Feasibility of discriminating uric acid from non-uric acid renal stones using consecutive spatially registered low- and high-energy scans obtained on a conventional CT scanner

• Published in: American journal of roentgenology (1976) Vol. 204; no. 1; pp. 92 - 97
• Main Authors: Leng, Shuai, Shiung, Maria, Ai, Songtao, Qu, Mingliang, Vrtiska, Terri J, Grant, Katharine L, Krauss, Bernhard, Schmidt, Bernhard, Lieske, John C, McCollough, Cynthia H
• Format: Journal Article
• Language: English
• Published: United States 01.01.2015
• Subjects: Adult; Aged; Aged, 80 and over; Diagnosis, Differential; Feasibility Studies; Humans; Image Enhancement - methods; Imaging, Three-Dimensional - methods; Kidney Calculi - chemistry; Kidney Calculi - diagnostic imaging; Middle Aged; Radiation Dosage; Radiography, Dual-Energy Scanned Projection - methods; Reproducibility of Results; Sensitivity and Specificity; Subtraction Technique; Tomography, X-Ray Computed - methods; Uric Acid - chemistry; Young Adult; CT; dual-energy CT; renal stone; stone composition; deformable registration
• ISSN: 0361-803X; 1546-3141
• DOI: 10.2214/AJR.13.11911

The objective of our study was to show the feasibility of distinguishing between uric acid (UA) and non-UA renal stones using two consecutive spatially registered low- and high-energy scans acquired on a conventional CT system. A total of 33 patients undergoing clinically indicated dual-source dual-energy CT examinations to differentiate UA from non-UA renal stones were enrolled in this study. Immediately after patients underwent clinically indicated dual-source dual-energy CT, two consecutive scans (one at 80 kV and one at 140 kV) were obtained on a conventional CT scanner over the region limited to the stones identified on the dual-source scans. After 3D deformable registration of the 80- and 140-kV images, UA and non-UA stones were identified using commercial software. The sensitivity, specificity, and accuracy of stone classification were calculated using the dual-source results as the reference standard. A total of 469 stones were identified in the dual-source examinations (26 UA and 443 non-UA stones). The average in-plane stone diameter was 4.4 ± 2.5 (SD) mm (range, 2.0-18.9 mm). The overall sensitivity, specificity, and accuracy for identifying UA stones were 73.1%, 90.1%, and 89.1%, respectively. The sensitivity, specificity, and accuracy were 94.7%, 96.9%, and 96.8% for stones 3 mm or larger (n = 341 [19 UA and 322 non-UA]). Accurate differentiation of UA from non-UA renal stones is feasible using two consecutively acquired and spatially registered conventional CT scans.