SPECT用脳機能診断薬剤

Diagnostic agents of brain function used for SPECT.

はじめに

　近年，コンピューター断層画像装置の進歩に伴って，SPECT（Single Photon Emission Computed Tomography）用生理，生化学的機能核医学診断薬剤の開発研究が非常に活発となり，新しい診断薬剤あるいはその候補化合物が続々と報告され始めた。周知のように，コンピューター断層画像による生理，生化学的機能診断の口火はPET（Positron Emission Tomography）で切られ，現在もなおPET診断が先頭となって診断内容を高めているが，一方，PET診断には，診断薬剤に用いる標識RI，¹¹C，¹³N，¹⁵O，¹⁸Fを製造するサイクロトロンの周辺に利用範囲が限定されること，および設備面のみでなく診断薬剤合成のソフトウエア面にかかわる経済性の問題が根本的に残されている。

　SPECT用診断薬剤は，このようなPET診断の現状を背景に，使用範囲が広く，かつ経済性にすぐれるSingle Photon RI，¹²³I，^99mTcの標識化合物にPET診断機能を求めようとする考えで現われ，さらにこれからも発展しようとしている新しい診断薬剤である。

　Recently, many kinds of radiopharmaceuticals labeled with single photon RI (abbreviated hereafter as SP-RI) such as ^99mTc, ¹²³I, etc., have been developed as the diagnostic agents used for SPECT, providing extensive information on changes in physiological and biochemical functions relating to various tissue diseases such as brain, heart, etc.

　It is well known that the functional diagnosis of these tissues was first demostrated by PET and those compounds labeled with the positron RI (abbreviated hereafter as P-RI), ¹¹C, ¹³N, ¹⁵O and ¹⁸F, ¹¹C, ¹³N, and ¹⁵O which are constituent elements of biochemicals and drugs or ¹⁸F processes the chemical characteristic, useful for synthesizing of these biochemically important compounds. Research on the development of biochemicals and drugs using P-RIs has in fact been very extensive. However, the omnipresence of P-RI-labeled radiopharmaceuticals is a rather difficult matter as it may be expected; the need to install cyclotrons in hospital to produce RI as well as installing in-house synthetic radiopharmaceutical systems is a definite obstacle to their clinical applications for practical and financial reasons.