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Background and purpose The aim of this study is to evaluate the effectiveness of a cervical muscle training intervention in decreasing setup errors in patients head and neck cancer (HNC) undergoing radiotherapy (RT). Materials and methods HNC patients opting for RT at our center. The patients were randomly allocated to either the muscle training group or the control group in a 1:1 ratio. The magnitude of the setup error was measured at the levels of the clivus, C4 and C7 vertebrae respectively. The Van Herk formula was used to determine appropriate planning target volume (PTV) margins. (Trial Registration: ChiCTR2000041009, registration date: 12/16/2020) Results A total of 221 patients were analyzed, with 109 assigned to the muscle training group and 112 enrolled in the control group. Compared with the control group, the setup errors in the X and Z direction of the clivus and the Z direction of C4 and C7 in the muscle training group were significantly lower ( p  = 0.031, < 0.001, < 0.001, < 0.001 respectively). The required PTV margins in the Z direction increased from 2.13 mm in the clivus to 3.63 mm in C7 in the muscle training group and from 2.89 mm in the clivus to 4.37 mm in C7 in the control group. Multivariate linear regression analysis demonstrated that the impact of neck muscle training, weight fluctuation, and cervical curvature on the setup error in the Z direction at C7 differed significantly ( p  = 0.000, 0.001, and 0.008, respectively). Conclusion Neck muscle training can reduce setup errors and PTV margins in the anterior-posterior direction in patients undergoing RT for HNC.

Purpose This study evaluated setup error and efficiency in patients with non-small cell lung cancer (NSCLC) receiving stereotactic body radiation therapy (SBRT), comparing surface-guided radiation therapy (SGRT) combined with a laser alignment system versus laser alignment alone, to assess the clinical value of the SGRT-assisted setup method in SBRT for NSCLC. Methods A total of 80 patients with NSCLC were divided into an experimental group and a control group according to the treatment setup method. In the experimental group, an integrated fixation platform, vacuum cushions, and a cervicothoracic thermoplastic mask were used for immobilization, and a SGRT system and laser alignment system were used for setup. In the control group, the same immobilization devices were used, but only a laser alignment system was used for setup. All patients underwent pretreatment cone‒beam computed tomography (CBCT) scans. The CBCT images were registered to planning computed tomography (CT) images using grayscale registration. Translational setup errors in the left–right (LR), superior–inferior (SI), and anterior–posterior (AP) directions and rotational errors in the pitch, roll, and rotation directions were recorded. The setup time was also recorded and compared between the groups. Results Significant differences in the overall mean setup error in all six degrees of freedom were observed between the experimental and control groups ( P  ≤ 0.001). Within the experimental group, the overall mean setup error differed significantly between the LR and SI directions ( P  = 0.006). Within the control group, significant differences were found between the SI and AP directions ( P  < 0.001), as well as between pitch and rotation ( P  = 0.001) and between roll and rotation ( P  < 0.001). The overall mean setup time also significantly differed between the two groups ( P  < 0.001). Conclusion Compared with the conventional laser-guided setup method, the combination of SGRT and a laser alignment system significantly reduced setup error and shortened the setup time in SBRT for NSCLC. This approach improves setup accuracy and treatment workflow efficiency, demonstrating clinical feasibility and potential for clinical application.

In modern radiotherapy, error reduction in the patients’ daily setup error is important for achieving accuracy. In our study, we proposed a new approach for the development of an assist system for the radiotherapy position setup by using augmented reality (AR). We aimed to improve the accuracy of the position setup of patients undergoing radiotherapy and to evaluate the error of the position setup of patients who were diagnosed with head and neck cancer, and that of patients diagnosed with chest and abdomen cancer. We acquired the patient's simulation CT data for the three‐dimensional (3D) reconstruction of the external surface and organs. The AR tracking software detected the calibration module and loaded the 3D virtual model. The calibration module was aligned with the Linac isocenter by using room lasers. And then aligned the virtual cube with the calibration module to complete the calibration of the 3D virtual model and Linac isocenter. Then, the patient position setup was carried out, and point cloud registration was performed between the patient and the 3D virtual model, such the patient's posture was consistent with the 3D virtual model. Twenty patients diagnosed with head and neck cancer and 20 patients diagnosed with chest and abdomen cancer in the supine position setup were analyzed for the residual errors of the conventional laser and AR‐guided position setup. Results show that for patients diagnosed with head and neck cancer, the difference between the two positioning methods was not statistically significant (P > 0.05). For patients diagnosed with chest and abdomen cancer, the residual errors of the two positioning methods in the superior and inferior direction and anterior and posterior direction were statistically significant (t = −5.80, −4.98, P < 0.05). The residual errors in the three rotation directions were statistically significant (t = −2.29 to −3.22, P < 0.05). The experimental results showed that the AR technology can effectively assist in the position setup of patients undergoing radiotherapy, significantly reduce the position setup errors in patients diagnosed with chest and abdomen cancer, and improve the accuracy of radiotherapy.

Purpose In stereotactic radiosurgery (SRS) with single‐isocentric treatments for brain metastases, rotational setup errors may cause considerable dosimetric effects. We assessed the dosimetric effects on HyperArc plans for single and multiple metastases. Methods For 29 patients (1–8 brain metastases), HyperArc plans with a prescription dose of 20–24 Gy for a dose that covers 95% (D95%) of the planning target volume (PTV) were retrospectively generated (Ref‐plan). Subsequently, the computed tomography (CT) used for the Ref‐plan and cone‐beam CT acquired during treatments (Rot‐CT) were registered. The HyperArc plans involving rotational setup errors (Rot‐plan) were generated by re‐calculating doses based on the Rot‐CT. The dosimetric parameters between the two plans were compared. Results The dosimetric parameters [D99%, D95%, D1%, homogeneity index, and conformity index (CI)] for the single‐metastasis cases were comparable (P > 0.05), whereas the D95% for each PTV of the Rot‐plan decreased 10.8% on average, and the CI of the Rot‐plan was also significantly lower than that of the Ref‐plan (Ref‐plan vs Rot‐plan, 0.93 ± 0.02 vs 0.75 ± 0.14, P < 0.01) for the multiple‐metastases cases. In addition, for the multiple‐metastases cases, the Rot‐plan resulted in significantly higher V10Gy (P = 0.01), V12Gy (P = 0.02), V14Gy (P = 0.02), and V16Gy (P < 0.01) than those in the Ref‐plan. Conclusion The rotational setup errors for multiple brain metastases cases caused non‐negligible underdosage for PTV and significant increases of V10Gy to V16Gy in SRS with HyperArc.

Background To investigate the effect of bladder volume (BV) and bladder shape on consistency and treatment interruption in prostate cancer radiotherapy (RT). Methods A total of 275 patients who underwent radical prostate cancer RT in our institution from April 2015 to December 2022 were enrolled. Bladder height, bladder width, and bladder length were defined and recorded. The receiver operating characteristic (ROC) curves were used to evaluate the best cut‐off point for bladder shape. Logistic regression analysis was used to analyze the relationship between setup errors and bladder shapes and BV. Results Based on the ROC curves for 275 patients, the bladder shapes were classified into three: (a) the elongated bladder, (b) the spherical bladder, and (c) the oval bladder. Sixty‐six prostate cancer patients (1611 CBCTs) were randomly selected proportionally. It was found that bladder shape has a greater impact on setup errors than BV (BV: OR = 1.470, p = 0.037; bladder shape: OR = 2.013, p < 0.001), and the setup error of the spherical bladder in anterior–posterior (AP) direction was greater than the others (p < 0.001). In addition, the shape consistency of the spherical bladder was the worst (43.0%) during RT. Compared with the inconsistent group, the group with the same bladder shape had higher consistency in BV(CBCT/CT) (p < 0.001), and a smaller setup error in the AP direction (p < 0.001). Similarly, the treatment interruption fractions were highest in spherical bladder RT. Conclusions More specific bladder filling requirements should be developed for different bladder shapes. More attention should be paid to the spherical bladder for precise RT.

Objective To evaluate the impact of the residual setup errors from differently shaped region of interest (ROI) and investigate if surface-guided setup can be used in radiotherapy with concurrent tumor treating fields (TTFields) for glioblastoma. Methods Fifteen patients undergone glioblastoma radiotherapy with concurrent TTFields were involved. Firstly, four shapes of region of interest (ROI) (strip-shaped, T-shaped, ⊥ -shaped and cross-shaped) with medium size relative to the whole face were defined dedicate for patients wearing TTFields transducer arrays. Then, ROI-shape-dependent residual setup errors in six degrees were evaluated using an anthropomorphic head and neck phantom taking CBCT data as reference. Finally, the four types of residual setup errors were converted into corresponding dosimetry deviations (including the target coverage and the organ at risk sparing) of the fifteen radiotherapy plans using a feasible and robust geometric-transform-based method. Results The algebraic sum of the average residual setup errors in six degrees (mm in translational directions and ° in rotational directions) of the four types were 6.9, 1.1, 4.1 and 3.5 respectively. In terms of the ROI-shape-dependent dosimetry deviations, the D 98% of PTV dropped off by (3.4 ± 2.0)% ( p  < 0.05), (0.3 ± 0.5)% ( p  < 0.05), (0.9 ± 0.9)% ( p  < 0.05) and (1.1 ± 0.8)% ( p  < 0.05). The D 98% of CTV dropped off by (0.5 ± 0.6)% ( p  < 0.05) for the strip-shaped ROI while remained unchanged for others. Conclusion Surface-guided setup is feasible in radiotherapy with concurrent TTFields and a medium-sized T-shaped ROI is appropriate for the surface-based guidance.

Purpose We investigated the immobilization accuracy of a new type of thermoplastic mask—the Double Shell Positioning System (DSPS)—in terms of geometry and dose delivery. Methods Thirty‐one consecutive patients with 1–5 brain metastases treated with stereotactic radiotherapy (SRT) were selected and divided into two groups. Patients were divided into two groups. One group of patients was immobilized by the DSPS (n = 9). Another group of patients was immobilized by a combination of the DSPS and a mouthpiece (n = 22). Patient repositioning was performed with cone beam computed tomography (CBCT) and six‐degree of freedom couch. Additionally, CBCT images were acquired before and after treatment. Registration errors were analyzed with off‐line review. The inter‐ and intrafractional setup errors, and planning target volume (PTV) margin were also calculated. Delivered doses were calculated by shifting the isocenter according to inter‐ and intrafractional setup errors. Dose differences of GTV D99% were compared between planned and delivered doses against the modified PTV margin of 1 mm. Results Interfractional setup errors associated with the mouthpiece group were significantly smaller than the translation errors in another group (p = 0.03). Intrafractional setup errors for the two groups were almost the same in all directions. PTV margins were 0.89 mm, 0.75 mm, and 0.90 mm for the DSPS combined with the mouthpiece in lateral, vertical, and longitudinal directions, respectively. Similarly, PTV margins were 1.20 mm, 0.72 mm, and 1.37 mm for the DSPS in the lateral, vertical, and longitudinal directions, respectively. Dose differences between planned and delivered doses were small enough to be within 1% for both groups. Conclusions The geometric and dosimetric assessments revealed that the DSPS provides sufficient immobilization accuracy. Higher accuracy can be expected when the immobilization is combined with the use of a mouthpiece.

The Catalyst™ HD (C‐RAD Positioning AB, Uppsala, Sweden) is surface‐guided radiotherapy (SGRT) equipment that adopts a deformable model. The challenge in applying the SGRT system is accurately correcting the setup error using a deformable model when the body of the patient is deformed. This study evaluated the effect of breast deformation on the accuracy of the setup correction of the SGRT system. Physical breast phantoms were used to investigate the relationship between the mean deviation setup error obtained from the SGRT system and the breast deformation. Physical breast phantoms were used to simulate extension and shrinkage deformation (−30 to 30 mm) by changing breast pieces. Three‐dimensional (3D) Slicer software was used to evaluate the deformation. The maximum deformations in X, Y, and Z directions were obtained as the differences between the original and deformed breasts. We collected the mean deviation setup error from the SGRT system by replacing the original breast part with the deformed breast part. The mean absolute difference of lateral, longitudinal, vertical, pitch, roll, and yaw, between the rigid and deformable registrations was 2.4 ± 1.7 mm, 1.3 ± 1.2 mm, 6.4 ± 5.2 mm, 2.5° ± 2.5°, 2.2° ± 2.4°, and 1.0° ± 1.0°, respectively. Deformation in the Y direction had the best correlation with the mean deviation translation error (R = 0.949) and rotation error (R = 0.832). As the magnitude of breast deformation increased, both mean deviation setup errors increased, and there was greater error in translation than in rotation. Large deformation of the breast surface affects the setup correction. Deformation in the Y direction most affects translation and rotation errors.

Purpose To analyze the differences in setup errors among patients with rectal cancer in the upper, middle and lower segments and evaluate the consistency between electronic portal imaging device (EPID) and iSCOUT image‐guided techniques. Methods We retrospectively included 277 patients with rectal cancer treated with radiotherapy at our center between January 2020 and June 2025 and divided them into upper (n = 23), middle (n = 115) and lower (n = 139) rectal cancer groups based on their pathological results. Setup errors and corresponding planning target volume (PTV) margins were calculated and compared across groups and between EPID and iSCOUT, with correlation and agreement between the two image‐guidance methods further evaluated. Results The required external margins (cm) in the left–right (LR, X), superior–inferior (SI, Y) and anterior–posterior (AP, Z) directions for patients with upper, middle and lower rectal cancers were (0.44, 0.83, 0.57), (0.50, 0.69, 0.59) and (0.43, 0.68, 0.53), respectively. The setup errors between the upper and lower rectal cancers in the Z direction (p = 0.013) were significantly different. The X and Y directions between the EPID and iSCOUT groups in the different segments of rectal cancer were significantly different. The registration results of the EPID in the X, Y and Z directions significantly correlated with the corresponding iSCOUT error data (p < 0.001). The 95% consistency limits of EPID and iSCOUT measurement results in the X, Y and Z were −3.65 to 4.38, −3.69 to 4.21 and −3.66 to 3.57 mm, respectively. Conclusion In the Y direction, different margin expansions should be adopted based on the different rectal cancer treatment segments. The iSCOUT guidance technology can replace the EPID when necessary.

Purpose This study calculates the needed margin from clinical target volume (CTV) to planning target volume (PTV) in IMRT for cervical cancer. It also assesses the impact of setup errors on target and organ at risk (OAR) dose distribution. Methods We retrospectively analyzed 50 cervical cancer patients who underwent IMRT, with 210 CBCT scans. We calculated the CTV-to-PTV margin and simulated setup errors in the TPS to reassess dose distribution impacts on targets and OAR. Results Setup errors in X(anterior–posterior,AP), Y(cranial–caudal,CC), and Z(left–right,LR) directions were (1.4 ± 1.0) mm, (2.3 ± 1.5) mm, and (1.9 ± 1.2) mm, respectively, leading to CTV-to-PTV margins of 4.4 mm, 6.4 mm, and 5.8 mm. X-axis errors did not significantly affect target dosimetry (P > 0.05), but Y and Z errors did (P < 0.05). X-axis errors impacted the small intestine and rectum (P < 0.05), Y-axis errors mainly affected the colon (P < 0.05), and Z-axis errors affected the colon, small intestine, and rectum (P < 0.05). Conclusion Our study underscores the need to account for setup errors in radiotherapy for cervical cancer. Customizing the CTV-to-PTV margin based on institutional error data is key to maintaining target dose coverage and optimizing treatment outcomes.