脳超音波減衰の本態に関する研究

A STUDY ON THE MECHANISMS OF ULTRASONIC ATTENUATION OF THE BRAIN

I．緒言

　1942年，Dussik^5）が医学領域における超音波応用の可能性を発表して以来，内外の多くの研究者の努力により超音波医学は長足の進歩を遂げ，近年は診断のみならず治療にも応用されるに至つた。

　脳神経外科の領域においても超音波応用が盛んに研究され，とりわけ診断的応用については従来の定性的応用に止まらず，定量的応用に関する研究もわが国においては盛んに行なわれている^{1）2）6）−8）17）20）25）32）34）−37）}　。

There are many debates on the machanisms of ultrasonic attenuation in the brain tissue (USA). Some hold that USA decreases in proportion to increasing of cerebral blood flow, but others main-tain the opposite results. There are also diversity of opinions concerning the mechanisms of USA in cerebral edema.

These facts might suggest any other factors concerning USA than the above mentioned.

An attempt was made to clarify the relationship between the following parameters by means of polygraph ; respiration, blood pressure, regional cerebral blood flow, intracranial blood pool, intracra-nial pressure and USA.

The following results were obtained.

1) CO₂ and amylnitrite inhalation and placing a pressure on the Jura through a burr hole revealed the same pattern of changes in the parameters in the each experiment except for USA.

2) In the experimental model, the direction of change in USA altered remarkably when the dura placed in water was moved slightly.

In conclusion ;

a: The quantitative change in the intracranial compo-nents would cause structural changes which is follow-ed by the displacement of reflecting interface to the ultrasonic beam.

b: The mechanisms of USA would have closer relationship with reflexion and scattering than ab-sorption and dispertion of ultrasonic energy.