Positioning error analysis
All patients underwent CBCT scanning and positioning corrections. After each positioning correction, the positioning error in the 3D direction was obtained, where the X-axis referred to the left–right directions (the left was positive, and the right was negative), the Y axis referred to the head–foot direction (the head was positive, and the foot was negative), and the Z axis represented the forward–backward direction (the forward was positive, and the backward was negative). The mean ± standard deviation in X axis (left and right), Y axis (up-down), and Z axis (front–back) directions were 0.014 ± 0.169, 0.07 ± 0.283, and 0.178 ± 0.2 cm in the 3D-printed oral stent group, respectively. The mean ± standard deviation of the simple glass bottle group was 0.084 ± 0.122 cm on the X axis, 0.09 ± 0.319 cm on the Y axis, and 0.48 ± 0.229 cm on the Z axis. The nonstent group had the mean ± standard deviation of 0.2 ± 0.17 cm on the X axis, − 0.032 ± 0.15 cm on the Y axis, and 0.52 ± 0.18 cm on the Z axis (Table Analysis of IMRT Posture Errors (mean ± standard deviation, cm)Comparisons of positioning errors among the three groups: *