将剂量体积特征与理论放射生物学指标相关联，以快速评估伽玛刀立体定向放射治疗计划。
Associating dose-volume characteristics with theoretical radiobiological metrics for rapid Gamma Knife stereotactic radiosurgery plan evaluation.
作者信息
Tien Christopher J, Bond James E, Chen Zhe Jay
机构信息
Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT, USA.
出版信息
J Appl Clin Med Phys. 2020 Oct;21(10):132-140. doi: 10.1002/acm2.13018. Epub 2020 Sep 10.
PURPOSE
To examine general dose-volume characteristics in Gamma Knife (GK) plans which may be associated with higher tumor control probability (TCP) and equivalent uniform dose (EUD) using characteristic curve sets.
METHODS
Two sets of dose-volume histograms (DVHs) were exported alongside an analytical purpose-generated DVH: (a) single-shot large collimator (8 or 16 mm) emulated with multiple shots of 4 mm collimator. (b) shot-within-shot (SWS) technique with isodose lines (IDLs) of 40-75%. TCP, average dose, EUD in single-fraction (EUD ) and 2 Gy fractionated regimens (EUD ) were examined for trends with cumulative DVH (cDVH) shape as calculated using a linear-quadratic cell survival model (α/β = 10.0 Gy, N = 1 × 10 ) with both α = 0.20 Gy and α = 0.23 Gy .
RESULTS
Using α = 0.20 Gy (α = 0.23 Gy ), plans in the analytical set with higher shoulder regions had TCP, EUD , EUD increased by 180%, 5.9%, 10.7% (11.2%, 6.3%, 10.0%), respectively. With α = 0.20 Gy (α = 0.23 Gy ), plans with higher heels had TCP, EUD , EUD increased by 4.0%, <1%, <1% (0.6%, <1%, <1%), respectively. In emulating a 16 (8) mm collimator, 64 (12) shots of the small collimators were used. Plans based on small collimators had higher shoulder regions and, with α = 0.20 Gy (α = 0.23 Gy ), TCP, EUD , EUD was increased up to 351.4%, 5.0%, 8.8% (270.4%, 5.0%, 6.8%) compared with the single-shot large collimator. Delivery times ranged from 10.2 to 130.3 min. The SWS technique used 16:8 mm collimator weightings ranging from 1:2 to 9.2:1 for 40-75% IDL. With α = 0.20 Gy (α = 0.23 Gy ), the 40% IDL plan had the highest shoulder with increased TCP, EUD , EUD by 130.7%, 9.6%, 17.1% (12.9%, 9.1%, 16.4%) over the 75% IDL plan. Delivery times ranged 6.9-13.8 min.
CONCLUSIONS
The magnitude of the shoulder region characteristic to GK cDVHs may be used to rapidly identify superior plan among candidates. Practical issues such as delivery time may require further consideration.
目的
使用特征曲线集研究伽玛刀（GK）计划中的一般剂量体积特征，这些特征可能与更高的肿瘤控制概率（TCP）和等效均匀剂量（EUD）相关。
方法
除了分析目的生成的剂量体积直方图（DVH）外，还导出了两组DVH：（a）用多个4毫米准直器的照射模拟单次大准直器（8或16毫米）。（b）40 - 75%等剂量线（IDL）的逐次照射（SWS）技术。使用线性二次细胞存活模型（α/β = 10.0 Gy，N = 1×10）计算累积DVH（cDVH）形状，研究TCP、平均剂量、单次分割（EUD）和2 Gy分割方案（EUD）随cDVH形状的变化趋势，其中α = 0.20 Gy和α = 0.23 Gy。
结果
使用α = 0.20 Gy（α = 0.23 Gy）时，分析集中肩部区域较高的计划，其TCP、EUD、EUD分别增加了180%、5.9%、10.7%（11.2%、6.3%、10.0%）。使用α = 0.20 Gy（α = 0.23 Gy）时，足跟较高的计划，其TCP、EUD、EUD分别增加了4.0%、<1%、<1%（0.6%、<1%、<1%）。在模拟16（8）毫米准直器时，使用了64（12）个小准直器的照射。基于小准直器的计划肩部区域较高，与单次大准直器相比，使用α = 0.20 Gy（α = 0.23 Gy）时，TCP、EUD、EUD分别增加高达351.4%、5.0%、8.8%（270.4%、5.0%、6.8%）。照射时间为10.2至130.3分钟。SWS技术在40 - 75% IDL时使用的16:8毫米准直器权重范围为1:2至9.2:1。使用α = 0.20 Gy（α = √23 Gy）时，40% IDL计划的肩部最高，与75% IDL计划相比，TCP、EUD、EUD分别增加了130.7%、9.6%、17.1%（12.9%、9.1%、16.4%）。照射时间为6.9至13.8分钟。
结论
GK cDVHs的肩部区域特征大小可用于在候选计划中快速识别出更优计划。诸如照射时间等实际问题可能需要进一步考虑。
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