強力集束超音波による脳深部限局破壊に関する実験的研究

AN EXPERIMENTAL NEUROPATHOLOGICAL STUDY OF THE EFFECT OF HIGH-FREQUENCY FOCUSED ULTRASOUND ON THE ANIMAL BRAIN

I．緒言

　近年超音波の動力的応用が開発され，その一つとして，強力集束超音波による中枢神経系への応用が注目をあびている。

　超音波^1）2）は空気よりも液体，固体を媒質とし，周波数が高く，波長が短いため光波に近く，方向性を有し，強度がいちじるしく大きいなどの特徴をもつている。これを適当な方法によつて，集束させることにより，焦域に大音場を作ることができる。すなわち途中の組織を損傷することなしに，焦域にのみ組織破壊をおよぼすことができる。

Well circumscribed pan-necrotic lesions were pro-duced in the brains of animals ; rabbit, cat, by means of irradiation with intensity focused Ultrasound ex-posed through the dura.

A concave barium titanate transducer was used. Ul-trasonic frequency was about 1 MC/sec., the focal len-gth 7 cm, the diameter of generation 6 cm, the peak intensity at the focus 870 W/cm² at all times and the durration of irradiation was 2 seconds. Focal lesions were produced in the white matter and gray matter. Animals were sacrificed to examine for varying periods of time ranging from one hour to one year following the irradiation.

At one year after the irradiation, no particular changes were noted in the foci, and replaced by gliosis and connective tissue scar.

There were no late changes comparable to those following X-ray irradiation.

There were no pathologic changes in the pathway of the Ultrasonic beam or the surrounding tissue of the focal lesion.