Theoretical and experimental quantification of carotid plaque volume measurements made by three‐dimensional ultrasound using test phantoms

Abstract

An accurate technique that exhibits low variability has practical importance for the quantification of carotid plaque volume. Such a technique is necessary to monitor plaque progression or regression that may result in response to nonsurgical therapy. In this study, we investigate the accuracy and variability of plaque volume measurement by three-dimensional ultrasound using vascular plaque phantoms over a range of 68.2 mm3 to 285.5 mm3. The agar plaques maintained a consistent cylindrical geometry with variations in the height, length, and echogenicity. The volume of each plaque was determined by water displacement. The three-dimensional (3D) ultrasound (US) images were acquired with a mechanical scanning system which creates a 3D US Cartesian volume, that was manipulated and viewed in any orientation, from a collection of conventional parallel two-dimensional (2D) US images. The plaque volumes were measured by serial 2D manual planimtery. The mean accuracy in plaque volume measurement was 3.1+/-0.9%. Variability in plaque volume measurement was calculated to be 4.0+/-1.0% and 5.1+/-1.4% for intraobserver and interobserver measurements, respectively. We have also developed a theoretical description for the variance in measurement of plaque volume using manual planimetry. Root-mean-square difference between experimentally and theoretically determined values of plaque volume fractional variance was 9%.

Measurement of Carotid Plaque Volume by 3-Dimensional Ultrasound

“…Our values of 6.5% and 6.9% obtained for the intraobserver and interobserver measurement variability of the plaques investigated are comparable to the corresponding variability reported by Delcker et al, 14 -16 as well as the results obtained in vitro on plaque phantoms. 19 In addition, coefficients of reliability in our study were similar to those reported by other investigators and very close to unity (see Table 2) for intraobserver and interobserver measurements, suggesting clinical utility. 17 Although other investigators have measured plaque volume spanning a similar range as ours, 17,18 our study differs in that we have reported the intraobserver and interobserver variabilities as a function of plaque volume.…”

“…19 The initial slice location and the variability in the plaque boundary for each slice are not dependent on selection of the ISD. Therefore, the nonlinear relation between measurement accuracy and ISD (Figure 4) is a result of the inaccurate determination of the final edge of the plaque for ISDs Ͼ3.0 mm.…”

“…The 3D US images of plaque volumes were measured by manual planimetry, a method that has been investigated on test phantoms 19 and patient anatomy. 14,15 Each observer sliced the 3D image with an ISD of 1.0 mm from 1 end of the plaque to the other (along the vessel axis in the scan direction) and traced the individual plaque boundaries on the image plane by using a mouse-driven cross-hair cursor.…”

Progression of Carotid Plaque Volume Predicts Cardiovascular Events

“…As previously described, 17,18 TPV was measured with a software update permitting semiautomated segmentation of the lumen.…”

Pulmonary Abnormalities and Carotid Atherosclerosis in Ex-Smokers without Airflow Limitation

“…Gain, focal points and time-depth compensation were optimized by the sonographer taking into consideration neck size, carotid anatomy and tissue depth. Two dimensional images were reconstructed into a 3D volume as previously described (39,40). MRI was performed on a whole body 3.0 Tesla Discovery 750MR (General Electric Health Care, Milwaukee, Wisconsin, USA) MRI system.…”