INVESTIGATING THE EFFECTS OF VASODILATOR DRUGS ON THE TURBULENT SOUNDCAUSED BY FEMORAL-ARTERY STENOSIS USING SHORT-TERM FOURIER AND WAVELET TRANSFORM METHODS

In this study, the effects of vasodilator drugs on the turbulent sound generation mechanisms during femoral artery stenoses were investigate d using the wavelet analysis of the turbulent sounds to characterize t hese sounds before and after the injection of vasodilator drugs. Resul ts showed that the injection of drugs drastically improved the diagnos tic performance of the turbulent sounds in detecting stenoses by incre asing the signal-to-noise ratio of the sounds. Results also suggested that the sound above 250 Hz was drastically increased in response to t he injection of the vasodilator drug for the partially occluded cases. The turbulence sounds caused by partially occluded femoral arteries a re directly related to the slope of baseline of blood Bow and to the v elocity of the flow. For the 0% occlusion case, initially, sounds were produced with the injection of drugs. However, the sounds totally dis appeared when the slope of average blood flow was zero, These results show that the diagnostic performance of diastolic heart sounds associa ted with occluded arteries can be improved by using vasodilator drugs, which increase the acoustic energy in the first and second wavelet ba ndwidths due to the turbulence. The short-term Fourier transform (STFT ) method was also applied to the same data base. Results using the STF T showed somewhat similar power distributions in that the acoustical p ower above 250 Hz was increased after the injection of drugs for the o ccluded cases. However, the WT method provided better time-frequency r esolution than the STFT method, showing details of the change in the f requency characteristics with respect to time after the injection of d rug.