Abstract

Objective: In magnetic particle hyperthermia, a promising least-invasive cancer treatment, malignant regions in proximity with magnetic nanoparticles undergo heat stress, while unavoidably surrounding healthy tissues may also suffer from heat either directly or indirectly by the induced eddy currents, due to the developed electric fields as well. Here, we propose a facile upgrade of a typical magnetic particle hyperthermia protocol, to selectively mitigate eddy currents' heating without compromising the beneficial role of heating in malignant regions.

Method: The key idea is to apply the external magnetic field intermittently (in an ON/OFF pulse mode), instead of the continuous field mode typically applied. The parameters of the intermittent field mode, such as time intervals (ON time: 25-100 s, OFF time: 50-200 s, Duty Cycle:16-100%) and field amplitude (30-70 mT) are optimized based on evaluation on healthy tissue and cancer tissue phantoms. The goal is to sustain in cancer tissue phantom the maximum temperature increase (preferably within 4-8°C above body temperature of 37°C), while in the healthy tissue phantom temperature variation is suppressed far below the 4°C dictating the eddy current mitigation.

Results: Optimum conditions of intermittent field (ON/OFF: 50/100 in s, Duty Cycle: 33%, magnetic field: 45mT) are then examined in ex-vivo samples verifying the successful suppression of eddy currents. Simultaneously, a well-elaborated theoretical approach provides a rapid calculation of temperature increase and, furthermore, the ability to quickly simulate a variety of duty cycle times and field controls may save experimental time.

Conclusion: Eventually, the application of an intermittent field mode in a magnetic particle hyperthermia protocol, succeeds in eddy current mitigation in surrounding tissues and allows for the application of larger field amplitudes that may augment hyperthermia efficiency without objecting typical biomedical applicability field constraints such as Brezovich criterion.

摘要

目的：在磁粉热疗中，一种有前途的微创癌症治疗方法，由于磁性磁粉热的产生，与磁性磁粉邻近的恶性区域会受到热应激，而不可避免地，周围健康组织也可能会直接或间接地受到感应涡流的加热。电场。在这里，我们建议对典型的磁粉热疗方案进行简便的升级，以选择性地减轻涡流的加热而又不损害在恶性区域加热的有益作用。

方法：关键思想是间歇性地施加外部磁场（以ON / OFF脉冲模式），而不是通常采用的连续磁场模式。时间间隔（ON时间：25-100 s，OFF时间：50-200 s，占空比：16-100％）和场振幅（30-70 mT）等间歇场模式的参数进行了优化健康组织和癌症组织模型的评估。目的是在癌症组织体模中维持最大温度升高（最好在高于体温37°C 4-8°C之内），而在健康组织中，体模温度变化被抑制到远低于指示涡流的4°C。减轻。

结果：然后在离体样品中检查间歇磁场的最佳条件（开/关：50/100 in s，占空比：33％，磁场：45mT），以验证涡流的成功抑制。同时，精心设计的理论方法可以快速计算出温度升高，此外，能够快速模拟各种占空比时间和现场控制的功能可以节省实验时间。

结论：最终，将间歇场模式应用在磁粉热疗方案中，成功缓解了周围组织中的涡流，并允许应用更大的磁场幅度，从而可以提高热疗效率，而无需反对典型的生物医学适用性领域约束，例如Br​​ezovich标准。