Dosimeteric calibration of thermoluminescence in helical tomotherapy system and linear accelerator(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2019年第11期
- Page:
- 1261-1266
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Dosimeteric calibration of thermoluminescence in helical tomotherapy system and linear accelerator
- Author(s):
- WANG Wei; SHEN Yichen; JIANG Mawei
- Department of Oncology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China
- Keywords:
- thermoluminescent dosimeter; helical tomotherapy; megavoltage dose calibration; calibration factor
- PACS:
- R815
- DOI:
- DOI:10.3969/j.issn.1005-202X.2019.11.004
- Abstract:
- Objective To compare the differences in scale factors of thermoluminescent dosimeters (TLD) between a linear accelerator (LINAC) and a helical tomotherapy system (TOMO) and to investigate the characteristics of TLD for providing basis for follow-up clinical applications. Methods The same batch of TLD was calibrated at 6 MV photon beams via LINAC and TOMO. The machine units of LINAC were 30, 50, 100, 150, 200 and 300 MU, respectively, while the delivery time of TOMO was 3, 5, 10, 15, 20, 30 and 40 s, respectively. Cross-calibration of an ionization chamber was applied at TLD measurement positions. Each set of measurement data was defined as the average of 3 TLD chips, and the dose as a function of TLD reading was calculated. The TLD dose calibration curves under LINAC and TOMO were compared with the linear model and the quadratic model fitting with least square method, respectively. Statistic analysis and paired t test were performed to calculate calibration factors. Meanwhile, the corresponding TLD characteristics such as sensitivity, repeatability, dispersibility and dose response performance were also verified. Results The correlation between TLD reading [y] and irradiation dose [x] in LINAC was [y]=94.754[x]＋0.001[x]2, R?=0.997 1. In TOMO, the correlation was [y]=93.835[x]＋0.000 3[x]2, R?=0.998 2. In the dose range of 0.30-3.74 Gy, the TLD dose-response curve of 6 MV photon beams was approximately linear. The measurement for the same batch was repeated 5 times at each cGy dose level, and the average change in reading was 1.48%. Conclusion The difference in TLD calibrated with LINAC and TOMO at the same energy was less than 3%. With the advantages of strong linear correlation of dose response, precise measurements, high repeatability, and stable performance, the proposed TLD system is appropriate for relevant clinical irradiation dose measurements.
Keywords: thermoluminescent dosimeter; helical tomotherapy; megavoltage dose calibration; calibration factor
Last Update: 2019-11-28