Ohira Shingo, Sagawa Tomohiro, Ueda Yoshihiro, Inui Shoki, Masaoka Akira, Akino Yuichi, Mizuno Hirokazu, Miyazaki Masayoshi, Koizumi Masahiko, Teshima Teruki
Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan; Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Japan.
Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan.
Med Dosim. 2020;45(1):85-91. doi: 10.1016/j.meddos.2019.07.004. Epub 2019 Aug 2.
We assessed the effect of collimator angle on the dosimetric parameters for targets and organs at risk (OARs) for collimator-optimized HA (CO-HA) and non-CO-HA (nCO-HA) plans. The nCO-HA and CO-HA plans were retrospectively generated for 26 patients (1 to 8 brain metastases). The dosimetric parameters for planning target volume (homogeneity index [HI]; conformity index [CI]; gradient index [GI]) and for OARs were compared. The modulation complexity score for volumetric modulated arc therapy (MCSV) and monitor units (MUs) were calculated. Doses were measured using the electronic portal imaging device and compared with the expected doses. Dosimetric parameters of the HI, CI, and GI for single (n = 12) and multiple (n = 14) metastases cases were comparable (p > 0.05). For multiple metastases cases, the CO-HA plan provided lower V, V, V, V for brain tissue compared to the nCO-HA plan (p < 0.05). Doses for OARs (D) (brainstem, chiasm, Hippocampus, lens, optic nerves, and retinas) were comparable (p > 0.05). For multiple metastases cases, the CO-HA plan resulted in less complex multileaf collimator (MLC) patterns (MCSV = 0.19 ± 0.04, p < 0.01), lower MUs (8596 ± 1390 MUs, p < 0.01), and shorter beam-on time (6.2 ± 1.0 min, p < 0.01) compared to the nCO-HA plan (0.16 ± 0.04, 9365 ± 1630, and 6.7 ± 1.2 for MCSV, MUs, and beam-on time, respectively). For both treatment approach, the equivalent gamma passing rate was obtained with the 3%/3 mm and 2%/2 mm criteria (p > 0.05). The collimator optimization in the HA planning reduced doses to brain tissues and improved the treatment efficacy.
我们评估了准直器角度对适形优化调强放射治疗（CO-HA）和非适形优化调强放射治疗（nCO-HA）计划中靶区和危及器官（OARs）剂量学参数的影响。对26例患者（1至8个脑转移瘤）回顾性生成了nCO-HA和CO-HA计划。比较了计划靶体积的剂量学参数（均匀性指数[HI]；适形指数[CI]；梯度指数[GI]）以及OARs的剂量学参数。计算了容积调强弧形治疗的调制复杂度评分（MCSV）和监测单位（MUs）。使用电子射野影像装置测量剂量，并与预期剂量进行比较。单发性（n = 12）和多发性（n = 14）转移瘤病例的HI、CI和GI剂量学参数具有可比性（p>0.05）。对于多发性转移瘤病例，与nCO-HA计划相比，CO-HA计划使脑组织的V、V、V、V更低（p<0.05）。OARs（D）（脑干、视交叉、海马体、晶状体、视神经和视网膜）的剂量具有可比性（p>0.05）。对于多发性转移瘤病例，与nCO-HA计划（MCSV、MUs和射束开启时间分别为0.16±0.04、9365±1630和6.7±1.2）相比，CO-HA计划导致多叶准直器（MLC）模式的复杂度更低（MCSV = 0.19±0.04，p<0.01），MUs更低（8596±1390 MUs，p<0.01），射束开启时间更短（6.2±1.0分钟，p<0.01）。对于两种治疗方法，采用3%/3 mm和2%/2 mm标准时等效伽马通过率均较高（p>0.05）。HA计划中的准直器优化降低了脑组织的剂量并提高了治疗效果。
