Technical Note: MRI only prostate radiotherapy planning using the statistical decomposition algorithm
Technical Note: MRI only prostate radiotherapy planning using the statistical decomposition algorithm
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DOI：
10.1118/1.4931417
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发表时间：
2015-10-01
期刊：
影响因子：
3.8
通讯作者：
Olsson, Lars E.
中科院分区：
文献类型：
--
作者：
Siversson, Carl;Nordstrom, Fredrik;Olsson, Lars E.
目的：为了在放疗治疗计划中实现仅磁共振成像（MRI）的工作流程，需要直接从MRI生成用于剂量计算的Hounsfield单元（HU）图（即合成计算机断层扫描，sCT）的方法。统计分解算法（SDA）是一种基于自动组织分类和使用多模态模板材料训练的模型，从单个MR图像体自动生成sCT图像的方法。本研究比较了SDA和常规CT在男性骨盆区的sCT剂量计算。方法：对10例前列腺癌患者进行三维T2加权MRI和常规计划CT检查。对于每个患者，使用SDA从获得的MRI生成sCT图像。为了将不同成像模式之间患者几何形状变化的影响与SDA不确定性的影响脱钩，常规CT与MRI进行非刚性注册，以确保其几何形状良好对齐。对于每位患者，为注册CT （rCT）创建了体积调制弧治疗计划，并重新计算了sCT和常规CT的治疗计划。使用几种方法评估结果，包括平均误差（MAE）、一组剂量-体积直方图参数和限制性伽马标准（2%局部剂量/1 mm）。结果：体廓内MAE为36.5 +/- 4.1 （1 s.d）。sCT与rCT之间的HU值。sCT和rCT对靶的平均吸收剂量差为0.0% +/- 0.2% (1 s.d)，而CT和rCT对靶的平均吸收剂量差为-0.3% +/- 0.3% （1 s.d）。sCT与rCT的平均伽马通过率为99.9%，而CT与rCT的平均伽马通过率为90.3%。结论：SDA为前列腺放疗计划提供了一个高度精确的MRI工作流程。来自SDA的剂量学不确定性似乎可以忽略不计，并且明显低于成像期间患者几何形状变化带来的不确定性。(C) 2015年美国医学物理学家协会。
Purpose: In order to enable a magnetic resonance imaging (MRI) only workflow in radiotherapy treatment planning, methods are required for generating Hounsfield unit (HU) maps (i.e., synthetic computed tomography, sCT) for dose calculations, directly from MRI. The Statistical Decomposition Algorithm (SDA) is a method for automatically generating sCT images from a single MR image volume, based on automatic tissue classification in combination with a model trained using a multimodal template material. This study compares dose calculations between sCT generated by the SDA and conventional CT in the male pelvic region.Methods: The study comprised ten prostate cancer patients, for whom a 3D T2 weighted MRI and a conventional planning CT were acquired. For each patient, sCT images were generated from the acquired MRI using the SDA. In order to decouple the effect of variations in patient geometry between imaging modalities from the effect of uncertainties in the SDA, the conventional CT was nonrigidly registered to the MRI to assure that their geometries were well aligned. For each patient, a volumetric modulated arc therapy plan was created for the registered CT (rCT) and recalculated for both the sCT and the conventional CT. The results were evaluated using several methods, including mean average error (MAE), a set of dose-volume histogram parameters, and a restrictive gamma criterion (2% local dose/1 mm).Results: The MAE within the body contour was 36.5 +/- 4.1 (1 s.d.) HU between sCT and rCT. Average mean absorbed dose difference to target was 0.0% +/- 0.2% (1 s.d.) between sCT and rCT, whereas it was -0.3% +/- 0.3% (1 s.d.) between CT and rCT. The average gamma pass rate was 99.9% for sCT vs rCT, whereas it was 90.3% for CT vs rCT.Conclusions: The SDA enables a highly accurate MRI only workflow in prostate radiotherapy planning. The dosimetric uncertainties originating from the SDA appear negligible and are notably lower than the uncertainties introduced by variations in patient geometry between imaging sessions. (C) 2015 American Association of Physicists in Medicine.