2076 SPECIFIC ORGAN DOSES UTILIZING A NEW TECHNIQUE FOR IMAGING NEPHROLITHIASIS: DIGITAL TOMOSYNTHESIS

INTRODUCTION AND OBJECTIVES: Digital tomosynthesis (DT) is a novel imaging technique for the evaluation of patients of with nephrolithiasis. It consists of a plain abdominal radiograph (KUB) and one tomographic sweep. Software is used to recreate a series of coronal images from the tomographic sweep. We determined organ specific dose and effective dose (ED) for DT and compared it to our institutional “low dose” non contrast computed tomography (NCCT). METHODS: A validated anthropomorphic male phantom was placed supine on a GE Definium 8000 CT scanner. High sensitivity metal oxide semiconductor field effect transistors (MOSFET) dosimeters were placed at 20 organ locations and used to measure organ doses (OD). A routine DT study was performed consisting of two KUB (scout) images and one tomographic sweep in a 60 degree arc over the phantom. OD were determined as the sum of the doses for the study. Equivalent doses were calculated by multiplying OD and the appropriate tissue weighting factor. ED was calculated by the summation of the equivalent doses. OD and ED were determined in a similar fashion for a renal stone protocol NCCT and the doses were compared. RESULTS: Specific organ doses for DT (2 scouts and 1 tomographic sweep) and NCCT are shown in the table. The ED for NCCT is 3.04 ( 0.34) mSv. The calculated ED for digital tomosynthesis is 0.54 ( 0.07) mSv (2 scouts at 0.10mSv and 0.08mSv 1 sweep at 0.36mSv), p 0.0002. CONCLUSIONS: Digital tomosynthesis exposes patients to substantially less radiation than NCCT. This is particularly true for radiation sensitive organs. Further studies are needed to compare the sensitivity and specificity of DT as compared to NCCT. However, its low overall radiation dose make it an ideal study for the follow up of the recurrent stone former in the office setting.