Low-Dose Computed Tomography Scanning Protocols for Online Adaptive Proton Therapy of Head-and-Neck Cancers.
Low-Dose Computed Tomography Scanning Protocols for Online Adaptive Proton Therapy of Head-and-Neck Cancers.
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作者：
自适应质子治疗需要在治疗过程中拍摄图像，以纠正解剖结构变化的计划。大多数工作流程都假设每天都有图像处理。相关的成像剂量可能是显著的，这可能损害质子治疗的目标之一：最小化对健康组织的剂量。低剂量扫描协议解决了这个问题。在本文中，我们评估的影响，低剂量CT协议的适应。我们使用头部体模来定义协议，并根据我们建立的适应框架模拟了10名头颈部患者的适应性治疗。我们评估了较低图像质量对轮廓传播和剂量计算的影响。我们证明，相对于我们的标准CT扫描协议，将成像剂量降低40倍不会影响适应性能。目的：评价低剂量CT方案对头颈部患者在线计划调整的适用性。方法：我们获得了头部模型的CT扫描，其方案对应于CT剂量指数体积CTDIvol，范围为4.2-165.9 mGy。最高值对应于研究中纳入的10名头颈部患者的CT模拟所用的标准方案。最小值对应于研究所用GE Discovery RT扫描仪的最低可实现管电流。对于每名患者和每种低剂量方案，将源自体模图像的相对于标准方案的噪声应用于虚拟CT（vCT）。vCT是从每日CBCT扫描中获得的，对应于具有最大解剖学变化的部分。我们使用高质量的每日vCT和相应的低剂量合成vCT，为每个低剂量方案运行了两次既定的自适应工作流程。为了对适应有效性进行相对比较，在高质量vCT中重新计算了两个适应计划，并使用通过计划CT的可变形配准获得的轮廓进行了评价。我们还使用标准CT方案作为参考，评估了低剂量CT体积中剂量计算的准确性。结果如下：低剂量方案和标准方案之间的D98的最大差异分别为0.6%和0.3%。OAR节省的差异高达3%。用低剂量和标准方案获得的传播轮廓之间的Dice相似系数在0.982以上。使用标准协议作为参考，最低剂量图像的平均2%/2 mm伽马通过率为99.99%。结论：低剂量方案和标准扫描方案之间的差异是微不足道的。因此，低剂量CT方案适用于头颈部癌症的在线自适应质子治疗。因此，考虑到我们诊所中使用的扫描协议，与用质子治疗的头颈癌的在线适应相关的成像剂量可以减少40倍。
Adaptive proton therapy requires taking images over the course of treatment to correct the plan for anatomy changes. Most workflows assume daily imaging for this purpose. The associated imaging doses can be significant, which may compromise one of the proton therapy aims: minimizing the dose to healthy tissue. Low-dose scanning protocols address this problem. In this paper, we evaluate the influence of low-dose CT protocols on adaptation. We used a head phantom to define the protocols and simulated adaptive treatments of 10 head-and-neck patients with our established adaptation framework. We assessed the influence of lower image quality on the contour propagation and dose calculation. We demonstrated that decreasing the imaging dose by a factor of 40 with respect to our standard CT scanning protocol does not affect the adaptation performance. Purpose: To evaluate the suitability of low-dose CT protocols for online plan adaptation of head-and-neck patients. Methods: We acquired CT scans of a head phantom with protocols corresponding to CT dose index volume CTDIvol in the range of 4.2–165.9 mGy. The highest value corresponds to the standard protocol used for CT simulations of 10 head-and-neck patients included in the study. The minimum value corresponds to the lowest achievable tube current of the GE Discovery RT scanner used for the study. For each patient and each low-dose protocol, the noise relative to the standard protocol, derived from phantom images, was applied to a virtual CT (vCT). The vCT was obtained from a daily CBCT scan corresponding to the fraction with the largest anatomical changes. We ran an established adaptive workflow twice for each low-dose protocol using a high-quality daily vCT and the corresponding low-dose synthetic vCT. For a relative comparison of the adaptation efficacy, two adapted plans were recalculated in the high-quality vCT and evaluated with the contours obtained through deformable registration of the planning CT. We also evaluated the accuracy of dose calculation in low-dose CT volumes using the standard CT protocol as reference. Results: The maximum differences in D98 between low-dose protocols and the standard protocol for the high-risk and low-risk CTV were found to be 0.6% and 0.3%, respectively. The difference in OAR sparing was up to 3%. The Dice similarity coefficient between propagated contours obtained with low-dose and standard protocols was above 0.982. The mean 2%/2 mm gamma pass rate for the lowest-dose image, using the standard protocol as reference, was found to be 99.99%. Conclusion: The differences between low-dose protocols and the standard scanning protocol were marginal. Thus, low-dose CT protocols are suitable for online adaptive proton therapy of head-and-neck cancers. As such, considering scanning protocols used in our clinic, the imaging dose associated with online adaption of head-and-neck cancers treated with protons can be reduced by a factor of 40.
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影响因子：
5.2
作者：
Nesteruk KP;Bobić M;Lalonde A;Winey BA;Lomax AJ;Paganetti H
通讯作者：
Paganetti H
DOI：
10.1186/s13014-016-0641-7
发表时间：
2016-04-30
期刊：
Radiation oncology (London, England)
影响因子：
--
作者：
Kurz C;Nijhuis R;Reiner M;Ganswindt U;Thieke C;Belka C;Parodi K;Landry G
通讯作者：
Landry G
影响因子：
3.8
作者：
Haelga, Roger A.;Besserer, Juergen;Schneider, Uwe
通讯作者：
Schneider, Uwe
影响因子：
3.5
作者：
Jia, Xun;Gu, Xuejun;Jiang, Steve B.
通讯作者：
Jiang, Steve B.
影响因子：
3.1
作者：
Nenoff, Lena;Matter, Michael;Albertini, Francesca
通讯作者：
Albertini, Francesca