Print out dataによる脳RI scan側面像の分析—isocount scanningを用いて

THE ANALYSIS OF RI BRAIN SCANNING WITH PRINT OUT DATA USING ISOCOUNT SCANNING

I．はじめに

　Isocount scanningはscanデータの収集にあたって確率論的考慮がなされた新しい記録方法である^7）。そのscanning法によれば，dataの信頼性が測定部位のradio　isotope （以下RI）濃度に左右されず，歓測対象全平面において均一となる。さらに，それは従来の機器に簡単な電子工学的修正を加えるだけで可能となる。この方法による脳RI scanに関する原理，臨床成績はすでに報告を重ねてきた如く，脳scan診断の精度を高めることが出来た^17,19）。

　このシステムには種々の表示方法がある。すなわち，photoscanning, color TV display, multilevel analysis，　perspective viewによる二次元表示である。とくにmultilevel analysis^8）はTVスクリーン上にscan像をアニメーション化するという，臨床上有用な方法であり，最も多用されている。

A new quantitative method for analyzing RI scintiscan data was presented. In this study, the scan data were obtained by the isocount scanning system of which principle and technique have been already reported. The count rates of RI activity at each measuring point in the lateral scanning were printed out with a line printer.

Three areas were selected from the printed numerical scintigram, the area of the lesion (L), of the brain (B) and of the transverse dural sinus (V). The ratios of L/B and B/V were estimated in each scintigram, showing the difference of RI uptake into the focus of lesion, normal brain tissue and the transverse dural sinus.

22 patients with various brain diseases were studied by this method. In 16 of 22 cases brain scans were repeated at various intervals after the injection of ^99mTc-pertechnetate. In normal con-trols, average B/V was 0.78±0.02 (SD) 30 minutes after the RI injection. Brain scans performed 30minutes after the RI injection showed that high B/V was obtained in one case of epidural hematoma, cerebral embolism and meningioma, 0.91,0.94 and 0.92 respectively. On the other hand, high L/B was obtained in one case of meningioma, sarcoma, glioblastoma multiforme and cerebral thrombosis, 2.00,1.44,1.37 and 1.39 respectively. The repeated scans revealed that L/B ratio reached to its maximum value 60 minutes after the RI injection in the glioblastoma. In the oligodendroglioma and the epidermoid maximum L/B ratio were obtained 2-3 hours after the injection. On the other hand, in non-neoplastic lesions, such as arachnoiditis, epidural hematoma, brain abscess and so forth, maximum L/B ratio were obtained 60 minutes after the RI injection.

Thus, it would be concluded that the scanning would be favorably delayed for 60 minutes after the injection of ^99mTc-pertechnetate as a radio-nuclide.

Isocount scanning system offer many possibilities for the processing scans to provide alternative dis-plays or to carry out numerical analysis.