Dosimetric study of the medical Agility grating system in radiotherapy of orbital lymphoma

Objective The spatial location of the orbital lymphoma target area is special; improving the quality of the orbital lymphoma plan and protecting the eye are important focus areas for doctors and physicists. This study aimed to investigate the dosimetric characteristics of the Agility grating system in orbital lymphoma. Methods A total of 10 patients with orbital lymphoma who underwent radiotherapy at the Ninth People's Hospital, affiliated with Shanghai Jiaotong University School of Medicine, from 1 May 2016 to 30 May 2018 were selected. The Monaco treatment planning system was used for calculation, and the MLCi2 and Agility grating data were selected, respectively. Dynamic intensity adjustment was carried out. In the calculation, the limit of other tissues is fixed, and only the limit of the patient's affected side crystal is changed. The limit range is changed from 4 to 20 Gy. The function is Serial, and each change is 2 Gy. The whole eye, the crystal, the optic nerve, and the target area's conformal index, homogeneity index, and planned hop count were calculated, respectively. Results With increased limitation of the affected side crystal, Agility was more advantageous in the parameters of conformal index, homogeneity index, the affected side of the optic nerve, the average amounts of the affected eye and side of the eye, and the planned number of hops. The conformal index difference rate was 27.12%. After dropping to 5.11%, the difference rate of the homogeneity index decreased from 11.52% to 1.57%, and the downward trend gradually slowed down ( P  < 0.01). There were statistically significant differences: the difference rate of the affected side optic nerve decreased from 11.99% to 1.53% ( P  < 0.01); the mean difference rate of the affected side crystals decreased from 20.59% to 3.55% ( P  < 0.01); and the mean value of the affected side eye was <10 Gy when the crystal limit was <10 Gy. The difference in learning was >10 Gy, and there was no statistical difference. The calculation results of the contralateral crystal, MLCi2, are more advantageous ( P  < 0.01), indicating there is a statistically significant difference. Conclusion The results of Agility gratings are more dosimetric than MLCi2 gratings in the treatment of orbital lymphoma. Agility grating should be used for radiotherapy of orbital lymphoma.