Dual-energy Computed Tomography gemstone spectral imaging: new horizons in visualization and differentiation of kidney stones composition

Abstract

Background: Optimization of viewing tools and understanding the chemical composition of renal calculi become essential for choosing the best treatment strategy. In this study we aimed to assess the localization and chemical composition of renal stones using gemstone spectral imaging (GSI) color map mode on a single-source dual-energy computed tomography (CT). Material and methods: A total of 45 urinary stones with an unknown chemical composition were imaged with a dual-energy CT scanner using special scanning protocols with different combinations of tube voltage and conventional polychromatic imaging. The mean attenuation value (in Hounsfield units) of each stone was recorded on both low- and high-energy CT images for each protocol. The dual-energy CT ratio of the mean attenuation value of each stone was computed for each protocol. The difference between the CT numbers obtained was compared among the stone groups. Results: The obtained data enabled us to classify the urinary stones into 3 main groups: uric acid (n = 11), oxalate (n = 24) and phosphate (n = 10) stones. The estimated sensitivity and specificity of dual-energy CT for detecting uric acid stones was 98.0 and 99.2%, calcium stones – 95.1% and 97%; and mixed stones – 93.0% and 94.5% accordingly. Conclusions: Single-source dual-energy CT with GSI represents a perspective modality for evaluating the characteristics and chemical composition of urinary stones. The CT results were consistent with the spectral data, suggesting that spectral CT imaging techniques can be accurately used to improve the stone differentiation capability of dual-energy CT imaging.