胸部CTガイド下IVRにおける逐次近似応用再構成法を用いたCT透視線量低減に関する検討

摘要

Computed tomography (CT)透視による超高速画像再構成(リアルタイム画像再構成)はスキャンとほぼ同時に断層像が出力されることから，片田らによる報告がなされて以降，これまでCTガイド下生検等のinterventional radiology (IVR)に多く用いられてきた.CT透視は，これを使わない方法に対して生検針を病変部まで到達させるまでの時間が短くなる利点がある一方で，ヘリカル撮影に比べて患者の被ばくが多くなること,更に生検針の刺入方向や到達位置確認の撮影ごとに退室する方法に比べると，X線照射中であっても医師は患者の近傍においてその手技を行う必要があるため少なからず術者の被ばくが生じることが問題となる.%The purpose of this study was to evaluate the radiation dose reduction to patients and radiologists in computed tomography (CT) guided examinations for the thoracic region using CT fluoroscopy. Image quality evaluation of the real-time filtered back-projection (RT-FBP) images and the real-time adaptive iterative dose reduction (RT-AIDR) images was carried out on noise and artifacts that were considered to affect the CT fluoroscopy. The image standard deviation was improved in the fluoroscopy setting with less than 30 mA on 120 kV. With regard to the evaluation of artifact visibility and the amount generated by the needle attached to the chest phantom, there was no significant difference between the RT-FBP images with 120 kV, 20 mA and the RT-AIDR images with low-dose conditions (greater than 80 kV, 30 mA and less than 120 kV, 20 mA). The results suggest that it is possible to reduce the radiation dose by approximately 34% at the maximum using RT-AIDR while maintaining image quality equivalent to the RT-FBP images with 120 V, 20 mA.