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In a prospective study using a multigate pulsed Doppler system, minor (less than 30% diameter reduction) carotid artery lesions were diagnosed by detecting not only abnormalities in the blood flow pattern, but also local changes in artery wall distensibility. For the diagnosis of more severe lesions, additional information was obtained from disturbances in the Doppler audio spectrum. Biplane arteriography was used as a reference. The observed agreement, sensitivity, and specificity were 86.6%, 90.3%, and 88.6%, respectively, for all lesions and 85.7%, 82.1%, and 88.6%, respectively, when only minor lesions were considered. kappa (a chance-corrected measure of agreement) was 81.7%. If only blood flow abnormalities were used to detect minor lesions, 43.5% would be missed. Our results indicate that minor carotid artery lesions can be diagnosed noninvasively more accurately when both local blood flow irregularities and local changes in vessel wall distensibility are taken into account.

In the present study the criteria of spectral broadening used in pulsed Doppler systems to diagnose minor disease in the cervical carotid arteries were evaluated in relation to the size of the sample volume. For this purpose the Doppler audio spectra as recorded in asymptomatic volunteers with an ATL Duplex scanner (relatively large sample volume) and a multi-gate pulsed Doppler system (relatively small sample volume) were compared with each other. The volunteers, randomly selected from the population registers, varied in age from 20-69 yr. Only in the common carotid artery at younger age, were normal spectra recorded, especially with the multi-gate system. In the internal carotid artery the number of spectra, supposed to be associated with low grade stenosis, increased significantly, especially when recorded with the Duplex scanner. More pronounced spectral broadening was found when the spectra were recorded distally in this artery. In the cervical carotid arteries normal spectra were found only when sampled in the middle of the bloodstream. These findings indicate that for the detection of vascular lesions in the cervical carotid arteries at an early stage of the disease on the basis of spectral broadening, small sample volumes and sampling in the centre of the vessel are required.

Basically two principles have to be distinguished in ultrasonic imaging of arteries. In velocity imaging blood flow velocities are visualized with continuous wave or pulsed Doppler devices. In pulsed echo-systems artery wall structures are visualized by picking up echoes reflected by the vessel walls. Velocity imaging is mainly used to localize the site of velocity sampling which is of importance in screening the carotid artery bifurcation and in follow-up studies. Although promising results have been obtained in diagnosing atherosclerotic lesions with echo-imaging systems, these systems have their limitations. To improve the diagnostic accuracy these systems should be combined with a single- or multi-gate pulsed Doppler system.

One hundred neurologically asymptomatic male subjects (aged 50-69 years), randomly selected through population registers, were screened for atherosclerotic lesions of the cervical carotid arteries, using a high resolution multi-gate pulsed Doppler system. In 93 subjects serum was assayed for total and HDL cholesterol. Besides, cuff arterial blood pressure measurements were made. Twenty-three of these subjects (Group III) were classified as abnormal according to the Doppler investigation (degree of narrowing less than 50% in 78% of the cases). Seven of these 23 subjects also had a history of ischemic heart disease or intermittent claudication. Of the 70 subjects with a normal Doppler examination 16 had a history of ischemic heart disease and/or intermittent claudication (Group II). The remaining 54 subjects served as controls (Group I). The frequency of asymptomatic atherosclerotic lesions of the cervical carotid arteries in the population under investigation was 23%. The HDL/total cholesterol ratio was lower and the frequency of high blood pressure higher in the Groups II and III than in Group I. The findings in this study support the idea that a low serum HDL/total cholesterol ratio and high blood pressure have a high degree of association with atherosclerotic lesions of the cervical carotid arteries. This association is already apparent at an early stage of the disease, i.e. in asymptomatic subjects with a slight to moderate degree of carotid artery narrowing.

The diagnostic accuracy of noninvasive detection of carotid artery lesions with a diameter of less than 50% (minor to moderate) and greater than 50% reduction (severe) with the use of a multi-gate pulsed Doppler system (spectral analysis combined with the detection of flow disturbances) was studied in patients with focal neurological symptoms. Biplane arteriography was used as a reference. For all lesions the diagnostic accuracy (observed agreement), sensitivity and specificity was 88, 92, and 84%, respectively, and 84, 83, and 84%, respectively, when only minor to moderate lesions were considered. Kappa, a chance-corrected measure of agreement, which takes into account the marginal distribution of the data and, hence, may be considered to be a better parameter to describe diagnostic accuracy, was found to be 82.2%. The results in this study compare favorably with those obtained in studies employing duplex techniques (B-mode image combined with single-gate pulsed Doppler) and indicate that minor to moderate carotid artery lesions are detected rather accurately with the use of a multi-gate pulsed Doppler system.