Hariharan Prasanna, Chang Isaac, Myers Matthew R, Banerjee Rupak K
Mechanical Engineering Department, University of Cincinnati, 688 Rhodes Hall, P.O. Box 210072, Cincinnati, OH 45221-0072, USA.
J Biomech Eng. 2007 Jun;129(3):354-64. doi: 10.1115/1.2720912.
This study uses a reconstructed vascular geometry to evaluate the thermal response of tissue during a three-dimensional radiofrequency (rf) tumor ablation. MRI images of a sectioned liver tissue containing arterial vessels are processed and converted into a finite-element mesh. A rf heat source in the form of a spherically symmetric Gaussian distribution, fit from a previously computed profile, is employed. Convective cooling within large blood vessels is treated using direct physical modeling of the heat and momentum transfer within the vessel. Calculations of temperature rise and thermal dose are performed for transient rf procedures in cases where the tumor is located at three different locations near the bifurcation point of a reconstructed artery. Results demonstrate a significant dependence of tissue temperature profile on the reconstructed vasculature and the tumor location. Heat convection through the arteries reduced the steady-state temperature rise, relative to the no-flow case, by up to 70% in the targeted volume. Blood flow also reduced the thermal dose value, which quantifies the extent of cell damage, from approximately 3600 min, for the no-flow condition, to 10 min for basal flow (13.8 cms). Reduction of thermal dose below the threshold value of 240 min indicates ablation procedures that may inadequately elevate the temperature in some regions, thereby permitting possible tumor recursion. These variations are caused by vasculature tortuosity that are patient specific and can be captured only by the reconstruction of the realistic geometry.
本研究使用重建的血管几何结构来评估三维射频（rf）肿瘤消融过程中组织的热响应。对包含动脉血管的肝脏组织切片的MRI图像进行处理，并转换为有限元网格。采用从先前计算的轮廓拟合得到的球形对称高斯分布形式的射频热源。通过对血管内热和动量传递进行直接物理建模来处理大血管内的对流冷却。在肿瘤位于重建动脉分叉点附近三个不同位置的情况下，对瞬态射频过程进行温度上升和热剂量计算。结果表明，组织温度分布对重建的脉管系统和肿瘤位置有显著依赖性。相对于无血流情况，通过动脉的热对流使目标体积内的稳态温度上升降低了高达70%。血流也降低了热剂量值，热剂量值量化了细胞损伤程度，从无血流条件下的约3600分钟降至基础血流（13.8厘米/秒）时的10分钟。将热剂量降低到240分钟的阈值以下表明消融过程可能在某些区域未能充分提高温度，从而可能导致肿瘤复发。这些变化是由患者特异性的血管曲折度引起的，并且只有通过重建实际几何结构才能捕捉到。
