肠道气腔不同CT值和体积占比对结直肠癌放疗剂量的影响及应对策略研究

摘要/Abstract

摘要： 选取30例结直肠癌放疗患者的计算机断层扫描(CT)定位图像,在计划系统(TPS)中修改计划靶区(PTV)内气腔CT值并构建不同体积占比模型,移植治疗计划至修改后图像并计算剂量分布。评估计划靶区剂量参数(D_max、D_mean、D_98%、D_50%、D_2%、适形性指数CI、均匀性指数HI)及危及器官剂量变化,采用配对样本t检验或Wilcoxon符号秩检验分析组间差异,量化肠道气腔CT值及体积占比变化对剂量分布的影响,建立风险预警阈值。结果表明:气腔CT值升高导致PTV的D_98%显著下降,平均相对偏差扩大至-1.215%,而D_2%保持相对稳定。CI和HI呈统计学显著变化(P＜0.05);除小肠的D_mean外其它危及器官剂量变化无统计学意义(P＞0.05)。CT值与体积占比的协同效应存在临界阈值:当气腔CT值≥250 HU且体积占比＞6%时,D_98%相对偏差最大增至-4.927%。因此,当二者同时达到阈值时,剂量算法失真与体积效应耦合可导致临床不可接受的冷区。需建立风险分层管理:高危患者(达阈值者)实施全链条干预(饮食控制、电子密度校正),并通过锥形束CT(CBCT)动态监测气腔变化;当PTV内气腔体积占比＞6%且CT值≥250 HU时,启动自适应放疗。

关键词: 剂量计算, 结直肠癌, 调强放射治疗, 气腔体积阈值, 计划评估

Abstract: Thirty cases of computed tomography (CT) localization images of patients with colorectal cancer undergoing radiotherapy were selected. The CT values of air cavities within the planning target volume (PTV) were modified in the treatment planning system (TPS), and models with different volume ratios were constructed. The treatment plans were transferred to the modified images, and the dose distributions were calculated. The dose parameters (D_max, D_mean, D_98%, D_50%, D_2%, conformity index CI, homogeneity index HI) of the PTV and the dose changes of organs at risk were evaluated. Paired sample t test or Wilcoxon signed rank test was used to analyze the differences between groups, quantify the influence of changes in the CT values and volume ratios of intestinal air cavities on dose distribution, and establish risk warning thresholds. The results showed that an increase in the CT values of air cavities led to a significant decrease in D_98% of the PTV, with the average relative deviation expanding to -1.215%, while D_2% remained relatively stable. CI and HI increased significantly (P<0.05). Except for the Dmean of the small intestine, there were no statistically significant changes in the doses of other organs at risk (P>0.05). There was a critical threshold for the synergistic effect of CT values and volume ratios: when the CT value of the air cavity was ≥250 HU and the volume ratio was >6%, the maximum relative deviation of D_98% increased to -4.927%. Therefore, when both reached the thresholds simultaneously, the coupling of dose algorithm distortion and volume effect could result in clinically unacceptable cold spots. Risk stratified management should be established: for high-risk patients (those reaching the thresholds), comprehensive interventions (diet control, electron density correction) should be implemented, and the changes in air cavities should be dynamically monitored through cone beam CT (CBCT). When the volume ratio of air cavities within the PTV was >6% and the CT value was ≥250 HU, adaptive radiotherapy should be initiated.

Key words: dose calculation, colorectal cancer, intensity-modulated radiotherapy, air cavity volume threshold, plan evaluation

中图分类号:

饶可, 叶芝甫, 蔡凯, 姚菲, 屈国普, 颜卓鑫. 肠道气腔不同CT值和体积占比对结直肠癌放疗剂量的影响及应对策略研究[J]. 辐射防护, 2026, 46(1): 18-28.

RAO Ke, YE Zhifu, CAI Kai, YAO Fei, QU Guopu, YAN Zhuoxin. Impact of different CT values and volume proportions of intestinal air cavities on radiotherapy dose for colorectal cancer and response strategies[J]. RADIATION PROTECTION, 2026, 46(1): 18-28.

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