磁流体的非均匀分布对磁感应热疗温度场的影响

Effect of Non-uniform Distribution of the Magnetic Induction of the Magnetic Fluid Hyperthermia Temperature Field

温度场分布的均匀性决定了磁流体热疗的治疗效果,温度场的分布特性与磁场分布和磁流体分布密切相关。针对实际亥姆霍兹线圈产生的非均匀分布磁场情况,在多点注射策略的基础上,进一步探究磁流体非均匀分布对温度场的影响,为磁流体热疗的临床应用提供理论依据。以磁流体热疗过程中生物组织内的温度场分布为研究对象,以最大化肿瘤组织内温度达到42~46℃的体积分数为研究目标,探究不同中心-边界注射体积比对温度场的影响,从而增加温度场分布的均匀性。将生物组织简化为同心球模型,通过建立结合磁场、磁流体产热功率及生物传热的物理模型,利用有限元方法对模型进行数值求解。为考虑磁流体热疗的实际情况,通过物理模型分析了随生物组织温度变化的血液灌注率和磁流体注射后浓度的分布差异。结果表明:考虑实际磁场非均匀分布时,温差随着生物组织中心与磁场中心偏移距离的增大而增大,偏移10 mm时会造成1℃的温度差异,因此,当生物组织中心与磁场中心有较大差异时要考虑实际磁场分布情况;非等剂量多点注射可以降低组织内的最高温度,使更多肿瘤组织处于合理治疗温度区间内,注射体积比k在1~2时对体积分数影响较大;注射体积不变,与5点注射相比,7点注射合理温度的体积分数更大,其温度空间分布也更加均匀。

Since the uniformity of the temperature field distribution determines the therapeutic effect of magnetic fluid hyperthermia,the distribution characteristics of the temperature field are closely related to the magnetic field distribution and the magnetic fluid distribution. In this article,the non-uniform distribution of the magnetic field produced by the actual Helmholtz coil was considered,and the influence of the non-uniform distribution of the magnetic fluid on the temperature field were further explored based on the multi-point injection strategy,and a theoretical basis for the clinical application of magnetic fluid hyperthermia was provided. This paper took the temperature field distribution in biological tissues during magnetic fluid hyperthermia as the research object,and aimed to maximize the volume fraction in tumor tissues up to 42 ~ 46 ℃ to explore the influence of different center-border injection ratios on the temperature field,thereby increasing the uniformity of the temperature field distribution. The biological tissue was simplified into a concentric sphere model,and a physical model combining the magnetic field,the heat generation power of the magnetic fluid and the biological heat transfer was established,and the finite element method was used to numerically solve the model. In order to consider the actual situation of magnetic fluid hyperthermia,the physical model analyzed the difference in the distribution of blood perfusion rate and the concentration of magnetic fluid after the temperature of the biological tissue changes. The results indicated that with the increasing of the offset distance between the center of the biological tissue and magnetic field,the temperature difference increased;when the offset was 10 mm,it would cause a temperature difference of 1 ℃;therefore,when there was a big difference between the center of the biological tissue and the center of the magnetic field,the actual magnetic field distribution should be considered;non-equal dose multi-point injection could make more tumor tissues be in a reasonable treatment temperature range. When the injection ratio k was 1 ~ 2,the volume fraction would be more affected;reduced the maximum temperature in the tissue,so that more tumor tissues were in a reasonable treatment temperature range;when the injection volume remained the same,compared with the 5-point injection,the 7-point injection had a larger volume fraction at a reasonable temperature,and its temperature spatial distribution was more uniform.