Effect of intestinal air cavity on dose distribution of volumetric intensity modulated arc therapy for cervical cancer
10.3760/cma.j.cn121382-20250120-00206
- VernacularTitle:肠道空腔对宫颈癌容积弧形调强放射治疗计划中剂量分布的影响
- Author:
Jiayi XU
1
;
Jian GUAN
;
Rui HU
;
Ying LI
;
Cheng LI
Author Information
1. 苏州市立医院 南京医科大学附属苏州医院放射治疗科，苏州 215001
- Keywords:
Cervical cancer;
Intestinal air cavity;
Volumetric intensity modulated arc therapy;
Field avoidance region plan
- From:
International Journal of Biomedical Engineering
2025;48(2):145-151
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To investigate the effect of intestinal air cavity on dose distribution of volumetric intensity modulated arc therapy (VMAT) for cervical cancer.Methods:A total of 10 patients who underwent radiotherapy for cervical cancer at Suzhou Municipal Hospital from January to May 2021 were retrospectively analyzed. For each patient, the same optimization parameters were used to design both a normal full-arc plan and a field avoidance-region plan. The intestinal air cavity identified on computed tomography (CT) imaging was outlined as a separate structure. The dose distribution of the two plans were compared before and after changing the CT value (the electron density of the intestinal air cavity) to 0, using a paired t-test. Additionally, consecutive three-week cone beam CT (CBCT) images were collected for each patient. The intestinal air cavities from the three-week CBCT images were mapped onto the original CT, and the dose distributions of both plans were calculated on the CBCT images. The differences in dose distributions compared to the original plan were analyzed to assess plan robustness. Results:The 105% prescription dose coverage of the target volume ( V105) [(43.62±5.18)%)] within the target area for the field avoidance-region plan was greater than that for the normal full-arc plan [(36.38±10.20)%], with a statistically significant difference ( P<0.05). After modifying the electron density of the intestinal air cavity, the dose distribution in the target area worsened for both plans. However, the V100 and V105 for the field avoidance-region plan [(?0.64±0.58)%, (?2.16±1.66)%] were smaller than those for the normal full-arc plan [(?2.52±1.91)%, (?6.79±2.02)%], with a statistically significant difference (both P<0.05).The V30 for the small intestine in the field avoidance-region plan [(40.28±4.77)%] was lower than that in the normal full-arc plan [(42.63±4.82)%]. The V40 for the rectum [(61.70±15.39)%] and the V20 [(36.32±3.09)%, (35.06±5.32)%] and V30 [(17.76±3.05)%, (16.67±8.14)%] for the left and right femoral heads were higher than those in the normal full-arc plan {(59.72±15.13)%, [(31.36±3.97)%, (27.00±7.79%)] and [(12.99±4.55)%, (11.11±7.20)%]}, respectively, with a statistically significant differences (all P<0.05). The changes in V105 on the weekly CBCT images [(3.27±2.91)%, (2.07±2.93)%, (2.14±2.08)%] and V100 on the second and third weeks′ images [(0.44±0.54)%, (0.54±0.50)%] for the field avoidance-region plan were smaller than those for the normal full-arc plan [(8.22±5.87)%, (5.31±3.97)%, (6.91±3.34)% and (1.70±1.53)%, (2.22±1.97)%], with a statistically significant difference (all P<0.05). Conclusions:The field avoidance-region plan demonstrates higher robustness and better small bowel protection than the normal full-arc plan. The influence of intestinal air cavities on dose distribution should be considered during VMAT planing for cervical cancer to guide optimal plan selection.
