Mitochondrial encephalomyopathyのpyruvate−1—11Cを用いたpositron emission tomography

POSITRON EMISSION TOMOGRAPHY USING PYRUVATE-1-11C ON MITOCHONDRIAL ENCEPHALOMYOPATHY

　抄録　Mitochondrial encephalomyopathy 2例，　Leigh diseaseの疑い1例とてんかん1例の脳内ピルビン酸代謝をin vivoで調べるため，　pyruvate−1—¹¹Cを用いてpositron emission tomography （PET）を施行した。てんかん患者では脳組織へのRIの集積が頭皮筋肉に比し少なく，且つ速やかなRIクリアランスを認めた。一方，mitochondrial encephalomyopathyおよびLeigh diseaseの疑いの患者では，いずれも大脳皮質，基底核ないし視床への強いRI集積を認め，且つRIクリアランスが低下していた。また，前者では脳室へのRI蓄積傾向がみられ，後者でも脳室のRIクリアランスの低下が認められた。これらの所見は，ミトコンドリア脳筋症ではピルビン酸代謝に異常をきたしていることを示し，主に脳組織での乳酸蓄積を示している可能性が考えられた。本症例のpyruvate−1—¹¹Cを用いたPETの検討から，本法がin vivoで脳内ピルビン酸代謝を調べる一方法として有効であり，ミトコンドリア脳筋症の診断に役立つものと考えられた。

In order to investigate in vivo metabolism of pyruvate in the brain, positron emission tomo-graphy (PET) using pyruvate-1-¹¹C were perform-ed on two patients with mitochondrial encepha-lomyopathy, one patient with Leigh disease and one patient with epilepsy.

PET images of epilepsy showed less RI uptakes in brain tissues than in skull muscles. And RI was cleared rapidly from the brain tissues. But PET images of mitochondrial encephalomyopathies showed increased RI uptakes and slow RI clear-ance in cerebral cortices, basal ganglias and thalamus. Also RI was cleared slowly or accumu-lated in ventricles.

This suggested that pyruvate metabolism may be impaired with metabolical trapping of ¹¹C by lactic acids, since it is said that ¹¹C of pyruvate-1-¹¹C is cleared rapidly from the normal brain tissues by decarboxylation of pyruvate.

The usefulness of PET studies with pyruvate-1-11C are suggested for investigating pyruvate metabolism in brain tissues, and for diagnosing mitochondrial encephalomyopathy.