脑转移瘤同步加量正向调强放疗计划的研究

Simultaneous integrated boost with forward IMRT in multiple brain metastases=a planning study

目的评价1～3个脑转移瘤患者全脑放疗同步加量正向调强放疗计划的适形度及可行性。方法应用Pinnacle6．2治疗计划系统设计10例1～3个脑转移瘤正向调强计划，每例患者设计A、B两组计划。A组全脑放疗计划靶区（PTV。）处方剂量为30Gy分10次，脑转移瘤计划靶区（PTVboost）处方剂量为50Gy分10次。B组PTV。处方剂量为30Gy分10次，PTVtoost处方剂量为40Gy分10次。计算PTVtoost的适形值（CN）、处方剂量靶区体积比（PITV）、靶区覆盖度（TC）、靶区均匀指数（HI）、接受95％处方剂量的体积（V95）、治疗时间（min）等指标．评价计划的适形度和可行性。结果A、B两组PTVbtoost的平均CN分别为0．73±0．07和0．68±0．07（t=5．244，P〈0.05）。平均PITV分别为1．28±0．11和1．37±0．13（t=326，P〈005），平均TC为0．964-0．01，0．96±0．02（P〉0．05），平均H1分别为0．06±004和0．05±0．03（t=2986，P〈0．05）。A、B两组PTVⅧ的平均TC分别为0．97±002和0．96±0．01（P〉0．05），平均H1分别为0．39±0．09和0．23±0．04（t=989，P〈0．05）。平均V95分别为99．72±027和99．69±0．29（P〉0．05）。A、B两组平均照射野数均为10个，每次平均治疗时间分别为（3．95±0．94）和（2．79±0．46）min（t=7574，P〈005）。结论全脑放疗同步脑转移瘤加量正向调强放疗计划可行，剂量分布与螺旋断层放疗技术相近，治疗时间短。

Objective TO evaluate the dose conformity and feasibility of whole brain radiotherapy with a simultaneous in- tegrated boost by forward intensity-modulated radiation therapy plan in patients with 1-3 brain metastases. Methods Two groups of forward intensity-modulated radiation therapy plans were generated for 10 patients with 1-3 brain metastases on Pin- nacle 6.2 Treatment Planning System. In group A, the prescribed dose was 30Gy to the whole brain （PTVwtrt）, 50Gy to individual brain metastases （Pl-Vtoost）simultaneously. In group B, the prescribed dose was 30Gy to the PTVt, 40Gy to the PI-Vtoost accord- ingly. Conformity and feasibility were evaluated regarding conformation number （ CN ）, prescription isodose volume to target volume ratio （PIFV）, target coverage（TC）, homogeneity index（HI ）, volume received at least 95% of the prescribed dose（ V96） and treatment delivery time. Results The average values of CN, PITV,TC and HI for PTVtoost, were 0.73 and 0.68 （t=5.244, P〈0.05）; 1.28 and 1.37（t=3.26, P〈0.05）; 0.96 and 0.96（P 〉0.05）; 0.06 and 0.05（t=2.986, P〈0.05）in group A and group B, respectively. The average values of TC, HI and V95 for the PTVwtrt were 0.97 and 0.96 （P 〉0.05 ）; 0.39 and 0.23 （t=9.89, P〈0.05 ）; 99.72% and 99.69%（P 〉0.05）in group A and group B, respectively. Ten beams were used on average in both group A and group B. The av- erage treatment delivery time was 3.95 min in group A and 2.79 rain in group B （t=7.574, P〈0.05）. Conclusion Whole brain radiotherapy with a simultaneous integrated boost by forward IMRT in 1-3 brain metastases is feasible. Dose conformity was comparable to those planned by helical tomotherapy in literature and treatment delivery time was short.