Development of the bruit analyzing system for cerebrovascular disease diagnosis

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For cerebrovascular disease diagnosis, intracranial blood flow noise (Bruit) analyzing system was developed. Three of the main works and corresponding results are summarized below.1.Development of Bruit transducer :Efficiency of Bruit sensor, such as signal-to-noise ratio (SNR) , sensitivity and frequency response, is important. Liquid-coupling-type transducer was newly developed using electret film improving the efficiency of previously developed PVDF-type sensor. In the clinical application, it showed good effectiveness.Development of analyzing system and database :To shorten the analyzing time and to realize the mass storage of clinical data, digital signal processor (DSP) and magneto-optical disk system were adopted. FFT,short time fourier transform and Wigner distribution were applied to the clinical data as signal analyzing method. Good improvement of SNR and possible diagnostic information were obtained with those methods. Twenty of the different items per patient including those results were stored in the database.Clinical data accumulation :More than 120 clinical data were measured and accumulated. Measuring system was refined based on the experience obtained during those measurements. Those clinical data suggested some possible diagnostic information as follows :(1) Detection of cerebrovascular disease was possible based on the level difference at specific two frequency components of Bruit.(2) Characteristics of aneurysm could be seen more clearly in the result of Wigner distribution.(3) Characteristics of stenosis could be seen more clearly in the time variance of the spectrum.