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Abstract：
BACKGROUND: To assess the feasibility of CBCT-based adaptive intensity modulated proton therapy (IMPT) using automated planning for treatment of head and neck (HN) cancers.
METHODS: Twenty HN cancer patients who received radiotherapy and had pretreatment CBCTs were included in this study. Initial IMPT plans were created using automated planning software for all patients. Synthetic CTs (sCT) were then created by deforming the planning CT (pCT) to the pretreatment CBCTs. To assess dose calculation accuracy on sCTs, repeat CTs (rCTs) were deformed to the pretreatment CBCT obtained on the same day to create deformed rCT (rCTdef), serving as gold standard. The dose recalculated on sCT and on rCTdef were compared by using Gamma analysis. The accuracy of DIR generated contours was also assessed. To explore the potential benefits of adaptive IMPT, two sets of plans were created for each patient, a non-adapted IMPT plan and an adapted IMPT plan calculated on weekly sCT images. The weekly doses for non-adaptive and adaptive IMPT plans were accumulated on the pCT, and the accumulated dosimetric parameters of two sets were compared.
RESULTS: Gamma analysis of the dose recalculated on sCT and rCTdef resulted in a passing rate of 97.9% ± 1.7% using 3 mm/3% criteria. With the physician-corrected contours on the sCT, the dose deviation range of using sCT to estimate mean dose for the most organ at risk (OARs) can be reduced to (- 2.37%, 2.19%) as compared to rCTdef, while for V95 of primary or secondary CTVs, the deviation can be controlled within (- 1.09%, 0.29%). Comparison of the accumulated doses from the adaptive planning against the non-adaptive plans reduced mean dose to constrictors (- 1.42 Gy ± 2.79 Gy) and larynx (- 2.58 Gy ± 3.09 Gy). The reductions result in statistically significant reductions in the normal tissue complication probability (NTCP) of larynx edema by 7.52% ± 13.59%. 4.5% of primary CTVs, 4.1% of secondary CTVs, and 26.8% tertiary CTVs didn\'t meet the V95 > 95% constraint on non-adapted IMPT plans. All adaptive plans were able to meet the coverage constraint.
CONCLUSIONS: sCTs can be a useful tool for accurate proton dose calculation. Adaptive IMPT resulted in better CTV coverage, OAR sparing and lower NTCP for some OARs as compared with non-adaptive IMPT.
METHODS: Twenty HN cancer patients who received radiotherapy and had pretreatment CBCTs were included in this study. Initial IMPT plans were created using automated planning software for all patients. Synthetic CTs (sCT) were then created by deforming the planning CT (pCT) to the pretreatment CBCTs. To assess dose calculation accuracy on sCTs, repeat CTs (rCTs) were deformed to the pretreatment CBCT obtained on the same day to create deformed rCT (rCTdef), serving as gold standard. The dose recalculated on sCT and on rCTdef were compared by using Gamma analysis. The accuracy of DIR generated contours was also assessed. To explore the potential benefits of adaptive IMPT, two sets of plans were created for each patient, a non-adapted IMPT plan and an adapted IMPT plan calculated on weekly sCT images. The weekly doses for non-adaptive and adaptive IMPT plans were accumulated on the pCT, and the accumulated dosimetric parameters of two sets were compared.
RESULTS: Gamma analysis of the dose recalculated on sCT and rCTdef resulted in a passing rate of 97.9% ± 1.7% using 3 mm/3% criteria. With the physician-corrected contours on the sCT, the dose deviation range of using sCT to estimate mean dose for the most organ at risk (OARs) can be reduced to (- 2.37%, 2.19%) as compared to rCTdef, while for V95 of primary or secondary CTVs, the deviation can be controlled within (- 1.09%, 0.29%). Comparison of the accumulated doses from the adaptive planning against the non-adaptive plans reduced mean dose to constrictors (- 1.42 Gy ± 2.79 Gy) and larynx (- 2.58 Gy ± 3.09 Gy). The reductions result in statistically significant reductions in the normal tissue complication probability (NTCP) of larynx edema by 7.52% ± 13.59%. 4.5% of primary CTVs, 4.1% of secondary CTVs, and 26.8% tertiary CTVs didn\'t meet the V95 > 95% constraint on non-adapted IMPT plans. All adaptive plans were able to meet the coverage constraint.
CONCLUSIONS: sCTs can be a useful tool for accurate proton dose calculation. Adaptive IMPT resulted in better CTV coverage, OAR sparing and lower NTCP for some OARs as compared with non-adaptive IMPT.
摘要：
背景：评估使用自动计划治疗头颈部（HN）癌症的基于CBCT的自适应强度调制质子治疗（IMPT）的可行性。
方法：本研究纳入了20例接受放疗并接受了CBCT预处理的HN癌症患者。使用自动计划软件为所有患者创建初始IMT计划。然后通过将计划CT(pCT)变形为预处理CBCT来创建合成CT(sCT)。为了评估sCT的剂量计算精度，重复CT（rCT）变形为同一天获得的预处理CBCT，以创建变形的rCT（rCTdef），作为黄金标准。使用Gamma分析比较了在sCT和rCTdef上重新计算的剂量。还评估了DIR生成的轮廓的准确性。为了探索适应性IMPT的潜在好处，为每个患者创建了两套计划，根据每周的sCT图像计算的非适应性IMPT计划和适应性IMPT计划。非适应性和适应性IMPT计划的每周剂量在pCT上累积，并比较两组累积剂量学参数。
结果：在sCT和rCTdef上重新计算的剂量的Gamma分析使用3mm/3％标准得出的通过率为97.9％±1.7％。在sCT上有医生校正的轮廓，使用sCT估计大多数危险器官（OAR）的平均剂量的剂量偏差范围可以降低到（-2.37％，2.19%)与rCTdef相比，而对于主要或次要CTV的V95，偏差可以控制在(-1.09%，0.29%）。自适应计划与非自适应计划的累积剂量的比较降低了收缩剂的平均剂量（-1.42Gy±2.79Gy）和喉（-2.58Gy±3.09Gy）。减少导致喉水肿的正常组织并发症概率（NTCP）的统计学显着减少7.52％±13.59％。4.5%的主要CTV，4.1%的次级CTV，26.8%的三级CTV不满足非适应性IMT计划的V95>95%限制。所有自适应计划都能够满足覆盖范围限制。
结论：sCT可以成为精确质子剂量计算的有用工具。自适应IMPT带来了更好的CTV覆盖率，与非自适应IMPT相比，某些OAR的OAR节省和NTCP较低。
方法：本研究纳入了20例接受放疗并接受了CBCT预处理的HN癌症患者。使用自动计划软件为所有患者创建初始IMT计划。然后通过将计划CT(pCT)变形为预处理CBCT来创建合成CT(sCT)。为了评估sCT的剂量计算精度，重复CT（rCT）变形为同一天获得的预处理CBCT，以创建变形的rCT（rCTdef），作为黄金标准。使用Gamma分析比较了在sCT和rCTdef上重新计算的剂量。还评估了DIR生成的轮廓的准确性。为了探索适应性IMPT的潜在好处，为每个患者创建了两套计划，根据每周的sCT图像计算的非适应性IMPT计划和适应性IMPT计划。非适应性和适应性IMPT计划的每周剂量在pCT上累积，并比较两组累积剂量学参数。
结果：在sCT和rCTdef上重新计算的剂量的Gamma分析使用3mm/3％标准得出的通过率为97.9％±1.7％。在sCT上有医生校正的轮廓，使用sCT估计大多数危险器官（OAR）的平均剂量的剂量偏差范围可以降低到（-2.37％，2.19%)与rCTdef相比，而对于主要或次要CTV的V95，偏差可以控制在(-1.09%，0.29%）。自适应计划与非自适应计划的累积剂量的比较降低了收缩剂的平均剂量（-1.42Gy±2.79Gy）和喉（-2.58Gy±3.09Gy）。减少导致喉水肿的正常组织并发症概率（NTCP）的统计学显着减少7.52％±13.59％。4.5%的主要CTV，4.1%的次级CTV，26.8%的三级CTV不满足非适应性IMT计划的V95>95%限制。所有自适应计划都能够满足覆盖范围限制。
结论：sCT可以成为精确质子剂量计算的有用工具。自适应IMPT带来了更好的CTV覆盖率，与非自适应IMPT相比，某些OAR的OAR节省和NTCP较低。
