Alterations in normal liver doses due to organ motion
Alterations in normal liver doses due to organ motion
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DOI：
10.1016/j.ijrobp.2003.08.025
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发表时间：
2003-12-01
影响因子：
7
通讯作者：
Haken, RKT
中科院分区：
文献类型：
--
作者：
Rosu, M;Dawson, LA;Haken, RKT
目的：为了评估基于静态计算机断层扫描（CT）的治疗计划计算与通过几何卷积方法对肝内病变的实际输送剂量进行更现实的预测之间差异的临床意义，该方法考虑了随机设置变化和呼吸诱导的器官运动。我们重新计算了40例既往接受过适形治疗剂量递增方案治疗的患者的靶向和正常肝脏剂量，以包括患者的设置不确定性和肝脏运动的影响。呼吸了将基于在正常呼气时自主屏气进行的预处理CT扫描的初始三维（3D）剂量计算与反映位置设置变化的群体测量值的3D各向异性概率分布函数进行卷积。卷积还包括分布函数（一维，仅走廊-上方方向）代表不对称的时间模式（偏向于呼气，基于群体测量）的典型呼吸周期，按每个患者的幅度缩放。在卷积之后，最小临床靶体积（CTV）剂量满足或超过静态计划中的最小计划靶体积（PTV）剂量，只有一例除外，表明PTV设计适当。然而，对于位于肝脏底部（顶部）的肿瘤，肝脏正常组织并发症概率（NTCP）相对于静态病例计算值的临床相关和统计学显著增加（降低），与呼气时扫描的这些患者的预测一致。肝脏NTCP的变化（从标称值20%）范围为+12.0%至-11.7%（平均幅度变化3.9% [sigma = 3.3%]）。恢复原始20% NTCP所需处方剂量的变化范围为-3.7戈伊至+7.9戈伊（平均幅度变化1.9戈伊[sigma = 1.9戈伊]）。结论：尽管PTV概念可以确保足够的CTV覆盖，但正常肝脏的剂量建模不正确，未包括患者相关的几何不确定性。(C)2003年爱思唯尔公司
Purpose: To assess the clinical significance of differences between treatment planning calculations based on static computed tomography (CT) and more realistic predictions of the actual delivered dose to intrahepatic lesions by a geometric convolution approach that accounts for random setup variations and breathing-induced organ motion.Methods and Materials: We recalculated target and normal liver doses for 40 patients previously treated on a conformal therapy dose escalation protocol to include the effect of setup uncertainties and liver motion due to patient breathing. Initial three-dimensional (3D) dose calculations based on pretreatment CT scans taken with voluntary breath-hold at normal exhalation were convolved with 3D anisotropic probability distribution functions reflecting population measurements of position setup variation. The convolution also included a distribution function (one-dimensional, inferior-superior direction only) representing the asymmetric temporal pattern (biased toward exhalation, based on population measurements) of a typical breathing cycle, scaled in amplitude for each patient.Results: After convolution, the minimum clinical target volume (CTV) dose met or exceeded the minimum planning target volume (PTV) dose from the static plan in all but one case, indicating adequate PTV design. However, clinically relevant and statistically significant increases (decreases) in liver normal tissue complication probability (NTCP) from values computed for the static cases occured for tumors located toward the bottom (top) of the liver, as predicted for these patients scanned at exhalation. The change in liver NTCP (from a nominal 20%) ranged from +12.0% to -11.7% (average magnitude change 3.9% [sigma = 3.3%]). Changes in prescription dose required to restore the original 20% NTCP ranged from -3.7 Gy to +7.9 Gy (average magnitude change 1.9 Gy [sigma = 1.9 Gy]).Conclusion: Although the PTV concept can ensure adequate CTV coverage, the doses to normal liver are incorrectly modeled without including patient-related geometric uncertainties. (C) 2003 Elsevier Inc.