LAUSR

comes the concern of radiation related cancer risk and the economic burden of multiple CT scans. Ultrasound (US) overestimates stone size and has lower sensitivity (w45%) in detecting ureteral stones. In our study, an initial diagnostic CT scan is used to create a map of the ureters. This map is then used on follow up Ultrasound-CT (US-CT) fusion, utilizing a 3d-coregistarion software. We examined whether patients with ureteral stones, diagnosed by CT, can be subsequently followed with US-CT Fusion technology. METHODS: In this prospective study, patients with a single ureteral stone detected on CT were invited for ureteroscopy. Upon admission, an US-CT fusion exam was performed (Logiq E9 ultrasound machine, GE healthcare). Fusion images, were evaluated by a senior radiologist. The radiologist was blinded to the ureteroscopy results. In case of a suspicion that the stone was spontaneously expelled, an additional abdominal plain film and/or NCCT were performed prior to the ureteroscopy. US-CT fusion results, were then compared to the ureteroscopy report. RESULTS: Thirty-one patients with a mean age of 52.2 15.1, and a BMI of 26.4 4.7 were included. Stone location: upper ureter in 16 cases (51%) and lower ureter in 15 cases (49%). Mean stone size on CT: 6.9 2.1 mm. The mean time from the US-CT fusion exam until the ureteroscopy was 1.8 4.5 days. The exam had a total sensitivity and specificity of 72.7% and 100% (respectively) for detecting a stone in the entire ureter, with accuracy of 80.6% (Table1). For the upper ureter, the exam had a sensitivity and specificity of 66.6% and 100% (respectively), with accuracy of 75%. CONCLUSIONS: Our preliminary study demonstrates that using US-CT fusion scan can help in the detection of ureteral stones. This is a first attempt to follow ureterolithiasis with US fusion technology. US-CT fusion technology might reduce the need of an additional CT scan in case a stone is identified. However it cannot rule out a stone when one is not detected. In the latter case an additional CT is required. We believe the exam offers a safe alternative that can reduce radiation exposure for stone formers. Additional research is needed to establish this technology as an alternative to CT.