Department of Imaging Physics, M.D. Anderson Cancer Center, University of Texas, Houston, TX 77030, USA.
Int J Hyperthermia. 2011;27(5):453-64. doi: 10.3109/02656736.2011.557028.
Magnetic resonance-guided laser-induced thermal therapy (MRgLITT) is currently undergoing initial safety and feasibility clinical studies for the treatment of intracranial lesions in humans. As studies progress towards evaluation of treatment efficacy, predictive computational models may play an important role for prospective 3D treatment planning. The current work critically evaluates a computational model of laser induced bioheat transfer against retrospective multiplanar MR thermal imaging (MRTI) in a canine model of the MRgLITT procedure in the brain.
A 3D finite element model of the bioheat transfer that couples Pennes equation to a diffusion theory approximation of light transport in tissue is used. The laser source is modelled conformal with the applicator geometry. Dirichlet boundary conditions are used to model the temperature of the actively cooled catheter. The MRgLITT procedure was performed on n = 4 canines using a 1-cm diffusing tip 15-W diode laser (980 nm). A weighted L₂norm is used as the metric of comparison between the spatiotemporal MR-derived temperature estimates and model prediction.
The normalised error history between the computational models and MRTI was within 1-4 standard deviations of MRTI noise. Active cooling models indicate that the applicator temperature has a strong effect on the maximum temperature reached, but does not significantly decrease the tissue temperature away from the active tip.
Results demonstrate the computational model of the bioheat transfer may provide a reasonable approximation of the laser-tissue interaction, which could be useful for treatment planning, but cannot readily replace MR temperature imaging in a complex environment such as the brain.
磁共振引导激光诱导热疗（MRgLITT）目前正在进行人体颅内病变治疗的初步安全性和可行性临床研究。随着研究向治疗效果评估的推进，预测性计算模型可能在前瞻性 3D 治疗计划中发挥重要作用。目前的工作对激光诱导生物传热的计算模型进行了严格评估，该模型通过回顾性多平面磁共振热成像（MRTI）对大脑中的 MRgLITT 程序进行了犬模型研究。
使用耦合了 Pennes 方程和组织中光传输扩散理论近似的 3D 有限元生物传热模型。激光源与热疗器的几何形状一致。使用狄利克雷边界条件来模拟主动冷却导管的温度。在 n = 4 只犬中进行了 1-cm 扩散尖端 15-W 二极管激光（980nm）的 MRgLITT 手术。采用加权 L₂范数作为比较时空 MR 衍生温度估计值与模型预测值的度量。
计算模型与 MRTI 之间的归一化误差历史记录在 MRTI 噪声的 1-4 个标准差范围内。主动冷却模型表明，热疗器温度对达到的最高温度有很强的影响，但不会显著降低远离主动尖端的组织温度。
结果表明，生物传热的计算模型可以合理地近似激光与组织的相互作用，这对于治疗计划可能是有用的，但在像大脑这样的复杂环境中，它不能轻易替代磁共振温度成像。
