Correlation between rotational errors and translational errors in intensity-modulated radiotherapy for nasopharyngeal carcinoma(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2018年第12期
- Page:
- 1365-1370
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Correlation between rotational errors and translational errors in intensity-modulated radiotherapy for nasopharyngeal carcinoma
- Author(s):
- HUANG Jiawen; ZHANG Meifang; LIU Libin; FU Wankai; YANG Haisong; ZHANG Xiuchun
- Radiation Therapy Center, the Affiliated Cancer Hospital of Fujian Medical University/Fujian Provincial Cancer Hospital, Fuzhou 350014, China
- Keywords:
- ; Keywords: nasopharyngeal carcinoma; intensity-modulated radiotherapy; cone beam CT; rotational error; translational errors; stability
- PACS:
- R739.63
- DOI:
- DOI:10.3969/j.issn.1005-202X.2018.12.001
- Abstract:
- Abstract: Objective To study the correlation between rotational errors and translational errors in the intensity-modulated radiotherapy (IMRT) of nasopharyngeal carcinoma (NPC), and explore the method to reduce the setup error of fractionated radiotherapy for improving the stability and accuracy of patient positioning in radiotherapy. Methods Seventy patients receiving IMRT for NPC between July 2015 and December 2017 were enrolled in this study. According to the rotational errors at the first setup, the patients were assigned into control group (rotational errors＜2°) and study group (rotational error≥2°). All patients received cone beam CT for a week. Before the first radiotherapy, cone beam CT was performed before and after correction. Results The first setup errors in X, Y, Z directions before and after correction were (1.05±0.73), (1.20±0.74), (1.44±1.20) mm and (0.43±0.29), (0.41±0.25), (0.39±0.30) mm in control group; (1.17±0.91), (1.61±1.27), (1.43±0.82) mm and (0.62±0.35), (0.83±0.39), (0.77±0.44) mm in study group. There was no significant difference in the setup error before correction (P>0.05). After correction, the setup errors of study group were significantly greater than those of control group (P<0.05). Significant differences were found in the passing rates of the first setup errors in X and Y directions which were higher in control group than in study group (88.57% vs 71.43%, 82.86% vs 60.00%, all P<0.05), not in the passing rates of the first setup errors in Z direction (71.43% vs 68.57%, P>0.05). The passing rates of the setup errors in fractionated radiotherapy in control group were 97.10%, 97.10%, 94.86%, respectively, significantly higher than 89.71%, 82.29%, 83.43% in study group (P<0.05). MPTV in X, Y, and Z directions in control group were increased by 0.84, 1.19, and 1.3 mm, compared with those values in control group. The analysis of rotational errors showed that Rx was strongly correlated with the Z axis, moderately correlated with the Y axis, and that RY was moderately correlated with the X, Y, and Z axes, and that Rz had a strong correlation with the X axis and a moderate correlation with the Y-axis. Conclusion Rotational errors have remarkable effects on the translational errors during radiotherapy. When the rotational error is large, the translational error is also large. Reducing the rotational error can effectively improve the accuracy and stability of patient positioning in radiotherapy for NPC.
Last Update: 2018-12-24