A dynamic ultrasound simulation of a pulsating three‐layered CCA for validation of two‐dimensional wall motion and blood velocity estimation algorithms

Abstract

Purpose: A dynamic ultrasound simulation model for the common carotid artery (CCA) with three arterial layers for validation of two-dimensional wall motion and blood velocity estimation algorithms is proposed in the present study. This model describes layers with not only characteristics of echo distributions conforming to clinical ones but also varying thicknesses, axial, and radial displacements with pulsatile blood pressure during a cardiac cycle. Methods: The modeling process is as follows: first, a geometrical model according with the clinical structure size of a CCA is built based on the preset layer thicknesses and the diameter of lumen. Second, a three-dimensional scatterer model is constructed by a mapping with a Hilbert space-filling curve from the one-dimensional scatterer distribution with the position and amplitude following Gamma and Gaussian distributions, respectively. The characteristics of three layers and blood are depicted by smoothly adjusting the scatterer density, the scale, and shape parameters of the Gamma distribution as well as the mean and standard deviation of the Gaussian distribution. To obtain the values of parameters of scatterer distributions, including the shape parameter, density, and intensity, for arterial layers and blood, the envelope signals simulated from different configurations of scatterer distribution are compared with those from different kinds of tissue of CCAs in vivo through a statistic analysis. Finally, the dynamic scatterer model is realized based on the blood pressure, elasticity modulus of intima-media (IM) and adventitia, varying IM thickness, axial displacement of IM as well as blood flow velocity at central axis during a cardiac cycle. Then, the corresponding radiofrequency (RF) signals, envelope signals, and Bmode images of the pulsatile CCA are generated in a dynamic scanning mode using Field II platform. Results: The three arterial layers, blood, and surrounding tissue in simulated B-mode ultrasound images are clearly legible. The results based on a statistical analysis for the envelope signals from 30 simulations indicate that the echo characteristics of blood, intima, media, and adventitia are in accordant with clinical ones. The maximum relative errors between the preset geometrical sizes and the measured ones from the simulated images for the diameter of the lumen and the thicknesses of the intima, media, and adventitia are 0.13%, 3.89%, 1.35%, and 0.06%, respectively. For the dynamic parameters, the variation in IM thickness, the radial displacements of lumen and adventitia as well as the axial displacement of IM and blood flow velocity are measured with the mean relative errors of 68.03%, 9.27%, 2.10%, 4.93%, and 17.34%, respectively. Conclusion:The simulated results present static sizes and dynamical variations according with preset values; echo distributions conforming to clinical versions. Therefore, the presented simulation model could be useful as a data source to evaluate the performance of studies on measurements of ultrasound-based tissue...

Fully Automatic Measurement of Intima-Media Thickness in Ultrasound Images of the Common Carotid Artery Based on Improved Otsu’s Method and Adaptive Wind Driven Optimization

“…The corresponding number of pixels is approximately 0.3SR-1.4SR. According to the structure characteristics of the IMCs of the carotid ultrasound images (see Figure 1) and the previous researches, 35 the gray level of the adventitia is far greater than that of both the intima and lumen, and the gray level of intima is far greater than that of the media. Thus, it can be assumed that the location of the LII in the far wall should meet one of the following two conditions: (a) the mean gray level of the pixels located at 1.4SR pixels under the LII is 1.3 times higher than that of the pixels of the LII; or (b) the mean gray level of the pixels of the LII is 1.3 times higher than that of the pixels located at 0.3SR pixels under the LII.…”

Simulation of Ultrasound RF Signals Backscattered from a 3D Model of Pulsating Artery Surrounded by Tissue

“…The PW is estimated from the in vivo RF signals of the vessel wall using a 1D normalized cross-correlation (NCC) algorithm based on echo tracking. For the motion in the radial direction, Hu et al [ 22 ] proposed an isotropous pulse model with elasticity to describe the relationship between radial displacement and blood pressure. However, neither of the previous studies consider the longitudinal motion of the artery together with radial and longitudinal motions slope deep into the tissue.…”