Chiang Jason, Birla Sohan, Bedoya Mariajose, Jones David, Subbiah Jeyam, Brace Christopher L
IEEE Trans Biomed Eng. 2015 Feb;62(2):657-63. doi: 10.1109/TBME.2014.2363173. Epub 2014 Oct 15.
Numerical simulation is increasingly being utilized for computer-aided design of treatment devices, analysis of ablation growth, and clinical treatment planning. Simulation models to date have incorporated electromagnetic wave propagation and heat conduction, but not other relevant physics such as water vaporization and mass transfer. Such physical changes are particularly noteworthy during the intense heat generation associated with microwave heating. In this paper, a numerical model was created that integrates microwave heating with water vapor generation and transport by using porous media assumptions in the tissue domain. The heating physics of the water vapor model was validated through temperature measurements taken at locations 5, 10, and 20 mm away from the heating zone of the microwave antenna in homogenized ex vivo bovine liver setup. Cross-sectional area of water vapor transport was validated through intraprocedural computed tomography (CT) during microwave ablations in homogenized ex vivo bovine liver. Iso-density contours from CT images were compared to vapor concentration contours from the numerical model at intermittent time points using the Jaccard index. In general, there was an improving correlation in ablation size dimensions as the ablation procedure proceeded, with a Jaccard index of 0.27, 0.49, 0.61, 0.67, and 0.69 at 1, 2, 3, 4, and 5 min, respectively. This study demonstrates the feasibility and validity of incorporating water vapor concentration into thermal ablation simulations and validating such models experimentally.
数值模拟越来越多地用于治疗设备的计算机辅助设计、消融生长分析和临床治疗规划。迄今为止的模拟模型已纳入电磁波传播和热传导，但未考虑其他相关物理过程，如水汽化和传质。在与微波加热相关的强烈发热过程中，这种物理变化尤为值得关注。在本文中，通过在组织域中使用多孔介质假设，创建了一个将微波加热与水蒸气生成和传输相结合的数值模型。通过在均质化离体牛肝装置中距微波天线加热区5、10和20毫米处进行温度测量，验证了水蒸气模型的加热物理过程。在均质化离体牛肝的微波消融过程中，通过术中计算机断层扫描（CT）验证了水蒸气传输的横截面积。使用杰卡德指数，在间歇性时间点将CT图像的等密度轮廓与数值模型的蒸汽浓度轮廓进行比较。一般来说，随着消融过程的进行，消融尺寸维度的相关性不断提高，在1、2、3、4和5分钟时的杰卡德指数分别为0.27、0.49、0.61、0.67和0.69。本研究证明了将水蒸气浓度纳入热消融模拟并通过实验验证此类模型的可行性和有效性。
