结合肺灌注影像参数的等效均匀剂量模型与放射性肺炎的相关性研究

背景与目的:目前,临床上用来预测放射性肺损伤的肺剂量体积参数准确度较低,且阈值不统一.该研究通过肺功能影像,探讨结合肺血流参数的等效均匀剂量(equivalent uniform dose,EUD)在预测放射性肺炎方面的价值.方法:将15例肺癌放疗患者肺灌注影像与定位CT影像形变融合,以肺灌注最高计数为归一点,将肺依功能状态分为四级区域,取每级区域中的平均计数与最高计数的比值作为肺灌注系数代入EUD模型中,获得肺部的功能等效均匀剂量(functional equivalent uniform dose,fEUD)模型.比较单肺及双肺的fEUD与不含肺功能指数的等效均匀剂量(general equivalent uniform dose,gEUD)、V5、V20在预测放射性肺炎方面的统计学差异,并进一步分析上述参数的统计学分布特征及彼此之间的相关性.放射性肺炎的判断标准采用不良事件常用术语评定标准(Common Terminology Criteria for Adverse Events,CTCAE)4.03版肺部症状3级以上,P<0.05为差异有统计学意义.结果:该研究的样本中,当V5、V20等指标显示与放射性肺炎无关时,高剂量侧肺的fEUD值呈现与放射性肺炎显著相关(P=0.007).单侧肺fEUD值与gEUD值呈显著线性关系(t=0.815,P=0.000).结论:单侧肺fEUD较传统剂量-体积指标更好地体现了肺功能不同区域间的放射生物学差异,可以作为放射性肺炎预测指标,建议阈值为21 Gy.

A modified equivalent uniform dose with the dosimetric parameters of perfusion imaging correlates with radiation pneumonitis in radiation therapy planning

Background and purpose: The literature on dose-volume parameters and pneumonitis is extensive. The results are inconsistent, both for the best predictive metrics and significant comorbid factors. This study aimed to investigate a prospective functional equivalent uniform dose (fEUD) with perfusion single photon emission computed tomography (SPECT) images as predictors of radiation pneumonitis (RP) in patients undergoing curative radiotherapy (RT). Methods: Functional lung imaging was performed using SPECT for perfusion imaging. Perfusion factors were defined as the mean percentile perfusion levels of the 4 areas, top to 75%, 75% to 50%, 50% to 25%, 25% to 0%, re-spectively. fEUD was calculated from perfusion factors and standard dose-volume parameters extracted from treatment planning computed tomography (CT) scans. Total lung (TL), ipsilateral (IL) and contralateral lung (CL) volumes minus gross tumor volume (GTV), whole-lung V5, V20, whole lung fEUD, IL and CL fEUD, and general equivalent uniform dose (gEUD) were analyzed to evaluate correlations between RP using Common Terminology Criteria for Adverse Events (CTCAE) version 4.03. Statistical significance was defined as P<0.05. Results: A total of 15 patients treated with intensity modulated RT or 3D conformal RT were analyzed, grades≥3 RP were observed in 6 patients. There was only a trend toward significance for unilateral (UL) fEUD of higher dose side (P=0.007). Whole-lung V5, V20 were almost identical between patients who developed pneumonitis and patients who did not, as the values were below the recommended thresholds from published papers. Unilateral fEUDs were linear with unilateral gEUDs (t=0.815, P=0.000). Conclusion: SPECT-based equivalent uniform dose appears to be a better predictor of RP compared to stan-dard dose-volume parameters. Planning constraints should aim to keep unilateral fEUD below 21 Gy.