Can Dual Energy CT with Fast kV-Switching Determine Renal Stone Composition Accurately?

To determine whether a single source computed tomography (CT) system utilizing fast kV switching and low dose settings can characterize (diameter and chemical composition) renal stones accurately when compared infrared spectroscopy. The chemical composition of 15 renal stones was determined using Fourier transform infrared spectroscopy. The stones were inserted into a porcine kidney and placed within a water tank for CT scanning using both fast kV switching dual energy and standard protocols. Effective atomic number of each stone was measured using scanner software. Stone diameter measurements were repeated twice to determine intra-rater variation and compared to actual stone diameter as measured by micro CT. The chemical composition of three stones (one calcium phosphate and two carbonite apatite) could not be determined using the scanner software. The composition of 10/12 remaining stones was correctly identified using dual energy computed tomography (83% absolute agreement; k = 0.69). No statistical difference (p = 0.051) was noted in the mean stone diameter as measured by clinical CT and micro CT. Dual energy computed tomography using fast kV switching may potentially be developed as a low dose clinical tool for identifying and classifying renal stones in vivo supporting clinical decision-making.

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