Objective: To compare the setup accuracy between Catalyst HD and skin markers in stereotactic body radiotherapy (SBRT) of lung cancer. Methods: A total of 24 cases treated with SBRT were selected and all patients were fixed with vacuum pad in the supine position. Patients in group A were positioned by Catalyst HD and those in group B were positioned by shin markers. All patients were matched with the CT images after CBCT scan by rigid registration and the setup errors in six directions (x-, y-, z-axis, Rtn, Pitch and Roll) were obtained. Results: The mean±SD in group A and B in the six directions were as follows: (0.13±0.12) cm, (0.25± 0.19) cm; (0.26±0.15) cm, (0.13±0.11) cm; (0.23±0.19) cm, (0.35±0.29) cm; (0.43°±0.40°), (0.80°±0.69°); (0.48°±0.47°), (0.79°±0.64°); (0.62°±0.60°) and (0.88°±0.70°), respectively. Except the x-axis data in group B, all the data in the six directions were not normally distributed. The obtained data significantly differed between two groups (all P<0.05). The out-of-tolerance errors (>0.5 cm/2°) also significantly differed between two groups (P<0.05). Conclusions The setup errors of Catalyst HD are less than those of the skin markers (except the y-axis). The setup accuracy of Catalyst HD is superior to that of traditional skin markers, which is worthy of application in clinical practice.

Objective:To develop a new method to set up patients using optical surface monitoring system and to compare it with the conventional method in head radiotherapy.Methods:A total of 358 set-ups (130 with the conventional method and 228 with the new method ), which were from 99 head tumor patients in Beijing Cancer Hospital treated between May 2018 to April 2019, obtained by using Image Guided Radiotherapy were retrospectively analyzed. The distributions of set-up errors, the number of abnormal positions, and the set-up time were compared to evaluate the potential advantages of the new method .Results:The mean (± standard deviation) absolute values of setup errors of the new method were (0.07±0.07) , (0.08±0.06) and (0.06±0.06) cm for the vertical, lateral, and longitudinal, (0.53±0.41)°, (0.59±0.44)° and (0.59±0.46)° for the rotation, pitch and roll, respectively. In the new method , the setup accuracy was improved( t=3.24-6.10, P<0.001)and the number of abnormal positions was greatly reduced(χ 2=60.66, P<0.001). Compared with the conventional method, the patient setup time was slightly reduced by the new method , but the difference was not statistically significant ( P>0.05). Conclusions:The new high-precision method to set up patients using optical surface monitoring system improves the accuracy of patients′ position, decreases the corrections applied by 6DoF couch, reduces the probability of abnormal positions, and suggests the potential benefit in head radiotherapy.

Objective:To build patient setup workflow based on the optical surface monitoring system (OSMS) in postoperative radiotherapy for breast cancer, and compare the setup accuracy and PTV margin between OSMS based setup and conventional skin marker based method.Methods:The setup data of 20 cases of postoperative radiotherapy for breast cancer were retrospectively analyzed and divided into two groups: OSMS setup group and conventional skin marker setup group with 10 patients in each group. All CBCT rigid registration values in six dimensions ( x, y, z, Rtn, Pitch, Roll) were obtained, and the absolute value and distribution of errors were statistically analyzed by single sample t-test and χ2-test respectively. Finally, the CTV-PTV margins were compared using the extension formula. Results:The mean values in OSMS setup group and conventional skin marker setup group in sixdirections were 0.18 and 0.18 cm, 0.12 and 0.13 cm, 0.13 and 0.23 cm, 0.55° and 0.74°, 0.63° and 0.99°, 0.67° and 0.68°, respectively, while the standard deviations were 0.13 and 0.12 cm, 0.09 and 0.09 cm, 0.11 and 0.16 cm, 0.37° and 0.55°, 0.53° and 0.65°, 0.42° and 0.55°, respectively. The setup error differed in both z and Pitch directions( t=3.53, 2.98, P<0.05), while the error distribution rate difference was statistically significant between two groups in z direction( χ2=11.090, P<0.05). The CTV-PTV margins in OSMS setup group and conventional skin marker setup group were 0.28 and 0.26 cm, 0.21 and 0.20 cm, 0.24 and 0.35 cm, respectively. Conclusions:The proposed OSMS-based patient setup work flow is better than the conventional skin marker based method in setup accuracy, with significant setup error differences in z and Pitch directions. The proposed OSMS workflow is of potential clinical benefit.

Objective:To analyze and compare the radiation dose and image quality of kilo-voltage cone beam CT systems on different Varian accelerator platforms, providing data to support clinical decisions on selecting optimal protocols for image-guided radiotherapy based on cost-effective ratio (image quality / radiation dose).Methods:The radiation dose and image quality of various CBCT systems and scanning protocols on Varian Edge, Truebeam and ix (new and old) LINACs were obtained using a CT dose index (CTDI) phantom combined with a CT ionization chamber and a Catphan604 phantom, respectively. Figure of merit (FOM) was used to evaluate the cost-effective ratio of the image guidance schemes.Results:Considerable inter-system varieties of FOMs were observed, varying from 0.65 (Image Gently-full trajectory) to 48.46 (Image Gently-half trajectory). The inter-protocol varieties were also large, where the mean±SD was 22.14±13.47.Conclusions:Considering the explicit inter-system and inter-protocol varieties, it is clinically favorable to evaluate the image guidance schemes based on machine-specific measurement. For instance, parameters and equipment with low CTDI w can be beneficial for dose-sensitive patients. High CNR regimen favors patients with high image quality requirements. For ordinary patients, cost-effective ratio in terms of FOM can be very helpful to guide the decision-making of clinical image-guided radiotherapy.

Objective:To propose a markless patient setup workflow based on the optical surface monitoring system (AlignRT) and open-face mask immobilization for whole-course head tumor radiotherapy, assess the setup time and repositioning frequency of the proposed workflow, and conduct a comparative analysis of the differences, correlation, and consistency of the setup errors of the AlignRT and cone beam CT (CBCT) systems.Methods:A retrospective analysis was conducted for the data on the errors of 132 fractionated setup based on open-face mask immobilization of 33 head tumor patients. AlignRT-guided markless patient setup workflow was applied throughout the radiotherapy. Meanwhile, the body structures automatically generated by the treatment planning system were used as body references. The 6-degree-of-freedom (6DoF) setup errors (lateral, vertical, longitudinal, rotation, pitch, roll, and yaw directions), setup time, and repositioning frequency of the AlignRT and CBCT systems were recorded and analyzed. The Wilcoxon and Spearman analyses were used to statistically assess the differences and correlation of the setup errors of the two systems. Moreover, the Bland-Altman analysis was employed to evaluate the consistency of the two systems.Results:The 6DoF setup errors of CBCT were within the clinical tolerance (linear motions: -0.30 to 0.30 cm; rotational motions: -2.0° to 2.0°). The setup time and repositioning frequency of CBCT were (98 ± 31) s and 1.51% (2/132), respectively. There was no significant difference in setup errors between the two systems except those in x-axis ( Z = -3.11, P= 0.002), y-axis ( Z = -7.40, P<0.001), and Pitch ( Z= -4.48, P<0.001). There was a significant positive correlation between the setup errors along lateral ( rs = 0.47, P<0.001) and vertical ( rs = 0.29, P = 0.001) directions, rotation (Rtn; rs = 0.47, P<0.001), pitch (Pitch; rs = 0.28, P = 0.001) and roll (Roll; rs = 0.45, P<0.001) of the two systems. The 95% limits of agreement (95% LoA) of 6DoF setup errors were -0.12 to 0.09 cm, -0.07 to 0.17 cm, -0.19 to 0.20 cm, -1.0° to 0.9 °, -1.0° to 1.5°, and -0.9° to 1.0°, respectively. The 95% confidence interval (95% CI) of 95% LoA was -0.14 to 0.11 cm, -0.09 to 0.19 cm, -0.23 to 0.23 cm, -1.2° to 1.1°, -1.2° to 1.7°, and-1.0° to 1.1°, respectively, all of which were within the permissible error ranges. The 6DoF setup error difference of 3.41% (27/792< 5%) was beyond the 95% LoA. The maximum absolute differences of 6DoF setup errors within the 95% LoA were 0.12, 0.16, 0.19 cm, 0.9°, 1.5°, and 1.0°, respectively. Conclusions:The proposed markless setup workflow based on AlignRT combined with open-face mask immobilization for whole-course head tumor radiotherapy exhibits reasonable agreement and consistency with the patient setup using CBCT, with acceptable clinical efficiency. It can be applied to the first radiotherapy and the real-time monitoring of therapy to improve the safety and thus is of value in clinical applications.