Shading correction for cone-beam CT in radiotherapy: validation of dose calculation accuracy using clinical images
Shading correction for cone-beam CT in radiotherapy: validation of dose calculation accuracy using clinical images
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放射治疗中锥束 CT 的阴影校正：使用临床图像验证剂量计算准确性
DOI：
10.1117/12.2254059
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
C. J. Moore
中科院分区：
文献类型：
--
作者：
T. Marchant;K. Joshi;C. J. Moore
锥形束CT （CBCT）图像通常用于在放疗（RT）中验证患者的位置，但通常不会在Hounsfield单元（HU）中进行校准，并且由于x射线散射和探测器持久性效应而具有不均匀性。这阻止了直接使用CBCT重新计算放射治疗剂量。我们之前开发了一种基于先验图像的校正方法来恢复HU值，提高CBCT图像的均匀性。在这里，我们使用45例患者的CBCT图像和RT计划，包括骨盆、肺部和头部部位，验证了校正后的CBCT可用于RT传递剂量学评估的准确性。根据每位患者的原始放疗计划计算剂量分布，并使用CBCT图像值进行组织异质性校正。计算临床相关剂量指标（如中位和最小目标剂量，最大器官危险剂量）。基于CBCT的剂量度量的准确性使用“覆盖比率”方法确定，其中剂量度量与在图像的体积密度分配版本上计算的剂量度量的比率假设对每个患者都是恒定的，允许与“金标准”CT进行比较。对于骨盆和头部图像，在进行阴影校正后，剂量误差bbb2%的比例从40%降低到1.3%。对于肺部图像，剂量错误的比例从66%降至2.2%。对CBCT图像进行阴影校正，极大地提高了其对放射治疗剂量学评估的效用，使CBCT剂量计算的准确性在2-3%以内。
Cone-beam CT (CBCT) images are routinely acquired to verify patient position in radiotherapy (RT), but are typically not calibrated in Hounsfield Units (HU) and feature non-uniformity due to X-ray scatter and detector persistence effects. This prevents direct use of CBCT for re-calculation of RT delivered dose. We previously developed a prior-image based correction method to restore HU values and improve uniformity of CBCT images. Here we validate the accuracy with which corrected CBCT can be used for dosimetric assessment of RT delivery, using CBCT images and RT plans for 45 patients including pelvis, lung and head sites. Dose distributions were calculated based on each patient's original RT plan and using CBCT image values for tissue heterogeneity correction. Clinically relevant dose metrics were calculated (e.g. median and minimum target dose, maximum organ at risk dose). Accuracy of CBCT based dose metrics was determined using an "override ratio" method where the ratio of the dose metric to that calculated on a bulk-density assigned version of the image is assumed to be constant for each patient, allowing comparison to “gold standard” CT. For pelvis and head images the proportion of dose errors >2% was reduced from 40% to 1.3% after applying shading correction. For lung images the proportion of dose errors >3% was reduced from 66% to 2.2%. Application of shading correction to CBCT images greatly improves their utility for dosimetric assessment of RT delivery, allowing high confidence that CBCT dose calculations are accurate within 2-3%.
影响因子：
3.8
作者：
Moteabbed, M.;Sharp, G. C.;Lu, H. -M.
通讯作者：
Lu, H. -M.
影响因子：
2.6
作者：
Marchant, T. E.;Price, G. J.;Moore, C. J.
通讯作者：
Moore, C. J.