肺多发转移瘤伽玛刀治疗的剂量分布研究

Dose Distribution of Body Gamma Rays Radiotherapy for Multiple Pulmonary Metastatic Tumor

目的对肺多发转移瘤患者γ刀治疗的剂量分布进行研究以评估其安全性和可行性。方法选取20例肺多发转移瘤(9~12个病灶,病灶直径≤2.3 cm)患者设计γ刀治疗计划(OUR-QGD型体部γ刀),采用仰卧体位的12例,俯卧体位的8例。在肺窗下勾画大体肿瘤靶区(gross target volume,GTV),GTV外放5 mm为计划靶区(planning target volume,PTV),50%等剂量线包绕PTV,70%等剂量线包绕90%GTV,处方剂量为50%等剂量线4 Gy/f,总剂量52 Gy,通过剂量体积直方图评估其剂量分布。结果处方总剂量为52 Gy时,90%的GTV靶区得到相当于常规放疗94 Gy剂量的照射,仰卧体位双肺的平均剂量为8.36 Gy,V20、V10和V5分别为12.60%、24.60%和37.40%,俯卧体位双肺的平均剂量为8.15 Gy,V20、V10和V5分别为12.67%、25.10%和40.40%。结论对于物理剂量而言,采用OUR-QGD型体部γ刀治疗数目较多的肺多发转移瘤是安全有效的。

Objective To investigate the dose distribution of OUR-QGD whole body γ rays radiotherapy for multiple pulmonary metastatic tumor and evaluate its safety and feasibility.Methods Twenty cases of lung metastatic tumor, with 9-12 foci and diameter≤2.3 cm,were treated with OUR-QGD whole body γ rays radiotherapy. Twelve cases were supine and eight cases were prone. Gross target volume(GTV) was delineated in lung window, and 5 mm was enlarged as planning target volume(PTV).50% isodose line was around PTV and 70% isodose line was around 90% of GTV.The reference dose was defi ned as 50% isodose line with 4 Gy per fraction, and the prescribed dose was 52 Gy with 13 fractions. The dose distribution was evaluated by dose volume histogram(DVH).Results 52 Gy of body γ rays radiotherapy to 90% of GTV was equivalent to 94 Gy of conventional radiotherapy to 90% of GTV. The average dose for total lung of the supine patients was 8.36 Gy, and V20, V10 and V5 for total lung were 12.6%, 24.60% and 37.40%, respectively. The average dose for total lung of the prone patients was 8.57 Gy, and V20, V10 and V5 were 12.67%, 25.10% and 40.40%, respectively.Conclusion As to physical dosage, OUR-QGD whole body γ rays radiotherapy is safe and feasible for patients with multiple pulmonary metastatic tumor.