New three-dimensional volumetric ultrasound probe for accurate quantification of atherosclerotic plaque volume
Authors: Lopez Melgar B , Mass V , Nogales P , Sanchez-Gonzalez J , Entrekin R , Collet-Billon A , Oliva B , Fernandez-Friera L , Sanz J , Fernandez-Ortiz A , Bentzon J.F , Bueno H , Ibanez B , Fuster V 
Published: November 2020

Abstract

Background
Atherosclerosis burden is directly related with the development of clinical cardiovascular events. Recent ESC guidelines endorse carotid and/or femoral plaque burden assessment as a complement for conventional cardiovascular risk evaluation. Compared with previous 3D probes, new 3D-matrix transducers for vascular ultrasound imaging are designed to improve functionality and image quality for an accurate study of atherosclerosis burden.

Purpose
We aimed to validate a commercially available 3D-matrix transducer for plaque volume measurement in early disease stages (small plaques) when accurate plaque detection and quantification is challenging, and intermediate-advanced (medium-large size) plaques in carotid and femoral arteries.

Methods
We performed an ex vivo study using carotid and femoral arterial specimens from a pig model of early atherosclerosis in which actual 3D vascular ultrasound (3DVUS) volume measurements obtained using the new 3D-matrix transducer (XL14–3) were correlated against gold-standard histological measurements. Moreover, we performed a clinical experiment in a subset of intermediate-high risk patients from the “Athero-Brain: Head to Heart (H2H)” study with patent carotid and femoral atherosclerosis for comparing plaque volume evaluated by the new XL14–3 3D-matrix transducer, based on “electronic” 3D-sweep technology, with that measured by previously validated VL13–5 “mechanical” 3D-sweep transducer that uses a mechanically steered linear-array.

Results
In the ex vivo setting, we evaluated 11 atherosclerotic plaques (6 carotid and 5 femoral plaques, mean plaque volume 16.5±22.5 mm3 ranging in size from 1 to 56 mm3), finding a strong correlation between 3DVUS measures and the histological gold-standard with an intraclass correlation coefficient (ICC) of 0.994 (95% CI [0.976; 0.998]). In the clinical setting, we measured 25 plaques (14 carotid and 11 femoral plaques; mean plaque volume 273.4±216.5 mm3 ranging in size from 10 to 859 mm3) from 8 patients (mean age 75±5 years old, 45% men) finding again a strong correlation between 3DVUS electronic-based and mechanical-based volume measurements (ICC=0.996 95% CI [0.991; 0.998]). Correlation and Bland-Altman plots for the measurements of both experiments are displayed in the figure and showed good agreement (Slope close to 1 in the Passing Bablock analysis) with small or lower than clinically relevant differences between measurements.

Conclusions
3DVUS using new matrix technology accurately measures plaque volumes of early (small-size) to intermediate-advanced plaques located in superficial arteries like carotid and femoral arteries.
Figure 1

Funding Acknowledgement
Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Institute of Health Carlos III Institute through an Integrated Excellence Project Grant