血管位置对HIFU焦域温度场的影响

目的 数值仿真研究不同位置的血管对高强度聚焦超声(HIFU)可治疗焦域的影响,为HIFU治疗安全性和可靠性提供理论依据.方法 应用超声非线性传播方程、Pennes生物热传导方程以及FDTD法数值仿真温度场分布.结果 考虑血流灌注与否,HIFU焦域温度场分布相一致.血管中心位于声轴时,焦域中心温升非常低;当血管偏离声轴小于3.0mm时,可治疗焦区不再关于声轴对称,焦域中心温升没有明显变化;当血管偏离声轴大于3.0 mm时,血管对可治疗区域的温度场分布基本无影响.结论 脂肪组织内血流灌注对HIFU焦域温度场的影响可以不予考虑;直径2 mm血管位于可治疗区域内,对血管内及周边组织温升影响很大,可能导致血管周围组织不完全致死;当直径2 mm血管距声轴小于3 mm对可治疗区域仍有影响,但大于3.0 mm时,血管对可治疗区域的影响可以不予考虑.

Effect of blood vessel locations on high intensity focused ultrasound temperature field

Objective To improve the safety and reliability in HIFU therapy, the effects of the vessel locations on the high intensity focused ultrasound temperature field were investigated. Methods The temperature distribution was obtained by combining the nonlinear acoustic propagation formula and the Pennes bio-heat transfer equation, as well as the finite difference time domain method. Results The HIFU temperature fields were almost unchangeable whether the vessels had perfusion or not. However, there was a significant reduction in the center temperature rise, while the vessel was located in the acoustic axis. If the distance between the vessel wall and the acoustic axis was leas than 3.0mm, the therapeutic focal region was no longer symmetric and the change in the peak temperature rise was negligible. Neither did the change in the temperature field if the distance was larger than 3.0 mm. Conclusion The effects of vessel perfusion on the HIFU temperature field may be ignored. When the vessel is located within the therapeutic region, the one with 2 mm diameter has a significant effect on the temperature rise of the endovascular and the surrounding tissues, leading to incomplete infarct of the tissues around the vessel. When the distance is leas than 3.0 mm, the vessel with 2 mm diameter might affect the distribution of temperature field. While the effect is negligible, if the distance is larger than 3.0 mm.