Department of Radiation Oncology, University of California, San Francisco, California, USA.
Int J Hyperthermia. 2012;28(3):235-49. doi: 10.3109/02656736.2012.662666.
A temperature superposition method has been developed for fast optimisation and planning of interstitial hyperthermia treatments with convectively cooled multi-transducer ultrasound applicators integrated within high dose rate (HDR) brachytherapy catheters.
Steady-state temperature distributions produced by individual tubular transducers capable of directional heating were pre-computed using finite element models (FEM) methods. The composite temperature distributions generated by multi-applicator implants were approximated as superposition sums of the pre-computed temperature profiles. Composite temperature distributions produced by the multi-applicator implants were also computed using accurate but computationally expensive FEM methods (considered here as the validation standard). Both methods were used for temperature calculation on a range of test implant geometries and representative patient cases (HDR implants in prostate (n = 13) and cervix (n = 2)), with optimised treatment plans created for the latter.
Difference between temperatures calculated by the superposition and FEM methods was below 0.37°C (95% confidence interval) in test implants at clinically relevant acoustic intensities (0.3-2.0 W/cm²) and blood perfusion (2 kg/m³/s). Difference in 41°C isothermal volumes was below 8.3%. Superposition-based optimisations followed by FEM forward calculations (hybrid plans) were completed 4-7 times faster than FEM-only plans (FEM optimisation + FEM forward). Mean T₉₀, T₅₀ and T₁₀ values from both plans were within 0.3°C, 0.4°C and 0.45°C respectively, and the mean acoustic intensities were within 0.23 W/cm².
Temperature superposition provides a fast technique for forward or optimised planning of interstitial ultrasound hyperthermia treatments with calculations comparable to more accurate but time consuming FEM methods.
针对集成在高剂量率（HDR）近距离治疗导管中的具有冷却功能的多换能器超声热疗应用，提出了一种基于温度叠加的快速优化和规划方法。
使用有限元模型（FEM）方法预先计算了单个能够实现定向加热的管状换能器产生的稳态温度分布。通过多应用器植入物产生的复合温度分布被近似为预先计算的温度分布的叠加和。还使用精确但计算成本高昂的 FEM 方法（被视为验证标准）计算了多应用器植入物产生的复合温度分布。这两种方法都用于一系列测试植入物几何形状和代表性患者病例（前列腺（n=13）和子宫颈（n=2）中的 HDR 植入物）的温度计算，并为后者创建了优化的治疗计划。
在临床相关声强（0.3-2.0 W/cm²）和血流灌注（2 kg/m³/s）下，测试植入物中叠加法和 FEM 法计算的温度差值低于 0.37°C（95%置信区间）。41°C 等温体积差值低于 8.3%。基于叠加的优化后再进行 FEM 正向计算（混合计划）比仅 FEM 计划（FEM 优化+FEM 正向）快 4-7 倍。两种计划的平均 T₉₀、T₅₀ 和 T₁₀ 值相差在 0.3°C 以内，0.4°C 以内和 0.45°C 以内，平均声强相差在 0.23 W/cm² 以内。
温度叠加为具有冷却功能的多换能器超声热疗的介入式超声热疗的正向或优化规划提供了一种快速技术，其计算结果可与更准确但耗时的 FEM 方法相媲美。
