Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030, USA.
Med Phys. 2010 Oct;37(10):5313-21. doi: 10.1118/1.3490085.
Minimally invasive thermal ablative therapies as alternatives to conventional surgical management of solid tumors and other pathologies is increasing owing to the potential benefits of performing these procedures in an outpatient setting with reduced complications and comorbidity. Magnetic resonance temperature imaging (MRTI) measurement allows existing thermal dose models to use the spatiotemporal temperature history to estimate the thermal damage to tissue. However, the various thermal dose models presented in the literature employ different parameters and thresholds, affecting the reliability of thermal dosimetry. In this study, the authors quantitatively compared three thermal dose models (Arrhenius rate process, CEM43, and threshold temperature) using the dice similarity coefficient (DSC).
The DSC was used to compare the spatial overlap between the region of thermal damage as predicted by the models for in vivo normal canine brain during thermal therapy to the region of thermal damage as revealed by contrast-enhanced T1-weighted images acquired immediately after therapy (< 20 min). The outer edge of the hyperintense rim of the ablation region was used as the surrogate marker for the limits of thermal coagulation. The DSC was also used to investigate the impact of varying the thresholds on each models' ability to predict the zone of thermal necrosis.
At previously reported thresholds, the authors found that all three models showed good agreement (defined as DSC > 0.7) with post-treatment imaging. All three models examined across the range of commonly applied thresholds consistently showed highly accurate spatial overlap, low variability, and little dependence on temperature uncertainty. DSC values corresponding to cited thresholds were not significantly different from peak DSC values.
Thus, the authors conclude that the all three thermal dose models can be used as a reliable surrogate for postcontrast tissue damage verification imaging in rapid ablation procedures and can also be used to enhance the capability of MRTI to control thermal therapy in real time.
由于在门诊环境下进行这些操作具有减少并发症和合并症的潜在益处，微创热消融治疗作为传统手术治疗实体瘤和其他病变的替代方法正在增加。磁共振温度成像（MRTI）测量允许现有的热剂量模型使用时空温度历史来估计组织的热损伤。然而，文献中提出的各种热剂量模型使用不同的参数和阈值，影响热剂量测量的可靠性。在这项研究中，作者使用 Dice 相似系数（DSC）定量比较了三种热剂量模型（Arrhenius 速率过程、CEM43 和阈值温度）。
DSC 用于比较模型预测的热疗过程中活体正常犬脑热损伤区域与热疗后立即获得的对比增强 T1 加权图像中显示的热损伤区域之间的空间重叠（<20 分钟）。消融区域的高信号边缘的外边缘被用作热凝固范围的替代标记物。DSC 还用于研究改变每个模型的阈值对其预测热坏死区域能力的影响。
在之前报道的阈值下，作者发现所有三种模型与治疗后成像均显示出良好的一致性（定义为 DSC>0.7）。在常见应用阈值范围内检查的所有三种模型均显示出高度准确的空间重叠、低变异性和对温度不确定性的依赖性低。与引用阈值相对应的 DSC 值与峰值 DSC 值无显著差异。
因此，作者得出结论，所有三种热剂量模型都可以作为快速消融过程中对比后组织损伤验证成像的可靠替代物，并且还可以用于增强 MRTI 实时控制热治疗的能力。
