低管電圧撮影,および逐次近似応用画像再構成法を利用した造影剤減量の試み: 頭部CTAを対象として

摘要

This study aimed to reduce contrast medium dose without reducing the diagnostic capability of computed tomography (CT) angiography of the head. We evaluated the advanced statistical iterative reconstruction (ASiR) settings to adjust to low tube voltage CT. A syringe phantom was constructed using dilute contrast medium and was imaged at tube voltages of 80-120 kV. The iodine volumes,CT values,and image noise were measured in these images. The noise-power spectrum and modulation transfer function were measured from quality assurance phantom images that had been obtained using the tube voltage selected after considering the image noise results as described above and reconstructed using different ASiR rate settings and convolution kernels. Our results suggested that imaging at 100 kV could reduce the contrast medium dose by 14%,compared with imaging at 120 kV,and that the resulting image quality could equal that of conventional imaging by performing reconstruction at a 40% ASiR rate and detail kernel.%造影検査におけるーつの問題点は,造影剤腎症(contrast-induced nephropathy:CIN)などの造影剤による副作用である.CINは造影剤使用後の急性腎障害であり,造影剤投与後の腎血流低下による腎髄質の虚血と尿細管細胞への造影剤の直接作用などの複数の要因が関与していると考えられている.CINの発症頻度は3～20%といわれ,糖尿病や慢性腎臓病を有する高リスク患者では40～50%に上るとされている.腎障害患者におけるョード造影剤使用に関するガイドラインによると,造影剤投与量の減量はCIN発症のリスクを低減させ.診断能を保つことのできる範囲で減量することを推奨している.