Sensitivity of postplanning target and OAR coverage estimates to dosimetric margin distribution sampling parameters.
Sensitivity of postplanning target and OAR coverage estimates to dosimetric margin distribution sampling parameters.
复制标题
计划后目标和 OAR 覆盖范围估计对剂量裕度分布采样参数的敏感性。
DOI：
10.1118/1.3544364
复制
发表时间：
2011
期刊：
影响因子：
3.8
通讯作者：
Siebers,JeffreyV
中科院分区：
文献类型：
--
作者：
Xu,Huijun;Gordon,JJames;Siebers,JeffreyV
目的剂量裕度 (DM) 是结构与指定等剂量表面之间指定方向的裕度，对应于处方剂量或耐受剂量。剂量裕度分布 (DMD) 是 DM 在所有方向上的分布。给定代表分次间或分次内设置不确定性或内部器官运动的几何不确定性模型，DMD 可用于计算覆盖范围，即实现的目标或风险器官 (OAR) 剂量指标超过相应处方或耐受剂量的概率。计划后覆盖评估量化了目标和 OAR 结构满足其预期剂量限制的不确定性百分比。目前工作的目标是评估 28 个前列腺治疗计划的覆盖概率，以确定 DMD 采样参数，确保计划后覆盖估计有足够的准确性。方法将正态分布的间隔设置不确定性应用于 28 个局部前列腺癌计划，规定剂量为 79.2 Gy，临床靶体积为计划靶体积 (CTV-to-PTV) 边缘 10 mm。使用角度或各向同性采样技术，假设剂量分布的位移不变性，确定 CTV、膀胱和直肠的剂量裕度。对于角度采样，以固定角度间隔对 DMD 进行采样（例如 ）。各向同性样本均匀分布在单位球体上，从而产生可变的角度增量，但计算的采样方向数与角度 DMD 相同，并相应地用有效角度增量来表征。在每个方向上，通过以一定尺寸的径向步长移动结构直到穿过指定的等剂量来计算 DM。覆盖估计精度被量化为采样参数 或 和 的函数。结果覆盖估计的精度取决于角度和径向 DMD 采样参数 或 和 ，以及所采用的采样技术。目标和 OAR 可以通过采样参数 或 来实现。使用 或 可以实现更好的精度（目标和 OAR）。随着采样点数量的减少，各向同性采样方法比固定角度采样保持了更好的精度。 结论 由于目标和 OAR 的覆盖值通常与基于静态裕度的计划隐含的值不同，因此规划后评估的覆盖率估计至关重要。对 DMD 进行更精细的采样可以更准确地评估治疗前几何不确定性对覆盖范围估计的影响。使用 或 和 进行 DMD 采样应足以满足规划目的。
PurposeA dosimetric margin (DM) is the margin in a specified direction between a structure and a specified isodose surface, corresponding to a prescription or tolerance dose. The dosimetric margin distribution (DMD) is the distribution of DMs over all directions. Given a geometric uncertainty model, representing inter‐ or intrafraction setup uncertainties or internal organ motion, the DMD can be used to calculate coverage, which is the probability that a realized target or organ‐at‐risk (OAR) dose metric exceeds the corresponding prescription or tolerance dose. Postplanning coverage evaluation quantifies the percentage of uncertainties for which target and OAR structures meet their intended dose constraints. The goal of the present work is to evaluate coverage probabilities for 28 prostate treatment plans to determine DMD sampling parameters that ensure adequate accuracy for postplanning coverage estimates.MethodsNormally distributed interfraction setup uncertainties were applied to 28 plans for localized prostate cancer, with prescribed dose of 79.2 Gy and 10 mm clinical target volume to planning target volume (CTV‐to‐PTV) margins. Using angular or isotropic sampling techniques, dosimetric margins were determined for the CTV, bladder and rectum, assuming shift invariance of the dose distribution. For angular sampling, DMDs were sampled at fixed angular intervals (e.g., ). Isotropic samples were uniformly distributed on the unit sphere resulting in variable angular increments, but were calculated for the same number of sampling directions as angular DMDs, and accordingly characterized by the effective angular increment . In each direction, the DM was calculated by moving the structure in radial steps of size until the specified isodose was crossed. Coverage estimation accuracy was quantified as a function of the sampling parameters or and .ResultsThe accuracy of coverage estimates depends on angular and radial DMD sampling parameters or and , as well as the employed sampling technique. Target and OAR can be achieved with sampling parameters or , . Better accuracy (target and OAR ) can be achieved with or , . As the number of sampling points decreases, the isotropic sampling method maintains better accuracy than fixed angular sampling.ConclusionsCoverage estimates for post‐planning evaluation are essential since coverage values of targets and OARs often differ from the values implied by the static margin‐based plans. Finer sampling of the DMD enables more accurate assessment of the effect of geometric uncertainties on coverage estimates prior to treatment. DMD sampling with or and should be adequate for planning purposes.
登录
查看更多内容
影响因子：
3.8
作者：
Gordon, J. J.;Sayah, N.;Siebers, J. V.
通讯作者：
Siebers, J. V.
有效利用连续、实时前列腺定位
影响因子：
3.5
作者：
K. Malinowski;C. Noel;M. Roy;T. Willoughby;Toufik Djemi;S. Jani;T. Solberg;David M. Liu;L. Levine;P. Parikh
通讯作者：
P. Parikh
DOI：
10.1016/s0360-3016(98)00266-1
发表时间：
1999-01-01
影响因子：
7
作者：
Lee, SW;Fraass, BA;Sandler, HM
通讯作者：
Sandler, HM
影响因子：
3.8
作者：
Gordon, J. J.;Siebers, J. V.
通讯作者：
Siebers, J. V.
DOI：
10.1016/s0360-3016(98)00468-4
发表时间：
1999-03-01
影响因子：
7
作者：
Stroom, JC;de Boer, HCJ;Visser, AG
通讯作者：
Visser, AG