Dosimetric effect of set-up errors on nasal NK/T cell lymphoma based on dose reconstruction
10.3760/cma.j.issn.1004-4221.2019.11.011
- VernacularTitle: 基于剂量重建分析摆位误差对鼻腔NK/T细胞淋巴瘤剂量学影响
- Author:
Zhanyu WANG
1
;
Junwen TAN
1
;
Yusong LONG
1
;
Xiantao HE
1
;
Gang LI
1
;
Yongfu FENG
1
;
Weixue LIANG
1
Author Information
1. Department of oncology, Fourth Affiliated Hospital of Guangxi Medical University, Liuzhou 545005, China
- Publication Type:Journal Article
- Keywords:
Nasal natural killer/T-cell lymphoma;
Set-up error;
Dosimetry
- From:
Chinese Journal of Radiation Oncology
2019;28(11):849-853
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To evaluate the dosimetric effects of set-up errors on nasal NK/T cell lymphoma by introducing set-up errors into the radiotherapy planning system for dose reconstruction.
Methods:Ten patients with nasal NK/T cell lymphoma were recruited. A non-coplanar volumetric modulated arc therapy plan was designed for CT image and clinical target area of each patient. After the completion of the plan, the set-up errors were introduced into the radiotherapy plan by changing the ISO of the treatment, and dose calculation was performed to reconstruct the dose distribution.
Results:With the increase of system set-up errors, the dose of target was decreased and the order affected by set-up errors in different directions was: left-right direction> head-foot direction> front-rear direction. When the translational set-up errors in each direction were -3 mm to 3 mm and the rotating set-up errors were -3° to 3°, the range of dose change in all targets was less than ±3%. When the set-up errors in all directions were ≤ 3 mm, the dose of organ at risk was less than or similar to the prescribed dose. When the set-up errors were> 3 mm, the doses of lens, spinal cord, parotid gland and optic nerve gradually exceeded the prescribed dose. Only when the rotating set-up errors were ≥ 3°, the dose of lens exceeded the prescribed dose. Special attention should be paid to the influence of the greater set-up errors in the left and right direction on lens, spinal cord and parotid gland, as well as on the spinal cord due to the larger set-up errors in the front and rear direction. After the actual set-up errors were introduced from our department, it exerted slight effect on the irradiation dose of GTV and CTV, which was less than ±2%. In a few cases, the dose of organ at risk potentially exceeded the prescribed dose limit, and special attention should be diverted to overdose of the lens and optic nerve.
Conclusions:The set-up errors will result in target dose deficiency and overdose of organ at risk in nasal NK/T cell lymphoma, especially upon the set-up errors in the left and right direction. The effect of 3 mm and 3° set-up errors on target and organ at risk is limited. Therefore, it is recommended to maintain the single direction set-up errors within 3 mm and 3°. The actual set-up errors introduced from our department exert little effect on the target dose, but a small number of organs are at risk of exceeding the prescribed dose limit. It is necessary to increase the evaluation of the extension region of organ at risk.
