Presentation Authors: Brenton Winship*, Justin Raudabaugh, Giao Nguyen, Evan Carlos, Terry Yoshizumi, Michael Ferrandino, Glenn Preminger, Michael Lipkin, Durham, NC
Introduction: Follow-up imaging to confirm passage of distal ureteral stones represents a dilemma in the outpatient setting. We have previously published on the substantial radiation reduction, cost savings and clinical usefulness of abdominal digital tomosynthesis in the evaluation of renal and proximal ureteral stones relative to stone protocol non-contrast computed tomography (NCCT). The aim of this study is to report on our early clinical experience using pelvic digital tomosynthesis for the evaluation of distal ureteral stones as well as to describe the effective dose (ED) and organ specific doses (ODs) for this technique compared to NCCT.
Methods: A validated anthropomorphic phantom was placed supine on a digital GE Definium 8000 radiological scanner. A 0.18cc ion chamber was placed on the phantom surface in the center of the imaged field to measure skin entrance exposure during 6 pelvic DTs. Using these data, PCXMC 2.0 software was used to calculate ODs by Monte Carlo simulation and ED using International Commission on Radiological Protection publication 103. Prior work at this institution used a similar phantom to determine the ODs and ED for renal stone protocol NCCT. We have recently used Pelvic DT in our ambulatory clinic to evaluate patients with suspected distal ureteral stones or suggestive symptoms.
Results: The ED for NCCT is significantly higher than pelvic DT (3.04 +/- 0.34mSv vs. 1.23+/- 0.65mSv, p=0.013). Mean ODs for pelvic DT are substantially lower compared with NCCT, especially to the testes (0.29 +/- 0.41mGy vs. 5.17 +/- 3.73mGy, respectively). Clinically, 14 patients had a distal ureteral stone identified on pelvic DT. Stone identification was confirmed in all by ureteroscopic visualization or CT. In 4 of these patients, the stone was not visible on plain KUB.
Conclusions: In our limited clinical experience, pelvic DT appears to be a useful imaging study for the evaluation of distal ureteral stones in an office setting. Pelvic DT exposes patients to less radiation than NCCT, especially to the radiosensitive gonads. Additionally, it provides cost savings relative to NCCT. Further study is required to compare the sensitivity and specificity of pelvic DT to NCCT for stone identification.