Multidedektör bilgisayarlı tomografi ile in-vitro üriner sistem taş dansite ölçümleri doğruluğunun saptanması
Purpose: Non-contrast multidetector computed tomography (MDCT) is the most effective imaging modality to detect urinary stones. It was shown in our previus study that the chemical compositions of the urinary stones can be determined by non-contrast MDCT in an in-vitro setting according to the differences between the densities measured in Hounsfield Units (HU). On this prospective study, our aim was to determine the accuracy of non-contrast MDCT in determination of chemical compositions of urinary stones in an in-vitro setting. Materials and Methods: Sixty-two pieces urinary stones were extracted through ESWL or endoscopic surgery and evaluated with non-contrast MDCT (Volume Zoom, Siemens). The images were obtained at the enery level of 120 kV with 1 mm slice thickness as determined in our previous in-vitro study. All stones were analyzed for their chemical compositions with integrated analysis approach. The chemical compositions of the urinary stones were assessed on the basis of the differences in the densities measured in HU. The results were compared to the density intervals obtained in our previous in-vitro study. The ratio of accuracy of our current results were calculated. Findings: 52 were pure stones, 10 stones had two components each. The density results ranged for pure stones (HU); calcium oxalate monohydrate: 1097-3388 (n=46), calcium oxalate dihydrate:1261-2467 (n=3), uric acid: 852 (n=1). The density results ranged for the two components of mixed stones; calcium oxalate monohydrate: 530-3014 (n=9), calcium oxalate dihydrate: 292-526 (n=2), calcium phosphate: 1377-2140 (n=3), struvite: 1286 (n=1), uric acid: 86-824 (n=4). Ratio of accuracy of pure stones were %80,3 and mixed stones were %57,8, pure calcium oxalate monohydrate stones were %84,7, mixed calcium oxalate monohydrate stones were %77,7. 55 Conclusion: In calcium oxalate monohydrate stones, CT density value determination of the composition was highly accurate whereas in other types of stones it was lower. These other chemical components of stones had limited numbers which made it difficult to determine with CT density alone. To correlate the density measurements with the patients’ clinical and laboratory findings will help the clinician to determine of the stone composition and the treatment option. This preliminary study shows that with increase of stone types and numbers, CT density measurement can be quite valuable in determination of chemical compositions in an in-vitro setting.