PDF(Pubmed)
Abstract：
OBJECTIVE: This study implemented a piecewise volumetric modulated arc therapy (P-VMAT) for realizing whole-brain radiation therapy (WBRT) with simultaneous integrated boost (SIB) for multiple brain metastases (> 40 metastases) with a conventional C-arm linear accelerator.
METHODS: This study retrospectively analyzed 10 patients with multiple brain metastases (40-120 metastases, median 76), who underwent WBRT and SIB using helical tomotherapy (HT). The prescribed doses were 40 Gy/20 f and 60 Gy/20 f for WBRT and SIB, respectively. Corresponding new HT plans were designed with P-VMAT using 7 arcs. For each arc, the collimator was rotated to 45°, and the field width was limited to 2.5 cm with 0.5 cm overlap with adjacent arcs. Thus, each arc covered only one section of the brain target volume. A conventional dual arc VMAT (DA-VMAT) plan was also designed. HT, P-VMAT, and DA-VMAT plans were compared using dose distribution reviews and dosimetric parameters. ArcCHECK phantom measurements were performed for verification of P-VMAT plans.
RESULTS: No significant differences in the mean coverage of the whole-brain target and metastases were observed between HT and P-VMAT (p > 0.05). The conformity index for the whole-brain target improved with P-VMAT compared with HT (p < 0.05). Furthermore, the volume of 44 Gy V44 (110% of prescribed dose for WBRT) received for whole-brain significantly reduced with P-VMAT from 38.2 ± 12.9% to 23.3 ± 9.4% (p < 0.05), and the maximum dose for organs at risks such as the hippocampus, optical nerve, optical chiasm, and spinal cord declined with P-VMAT (p < 0.05). Unlike HT and P-VMAT, DA-VMAT was clinically unacceptable because V44 in the whole-brain was too high (54.7 ± 8.2%). The mean absolute dose gamma passing rate for P-VMAT plans was 97.6 ± 1.1% (3%/3 mm criterion, 10%).
CONCLUSIONS: P-VMAT is favorable for WBRT and SIB for multiple brain metastases. It provides comparable coverage of whole-brain target and SIB, with better conformity, lower V44, and better dose sparing of organs at risk compared with HT. Furthermore, results show that DA-VMAT fails clinical practice even for a relatively large number of brain metastases with a high degree of plan complexity. The patient specific verification demonstrates the feasibility of P-VMAT for clinical application.
METHODS: This study retrospectively analyzed 10 patients with multiple brain metastases (40-120 metastases, median 76), who underwent WBRT and SIB using helical tomotherapy (HT). The prescribed doses were 40 Gy/20 f and 60 Gy/20 f for WBRT and SIB, respectively. Corresponding new HT plans were designed with P-VMAT using 7 arcs. For each arc, the collimator was rotated to 45°, and the field width was limited to 2.5 cm with 0.5 cm overlap with adjacent arcs. Thus, each arc covered only one section of the brain target volume. A conventional dual arc VMAT (DA-VMAT) plan was also designed. HT, P-VMAT, and DA-VMAT plans were compared using dose distribution reviews and dosimetric parameters. ArcCHECK phantom measurements were performed for verification of P-VMAT plans.
RESULTS: No significant differences in the mean coverage of the whole-brain target and metastases were observed between HT and P-VMAT (p > 0.05). The conformity index for the whole-brain target improved with P-VMAT compared with HT (p < 0.05). Furthermore, the volume of 44 Gy V44 (110% of prescribed dose for WBRT) received for whole-brain significantly reduced with P-VMAT from 38.2 ± 12.9% to 23.3 ± 9.4% (p < 0.05), and the maximum dose for organs at risks such as the hippocampus, optical nerve, optical chiasm, and spinal cord declined with P-VMAT (p < 0.05). Unlike HT and P-VMAT, DA-VMAT was clinically unacceptable because V44 in the whole-brain was too high (54.7 ± 8.2%). The mean absolute dose gamma passing rate for P-VMAT plans was 97.6 ± 1.1% (3%/3 mm criterion, 10%).
CONCLUSIONS: P-VMAT is favorable for WBRT and SIB for multiple brain metastases. It provides comparable coverage of whole-brain target and SIB, with better conformity, lower V44, and better dose sparing of organs at risk compared with HT. Furthermore, results show that DA-VMAT fails clinical practice even for a relatively large number of brain metastases with a high degree of plan complexity. The patient specific verification demonstrates the feasibility of P-VMAT for clinical application.
摘要：
目的：本研究采用常规C臂线性加速器实现多脑转移瘤（>40转移瘤）的全脑放射治疗（WBRT）和同步综合增强（SIB）。
方法：本研究回顾性分析了10例多发性脑转移患者（40-120转移，中位数76)，谁接受了WBRT和SIB使用螺旋断层治疗（HT）。WBRT和SIB的处方剂量为40Gy/20f和60Gy/20f，分别。用P-VMAT使用7条弧线设计了相应的新HT计划。对于每个弧，准直器旋转到45°，场宽度限制为2.5厘米，与相邻弧重叠0.5厘米。因此，每个弧仅覆盖大脑目标体积的一部分。还设计了传统的双电弧VMAT(DA-VMAT)计划。HT,P-VMAT,使用剂量分布评价和剂量学参数比较DA-VMAT计划。进行ArcCHECK体模测量以验证P-VMAT计划。
结果：在HT和P-VMAT之间没有观察到全脑靶和转移的平均覆盖率的显着差异（p>0.05）。与HT相比，P-VMAT改善了全脑目标的符合性指数（p<0.05）。此外，使用P-VMAT，全脑接受的44GyV44（WBRT处方剂量的110％）的体积显着减少，从38.2±12.9％降至23.3±9.4％（p<0.05），以及海马等危险器官的最大剂量，视神经,视交叉，脊髓下降与P-VMAT（p<0.05）。与HT和P-VMAT不同，DA-VMAT在临床上是不可接受的,因为全脑中的V44过高(54.7±8.2%)。P-VMAT计划的平均绝对剂量γ通过率为97.6±1.1％（3％/3毫米标准，10%)。
结论：P-VMAT对于多发性脑转移的WBRT和SIB是有利的。它提供了全脑目标和SIB的可比覆盖，更好的一致性，与HT相比，V44更低，并且有风险器官的剂量节省更好。此外，结果表明，即使对于相对大量的脑转移瘤，DA-VMAT的计划复杂性也很高，但在临床实践中失败。患者特异性验证证明了P-VMAT临床应用的可行性。
方法：本研究回顾性分析了10例多发性脑转移患者（40-120转移，中位数76)，谁接受了WBRT和SIB使用螺旋断层治疗（HT）。WBRT和SIB的处方剂量为40Gy/20f和60Gy/20f，分别。用P-VMAT使用7条弧线设计了相应的新HT计划。对于每个弧，准直器旋转到45°，场宽度限制为2.5厘米，与相邻弧重叠0.5厘米。因此，每个弧仅覆盖大脑目标体积的一部分。还设计了传统的双电弧VMAT(DA-VMAT)计划。HT,P-VMAT,使用剂量分布评价和剂量学参数比较DA-VMAT计划。进行ArcCHECK体模测量以验证P-VMAT计划。
结果：在HT和P-VMAT之间没有观察到全脑靶和转移的平均覆盖率的显着差异（p>0.05）。与HT相比，P-VMAT改善了全脑目标的符合性指数（p<0.05）。此外，使用P-VMAT，全脑接受的44GyV44（WBRT处方剂量的110％）的体积显着减少，从38.2±12.9％降至23.3±9.4％（p<0.05），以及海马等危险器官的最大剂量，视神经,视交叉，脊髓下降与P-VMAT（p<0.05）。与HT和P-VMAT不同，DA-VMAT在临床上是不可接受的,因为全脑中的V44过高(54.7±8.2%)。P-VMAT计划的平均绝对剂量γ通过率为97.6±1.1％（3％/3毫米标准，10%)。
结论：P-VMAT对于多发性脑转移的WBRT和SIB是有利的。它提供了全脑目标和SIB的可比覆盖，更好的一致性，与HT相比，V44更低，并且有风险器官的剂量节省更好。此外，结果表明，即使对于相对大量的脑转移瘤，DA-VMAT的计划复杂性也很高，但在临床实践中失败。患者特异性验证证明了P-VMAT临床应用的可行性。
