Watanabe Hiroyuki, Sugimoto Satoru, Kawabata Toru, Nagata Hironori, Kurokawa Chie, Usui Keisuke, Inoue Tatsuya, Takatsu Jun, Kato Kyoichi, Sasai Keisuke
Juntendo Iji Zasshi. 2022 Aug 2;68(4):375-386. doi: 10.14789/jmj.JMJ22-0003-OA. eCollection 2022.
In radiation therapy, the field-in-field (FIF) technique is used to prevent the administration of unnecessarily high doses to reduce toxicity. Recently, the FIF technique has been used for whole brain irradiation (WBI). Using the FIF technique, the volume that receives a higher than prescribed dose (hotspot) can be largely reduced; however, the treatment planning requires time. Therefore, to reduce the burden on the treatment planners, we propose a semiautomatic treatment planning method for the FIF technique.
In the semiautomatic FIF technique, hotspot regions in a treatment plan without the FIF technique are identified three-dimensionally, and beams with blocks that cover the hotspot regions using a multileaf collimator (sub-beams) are automatically created. The sub-beams are added to the original plan, and weights are assigned based on the maximum dose of the original plan to decrease the doses in the hotspot regions. This method was applied to 22 patients previously treated with WBI, wherein treatment plans were originally created without the FIF technique.
In the semiautomatic FIF plans, the hotspots almost disappeared. The dose to 95% of the volume and the volume receiving at least 95% of the prescribed dose in the planning target volume decreased by only 0.3% ± 0.2% and 0.0% ± 0.1%, respectively, on average compared with those in the original plan. The average semiautomatic FIF processing time was 28 ± 4 s.
The proposed method reduced the hotspot regions with a slight change in the target coverage.
在放射治疗中，野中野（FIF）技术用于避免给予不必要的高剂量以降低毒性。最近，FIF技术已用于全脑照射（WBI）。使用FIF技术，可以大幅减少接受高于处方剂量（热点）的体积；然而，治疗计划需要时间。因此，为减轻治疗计划制定者的负担，我们提出了一种FIF技术的半自动治疗计划方法。
在半自动FIF技术中，三维识别无FIF技术的治疗计划中的热点区域，并自动创建使用多叶准直器覆盖热点区域的带有挡块的射束（子射束）。将子射束添加到原始计划中，并根据原始计划的最大剂量分配权重，以降低热点区域的剂量。该方法应用于22例先前接受WBI治疗的患者，这些患者的治疗计划最初是在没有FIF技术的情况下制定的。
在半自动FIF计划中，热点几乎消失。与原始计划相比，计划靶体积中95%体积所接受的剂量和至少接受95%处方剂量的体积平均仅分别降低了0.3%±0.2%和0.0%±0.1%。半自动FIF的平均处理时间为28±4秒。
所提出的方法在靶区覆盖仅有轻微变化的情况下减少了热点区域。
