-UA stones require surgical intervention.
Keywords: Tomography; uric acid; urolithiasis.