Radiation exposure levels of routine SPECT/CT imaging protocols

Abstract

Aims To assess incremental and total patient exposure from clinical SPECT/CT imaging by means of effective dose estimations with regards to different protocols and SPECT/CT systems. Materials and methods Consecutive patient exposure levels were documented prospectively from SPECT/CT operations at three European imaging centers. Documentation included the volume-weighted computed tomography (CT) dose index, the CT dose length product (DLP) and the amount of applied radiopharmaceutical. SPECT/CT examinations were categorized regionally into head, neck, myocardium, thorax, abdomen, extremities and whole-body. Effective dose from the CT (EDCT) was estimated from the DLP using gender specific conversion factors. EDSPECT was estimated from the injected activity levels and corresponding conversion factors (ICRP 106). Results This study included 678 SPECT/CT examinations. EDCT per indication and EDSPECT per tracer ranged from 0.01 mSv to 7.4 mSv and from 1.1 mSv to 12.2 mSv, respectively. In general, EDSPECT contributed most to overall patient exposure. Total EDSPECT/CT averaged across all protocol categories was 6.7 mSv. Conclusion Total patient exposure from clinical SPECT/CT is 7 mSv on average. Individual dose levels vary with the clinical indication and on-site protocol parameters.