Reflectance spectrophotometry法による局所脳血液量測定—測定法の一工夫と定量化の試み

MEASUREMENT OF CEREBRAL BLOOD VOLUME BY REFLECTANCE SPECTROPHOTOMETRY:METHODOLOGICAL IMPROVEMENT AND QUANTITATIVE EVALUATION

　抄録　Reflectance spectrophotometry法による脳血液量測定において測定法上の改良と定量化の試みを行った。本法において最も重要である測定用センサーと脳組織との良好な接触を保つためbalance armを考案した。このarmは支点を中心として一側にセンサーを固定し，他側に重りを装着しこの重りを移動することによってセンサーの測定脳組織への圧を一定に保とうとするものである。またこの重りはストッパーによって支持され一定以上下降しないようにした。これによって脳の縮小時ばかりでなく腫脹時においても正確に脳血液量の測定ができる。またセンサー圧の調節を容易にし，脳組織が観察できるようセンサーに透明なアクリル製のキャップを付けた。この方法により猫の脳において脳虚血およびCO₂負荷による脳血液量の低下，増加の変化が捉えられ，またその再現性が示された。定量化に際しては猫の脳組織を脱血後にホモジェナイズし，これに既知量のヘモグロビンを一定量加えこの時の表示値と加えたヘモグロビン量より計算した脳組織のヘモグロビンの濃度とを比較した。この両者には生理学的な脳血液量の範囲で良好な直線関係が成り立った。以上の結果より本法により連続的にしかも定量的な脳血液量測定の可能性が示唆された。

The authors described methodological improve-ment and quantitative evaluation in measurement of cerebral blood volume (CBV) by reflectance spectrophotometry. The measurement of blood volume by this method has not been applied to the brain tissue because of the methodological diffi-culties. In order to obtain the accurate CBV values with this method, it is necessary to keep the proper contact between the sensor for the mea-surement and the brain tissue to be measured. For this purpose we developed a balance arm. A sensor for CBV measurement was fixed with the one side of the arm and a weight was installed to the other side. The pressure of the sensor to the brain can be adjusted by moving the weight, and the sensor was placed on the brain tissue with the proper pressure. Moreover, the sensor was attach-ed with an acryl-made cap to make the pressure adjustment easier by enlarging the contact surface and to enable to observe the vasculature on the surface of the brain. With this improved method the reasonable changes of CBV could be obtained when the CO₂ gas was inhalated and cerebral ischemia was produced in cats.

The possibility of the quantitative evaluation was investigated using the homogenized brain tissue of cats. After the elimination of the blood from the brain by the perfusion with the saline, the brain was removed and homogenized. Then, the definite volume of blood, of which hemoglobin volume was already known, was added and mea-sured by this method. These values were com-pared with those of hemoglobin concentration of brain tissue which was calculated from the blood volume added, and a linear relationship was obtained. From the present results the possibility of the quantitative evaluation was suggested in addition to reliable and reproducible continuous measurement of CBV.