Comparison of CT number calibration techniques for CBCT-based dose calculation.
Comparison of CT number calibration techniques for CBCT-based dose calculation.
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DOI：
10.1007/s00066-015-0890-7
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发表时间：
2015-12
期刊：
影响因子：
--
通讯作者：
Oelfke U
中科院分区：
文献类型：
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作者：
Dunlop A;McQuaid D;Nill S;Murray J;Poludniowski G;Hansen VN;Bhide S;Nutting C;Harrington K;Newbold K;Oelfke U
这项工作的目的是比较和验证各种计算机断层扫描 (CT) 数字校准技术在锥形束 CT (CBCT) 剂量计算精度方面的作用。使用两种方法评估骨盆、肺部和头颈 (H&N) 治疗部位的 CBCT 剂量计算准确性：(1) 基于物理的散射校正方法 (CBCTr)； (2)密度覆盖方法，包括将水密度分配给整个CBCT (W)、分配水或骨密度(WB)以及分配水或肺密度(WL)。对商用治疗计划系统 (RSauto) 中 CBCT 密度分配的方法进行了评估和验证，其中 CBCT 体素被分为六个密度级别。使用剂量差图和剂量体积统计数据将 CBCT 剂量分布与 CBCT 当天获取的计划 CT 的真实情况进行比较。对于盆腔病例，所有 CTN 校准方法的平均剂量体积偏差均低于 1.5%。 RSauto 为具有大量脂肪组织的患者提供了高于平均水平的盆腔治疗误差。对于 H&N 病例，所有 CTN 校准方法的平均剂量体积差异均低于 1.0%，其中 CBCTr (0.5%) 和 RSauto (0.6%) 表现最佳。对于肺部病例，WL 和 RSauto 方法生成的剂量分布与真实情况最相似。 RSauto 密度覆盖方法对于各种解剖部位的 CTN 调整来说是一个有吸引力的选择。 RSauto 方法经过验证，得出的剂量计算结果与根据诊断质量 CT 图像、肺部获得的 CBCT 图像、在没有多余脂肪组织的情况下接受盆腔放疗的患者以及 H&N 病例计算的剂量一致。
The aim of this work was to compare and validate various computed tomography (CT) number calibration techniques with respect to cone beam CT (CBCT) dose calculation accuracy. CBCT dose calculation accuracy was assessed for pelvic, lung, and head and neck (H&N) treatment sites for two approaches: (1) physics-based scatter correction methods (CBCTr); (2) density override approaches including assigning water density to the entire CBCT (W), assignment of either water or bone density (WB), and assignment of either water or lung density (WL). Methods for CBCT density assignment within a commercially available treatment planning system (RSauto), where CBCT voxels are binned into six density levels, were assessed and validated. Dose-difference maps and dose-volume statistics were used to compare the CBCT dose distributions with the ground truth of a planning CT acquired the same day as the CBCT. For pelvic cases, all CTN calibration methods resulted in average dose-volume deviations below 1.5 %. RSauto provided larger than average errors for pelvic treatments for patients with large amounts of adipose tissue. For H&N cases, all CTN calibration methods resulted in average dose-volume differences below 1.0 % with CBCTr (0.5 %) and RSauto (0.6 %) performing best. For lung cases, WL and RSauto methods generated dose distributions most similar to the ground truth. The RSauto density override approach is an attractive option for CTN adjustments for a variety of anatomical sites. RSauto methods were validated, resulting in dose calculations that were consistent with those calculated on diagnostic-quality CT images, for CBCT images acquired of the lung, for patients receiving pelvic RT in cases without excess adipose tissue, and for H&N cases.