Yusei Nishihara

Abstract In diagnostic computed tomography (CT), radiological technologists and assisting staff may need to remain inside the CT room during patient assistance. Understanding temporal changes in scattered radiation distribution is therefore important for reducing occupational exposure. Conventional measurements mainly provide instantaneous dose rates or accumulated doses and are less suited to intuitively capturing temporal changes during CT scanning. This study conducted a fundamental investigation of a visualization approach, defined as dynamic dose distribution (DDD), based on time-resolved air kerma measurements obtained with a semiconductor survey meter. Scattered radiation was measured during chest-to-pelvis helical CT scanning of an anthropomorphic phantom under fixed tube current and automatic exposure control conditions. DDD allowed temporal changes in scattered radiation distribution to be visually identified in relation to tube current modulation, patient table position, and measurement height. DDD may provide useful temporal information for considering staff positioning and reducing occupational exposure.