Robert R. Entrekin

Real-time spatial compound imaging: Application to breast, vascular, and musculoskeletal ultrasound

Real-time spatial compound imaging (SonoCT) is an ultrasound technique that uses electronic beam steering of a transducer array to rapidly acquire several (three to nine) overlapping scans of an object from different view angles. These single-angle scans are averaged to form a multiangle compound image that is updated in real time with each subsequent scan. Compound imaging shows improved image quality compared with conventional ultrasound, primarily because of reduction of speckle, clutter, and other acoustic artifacts. Early clinical experience suggests that real-time spatial compound imaging can provide improved contrast resolution and tissue differentiation that is beneficial for imaging the breast, peripheral blood vessels, and musculoskeletal injuries. Future development of real-time spatial compound imaging will help address the bulk of general imaging applications by extending this technology to curved array transducers, tissue harmonics, panoramic imaging, and three-dimensional sonography.

Fetal heartbeat doppler transducer

A doppler transducer which is particularly well adapted for use in fetal heartbeat measurements is comprised of a piston type transducer with a pair of lenses, which together provide both a divergent acoustic pattern and a flat surface for good acoustic coupling between the transducer and the mothers abdomen.

Characterization of Carotid Plaques on 3-Dimensional Ultrasound Imaging by Registration With Multicontrast Magnetic Resonance Imaging

The ability of magnetic resonance imaging (MRI) in carotid plaque component identification has been well established. However, compared to the costly nature of MRI, 3‐dimensional (3D) ultrasound imaging is a more cost‐effective assessment tool. Thus, an attractive alternative for carotid disease monitoring would be to establish a strategy in which 3D ultrasound imaging is used as a screening tool that precedes MRI. To develop and validate such a protocol, registration between ultrasound and MR images is required. This article introduces a surface‐based algorithm for efficient ultrasound imaging‐MRI registration.

Real-Time Spatial Compound Imaging: Technical Performance in Vascular Applications

Spatial compound imaging is a technique in which a number of co-planar, tomographic ultrasound images of an object are obtained from different directions, then combined into a single compound image. Real-time spatial compounding uses electronic beam steering to rapidly acquire component frames from different view angles. The component frames are combined at real-time frame rates to produce compound images with reduced speckle and improved continuity of specular reflectors. Real-time spatial compounding was first reported over 30 years ago, but it has only recently become available on commercial ultrasound systems. This paper describes the technical performance characteristics of real-time spatial compound imaging on the ATL HDI 5000 system, and considers the clinical relevance of these characteristics in vascular sonography.

Reproducibility of Two 3-D Ultrasound Carotid Plaque Quantification Methods

Compared with single 2-D images, emerging 3-D ultrasound technologies hold the promise of reducing variability and increasing sensitivity in the quantification of carotid plaques for individual cardiovascular risk stratification. Inter- and intra-observer agreement between a manual, cross-sectional, 2-D freehand sweep and a mechanical 3-D ultrasound investigation of 62 carotid artery plaques is reported with intra-class correlation coefficients (with 95% confidence intervals). Inter-observer agreement was 0.60 (0.29-0.77) for the freehand method and 0.89 (0.83-0.93) for the mechanical 3-D acquisition. The use of semi-automated computerized planimetric measurements of plaque burden has high intra-observer repeatability, but is vulnerable to systematic inter-observer differences. For the 2-D freehand sweep, a considerable contribution to variation is introduced by the scanning procedure itself, that is, the lack of controlled motion along the third dimension. Future implementation of 3-D ultrasound quantification in large-scale studies of inter-individual cardiovascular risk assessment seems justified using the methods described.

Inter-Scan Reproducibility of Carotid Plaque Volume Measurements by 3-D Ultrasound

We tested a novel 3-D matrix transducer with respect to inter-scan reproducibility of carotid maximum plaque thickness (MPT) and volume measurements. To improve reproducibility while focusing on the largest plaque/most diseased part of the carotid artery, we introduced a new partial plaque volume (PPV) measure centered on MPT. Total plaque volume (TPV), PPV from a 10-mm segment and MPT were measured using dedicated semi-automated software on 38 plaques from 26 patients. Inter-scan reproducibility was assessed using the t-test, Bland-Altman plots and Pearsons correlation coefficient. There was a mean difference of 0.01 mm in MPT (limits of agreement: -0.45 to 0.42 mm, Pearsons correlation coefficient: 0.96). Both volume measurements exhibited high reproducibility, with PPV being superior (limits of agreement: -35.3 mm3 to 33.5 mm3, Pearsons correlation coefficient: 0.96) to TPV (limits of agreement: -88.2 to 61.5 mm3, Pearsons correlation coefficient: 0.91). The good reproducibility revealed by the present results encourages future studies on establishing plaque quantification as part of cardiovascular risk assessment and for follow-up of disease progression over time.