脳腫瘍および腫瘍周辺浮腫部のpositron emission tomography （PET）による脳循環およびブドウ糖代謝の検討

POSITRON EMISSION TOMOGRAPHIC EVALUATIONS ON HEMODYNAMICS AND GLUCOSE METABOLISM OF BRAIN TUMORS AND PERIFOCAL EDEMATOUS TISSUES

　抄録　髄膜腫9症例，転移性脳腫瘍3症例とグリオーマ19症例（合計31症例）にPET検査を行った。脳腫瘍自体の循環代謝検討では，1）髄膜腫の血流量と血液量は有意に高値を，酸素とブドウ糖代謝率ならびに酸素摂取率は低値を示した。2）転移性脳腫瘍の血流量，酸素代謝率と酸素摂取率は低値を示した。3）グリオーマ群では，血流量とブドウ糖代謝率は悪性度と相関はなかった。一方悪性化とともに血液量は増加し，酸素摂取率は低下し，酸素代謝率は低下傾向を示した。腫瘍周辺浮腫部の循環代謝検討では，1）血流量は転移性脳腫瘍例で低下傾向を，酸素代謝率は転移性脳腫瘍とグリオーマ例で低下傾向を示した。2）ブドウ糖代謝率はすべての症例で低下傾向を示した。3）酸素摂取率の結果から，グリオーマの一部では浮腫とした部位に腫瘍浸潤の可能性が示唆された。腫瘍におけるブドウ糖代謝率との関連については，再検討の時期にきていると考えられた。

Blood flow and glucose metabolism of the tumors and perifocal edematous tissues were evaluated using positron emission tomography (PET). Thiry-one brain tumor cases were investigated 12 non glial tumors (9 meningiomas and 3 metastatic tumors) and 19 gliomas (these were classified in 5 astro-cytomas, 7 anaplastic astrocytomas and 7 glioblasto-mas, according to the malignancy). The diagnosis were confirmed pathologically in 30 cases. Cerebral blood flow (CBF) , cerebral metabolic rate for oxy-gen (CMRO2), oxygen extraction fraction (OEF) and cerebral blood volume (CBV) were measured by 0-15 labeled gases inhalation methods. Cerebral metabolic rate for glucose (CMFglu) were mea-sured by F-18 Deoxyglucose intravenous injection method and calculated by Hutchins's formula. The rate constans (ks) and lumped constant (LC) used in this study were the same as those published by Phelps et al. in 1979. The blood flow and glucose metaboic rates of tumors were measured by the same methods.

The results were as follows : 1) Meningiomas showed very high blood flow and blood volume with a wide range. The OEF and metabolic rate for glucose (MRglu) values were very low. 2) Me-tastatic tumors showed the low values of blood flow, metabolic rate for oxygen (MRO₂) and OEF. 3) The blood flow and MRglu values on gliomas were varied with no significant differences between the three subgroups. On the other hands, as the malignancy of the glioma increased, a sta-tistically significant increase in blood volume and a decrease in OEF were noted. 4) The OEF values from the various types of tumors studied were sig-nificantly lower than those obtained from the normal tissue. 5) The CMRglu values obtained from the peritumoral edematous tissues of all types of tumors were lower than those of normal white matter. 6) The OEF values from the peritumoral edematous tissues in meningiomas showed very high or normal values. On the while, the OEF values obtained from the edematous tissues in some glioma cases were very low. These facts suggested us that in those cases of gliomas, tumor invaded to the peritumoral edematous tissues. 7) The absolu-te values of MRglu on tumors and the malignancy of the tumors showed no correlations. 8) The new methods for the evaluation of the MRglu on tumors should be developed in near future.