Dosimetric evaluation of adaptive radiotherapy for nasopharyngeal carcinoma based on deformable registration and synthetic CT(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2019年第8期
- Page:
- 892-897
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Dosimetric evaluation of adaptive radiotherapy for nasopharyngeal carcinoma based on deformable registration and synthetic CT
- Author(s):
- ZHOU Qiong; LI Yongwu; WANG Qi; SHI Guozhi; PANG Xiaoyan; ZHOU Qinxuan
- Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310016, China
- Keywords:
- ; Keywords: nasopharyngeal carcinoma; deformable registration; adaptive radiotherapy; kV cone beam computed tomography; synthetic CT; Velocity software
- PACS:
- R730.55；R312
- DOI:
- DOI:10.3969/j.issn.1005-202X.2019.08.006
- Abstract:
- Abstract：Objective To evaluate the advantages and importance of adaptive radiotherapy for nasopharyngeal carcinoma based on the synthetic CT image generated by the deformable image registration of kV cone-beam CT (kV CBCT). Methods The weekly acquired kV CBCT images of 10 patients with nasopharyngeal carcinoma and a set of positioning CT image of one patient were selected in the study. A total of 6 sets of synthetic CT images were generated with the deformable image registration of Velocity software. The Arc plan (Plan0) designed based on the positioning image (CT0) was copied to 6 sets of synthetic CT images. In group A, the final dose was directly calculated without changing the parameters, while the dose in group B was re-calculated after the design was re-optimized. The doses of 6 plans in groups A and B were accumulated into CT0 to obtain the cumulative doses, namely Dose_actual and Dose_replan. The original plan (Plan0) was compared with plans in group A and group B, and the changes in the weekly volume and accumulative dose of tumor target areas and organs-at-risk were evaluated. Results The volume shrinkage rates of PGTVnx, GTVnd, PTV, left and right parotid glands in the 10 patients was 3.81%±7.67%, 11.45%±9.89%, 3.50%±2.50%, 23.67%±7.39%, 24.18%±6.69%, respectively. Compared with those in the original plan (Plan0), the weekly mean doses of the D95 of PGTVnx, GTVnd and PTV in 6 plans in group A were reduced by 0.946, 1.054, 0.809, 0.848, 1.426, 0.799 Gy, 1.407, 1.501, 1.627, 1.236, 2.028, 1.373 Gy, and 2.330, 3.419, 3.938, 2.696, 4.213, 2.574 Gy, respectively. The prescription dose of group B had a higher degree of agreement with that of original plan. Compared with the original plan (Plan0), group A had higher D50, Dmean of left parotid gland and D50, Dmean, V30 of right parotid gland which were increased by 0.43 Gy, 0.10 Gy, 2.59 Gy, 2.81 Gy, 8.97%, and a lower V30 of left parotid gland which were decreased by 1.94%. Compared with the original plan (Plan0), the D50, Dmean, V30 of left parotid gland in group B were decreased by 1.22 Gy, 1.13 Gy, 4.15%, while the D50, Dmean, V30 of right parotid gland were increased by 2.8 Gy, 3.09 Gy, 5.44%. Conclusion The adaptive radiotherapy for nasopharyngeal carcinoma which is designed based on synthetic CT generated by the deformable image registration of kV CBCT can guarantee that the target dose coverage is consistent with that of Plan0 and reduce the cumulative dose of organs-at-risk, with significant dosimetric advantages.
Last Update: 2019-08-26