Evaluations of an adaptive planning technique incorporating dose feedback in image-guided radiotherapy of prostate cancer
Evaluations of an adaptive planning technique incorporating dose feedback in image-guided radiotherapy of prostate cancer
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DOI：
10.1118/1.3658567
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发表时间：
2011-12-01
期刊：
影响因子：
3.8
通讯作者：
Wu, Qiuwen
中科院分区：
文献类型：
--
作者：
Liu, Han;Wu, Qiuwen
目的：在线图像引导（IG）已被用于有效地纠正前列腺癌的摆位误差和分割间刚性器官运动。然而，规划余量仍然是必要的，以考虑到不确定性，如变形和部分内运动。本研究的目的是研究结合离线剂量反馈的自适应计划技术的有效性，以管理分次间运动和在线校正的残留。方法：本研究纳入了28名患者的重复螺旋CT扫描。在每个CT上描绘前列腺和危险器官（OAR）的轮廓，通过匹配治疗CT和计划CT之间的前列腺质心来模拟在线IG。在计划CT上为每位患者设计了7束调强放射治疗（IMRT）计划，共15次。根据靶区的实际轮廓和来自该部分的OAR评价每个部分的剂量分布。通过基于可变形配准算法跟踪每个体素来计算每个部分的累积剂量。将累积剂量与初始计划的剂量进行比较。如果偏差超过预定义的阈值，例如前列腺D99的2%，则调用称为剂量补偿的自适应计划技术，其中累积剂量分布被反馈到治疗计划系统，并且剂量不足通过在未来治疗部分中的增强辐射来弥补。通过IMRT逆向计划实现剂量补偿。模拟了两种每周补偿递送策略：一种旨在在所有未来部分中递送加强剂量（方案A），另一种仅在下周递送加强剂量（方案B）。计算前列腺的D（99）和直肠壁及膀胱的广义等效均匀剂量（gEUD），并与无剂量补偿的结果进行比较。如果在每周结束时（每五个部分）评估相同的标准，则14名患者失败，其中3名患者在第1周或第2周失败，但在结束时通过。这14例患者的平均剂量不足为4.4%。在每周补偿后，他们提高到2%。在这14例需要剂量补偿的患者中，10例患者在每周剂量补偿后通过了剂量标准，3例患者轻微失败，1例患者仍显著失败（10%不足），占患者人群的3.6%。更积极的补偿频率（每三次）可以成功地将剂量不足降低到该患者的可接受水平。对于方案A（B）给药策略，每例患者所需的剂量补偿重新计划平均次数为0.82（0.79）例。OARs的剂量没有显着不同的在线IG只有计划没有剂量compensation.Conclusions：我们已经证明了离线剂量补偿技术在图像引导放射治疗前列腺癌的有效性。它可以有效地考虑剩余的不确定性，不能通过在线IG校正。剂量补偿允许进一步减少边缘和保留关键器官。VC 2011美国医学物理学家协会。[DOI电话：10.1118/1.3658567]
Purpose: Online image guidance (IG) has been used to effectively correct the setup error and interfraction rigid organ motion for prostate cancer. However, planning margins are still necessary to account for uncertainties such as deformation and intra-fraction motion. The purpose of this study is to investigate the effectiveness of an adaptive planning technique incorporating offline dose feedback to manage inter-fraction motion and residuals from online correction.Methods: Repeated helical CT scans from 28 patients were included in the study. The contours of prostate and organs-at-risk (OARs) were delineated on each CT, and online IG was simulated by matching center-of-mass of prostate between treatment CTs and planning CT. A seven beam intensity modulated radiation therapy (IMRT) plan was designed for each patient on planning CT for a total of 15 fractions. Dose distribution at each fraction was evaluated based on actual contours of the target and OARs from that fraction. Cumulative dose up to each fraction was calculated by tracking each voxel based on a deformable registration algorithm. The cumulative dose was compared with the dose from initial plan. If the deviation exceeded the pre-defined threshold, such as 2% of the D99 to the prostate, an adaptive planning technique called dose compensation was invoked, in which the cumulative dose distribution was fed back to the treatment planning system and the dose deficit was made up through boost radiation in future treatment fractions. The dose compensation was achieved by IMRT inverse planning. Two weekly compensation delivery strategies were simulated: one intended to deliver the boost dose in all future fractions (schedule A) and the other in the following week only (schedule B). The D(99) to prostate and generalized equivalent uniform dose (gEUD) to rectal wall and bladder were computed and compared with those without the dose compensation.Results: If only 2% underdose is allowed at the end of the treatment course, then 11 patients fail. If the same criteria is assessed at the end of each week (every five fractions), then 14 patients fail, with three patients failing the 1st or 2nd week but passing at the end. The average dose deficit from these 14 patients was 4.4%. They improved to 2% after the weekly compensation. Out of these 14 patients who needed dose compensation, ten passed the dose criterion after weekly dose compensation, three patients failed marginally, and one patient still failed the criterion significantly (10% deficit), representing 3.6% of the patient population. A more aggressive compensation frequency (every three fractions) could successfully reduce the dose deficit to the acceptable level for this patient. The average number of required dose compensation re-planning per patient was 0.82 (0.79) per patient for schedule A (B) delivery strategy. The doses to OARs were not significantly different from the online IG only plans without dose compensation.Conclusions: We have demonstrated the effectiveness of offline dose compensation technique in image-guided radiotherapy for prostate cancer. It can effectively account for residual uncertainties which cannot be corrected through online IG. Dose compensation allows further margin reduction and critical organs sparing. VC 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3658567]