Evaluation of urinary stone composition and differentiation between urinary stones and phleboliths using single-source dual-energy computed tomography

The aim of this study was to investigate the utility of single-source dual-energy computed tomography (SS-DECT) composition analysis in characterizing different types of urinary stones and differentiating them from phleboliths. This study included 29 patients with urinary stones who were scheduled for surgery. All patients were scanned, first using single-energy computed tomography acquisition and then DECT acquisition on SS-DECT. Dual-energy data were archived to a Gemstone spectral imaging (GSI) viewer (GE Healthcare, Milwaukee, WI, USA). Hounsfield units (HU) and effective atomic numbers (Z^eff) were estimated using the GSI viewer. The results of dual-energy analysis were compared with the biochemical constitution of the stones. The chemical analysis determined that the stones included 32 calcium-based, 6 cystine and 1 struvite stone. Both HU and Z^eff values were helpful in differentiating calcium-based stones from cystine and struvite stones and phleboliths. The Z^eff values of phleboliths were significantly higher than those for struvite and cystine stones, whereas it was difficult to distinguish phleboliths from struvite and cystine stones using the HU values. Composition analysis using SS-DECT is helpful for distinguishing urinary stone types and discriminating phleboliths from urinary stones. Z^eff values may be more useful than HU values for differentiating urinary stones from phleboliths.