Pulsed multigated Doppler ultrasonography in the diagnosis of carotid artery disease

A method to create reference maps for evaluation of ultrasound images of carotid atherosclerotic plaque

Ten formalin-fixed atherosclerotic carotid plaques removed by endarterectomy were molded into rectangular agar blocks containing fiducial markers on the top surface. Plaque and fiducial markers were imaged with 3-D multiangle ultrasound (US) spatial compounding as well as planar X ray. Subsequently, the blocks were decalcified, sliced, photographed and analyzed histologically. This gave a total of 123 slices. The plaque regions of the photographs were outlined and the outline adjusted to partly compensate for occasional displacement during slicing. Inside this outline, the material constitutions were found by incorporating the histologic information. From this set, slices with 1. too much tissue displacement due to cutting or 2. lack of identification of calcification as found by x ray, were removed. This resulted in 53 reference maps. The material types identified covered soft tissues, fibrous tissue, calcified tissue and unidentified tissues. The 53 reference maps can be used for direct automated quantitative comparison with US images.

Duplex ultrasound for assessment of superior mesenteric artery blood flow

Duplex ultrasound (DU) is recognised as a valuable tool for the assessment of blood flow in many vascular territories. The application of this technique to the superior mesenteric artery (SMA) has increased rapidly throughout the last decade. The purpose of this review is to collate currently available information on the utility of SMA DU, both in terms of research and clinical practice. Research investigations have revealed low intra- and interobserver variability in the estimation of Doppler variables, while reliable evaluation of B-mode dimensions requires repeated measurements. SMA blood flow velocity has been found to be dependent upon changes in central haemodynamics and in peripheral resistance, which was documented in studies with hypotension, medication and post-prandially. Food intake induces mesenteric vasorelaxation reflected by a 10-fold increase in the diastolic velocity. This feature has been utilised in studies on mesenteric physiology, which confirmed parasympathetic activity during hypovolaemia, and showed that exercise increases splanchnic resistance and reduces its blood flow following a 50% reduction in the hepato-splenic and a 25% reduction in the mesenteric blood flow. Clinical studies have documented high sensitivity and specificity of DU in detection of disease in splanchnic arteries. Diastolic velocity was found to be the most accurate indicator of SMA stenosis, while an absent Doppler signal from a well visualised vessel has been found to be a reliable predictor of occlusion. The high predictive value of DU in the detection of mesenteric artery disease, together with its simplicity and non-invasiveness, suggests that DU should take precedence over arteriography in both clinical practice and laboratory investigations.