Faridi Pegah, Keselman Paul, Fallahi Hojjatollah, Prakash Punit
Mike Wiegers Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, 66506, USA.
Hoglund Brain Imaging Center, University of Kansas Medical Center, Kansas City, KS, 66160, USA.
Med Phys. 2020 Sep;47(9):3777-3788. doi: 10.1002/mp.14318. Epub 2020 Jul 16.
Computational models are widely used during the design and characterization of microwave ablation (MWA) devices, and have been proposed for pretreatment planning. Our objective was to assess three-dimensional (3D) transient temperature and ablation profiles predicted by MWA computational models with temperature profiles measured experimentally using magnetic resonance (MR) thermometry in ex vivo bovine liver.
We performed MWA in ex vivo tissue under MR guidance using a custom, 2.45 GHz water-cooled applicator. MR thermometry data were acquired for 2 min prior to heating, during 5-10 min microwave exposures, and for 3 min following heating. Fiber-optic temperature sensors were used to validate the accuracy of MR temperature measurements. A total of 13 ablation experiments were conducted using 30-50 W applied power at the applicator input. MWA computational models were implemented using the finite element method, and incorporated temperature-dependent changes in tissue physical properties. Model-predicted ablation zone extents were compared against MRI-derived Arrhenius thermal damage maps using the Dice similarity coefficient (DSC).
Prior to heating, the observed standard deviation of MR temperature data was in the range of 0.3-0.7°C. Mean absolute error between MR temperature measurements and fiber-optic temperature probes during heating was in the range of 0.5-2.8°C. The mean DSC between model-predicted ablation zones and MRI-derived Arrhenius thermal damage maps for 13 experimental set-ups was 0.95. When comparing simulated and experimentally (i.e. using MRI) measured temperatures, the mean absolute error (MAE %) relative to maximum temperature change was in the range 5%-8.5%.
We developed a system for characterizing 3D transient temperature and ablation profiles with MR thermometry during MWA in ex vivo liver tissue, and applied the system for experimental validation of MWA computational models.
计算模型在微波消融（MWA）设备的设计和特性描述过程中被广泛应用，并且已被提议用于治疗前规划。我们的目标是评估MWA计算模型预测的三维（3D）瞬态温度和消融轮廓，并与在离体牛肝中使用磁共振（MR）测温法实验测量的温度轮廓进行比较。
我们在MR引导下，使用定制的2.45 GHz水冷式消融器在离体组织中进行MWA。在加热前2分钟、微波照射5 - 10分钟期间以及加热后3分钟采集MR测温数据。使用光纤温度传感器验证MR温度测量的准确性。在消融器输入端施加30 - 50 W的功率，共进行了13次消融实验。使用有限元方法实现MWA计算模型，并纳入了组织物理特性随温度的变化。使用骰子相似系数（DSC）将模型预测的消融区范围与MRI衍生的阿伦尼乌斯热损伤图进行比较。
加热前，MR温度数据的观测标准差在0.3 - 0.7°C范围内。加热期间MR温度测量值与光纤温度探头之间的平均绝对误差在0.5 - 2.8°C范围内。13个实验设置的模型预测消融区与MRI衍生的阿伦尼乌斯热损伤图之间的平均DSC为0.95。在比较模拟温度和实验测量温度（即使用MRI测量）时，相对于最大温度变化的平均绝对误差（MAE%）在5% - 8.5%范围内。
我们开发了一个系统，用于在离体肝组织的MWA过程中通过MR测温法表征3D瞬态温度和消融轮廓，并将该系统应用于MWA计算模型的实验验证。
