Matteo Bonatti MD, Presenter: Nothing to Disclose

Federica Ferro, Abstract Co-Author: Nothing to Disclose

Patrizia Perner, Abstract Co-Author: Nothing to Disclose

Armin Pycha, Abstract Co-Author: Nothing to Disclose

Giampietro Bonatti, Abstract Co-Author: Nothing to Disclose

To compare in vivo accuracy of 100/140 kV dual-energy CT with 120 kV single energy CT in determining renal stone composition by means of an automated software.

Retrospective study (Jan 2013-Dec 2013) approved by our Institutional Review Board; informed consent was obtained. We included in our study 30 consecutive patients who underwent a CT on our second-generation dual-source scanner according to a “renal stone protocol”, which included a 120 kV single-energy acquisition of the whole abdomen followed by a 100/140 kV dual-energy acquisition of to the region(s) where one or more stones were identified, with subsequent renal stone surgical extraction or spontaneous expulsion within 1 month and stone examination by means of infrared spectroscopy. Stone largest diameter, estimated volume, attenuation values at 100, 120 and 140 kV, and 100/140 kV attenuation ratios were calculated by means of an automated software (Syngo.via, “CT Dual Energy - Kidney Stones” application). At CT, renal stones were classified as follows: uric acid (attenuation at 120 kV 1064HU; >1.24).

50 stones were detected in 30 patients. At laboratory, 17/50 (34%) of the stones were prevalently composed by uric acid, 4/50 (8%) by cystine and 29/50 (58%) of calcium oxalates and phosphates. Stones showed a median diameter of 4.8mm (range 1.0-24.1mm) and a median volume of 35.7mm3 (1.9-1390.0mm3). 120kV single-energy CT correctly assessed stone composition in 26/50 (52%) of the cases, whereas dual-energy CT in 45/50 (90%) of them (p<0.05); results were concordant between the two methods in 26/50 (52%) of the cases. Single-energy CT correctly differentiated uric acid vs. non-uric acid stones in 40/50 (80%) of the cases, whereas dual-energy CT in 48/50 (96%) of them (p<0.05); in both the 2 wrongly assessed cases at dual-energy CT the stone was located in the ureter and a ureteral catheter was on site.

Dual-energy CT performs significantly better then single-energy CT in renal stone composition determination and reliably discriminates between uric acid and non-uric acid stones. Ureteral catheters may reduce dual-energy CT accuracy in ureteral stones composition determination.

Automated dual-energy CT renal stone evaluation reliably determines renal stone composition in vivo and, therefore, represents an useful tool for therapeutic planning.

Bonatti, M, Ferro, F, Perner, P, Pycha, A, Bonatti, G, Renal Stone Composition in Vivo Determination: Comparison between 100/140 kV Dual-energy CT and 120 kV Single-energy CT.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012563.html