HIFU治疗中血流对加热影响的仿真研究

Simulation Research on Influence of Blood Flow on Heating During HIFU Treatment

血管存在于肿瘤组织内部时,肿瘤组织靠近血管的边界部分会受到血管冷却效应的较大影响,这种影响会导致肿瘤治疗不彻底。针对此种情况,以凹球面换能器作为仿真热源,通过瑞利积分求得声强分布,并利用有限差分法对生物热传导方程进行求解,结合加热时间和温度的定量关系,计算出热剂量分布情况来判定组织的热损伤程度,研究血流对加热的影响。仿真结果表明:由于血管的存在,损伤区域被分成两部分,焦域内热剂量减小;血管尺寸、血流速度或血液灌注率增大,有效热剂量范围明显减小;血管越靠近焦域中心,其影响越大。

When blood vessel exists in the tumor tissue, and its boundary portion close to the vessel will be strongly influenced by the cooling effect of the blood vessel. This influence will lead to the incomplete cancer treatment. To study the influence of blood flow on heating towards the above situation, concave spherical transducer was used as the heat source, and sound intensity distribution was obtained by Rayleigh integral. Pennes equation was solved with finite difference method, then the dose distribution was calculated to determine the thermal damage degree of tissue using quantitative relationship between the heating time and temperature. The simulation results show that damage area is divided into two parts, and thermal dose of internal focus field decreases as a result of the existence of blood vessel; while the size of blood vessel, blood flow velocity or blood perfusion rate increase, the ranges of effective thermal dose obviously decrease; blood vessel is closer to internal focus field, the influence is bigger.