心房中隔欠損症の診断に関するdynamic computed tomographyの有用性

Usefulness of dynamic computed tomographic scanning in the diagnosis of atrial septal defect

　X線CTは空間的分解能にすぐれ，またそれ故に近年臨床各領域にめざましい進出をとげつつある。心臓血管領域においてもAC-bypass graftの開存^1〜2），解離性大動脈瘤^3,4），心腔内血栓^5）等の診断に広くその応用がこころみられている。他方，時間的分解能という点については，現在の装置がscan時間に1〜5秒を要するため，心エコー図や核医学的検査法に比すればその地位を一歩譲っており，したがってX線CTを血流動態の解析に用いた報告は今のところ少ない。しかし，本装置のすぐれた空間的分解能を生かし，時間的分解能の弱点を最少限とする血流動態の検索もこころみられて然るべきといえよう。そこで我々は従来のX線CT装置を用いdynamic scanで造影剤1回静注後の血流を追跡し，心血管系疾患における本法の臨床診断上の有用性を検討した。今回はshunt性心疾患のうち，特に心房中隔欠損症（ASD）への応用をこころみた結果を報告する。

Dynamic computed tomography was performed in S normal subjects and 6 patients with an atrial slptal defect (ASD). Thirty ml of 60% meglumine iothalamate was administered as a bolus injection in a 5 second period to the antecubital vein. Se-quential scan was begun immediately after the start of the injection and 6-S scans were obtained using a -I chamber plane. In control subjects, the contrast medium passed from the bolus through the right and left side of the heart. However, in patients with ASD, the contrast medium reappeared in the right atrium and right ventricle. The dilution curves obtained from the change of CT numbers in each four chambers, were clearly different from ASD patients and control subjects. The C/A and C B which are the ratio between peak CT number of right side (Al or left side (B) and the lowest CT number of right side (C1, were significantly higher in ASD patients than in the controls. From these results, it was suggested that dynamic computed tomography was useful in the clinical and non-invasive diagnosis of ASD.