Abstract

Objective

To create an improved planning method for pediatric regional hyperthermia (RHT) using the SIGMA-30 applicator (SIGMA-30).

Materials and Methods

An electromagnetic model of SIGMA-30 was generated for use with the finite-difference time-domain (FDTD) method. Applying special MATLAB-based algorithms, voxel models of a pediatric patient with pelvic rhabdomyosarcoma were created from Computed-Tomography (CT) contours for use with the FDTD method and the finite-difference (FD) method capable of using either temperature-independent or temperature-dependent perfusion models for solving the Bioheat Transfer Equation (BHTE). Patient models were parametrized regarding, first, the positioning in the applicator, second, the absorbed power range and, third, different perfusion models, resulting in the so-called Parametrized Treatment Models (PTMs). A novel dedicated optimization procedure was developed based on quantitative comparison of numerical calculations against temperature and power measurements from two RHT therapies.

Results

Using measured data, a realistic absorbed power range in the patient model was estimated. Within this range, several FDTD and BHTE runs were performed and, applying the aforementioned optimization scheme, the best PTMs and perfusion models were identified for each therapy via a retrospective comparison with measurements in 14 temperature sensor positions: 5 in the tumor, 8 in rectum and one in bladder.

Conclusion

A novel dedicated optimization procedure for identification of suitable patient-specific electromagnetic and thermal models, which can be used for improved patient planning, was developed and evaluated by comparison with treatment-derived measurements using SIGMA-30. The optimization procedure can be extended to other hyperthermia applicators and to other patient types, including adults.

中文翻译：

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基于针对SIGMA-30涂药器的参数化电磁和热模型改进的针对患者的热疗计划

摘要

客观的

使用SIGMA-30涂药器（SIGMA-30）创建小儿局部热疗（RHT）的改进计划方法。

材料和方法

生成了SIGMA-30的电磁模型，用于时域有限差分（FDTD）方法。应用基于MATLAB的特殊算法，从计算机断层扫描（CT）轮廓创建儿童盆腔横纹肌肉瘤患者的体素模型，以与FDTD方法和能够使用温度无关或温度无关的有限差分（FD）方法一起使用依赖的灌注模型来求解生物热传递方程（BHTE）。对患者模型进行参数设置，首先考虑到施药器中的位置，其次，确定吸收功率范围，其次是不同的灌注模型，从而形成所谓的参数化治疗模型（PTM）。基于对两种RHT疗法的温度和功率测量值的数值计算的定量比较，开发了一种新颖的专用优化程序。

结果

使用测量的数据，可以估算出患者模型中的实际吸收功率范围。在此范围内，进行了几次FDTD和BHTE运行，并应用上述优化方案，通过回顾性比较并在14个温度传感器位置进行测量，确定了每种疗法的最佳PTM和灌注模型：在肿瘤中5个位置，在直肠中8个位置还有一个在膀胱中。

结论

通过与使用SIGMA-30的治疗衍生测量结果进行比较，开发并评估了一种新颖的专用优化程序，用于识别合适的特定于患者的电磁和热模型，该模型可用于改进患者计划。优化程序可以扩展到其他热疗器和其他患者类型，包括成人。