This study will evaluate the accuracy of Dual-energy CT (DECT) to characterise urinary tract stone composition on patients presenting to a UK hospital with renal colic. The study will also assess the additional radiation dose burden of DECT over standard protocol.
Data from 106 DECTs between October 2011 and October 2015 were retrospectively analysed. Patients were imaged using a Toshiba Aquilion ONE™ CT scanner. All patients received a low-dose non-contrast CT of the abdomen and pelvis prior to a stone-targeted DECT at 80 and 135 peak kilovoltages and 40mm field of view. Radiation dose output was evaluated using Dose Length Product (DLP). Nineteen stones were recovered and their composition analysed using Fourier transform infrared spectroscopy.
137 stones were characterised. Mean stone diameter was 8.8mm (range 3-48). There was an 18.7% increase in mean DLP for DECT over standard CT protocol (319.4 vs. 269.1 mGycm; p < .001). Infrared spectroscopy analysis of 19 recovered stones identified 15 as calcium, 2 as cystine and 2 as mixed composition. Dual-energy correctly predicted 11 of 14 calcium (78.6%), 2 of 2 mixed (100%), and 0 of 2 cystine stones (0%), resulting in a fair agreement (Cohen's κ = .374, p = .009).
DECT is able to determine the composition of urinary tract stones with fair accuracy. Its utility is offset by a small but significant supplementary radiation exposure.
DECT can provide urological surgeons with useful diagnostic stone material information prior to planning optimal management of stone disease.
The British journal of radiology. 2016 Sep 02 [Epub ahead of print]
Richard J Chaytor, Krishnamoorthy Rajbabu, Paul A Jones, Liam McKnight
1 Department of Urology, Morriston Hospital, Swansea, United Kingdom., 2 Department of Radiology, Morriston Hospital, Swansea, United Kingdom.