64列MDCTを用いた上腹部撮影におけるオーバレンジングに関する検討

摘要

広範囲を高速に撮影することができるmulti-detector computed tomography（MDCT）が急速に臨床現場に普及してきている．MDCTは1回のスキャンで，従来のsingle-detector CT（SDCT）よりも高分解能のデータを高速で得られるため，さまざまな部位の検査に有用であることが報告されている．一方，MDCTが導入されはじめた当初から，青山らが報告するように患者への被曝の増加が懸念されている．%64-slice multidetector-row computed tomography (MDCT) have become widely used in recent years, but there is a possibility that a large volume of dose is radiated at the outside of the scope of scanning due to the effect of over ranging (OR). In this research, the dose volume change at the outside of the scope of scanning in the case of X-ray beam width (BW) and pitch factor (PF) is measured, and the effect of BW and PF on OR is considered. We scanned the upper abdomen of an acrylic human phantom using 64-slice multidetector-row CT in 4 conditions while changing BW and PF. We then measured the dose volume absorbed in the breasts, ovary, uterus, and the dose profile on the surface of phantom. As a result, when BW and PF are increased, the dose volume radiated at the outside of the scope of scanning increased, and the effect of OR appeared. Therefore, when BW and PF are set, X-ray radiated at the outside of the scope of scanning should also be considered.