Physical modeling of microwave ablation zone clinical margin variance
Physical modeling of microwave ablation zone clinical margin variance
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DOI：
10.1118/1.4942980
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发表时间：
2016-04-01
期刊：
影响因子：
3.8
通讯作者：
Prakash, Punit
中科院分区：
文献类型：
--
作者：
Deshazer, Garron;Merck, Derek;Prakash, Punit
目的：本研究的目的是通过模拟测量以下因素的影响：(1) 肿瘤与健康组织中生物物理参数的异质性，(2) 施源器相对于肿瘤的放置位置，以及 (3) 与大血管的接近程度对微波消融 (MWA) 治疗效果区域的影响。这将有助于确定对改善 MWA 手术临床建模影响最大的生物物理特性。 方法：作者的方法是开发具有可变组织特性的两室模型，并模拟使用 Perseon Medical 的 915 MHz 短尖施药器在肝脏中进行的 MWA 手术。本研究中考虑的介电和热特性的输入参数基于之前文献中报道的健康和恶性（原发性或转移性）肝组织的测量。隔室 1 (C1) 代表正常、脂肪或肝硬化肝脏，隔室 2 (C2) 代表嵌入 C1 内的原发性肝细胞癌肿瘤样本。为了评估对组织参数的敏感性，模拟了一系列临床相关的组织特性。为了评估 MWA 天线位置的影响，作者模拟了天线前后移动 5 mm 的各种肿瘤灌注模型。为了评估局部脉管系统的影响，作者模拟了不同直径和距肿瘤距离的额外散热器。使用骰子系数统计来评估这些局部散热器的消融区域效应。结果：当考虑恶性和健康肝组织之间的相对介电常数和电导率差异时，模型显示消融治疗效应区域的体积变异性（1 cm(3) 增加）小于 11%。与基线模拟相比，模拟脂肪肝疾病的热导率时体积增加了 27%。模拟肝硬化周围肝组织时，消融区体积增加了36%以上。相对于肿瘤的天线放置对治疗效果区域的绝对大小的敏感性最小，变化小于 1.5 毫米。然而，当考虑天线前后移位5mm时消融区域与理想临床边缘之间的重叠时，边缘存在大约6mm的差异。 Dice 系数统计显示，由于模型中存在血管散热器，消融余量减少了 11%。 结论：模拟恶性组织热和电特性变化的结果将有助于指导 MWA 治疗的更好近似。结果表明，假设恶性和健康肝组织具有相似的介电特性是合理的第一近似值。相对于肿瘤的天线放置对消融区域的绝对大小影响很小，但它确实会导致所需治疗边缘和消融区域之间的相关变化。血管冷却，尤其是靠近感兴趣区域的肝血管，可能是治疗计划中需要考虑的重要因素。需要收集更多数据来评估 MWA 建模在此背景下的治疗计划效用。 (C) 2016 年美国医学物理学家协会。
Purpose: The objective of this study is to measure through simulation the impact of (1) heterogeneity of biophysical parameters in tumor vs healthy tissue, (2) applicator placement relative to the tumor, and (3) proximity to large blood vessels on microwave ablation (MWA) treatment effect area. This will help identify the biophysical properties that have the greatest impact on improving clinical modeling of MWA procedures.Methods: The authors' approach was to develop two-compartment models with variable tissue properties and simulate MWA procedures performed in liver with Perseon Medical's 915 MHz short-tip applicator. Input parameters for the dielectric and thermal properties considered in this study were based on measurements for healthy and malignant (primary or metastatic) liver tissue previously reported in the literature. Compartment 1 (C1) represented normal, fatty, or cirrhotic liver, and compartment 2 (C2) represented a primary hepatocellular carcinoma tumor sample embedded within C1. To evaluate the sensitivity to tissue parameters, a range of clinically relevant tissue properties were simulated. To evaluate the impact of MWA antenna position, the authors simulated various tumor perfusion models with the antenna shifted 5 mm anteriorly and posteriorly. To evaluate the effect of local vasculature, the authors simulated an additional heat sink of various diameters and distances from the tumor. Dice coefficient statistics were used to evaluate ablation zone effects from these local heat sinks.Results: Models showed less than 11% of volume variability (1 cm(3) increase) in ablation treatment effect region when accounting for the difference in relative permittivity and electrical conductivity between malignant and healthy liver tissue. There was a 27% increase in volume when simulating thermal conductivity of fatty liver disease versus the baseline simulation. The ablation zone volume increased more than 36% when simulating cirrhotic surrounding liver tissue. Antenna placement relative to the tumor had minimal sensitivity to the absolute size of the treatment effect area, with less than 1.5 mm variation. However, when considering the overlap between the ablation zone and the ideal clinical margin when the antenna was displaced 5 mm anteriorly and posteriorly, there was approximately a 6 mm difference in the margins. Dice coefficient statistics showed as much as an 11% decrease in the ablation margin due to the presence of vessel heat sinks within the model.Conclusions: The results from simulating the variance in malignant tissue thermal and electrical properties will help guide better approximations for MWA treatments. The results suggest that assuming malignant and healthy liver tissues have similar dielectric properties is a reasonable first approximation. Antenna placement relative to the tumor has minimal impact on the absolute size of the ablation zone, yet it does cause relevant variation between desired treatment margin and ablation zone. Blood vessel cooling, especially hepatic vessels close to the region of interest, may be a significant factor to consider in treatment planning. Further data need to be collected for assessing treatment planning utility of modeling MWA in this context. (C) 2016 American Association of Physicists in Medicine.