Analysis of Setup Errors in Radiotherapy Between Three-Dimensional Treatment Couch and
Six-Dimensional Treatment Couch Registration by Cone Beam CT Image
YI Liangbo1, YUE Haizhen2, LI Junyu2, HU Jianqi2, CHEN Jixiang2, MAO Ji2, LU Zihong2, WANG Qin3
1. Department of Radiation Oncology, Shifang People’s Hospital, Deyang Sichuan 618400, China; 2. Department of Radiotherapy,
Beijing Cancer Hospital & Beijing Institute for Cancer Research, Key Laboratory of Carcinogenesis and Translational Research
(Ministry of Education/Beijing), Beijing 100142, China; 3. Department of Radiotherapy, Beijing Shijitan Hospital, Capital Medical
University, Beijing 100038, China
Abstract：Objective To analyze the setup error of radiotherapy by using the registration accuracy of cone beam CT imageguided
three-dimensional and six-dimensional radiotherapy couch, and to provide reference for the management of radiotherapy
process using three-dimensional radiotherapy couch in clinical practice. Methods The cone beam CT images of 50 patients with
nasopharyngeal carcinoma, 49 patients with esophageal cancer, and 25 patients with rectal cancer before radiotherapy were selected
as the research objects. The same region of interest was set using offline registration. Rigid registration was performed separately
in the linear direction of the three-dimensional radiotherapy couch and the linear and rotational directions of the six-dimensional
radiotherapy couch. The resulting setup errors after registration were analyzed. Results There was a significant difference in both
the vertical (Vrt) and lateral (Lat) directions (P<0.05) in patients with nasopharyngeal carcinoma using rank sum test while rectal
cancer using independent sample test for homogeneity of variance, but there was no significant difference in longitudinal (Lng)
direction (P>0.05). Rank-sum test was conducted on patients with esophageal cancer. There was a statistically significant difference
(P<0.05) in the Vrt direction, but no significant difference (P>0.05) was found in the Lng and Lat directions. There was no significant
difference (P>0.05) in the Lng direction across all three sites. For patients with nasopharyngeal cancer, rectal cancer, and esophageal
cancer, when the tolerance values in the linear direction were 3, 5, and 5 mm, respectively, the quantities of tolerance ranges of 2, 4, and 4 mm
accounted for a significant proportion. In the translation direction, the setup errors for both registration methods were basically
within the clinically set range. With six-dimensional registration, it was observed that there were larger setup errors in the headto-
foot direction for patients with nasopharyngeal cancer compared to the three rotational directions for patients with esophageal
cancer and rectal cancer. Conclusion The amount of setup error information provided during registration with a three-dimensional
radiotherapy couch is lower compared to a six-dimensional radiotherapy couch. When using a three-dimensional radiotherapy couch
for positioning, it is necessary to strengthen the management of the entire radiotherapy process and rotational direction positioning
techniques in order to improve the efficiency of radiotherapy positioning and the therapeutic gain ratio.
易良波1，岳海振2，李俊禹2，胡鉴颀2，陈吉祥2，毛继2，卢子红2，王钦3. CBCT引导下对三维治疗床与六维治疗床
配准放疗摆位误差的研究[J]. 中国医疗设备, 2024, 39(4): 47-52.
YI Liangbo1, YUE Haizhen2, LI Junyu2, HU Jianqi2, CHEN Jixiang2, MAO Ji2, LU Zihong2, WANG Qin3. Analysis of Setup Errors in Radiotherapy Between Three-Dimensional Treatment Couch and
Six-Dimensional Treatment Couch Registration by Cone Beam CT Image. China Medical Devices, 2024, 39(4): 47-52.
