Xiao Haonan, Guo Qiufen, Ma Junjie, Chen Jian, Xie Peng, Yin Yong
Department of Radiation Oncology and Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, CHN.
Department of Radiation Oncology and Physics, Shandong Provincial Key Medical and Health Laboratory of Pediatric Cancer Precision Radiotherapy, Shandong Cancer Hospital, Jinan, CHN.
Cureus. 2024 Sep 9;16(9):e69029. doi: 10.7759/cureus.69029. eCollection 2024 Sep.
Online adaptive radiation therapy (ART) eliminates interfraction uncertainties by adaption before each treatment session. However, intrafraction motions still exist and could become more severe due to long treatment time. Large isotropic margins can ensure clinical target volume (CTV) coverage but at the cost of more organs at risk damage. In this study, we proposed a novel personalized anisotropic margin search algorithm for cervical cancer radiation therapy under the guidance of daily iterative cone-beam computed tomography (iCBCT) to find the optimal margin values for each patient, which achieves the smallest possible planning target volume (PTV) and maintains CTV coverage. Twenty-two online Ethos ART treatment sessions were included for analysis. Two iCBCT scans were taken in each session. The first one (iCBCT) was taken after positioning, and the second one (iCBCT) was taken before beam delivery. Corresponding CTV and CTV were contoured in the two scans. In each session, minimal isotropic margins were first searched by iteratively increasing the magnitude until the resulting PTV covers 99% of CTV. Afterward, the margin values in all six directions were decreased iteratively until CTV coverage was smaller than 99% to get the personalized margin and target volume PTV. In addition, the uterus was considered separately, and different margins were found for it and the remaining CTV, respectively, to reduce the target volume of PTVfurther. PTV, PTV, and PTV were compared in terms of CTV coverage and absolute volume. The algorithm successfully generated PTV, PTV, and PTV for all online ART treatment sessions. The mean ± SD values for PTV , PTV , PTV , PTV, and PTV were 1,074.0 ± 78.1, 1,519.5 ± 100.4, 2,006.4 ± 122.5, 929.3 ± 73.4, and 845.1 ± 72.5 mL, respectively. The volume difference between PTV and PTV was significant (p < 0.001). All the PTVs ensured an average coverage larger than 99%, and the differences between any two PTVs were insignificant. This study proposed a novel personalized anisotropic margin search algorithm for cervical cancer online ART. Compared to the conventional 5 or 10 mm isotropic margins, the personalized anisotropic margin reduced PTV volume by 13.5% and 38.8%, respectively; if the uterus was considered separately, the volume can be further reduced by 21.3% and 44.3%, respectively, while CTV coverage was still maintained. This algorithm could reduce target volume and potentially spare normal tissue better than isotropic margin expansion.
在线自适应放射治疗（ART）通过在每次治疗疗程前进行调整来消除分次间的不确定性。然而，分次内运动仍然存在，并且由于治疗时间长可能会变得更加严重。大的各向同性边界可以确保临床靶区（CTV）覆盖，但代价是更多危及器官受到损伤。在本研究中，我们提出了一种新颖的个性化各向异性边界搜索算法，用于在每日迭代锥形束计算机断层扫描（iCBCT）引导下的宫颈癌放射治疗，以找到每个患者的最佳边界值，从而实现尽可能小的计划靶区（PTV）并维持CTV覆盖。纳入了22个在线Ethos ART治疗疗程进行分析。每个疗程进行两次iCBCT扫描。第一次（iCBCT）在定位后进行，第二次（iCBCT）在束流照射前进行。在两次扫描中勾勒出相应的CTV和CTV轮廓。在每个疗程中，首先通过迭代增加幅度来搜索最小各向同性边界，直到得到的PTV覆盖CTV的99%。之后，在所有六个方向上迭代减小边界值，直到CTV覆盖率小于99%，以获得个性化边界和靶区体积PTV。此外，将子宫单独考虑，分别为其和其余CTV找到不同的边界，以进一步减小PTV的靶区体积。比较了PTV、PTV和PTV在CTV覆盖和绝对体积方面的情况。该算法成功地为所有在线ART治疗疗程生成了PTV、PTV和PTV。PTV、PTV、PTV、PTV和PTV的平均值±标准差分别为1074.0±78.1、1519.5±100.4、2006.4±122.5、929.3±73.4和845.1±72.5 mL。PTV和PTV之间的体积差异显著（p<0.001）。所有PTV确保平均覆盖率大于99%，并且任意两个PTV之间的差异不显著。本研究提出了一种用于宫颈癌在线ART的新颖的个性化各向异性边界搜索算法。与传统的5或10 mm各向同性边界相比，个性化各向异性边界分别使PTV体积减少了13.5%和38.8%；如果将子宫单独考虑，体积可分别进一步减少21.3%和44.3%，同时仍维持CTV覆盖。该算法比各向同性边界扩展能更好地减小靶区体积并可能更好地保护正常组织。
