TC DOUBLE SOURCE DUAL ENERGY PRE SWL: PREDICTION OF STONE COMPOSITION AND TREATMENT RESULTS

Aim of the study The composition and density of urinary stones determine the treatment choice ( SWL, URS, RIRS, PCNL) and influence treatment results. Thereafter preoperative knowledge of these two parameters is considered usefull. TCDS (SOMATOM Definition Dual Source Siemens) is a multislice computerized tomography with 2 x-ray sources using two different voltages (140 Kv and 80 Kv respectively) and 2 detectors laid at 90° angle . The system works as a traditional CT : is able to epitomize the stone in terms of chemical composition through the application of a dedicated software ( Leonardo DE Kidney Stone) and to indicate stone density in Hounsfield units. We investigate how these two parameters influence SWL success rate in a subset of calcium oxalate stones Material and Methods In February through July 2008 40 patients underwent TCDS dual energy: out of them 28 patients were diagnosed by TCDS to be affected by calcium oxalate stones ( renal stones 23 pts., ureteral stones 5 pts). . The Hounsfield density was < 500 HU (1pt.), between 500 and 1000 HU (17 pts) and > 1000 HU (10 pts). All the patients underwent SWL (HMT Lithotron LSH 171). The fragments passed were analyzed FT-IR Nicolet IS10 ThermoFisher. We considered the treatment successful if the patient was at three months follow-up stone free or with fragments < 4mm. Results SWL success rate was 100% and 88,2% in treating stones below 500 HU and between 500 and 1000 HU respectively, while it proved to be uneffective in patients with calcium oxalate stones above 1000 HU (10% success rate). Statistical analisys with the χ2 test showed a correlation between calcium oxalate stones, whose composition was identified by TCDS, stone density in HU and stone free rate (p<0.001). Conclusions. Dual Energy TCDS allows for a more accurate evaluation of urolithiasis than traditional multislice CT scan with respect to chemical composition and HU density. These parameters showed a significant impact for treatment efficacy in our test subjects. High density calcium oxalate stones in have a dense structure as a possible result of the presence of monohydrate calcium oxalate. The definition of chemical composition and density in urinary stones supplies usefull parameters that are able to predict SWL results. High HU density calcium oxalate lithiasis showed an extreme , indipendent from stone size, resistance to ESWL in our study