The method utilizing the Doppler effect of ultra sound has been applied to the screening of the obstruction or narrowing of internal carotid and middle cerebral arteries. When the Doppler sound is processed by frequency analysis to give power spectrogram, the acoustic characteristic of the hemodynamics may be clearly indicated by the spectrogram.
The patients subjected to this study consisted of 6 internal carotid arterial obstruction, 7 cases of the narrowing of internal carotid artery, 14 cases of the obstruction or narrowing of middle cerebral artery, 15 cases with the elongation of internal carotid artery or arteriosclerosis, and 10 cases from which the Doppler sound was recorded directly from intracranial internal carotid artery at the time of operation. The Doppler sound recording from other patients was made from common carotid artery, superficial temporal artery and supraorbital artery. The doppler sound recorded were analyzed a data processer ATAC-450, and resultant power spectrograms were compared with corresponding angiograms in order to examine the usefulness of the power spectrogram.
The normal pattern of the spectrogram obtained from common carotid artery consisted of frequency components which distributed from low frequency range to high frequency range. The maximum energy was found at the frequency of 670±99 Hz. Thus the spectrogram was in the shape of an one peak hill. The power of this maximum energy was reduced and the peak frequency was also shifted to the frequency range lower than 500 Hz, when there existed the narrowing or obstruction of internal carotid artery, namely, the peak value became 441±97 Hz for the narrowing and 364±78 Hz for the obstruction, and the overall shape of the spectrogram changed to a steep hill type. In the cases of middle cerebral arterial obstruction and narrowing, the peak appeared at 360±72 Hz and the spectrogram did not show the hill shape with a single peak.
It is concluded that the power spectrogram of Doppler ultra sound is a useful non invasive method for the diagnosis and screening of obstructive cerebrovascular diseases.
