目的:本研究旨在探讨基于直线加速器的立体定向放射治疗单发脑转移瘤的最佳等剂量线(IDL)。使用HyperArc。我们比较了具有不同IDL的六个计划中目标和正常脑组织的剂量学参数。
方法:本研究纳入30例单发脑转移患者。我们回顾性地为每个具有不同IDL的肿瘤生成了六个计划(80%,70%,60%,50%,40%,和33%)使用HyperArc。所有治疗计划均标准化为35Gy的处方剂量,分为五个部分,占计划目标体积(PTV)的95%。通过在总肿瘤体积(GTV)上增加1.0毫米的边缘来定义。在六个计划中比较了剂量学参数。
结果:对于GTV>0.1cm3,接受25Gy的脑GTV体积与PTV的比率(V25Gy/PTV)在IDL为40%-70%时明显低于IDL为80%和33%(回顾性地,p<0.01)。对于GTV<0.1cm3,V25Gy/PTV随着IDL降低而持续降低。GTV的D99%和D80%值随着IDL的降低而增加。需要50%或更小的IDL来实现大于43Gy的D99%和大于50Gy的D80%。IDL50%的D99%和D80%的平均值分别为44.3和51.9Gy。
结论:对于GTV>0.1cm3,最佳IDL为40%-50%。这些较低的IDL可以增加GTV的D99%和D80%,同时降低正常脑组织的V25Gy,这可能有助于降低放射性坏死的风险并改善局部控制。
OBJECTIVE: The study aimed to investigate the optimal isodose line (IDL) in linear accelerator-based stereotactic radiotherapy for single brain metastasis, using HyperArc. We compared the dosimetric parameters for target and normal brain tissue among six plans with different IDLs.
METHODS: This study included 30 patients with single brain metastasis. We retrospectively generated six plans for each tumor with different IDLs (80%, 70%, 60%, 50%, 40%, and 33%) using HyperArc. All treatment plans were normalized to the prescription dose of 35 Gy in five fractions which was covered by 95% of the planning target volume (PTV), defined by adding a 1.0 mm margin to the gross tumor volume (GTV). The dosimetric parameters were compared among the six plans.
RESULTS: For GTV > 0.1 cm3, the ratio of brain-GTV volumes receiving 25 Gy to PTV (V25Gy/PTV) was significantly lower at IDL 40%-70% than at IDL 80% and 33% (p < 0.01, retrospectively). For GTV < 0.1 cm3, V25Gy/PTV decreased continuously as IDL decreased. The values of D99% and D80% for GTV increased with decreasing IDL. An IDL of 50% or less was required to achieve D99% of greater than 43 Gy and D80% of greater than 50 Gy. The mean values of D99% and D80% for IDL 50% were 44.3 and 51.9 Gy.
CONCLUSIONS: The optimal IDL is 40%-50% for GTV > 0.1 cm3. These lower IDLs could increase D99% and D80% of GTV while lowering V25Gy of normal brain tissue, which may help reduce the risk of radiation necrosis and improve local control.