H215O瞬時静注法による局所脳血流量測定法とその応用

CEREBRAL BLOOD FLOW MEASUREMENT USING H215O INTRAVENOUS INJECTION AND POSITRON EMISSION TOMOGRAPHY:DESCRIPTION OF IMPLEMENTATION AND APPLICATIONS TO CEREBROVASCULAR REACTIVITY MEASUREMENT

　抄録　H₂¹⁵O瞬時静注法とポジトロンエミッショントモグラフィ（PET）による局所脳血流量（CBF）測定法について述べた。30〜40mCi H₂¹⁵O静注と同時に，ベータ線検出器により動脈血中H₂¹⁵O濃度を持続的に測定しながら，HEADTOME IIIにより5横断面の脳組織H₂¹⁵O濃度を1分間測定する。これらよりオートラジオグラフ法の原理に基づいてCBFが計算される。本法の最大の誤差要因は動脈血測定濃度曲線に含まれるボケの影響と考えられるが，この影響はPETのスキャン時間を長くすることにより軽減可能であった。本法を用いて正常脳のPaCO₂変化に対する脳血管反応性を調べたが，テント下領域でわずかに高い他は局所的な差異は観察されなかった。また，虚血脳においては酸素摂取率と，PaCO₂変化に対する反応性低下，および昇圧負荷に対する自己調節機序の喪失との間に著しい相関関係が見られた。

The method for cerebral blood flow (CBF) mea-surement using an H₂¹⁵O intravenous injection and positron emission tomography (PET) was imple-mented, examined and applied to measure cerebro-vascular reactivity to PaCO₂(VRCO₂) and to MABP (VRBP) in normal brain and in ischemic brain. Immediatly after bolus intravenous injection of 30-40 mCi H₂¹⁵O, a time-activity curve of H₂¹⁵O con-centration in the arterial blood and in the brain were measured for 60 sec by a beta detector and a PET, respectively. The PET was HEADTOME III and measured five planes. CBF was determined by the table-lookup method based on the autoradio-graphic principle. Six volunteers were studied to examine regionality of VRCO₂, and a moyamoya patient and a stroke patient with a bilateral-intra-carotid circulation defect were studied to examineVRCO₂ and VRBP in ischemic brain. The studies were carried out so as to be followed two or three H₂¹⁵O CBF measurements with changing PaCO₂ or MABP after control study at rest condition. In addition, prior to the H₂¹⁵O study O15 gas steady state study was performed on all subjects. Vali-dity of the method examined by simulation studies showed 3% error per 1 sec time shift of the artery curve for 60 sec PET scan duration and the error was rapidly increased to the shorter scan duration. Inhomogeneity of a brain tissue gave mild under-estimation by 5% for 60 sec PET scan duration. VRCO₂ in normal brain was revealed to be almost uniform except that the infratentorium area show-ed a slight higher VRCO₂ than the supratentorium area. The ischemic brain showed a negative cor-relation between VRCO₂ and oxygen extraction fraction (OEF), and a positive correlation between VRBP and OEF.