Kolios M C, Worthington A E, Sherar M D, Hunt J W
The Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Canada.
Phys Med Biol. 1998 Nov;43(11):3325-40. doi: 10.1088/0031-9155/43/11/011.
Thermal models are used to predict temperature distributions of heated tissues during thermal therapies. Recent interest in short duration high temperature therapeutic procedures necessitates the accurate modelling of transient temperature profiles in heated tissues. Blood flow plays an important role in tissue heat transfer and the resultant temperature distribution. This work examines the transient predictions of two simple mathematical models of heat transfer by blood flow (the bioheat transfer equation model and the effective thermal conductivity equation model) and compares their predictions to measured transient temperature data. Large differences between the two models are predicted in the tissue temperature distribution as a function of blood flow for a short heat pulse. In the experiments a hot water needle, approximately 30 degrees C above ambient, delivered a 20 s heating pulse to an excised fixed porcine kidney that was used as a flow model. Temperature profiles of a thermocouple that primarily traversed the kidney cortex were examined. Kidney locations with large vessels were avoided in the temperature profile analysis by examination of the vessel geometry using high resolution computed tomography angiography and the detection of the characteristic large vessel localized cooling or heating patterns in steady-state temperature profiles. It was found that for regions without large vessels, predictions of the Pennes bioheat transfer equation were in much better agreement with the experimental data when compared to predictions of the scalar effective thermal conductivity equation model. For example, at a location r approximately 2 mm away from the source, the measured delay time was 10.6 +/- 0.5 s compared to predictions of 9.4 s and 5.4 s of the BHTE and ETCE models, respectively. However, for the majority of measured locations, localized cooling and heating effects were detected close to large vessels when the kidney was perfused. Finally, it is shown that increasing flow in regions without large vessels minimally perturbs temperature profiles for short exposure times; regions with large vessels still have a significant effect.
热模型用于预测热疗过程中受热组织的温度分布。近期对短时长高温治疗程序的关注使得准确模拟受热组织中的瞬态温度分布成为必要。血流在组织热传递及由此产生的温度分布中起着重要作用。本研究考察了两种关于血流热传递的简单数学模型（生物热传递方程模型和有效热导率方程模型）的瞬态预测，并将它们的预测结果与实测的瞬态温度数据进行比较。对于短热脉冲，预测结果显示这两种模型在组织温度分布随血流变化方面存在很大差异。在实验中，一根比环境温度高约30摄氏度的热水针向一个用作血流模型的切除固定猪肾输送了一个20秒的加热脉冲。研究了主要穿过肾皮质的热电偶的温度分布。在温度分布分析中，通过使用高分辨率计算机断层血管造影检查血管几何形状，并在稳态温度分布中检测特征性的大血管局部冷却或加热模式，避开了有大血管的肾脏位置。结果发现，对于没有大血管的区域，与标量有效热导率方程模型的预测相比，彭尼斯生物热传递方程的预测与实验数据的吻合度要好得多。例如，在距离热源约2毫米处，实测延迟时间为10.6±0.5秒，而生物热传递方程模型和有效热导率方程模型的预测分别为9.4秒和5.4秒。然而，对于大多数测量位置，当肾脏被灌注时，在靠近大血管处检测到了局部冷却和加热效应。最后，研究表明，在短暴露时间内，增加无大血管区域的血流对温度分布的扰动最小；有大血管的区域仍然有显著影响。
