Abstract

Purpose

In pancreatic cancer treatment, hyperthermia can be added to increase efficacy of chemo- and/or radiotherapy. Gas in stomach, intestines and colon is often in close proximity to the target volume. We investigated the impact of variations in gastrointestinal gas (GG) on temperature distributions during simulated hyperthermia treatment (HT).

Methods

We used sets of one CT and eight cone-beam CT (CBCT) scans obtained prior to/during fractionated image-guided radiotherapy in four pancreatic cancer patients. In Plan2Heat, we simulated locoregional heating by an ALBA-4D phased array radiofrequency system and calculated temperature distributions for (i) the segmented CT (sCT), (ii) sCT with GG replaced by muscle (sCT₀), (iii) sCT₀ with eight different GG distributions as visible on CBCT inserted (sCT_CBCT). We calculated cumulative temperature-volume histograms for the clinical target volume (CTV) for all ten temperature distributions for each patient and investigated the relationship between GG volume and change in ΔT₅₀ (temperature increase at 50% of CTV volume). We determined location and volume of normal tissue receiving a high thermal dose.

Results

GG volume on CBCT varied greatly (9-991 cm³). ΔT₅₀ increased for increasing GG volume; maximum ΔT₅₀ difference per patient was 0.4–0.6 °C. The risk for GG-associated treatment-limiting hot spots appeared low. Normal tissue high-temperature regions mostly occurred anteriorly; their volume and maximum temperature showed moderate positive correlations with GG volume, while fat-muscle interfaces were associated with higher risks for hot spots.

Conclusions

Considerable changes in volume and position of gastrointestinal gas can occur and are associated with clinically relevant tumor temperature differences.

中文翻译：

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胃肠道气体对胰腺癌热疗计划中温度分布的影响

摘要

目的

在胰腺癌的治疗中，可以添加热疗以增加化学疗法和/或放射疗法的功效。胃，肠和结肠中的气体通常非常接近目标体积。我们调查了模拟高温治疗（HT）期间胃肠道气体（GG）变化对温度分布的影响。

方法

我们对4例胰腺癌患者进行了分级图像引导放疗之前/期间，使用了一套CT和八台锥形束CT（CBCT）扫描。在Plan2Heat中，我们通过ALBA-4D相控阵射频系统模拟了局部区域加热，并计算了（i）分段CT（sCT），（ii）GG替换为肌肉（sCT ₀），（iii）sCT _{0的温度分布}在插入的CBCT（sCT _CBCT）上可以看到八种不同的GG分布。我们计算出的累计温度体积直方图对所有10的温度分布对于每个患者临床目标体积（CTV）和研究在ΔTGG体积和变化之间的关系₅₀（温度升高到CTV体积的50％时）。我们确定了接受高热剂量的正常组织的位置和体积。

结果

CBCT上的GG体积变化很大（9-991 cm ³）。ΔT ₅₀增加用于增加GG体积; 最大ΔT ₅₀每个患者差异0.4-0.6℃。与GG相关的限制治疗的热点的风险似乎较低。正常组织的高温部位多发生在前部。它们的体积和最高温度与GG体积呈中等正相关，而脂肪-肌肉界面与热点风险更高。

结论

胃肠道气体的体积和位置可能发生相当大的变化，并与临床上相关的肿瘤温度差异有关。