Almekkaway Mohamed K, Shehata Islam A, Ebbini Emad S
Western New England university Springfield , MA .
Int J Hyperthermia. 2015 Jun;31(4):433-42. doi: 10.3109/02656736.2015.1018966. Epub 2015 Apr 15.
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.
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/cm2, 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.
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.
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.
本研究旨在模拟高强度聚焦超声（HIFU）在非均匀介质中对体内动脉粥样硬化斑块的靶向作用。
根据治疗区域的超声图像，建立了治疗区域声学和热组织响应的时域有限差分非均匀模型。使用了一种适用于靶向外周血管的3.5 MHz双模超声阵列。该阵列在40 mm处有横向和仰角聚焦，中心有开窗，可通过该开窗放置一个7.5 MHz诊断换能器。模拟了两种情况，在股动脉内的斑块组织上进行七次相邻的HIFU照射（~5000 W/cm²，2秒暴露时间）。使用带有对流项以考虑血流的瞬态生物热方程来预测热剂量。然后将模拟模型的结果与组织学数据进行验证。
模拟模型预测了两种情况下HIFU引起的损伤，并且与组织学数据相关性良好。对于第一种情况，在靶向斑块内检测到热损伤，而对于第二种情况，在焦前区域检测到热损伤。
结果表明，基于图像的治疗区域声学和热模型能够预测对目标斑块组织的热损伤程度。该模型考虑了大动脉壁厚的影响和流动血液的散热效应。该模型用于预测体内HIFU损伤的大小和模式。
