伊藤 淳樹¹, 口脇 博治¹, 長坂 昌登¹, 石栗 仁¹, 景山 直樹¹, 佐久間 宣光², 小倉 幸夫²

Junki ITOH¹, Hiroji KUCHIWAKI¹, Masato NAGASAKA¹, Hitoshi ISIGURI¹, Naoki KAGEYAMA¹, Nobumitsu SAKUMA², Sachio OGURA²

¹名古屋大学医学部脳神経外科学教室, ²日立建機株式会社

¹Department of Neurosurgery, Nagoya University School of Medicine, ²Hitachi Construction Machinery Co., Ltd

キーワード : Interference, Reflection coefficient, Cepstrum analysis, Ultrasonic wave, Intracranial pressure

It is known that reflected waves are affected by interference when ultrasonic waves pass through thin layers. These phenomena are theoretically proved for the reflection coefficients. Waves reflected from thin layers, such as dura mater or subarachnoid space, are found to yield considerable information about the region of reflection.
The aim of our studies was to prove the suitability of these measures for determining thickness of dura mater or/and subarachnoid space from changes in reflection coefficients and to demonstrate a correlation between change in thickness and that of intracranial pressure (ICP).
First, FFT-cepstrum analysis was applied to resolve the waves reflected from a thin layer. This analysis effectively resolved the thickness of an oil layer model within 10 μm.
Then, in animal experiments, data collected by ultrasonic probe (5 MHz) were simultaneously recorded with data from epidural pressure (EDP) transducer. ICP was elevated by saline injection through cisterna magna. A significant correlation between degree of the thin layer's thickness change and EDP was observed.
As a preliminary result, the transcranial pulse echo method and FFT-cepstrum analysis were found to be valuable for the measurement of thin layers thickness and its pulsatile change indicated a close correlation with ICP. But strict identification of the method's sensitivity was left for further study.