Feasibility and Accuracy of Measuring Carotid Plaque Volume (Burden) With Contrast-Enhanced Tomographic 3D Ultrasound and Ultrasound Image Fusion

Abstract

Stenosis severity has been the indication for carotid endarterectomy (CEA) for four decades, but the annual stroke risk in asymptomatic carotid stenosis >70% is under 2%. Atherosclerotic volume has emerged as a risk factor for future stroke, but needs to be measured non-invasively. Tomographic ultrasound (tUS) is a novel technology that assembles 3D images in seconds. We evaluated accuracy of measuring Carotid Plaque Volume (CPV) with tUS in patients undergoing CEA. Consecutive patients were imaged immediately before CEA by tUS and contrast-enhanced tUS (CEtUS). CPV was measured using tUS, CEtUS and a fused images incorporating both tUS and CEtUS by trained vascular scientists. Precise volume of the endarterectomy specimen was measured using Archimedes technique. Mean±sd(range) CPV in 129 endarterectomy specimens was 0.75±0.43cm3(0.10-2.47cm3). Mean±sd CPV measured by tUS (n=114) was 0.87±0.51cm3, CEtUS (n=104) was 0.75±0.45cm3 and with fusion (n=95) was 0.83±0.49cm3. Differences between specimen volume and CPV measured by tUS (0.13±0.24cm3), CEtUS (-0.01±0.21cm3) or fusion (-0.08±0.20) were clinically insignificant. Intra-/inter-observer differences were minimal. TUS accurately measures CPV with excellent intra-/inter-observer agreement. CEtUS improves accuracy if precise CPV measurement is needed for research but tUS alone would be sufficient for population screening.