Anatomical-based model for simulation of HIFU-induced lesions in atherosclerotic plaques

Abstract

Purpose: The aim of this study was to simulate the effect of high intensity focused ultrasound (HIFU) in non-homogenous medium for targeting atherosclerotic plaques in vivo. Materials and methods: A finite-difference time-domain heterogeneous model for acoustic and thermal tissue response in the treatment region was derived from ultrasound images of the treatment region. A 3.5 MHz dual mode ultrasound array suitable for targeting peripheral vessels was used. The array has a lateral and elevation focus at 40 mm with fenestration in its centre through which a 7.5 MHz diagnostic transducer can be placed. Two cases were simulated where seven adjacent HIFU shots ($5000 W/cm 2 , 2-s exposure time) were targeted on the plaque tissue within the femoral artery. The transient bioheat equation with a convective term to account for blood flow was used to predict the thermal dose. The results of the simulation model were then validated against the histology data. Results: The simulation model predicted the HIFU-induced damage for both cases, and correlated well with the histology data. For the first case thermal damage was detected within the targeted plaque, while for the second case thermal damage was detected in the pre-focal region. Conclusion: The results suggest that a realistic, image-based acoustic and thermal model of the treatment region is capable of predicting the extent of thermal damage to target plaque tissue. The model considered the effect of the wall thickness of large arteries and the heat-sink effect of flowing blood. The model is used for predicting the size and pattern of HIFU damage in vivo.

Integration of gene expression and DNA methylation profiles provides a molecular subtype for risk assessment in atherosclerosis

“…Atherosclerosis (AS) of the carotid arteries is a major cause of stroke and transient ischemic attack, which remains the leading cause of mortality in China and is currently the most common cause of mortality worldwide (1,2). The symptoms of AS are not always detected by patients until complications arise and the therapeutic methods to treat AS are poor; therefore, it is particularly important to establish an appropriate, rigorous and efficient detection strategy for early-phase AS, in order to limit disease progression before it results in clinical consequences (3). There are two prevalent methods for diagnosing AS: Doppler ultrasound and computed tomographic angiography (CTA), which have become the standard methods for diagnosing AS (4,5).…”

Safety and feasibility of arterial wall targeting with robot-assisted high intensity focused ultrasound: a preclinical study

“…HIFU/DMUA therapy was applied with an initial intensity of approximately 6.25 kW/cm 2 , in situ, which was estimated based on array modeling and estimated tissue attenuation/ absorption in the treatment region [21]. At this intensity level, tissue boiling is expected to occur within 40-200 ms of the initiation of the HIFU shot [29][30][31].…”

“…Focusing HIFU beams will result in a rapid rise of local tissue temperature, which will result in local tissue damage through coagulative necrosis. Using the HIFU/DMUA system, real-time closed-loop control is used to monitor the lesion formation [21,22].…”

“…HIFU/DMUA-treatment of the atherosclerotic plaque and adjacent vasa vasorum might interrupt the cycle of cholesterol accumulation, inflammation, cholesterol crystallization and plaque destabilization, by attenuating and destroying the intraplaque macrophages and foam cells [11,23,24] and by occluding the leaky vasa vasorum [13][14][15][16]. It is hypothesized that ablation of the plaque will lead to renewed efferocytosis and healing by fibrosis [25], caused by an influx of phagocytes from surrounding tissue, after which the newly formed fibrotic tissue will retract over time, leading to plaque stabilization and shrinkage [21]. HIFU/DMUA has been shown feasible in targeting atherosclerotic plaques by creating discrete thermal lesions within the plaque, without damaging the vascular endothelium [26].…”

A fast full-wave solver for calculating ultrasound propagation in the body

“…However, HAS does not resolve the fullwave physics of multiple scattering and internal reflections within each https://doi.org/10.1016/j.ultras.2020.106240 medium [6,10]. Such deficiencies can be addressed using full-wave models such as finite-difference time domain (FDTD) approaches [11][12][13], and k-space pseudospectral methods [5,14,15]. In 3D however, these methods require the use of very dense volumetric grids to counteract the accumulation of numerical dispersion [5].…”