頭蓋底腫瘍診断へのYb-cisternographyの応用

Yb-169-DTPA CISTERNOGRAPHY AS A DIAGNOSTIC METHOD IN THE DETECTION OF BASAL TUMORS

　頭蓋内疾患に対するRI診断法は，1948年のMoore^1）の報告に端を発し，もつぱら，脳腫瘍の診断を目的としたbrain scintigraphyを中心として発展してきた。このbrain scintigraphyは，今日，盛んに用いられている^99mTc，^113mInなどの短半減期pure gamma emitterの開発と，scannerからgamma cameraにいたる核医学機器の進歩により，現在，一応その補助診断法としての地位を確立したといつてもよい。しかしながら，天幕上腫瘍の診断率が80〜90％と高率であるのに反し，天幕下，頭蓋底腫瘍では，いまだ十分ではなく，これが本法の問題点の一つとなつている。

　一方，1964年Di Chiro^2）3）によつて，RISAを用いて始められたRI-cisternographyは，CSF循環動態を簡単に把握しうる方法として，近年，急速に利用されはじめた。なかでも，1968年Wagner^4）〜7）らによつて開発された¹⁶⁹Yb-DTPA （Ytterbium−169 Diethylene—triaminepentaacetic acid）は，cisternography用の放射性医薬品として，これまでのRISA,Tc-albuminと異なり，副作用をみることなく，安定性，半減期，分子量などの面からもいくつかの利点を有している。

In recent years, brain scintigraphy has become a widely used method for the detection and localiza-tion of intracranial tumors. The diagnostic accuracy of brain scintigraphy for the detection of supra-tentorial tumors is high, but unfortunately infra-tentorial and basal tumors are difficult to be localized. This is the weak point of this method, and we tried to raise the rate of diagnosis of these tumors using Tc-brain scintigraphy and Yb-cisternography.

The present study describes the clinical application of Yb-cisternography to the diagnosis of 3 basal tumors. One-half mCi of Yb-169-DTPA (Ytterbium-169-diethylenetriaminepentaacetic acid) was injected intrathecally by a lumbar tap. Scintigraphy of the subarachnoid space was performed by a scintillation camera in the usual 4 directions (antero-posterior, postero-anterior and bilateral lateral views) and the dynamic distribution of Yb-169-DTPA was follow-ed up from 1 to 24 hours after the intrathecal injection.

All these 3 cases of basal tumors were correctly localized by Yb-cisternography showing the obst-ruction or narrowing of the subarachnoid spaces and the abnormal CSF dynamics. And this radio-isotopic cisternography is a safer and simpler method than air study or myodilcisternography. From these results, it might be concluded that Yb-cisternogra-phy is valuable as a clinically useful test for the diagnosis of the basal tumors which can hardly be detected by Tc-brain scintigraphy.