Ultrasonic gray scale doppler imaging angiography

Examination of the carotid artery stenosis is very important in the diagnosis of cerebrovascular diseases. New possibilities in the diagnosis of stenotic lesions are provided by ultrasonic Doppler angiography. The aim of this paper is to present a Doppler imaging system developed by the authors for the examination of blood flowing in carotid arteries. The system is based upon a 5 MHz bi-directional c.w. Doppler flowmeter with a separate output for anterograde and retrograde flows. A special bank of filters converts signals into various levels of the gray-scale display which correspond to the value of the blood flow velocity. The ultrasonic probe is held by the scanning arm. The position of the probe on the skin of the patient is electronically sensed by the position-sensing circuity which causes the bright spot on the image display to move according to the position of the probe. The Doppler image from the artery is stored in a digital memory system. The clinical results obtained by means of this system showed good agreement with X-ray arteriography for obstructions occluding more than 50 per cent of the arterial diameter.