Methodological establishment of PTV and PRV margins for MRI guided online adapt-to-position radiotherapy for intracranial tumors
10.3760/cma.j.cn113030-20240430-00173
- VernacularTitle:磁共振加速器ATP模式颅内肿瘤靶区和危及器官外放研究
- Author:
Qiu GUAN
1
;
Nan LIU
;
Xin LIAN
;
Tingting DONG
;
Yunliang SUN
;
Hao LIANG
;
Wei TIAN
;
Lang YU
;
Bo YANG
;
Jie QIU
Author Information
1. 中国医学科学院 北京协和医学院 北京协和医院放射治疗科，北京 100730
- Keywords:
Brain neoplasms;
Magnetic resonance linac;
Adapt-to-position;
Margin;
Image registration
- From:
Chinese Journal of Radiation Oncology
2024;33(12):1106-1111
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To establish a method for obtaining planning target volume (PTV) and planning risk volume (PRV) margins caused by rotation in the use of adapt-to-position (ATP) modality of magnetic resonance linear accelerator (MRL) for patients with intracranial tumors.Methods:Clinical data of 6 patients with intracranial tumors (150 fractions in total) who received MRI-guided online ATP radiotherapy in Peking Union Medical College Hospital from November 2023 to January 2024 were retrospectively analyzed. The pre-planned CT structure was copied onto each segmented MR image and then the structures were traced back to the CT image according to the three-dimensional registration relationship. The anisotropic distance of the structure based on the original CT structure was calculated to obtain the variation range of the target and the organs at risk. The maximum anisotropic value was taken as the result of the PTV and the relationship between the results and intracranial location of different patients was analyzed. Group comparison was performed by Chi-square test. Two group comparison was conducted by post-hoc Wilcoxon signed-rank test. Results:After the rotation deviation was included, the range of target changes in the six directions of left and right (L/R), anterior and posterior (A/P) and superior and inferior (S/I) of the 6 patients were: (1.24± 0.86) mm/(1.91± 1.07) mm, (2.02± 1.26) mm/(1.66± 1.07) mm, (1.84± 1.84) mm /(2.94±1.93) mm, respectively. The results in the SI direction were significantly different, and the values in the I direction in 2 patients exceeded 4 mm, the margins suitable for all patients were 3.01 mm/2.4 mm(A/P), 1.9 mm/2.93 mm(L/R) and 3.14 mm/4.62 mm(S/I) in different directions, respectively. The L/R direction of the lens and the S/I direction of the optic nerve were significantly changed, and the A/P direction of the brain stem was (3.99± 4.64) mm. Larger values might be required when the target was in the posterior brain (left-down area, right-down area).Conclusions:The rotation deviation, organ movement and intracranial location affect the PTV and the organs at risk PRV in the MRI-guided ATP modality in intracranial tumors patients. The margin generation method based on image fusion can help to quantify the margin value reasonably.
