Although state-of-the-art CT provides accurate sub millimeter details of the size and location of renal stones, current routine clinical image analysis does not differentiate stone composition. This is particularly important in the case of uric acid (UA) stones (∼10% of cases), since urinary alkalinization can be prescribed to dissolve UA stones. Therefore, simple and reliable differentiation of UA vs. non-UA stone composition could potentially allow patients with UA stones to avoid invasive interventional urinary procedures for stone removal or external shock wave lithotripsy. This chapter describes a novel Dual-Energy CT (DECT) technique for renal stone differentiation, which is based on the difference in X-ray attenuation properties at high and low kV between UA- and non-UA-containing stones. The technique has been implemented on modern Dual-Source CT scanners which allow simultaneous Dual-Energy acquisition with high spatial resolution and immediate postprocessing using commercial algorithm available on the system. Principles of DECT imaging, acquisition parameters and postprocessing details are discussed. Diagnostic evaluation of three clinical cases is provided together with a summary of the results of all known validation studies performed both in vitro and in vivo. The reported accuracy and sensitivity of the UA vs. non-UA differentiation using DECT varied from 88 to 100%. Further improvement is expected with the second generation of Dual-Source scanners due to increased spectral separation.
KeywordsUric Acid Calcium Oxalate Renal Stone Uric Acid Stone Stone Composition
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