Objective:Based on HyperArc stereotactic radiotherapy(SRT)technique,six-dimensional free bed combined with double mask fixation was used to treat intracranial tumors,and the positioning errors of within batch and between batches were analyzed,so as to provide basis for the accuracy of clinical treatment of this technique.Methods:A total of 13 patients with intracranial tumors who admitted to Peking Union Medical College Hospital from March to July 2023 were retrospectively selected,and they were treated by using HyperArc SRT technique.The validation images of cone-beam computed tomography(CBCT)of within batch and between batches during treatment were analyzed.The positioning errors of three translational direction[left and right(x),head and foot(y)and abdominal and dorsal(z)]and rotational direction were analyzed.The each positioning error was set as group A,and the remaining error after the positioning error was corrected through six-dimensional free bed was set as group B,and the error post treatment was set as group C.The difference between group B and group C was defined as the change of within batch.According to the margin formula,the positioning error of within batch was used to calculate the required range of margin.Results:Under the mode of six-dimensional free bed correction combined with double mask fixation,a total of 59 times of HyperArc SRT on head were performed.In the comparison of the average errors on the six-dimensional direction among groups A,B and C,the errors of group A on x direction and y direction were respectively(0.119±0.039)and(-0.133±0.047)cm,and the differences of them between group A and group B[(0.004±0.002)and(0.018±0.005)cm]were significant(t=2.890,-3.224,P<0.05).There were no significant differences on other directions between the two groups(P>0.05).The error of RX direction of group B was(0.033±0.021)°,and the difference of that between group B and group C[(0.122±0.045)°]was significant(t=-2.306,P<0.05),while there were no significant differences on other directions(P>0.05).In the margin of the design of the plan of intracranial tumors,the x,y and z directions were respectively 0.6,0.9 and 0.4 mm.Conclusion:In the radiotherapy of using HyperArc SRT technique for intracranial tumors,the use of six-dimensional free bed combined with double mask treatment can significantly shorten the margin,and ensure accurate irradiation for gross tumor volume(GTV)and simultaneously reduce the irradiation volume and dose of surrounding normal tissue.

Objective:Based on HyperArc stereotactic radiotherapy(SRT)technique,six-dimensional free bed combined with double mask fixation was used to treat intracranial tumors,and the positioning errors of within batch and between batches were analyzed,so as to provide basis for the accuracy of clinical treatment of this technique.Methods:A total of 13 patients with intracranial tumors who admitted to Peking Union Medical College Hospital from March to July 2023 were retrospectively selected,and they were treated by using HyperArc SRT technique.The validation images of cone-beam computed tomography(CBCT)of within batch and between batches during treatment were analyzed.The positioning errors of three translational direction[left and right(x),head and foot(y)and abdominal and dorsal(z)]and rotational direction were analyzed.The each positioning error was set as group A,and the remaining error after the positioning error was corrected through six-dimensional free bed was set as group B,and the error post treatment was set as group C.The difference between group B and group C was defined as the change of within batch.According to the margin formula,the positioning error of within batch was used to calculate the required range of margin.Results:Under the mode of six-dimensional free bed correction combined with double mask fixation,a total of 59 times of HyperArc SRT on head were performed.In the comparison of the average errors on the six-dimensional direction among groups A,B and C,the errors of group A on x direction and y direction were respectively(0.119±0.039)and(-0.133±0.047)cm,and the differences of them between group A and group B[(0.004±0.002)and(0.018±0.005)cm]were significant(t=2.890,-3.224,P<0.05).There were no significant differences on other directions between the two groups(P>0.05).The error of RX direction of group B was(0.033±0.021)°,and the difference of that between group B and group C[(0.122±0.045)°]was significant(t=-2.306,P<0.05),while there were no significant differences on other directions(P>0.05).In the margin of the design of the plan of intracranial tumors,the x,y and z directions were respectively 0.6,0.9 and 0.4 mm.Conclusion:In the radiotherapy of using HyperArc SRT technique for intracranial tumors,the use of six-dimensional free bed combined with double mask treatment can significantly shorten the margin,and ensure accurate irradiation for gross tumor volume(GTV)and simultaneously reduce the irradiation volume and dose of surrounding normal tissue.

Objective:To present a set of clinically representative quality assurance (QA) test cases for stereotactic radiosurgery (SRT) plans of multiple intracranial metastases, in order to assess the plan quality and machine execution capabilities.Methods:Based on the clinical characteristics of multiple brain metastases, four groups of test cases with three target volumes (TVs), six TVs, nine TVs, and TVs near organs at risk (OARs) were designed. For these cases, SRT plans were developed, and plan quality was assessed using metrics including the Radiation Therapy Oncology Group conformality index (RTOG CI), gradient index (GI), homogeneity index (HI), and the volume of normal brain tissue receiving a dose of 24 Gy ( V24 Gy), which was defined as the volume enclosed by the 24 Gy isodose line around the Brain-PTV ( V24 Gy of Brain-PTV). Verification plans were generated for each test case, including the verification of point doses, planar doses (PD), and SRS MapCHECK (SMC) semiconductor matrix planar doses. Compared with the calculated result of the treatment planning system (TPS), the criteria for the γ analysis of planar doses were set at 1 mm/2% and 2 mm/2%. Results:For the four groups of test cases, the mean CI, GI, HI, and V24 Gy of Brain-PTV were 1.04±0.03, 3.79±0.40, 0.73±0.01 and (7.46±3.80) cm 3, respectively. The mean deviations of the point doses were 0.88%±0.98%, 1.47%±0.79%, 1.52%± 0.76%, and 1.17% ± 0.38%, respectively. The mean γ passing rates of the single fields for PDs were greater than 98% at 2 mm/2% and exceeding 96% at 1 mm/2%, and the mean γ pass rates of the SMC semiconductor matrix for PDs were 97.75% ± 2.31% and 99.33% ± 0.62%, at 1 mm/2% and 2 mm/2% respectively. Conclusions:The proposed QA test cases for SRT of multiple intracranial metastases allow for the effective assessments of the plan quality and machine execution capabilities and, thus, can assist various centers in clinical applications.

Objective:To compare the immobilization effect of two different immobilization methods in treatment with CyberKnife for intracranial tumors.Methods:A retrospective analysis was conducted on 48 patients with intracranial tumors who received treatment with CyberKnife in the Department of Radiotherapy at Peking Union Medical College Hospital from June 2023 to July 2024.Based on the different immobilization method,patients were divided into two groups:the Double Shell Positioning System(DSPS)group(n=22)and the Qfix group(n=26).The DSPS group was immobilized using an American full-body integrated positioning frame combined with a carbon fiber bracket and DSPS film,while the Qfix group was immobilized using an Encompass board and Qfix film.All patients were treated with 6 dimensions(6D)-skull tracking technique.During treatment,images were acquired as one times per 60 seconds,which were registered with digitally reconstructed radiograph(DRR)to record and compare the overall relative errors.The data of relative displacement error during treatment was calculated as|dx|=d1-d0,and differences between the two groups were compared.The maximum displacement(|d|=dmax-dmin)was also calculated,and difference in maximum displacement between the two kinds of immobilization methods was analyzed.Results:In the comparison of the overall relative errors between the two kinds of immobilization methods,the median values in the errors of superior-inferior(SI),anterior-posterior(AP),Roll,Pitch,and Yaw directions in the Qfix group were respectively 0.174,0.309,0.150,0.147,and 0.477,which were significantly less than those(0.224,0.316,0.175,0.221,and 0.584)of DSPS group,and the differences were statistically significant(Z=-4.358,-1.698,-2.595,-6.833,-5.371,P<0.05).The difference of the relative displacement errors between two kinds of immobilization methods was not significant(P>0.05),while the median values in all directions were not zero.The comparison of the maximum displacement value between the two kinds of immobilization methods indicated the displacement amounts of Qfix group was less than those of DSPS group on SI,left-right(LR),AP,roll,pitch,and yaw directions,and the differences of them were significant(Z=-3.373,-2.525,-2.488,-3.169,-5.130,-5.166,P<0.05).Conclusion:Both immobilization methods can meet the requirements of clinical treatment.The results of comparison indicate the immobilization effect of Qfix group is best,and the combination of Encompass board and Qfix film is recommended as the immobilization method of CyberKnife-based radiotherapy for intracranial tumors.

Objective:To present a set of clinically representative quality assurance (QA) test cases for stereotactic radiosurgery (SRT) plans of multiple intracranial metastases, in order to assess the plan quality and machine execution capabilities.Methods:Based on the clinical characteristics of multiple brain metastases, four groups of test cases with three target volumes (TVs), six TVs, nine TVs, and TVs near organs at risk (OARs) were designed. For these cases, SRT plans were developed, and plan quality was assessed using metrics including the Radiation Therapy Oncology Group conformality index (RTOG CI), gradient index (GI), homogeneity index (HI), and the volume of normal brain tissue receiving a dose of 24 Gy ( V24 Gy), which was defined as the volume enclosed by the 24 Gy isodose line around the Brain-PTV ( V24 Gy of Brain-PTV). Verification plans were generated for each test case, including the verification of point doses, planar doses (PD), and SRS MapCHECK (SMC) semiconductor matrix planar doses. Compared with the calculated result of the treatment planning system (TPS), the criteria for the γ analysis of planar doses were set at 1 mm/2% and 2 mm/2%. Results:For the four groups of test cases, the mean CI, GI, HI, and V24 Gy of Brain-PTV were 1.04±0.03, 3.79±0.40, 0.73±0.01 and (7.46±3.80) cm 3, respectively. The mean deviations of the point doses were 0.88%±0.98%, 1.47%±0.79%, 1.52%± 0.76%, and 1.17% ± 0.38%, respectively. The mean γ passing rates of the single fields for PDs were greater than 98% at 2 mm/2% and exceeding 96% at 1 mm/2%, and the mean γ pass rates of the SMC semiconductor matrix for PDs were 97.75% ± 2.31% and 99.33% ± 0.62%, at 1 mm/2% and 2 mm/2% respectively. Conclusions:The proposed QA test cases for SRT of multiple intracranial metastases allow for the effective assessments of the plan quality and machine execution capabilities and, thus, can assist various centers in clinical applications.

Objective:To compare the immobilization effect of two different immobilization methods in treatment with CyberKnife for intracranial tumors.Methods:A retrospective analysis was conducted on 48 patients with intracranial tumors who received treatment with CyberKnife in the Department of Radiotherapy at Peking Union Medical College Hospital from June 2023 to July 2024.Based on the different immobilization method,patients were divided into two groups:the Double Shell Positioning System(DSPS)group(n=22)and the Qfix group(n=26).The DSPS group was immobilized using an American full-body integrated positioning frame combined with a carbon fiber bracket and DSPS film,while the Qfix group was immobilized using an Encompass board and Qfix film.All patients were treated with 6 dimensions(6D)-skull tracking technique.During treatment,images were acquired as one times per 60 seconds,which were registered with digitally reconstructed radiograph(DRR)to record and compare the overall relative errors.The data of relative displacement error during treatment was calculated as|dx|=d1-d0,and differences between the two groups were compared.The maximum displacement(|d|=dmax-dmin)was also calculated,and difference in maximum displacement between the two kinds of immobilization methods was analyzed.Results:In the comparison of the overall relative errors between the two kinds of immobilization methods,the median values in the errors of superior-inferior(SI),anterior-posterior(AP),Roll,Pitch,and Yaw directions in the Qfix group were respectively 0.174,0.309,0.150,0.147,and 0.477,which were significantly less than those(0.224,0.316,0.175,0.221,and 0.584)of DSPS group,and the differences were statistically significant(Z=-4.358,-1.698,-2.595,-6.833,-5.371,P<0.05).The difference of the relative displacement errors between two kinds of immobilization methods was not significant(P>0.05),while the median values in all directions were not zero.The comparison of the maximum displacement value between the two kinds of immobilization methods indicated the displacement amounts of Qfix group was less than those of DSPS group on SI,left-right(LR),AP,roll,pitch,and yaw directions,and the differences of them were significant(Z=-3.373,-2.525,-2.488,-3.169,-5.130,-5.166,P<0.05).Conclusion:Both immobilization methods can meet the requirements of clinical treatment.The results of comparison indicate the immobilization effect of Qfix group is best,and the combination of Encompass board and Qfix film is recommended as the immobilization method of CyberKnife-based radiotherapy for intracranial tumors.

Objective:To explore the radiation dose of brachytherapy plan for cervical cancer patients under different image-guided method and the time efficiency characteristics of each part of the clinical workflow, so as to provide reference for the overall arrangement of clinical brachytherapy.Methods:The workflow of 223 patients with brachytherapy was retrospectively analyzed. The whole workflow was divided into 5 parts: applicator placement, image acquisition, delineation of target and organs at risk, plan design and review, and treatment implementation. The image-guided brachytherapy was divided into X-ray guided 2D treatment groups, and computed tomography(CT)and magnetic resonance imaging (MRI) guided 3D treatment groups. The radiation dose and the time spent in each part of the three image-guided brachytherapy workflow were calculated. The radiation dose was evaluated using total reference air kerma (TRAK). The results were analyzed using the nonparametric test of SPSS 20 software.Results:TRAK 4.2(4.4, 3.9) cGy was significantly higher in X-ray guided 2D treatment group than in the CT guided 3D treatment group [3.5(3.9, 2.7) cGy, H =90.73, P < 0.01] and the MRI guided 3D treatment group[2.7(2.9, 2.4) cGy, H =90.73, P < 0.01]. The total workflow time of the X-Ray film guidance group was the shortest [55.0(67.0, 50.0) min], followed by the CT guidance group [80.0(91.0, 72.0) min], and the total workflow time of the MRI image guidance group was the longest [119.0(143.0, 105.5) min, H =106.39, P <0.01]. The image acquisition time of the MRI-guided group was significantly higher than that of the X-ray film guidance group and the CT-guided group ( H =44.80, P<0.01). The time of target delineation in the MRI-guided group was significantly longer than that in the CT-guided group ( Z=-5.10, P<0.01). The MRI-guided group took the longest time for planning, followed by the CT-guided group, and the X-ray guided group took the shortest time ( H =57.93, P<0.01). Conclusions:The 2D brachytherapy mode guided by X-ray film had the shortest process time but higher TRAK, while the 3D brachytherapy mode guided by MR had the longest process time, and the planned TRAK result were comparable to those guided by CT. When multiple patients are treated with brachytherapy at the same time, the work efficiency can be improved by interspersing different phases and the waiting time can be avoided.

Objective:To evaluate the clinical application of online adaptive radiotherapy based on iterative cone-beam computed tomography (iCBCT) for the pelvic malignancies.Methods:This was a prospective clinical trial of iCBCT guided online adaptive radiotherapy for pelvic malignancies in Department of Radiation Oncology, Peking Union Medical College Hospital. Clinical data of 13 patients with pelvic malignancies who received online adaptive radiotherapy from August to November, 2022 were preliminarily analyzed (2 cases of cervical cancer, 4 postoperative cervical cancer, 3 postoperative endometrial cancer, 3 bladder cancer and 1 prostate cancer). The feasibility of online adaptive radiotherapy, adaptive radiotherapy time, the frequency and magnitude of edits for organs at risk and target volume, target volume coverage and organs at risk doses were analyzed. Statistical analysis was performed by SPSS software. Data conforming to normal distribution were described by Mean±SD, and data with non-normal distribution were expressed by M ( Q1, Q3). Data with homogeneous variances were analyzed by t-test, and data with non-normal distribution or heterogeneous variances were analyzed by nonparametric test. Results:The average adaptive time was 15 min and 38 s (from acceptance of acquired CBCT scan to completion of the final plan selection). 85.4% (830/972 fractions) of influencer structures (system-defined organs adjacent to and with high impact on the generation of clinical target volume and planning target volume, primarily bladder, rectum and small intestine in pelvic neoplasms) automatically generated by artificial intelligence required no edits or minor editors, and 89.8% (491/547 fractions) of clinical target volume automatically generated by artificial intelligence required no edits or minor editors. The adapted plan was adopted in 98.5% (319/324 fractions) of radiotherapy fractions. Compared with the scheduled plan, the adapted plan showed better target volume coverage and reduced the dose of organs at risk.Conclusions:iCBCT guided online adaptive radiotherapy for the pelvic malignancies can be achieved within clinically acceptable timeslots. In addtion, better dose coverage of target volume shows the advantages of online adaptive radiotherapy.

Objective:To compare the calculation result and analyzes the reasons for their differences so as to provide reference for the revision and improvement of the current national standards on radiation shielding design for the room of brachytherapy.Methods:For the initial activity 10 Ci (1 Ci=3.7×10 10 Bq) of radioactive sources, the shielding schemes of brachytherapy room were designed in accordance with UK Institnte of Physics and Engineering in Medicine(IPEM) Report 75, USA NCRP Report 151 and the national standard GBZ/T 201.3-2014, respectively. The differences in shielding limits, occupancy factors and other relevant factors are compared in detail. Results:The annual exposure time in a typical brachytherpy room was about 330 h. The point-specific concrete thickness were 70, 65, 61, 70, 50 cm as required by NCRP Report 151, 41, 43, 30, 40, 39 cm by IREM regulations and 84, 79, 46, 88, 39 cm by GBZ/T 201.3, respectively. The concerned concrete shielding thickness calculated under the GBZ/T 201.3-2014 was generally thicker, with lesser difference from NCRP Report 151 result, whereas that from the IPEM75 report was thinnest. The equivalent lead shielding thicknesses of the protective doors calculated using the three method are 1.170, 0.854 and 1.040 cm, respectively.Conclusions:The shielding thickness calculated using the calculation method and evaluation index recommended by the current Chinese shielding standards for brachytherapy bunker is similar to that reported in NCRP151, but is conservative. In particular, the evaluation index of instantaneous dose equivalent rate required by the current national standards and the relative conservative value of occupancy factor will significantly increase the shielding thickness required by the main shielding area.

Objective:Objective To investigate the role of radiotherapy in the treatment of refractory keloids, evaluate the self-assessment degree of satisfaction of patients and compare with the objective outcomes.Methods:A total of 144 patients (290 lesions) with refractory keloids admitted to Peking Union Medical College Hospital from 2013 to 2018 were included in this study. The median age was 28 years old (range: 15-81 years old). All lesions were subjected to electronic radiation at postoperative 24h. The regime of 5 to 7MeV electron beam radiation therapy was adopted. The total dose was ranged from 16 to 18 Gy/2f (at 1-week interval). The median follow-up time was 48 months (range: 35-91 months). Patient and Observer Scar Assessment Scale (POSAS) was used to evaluate the degree of satisfaction. Multivariate analysis was performed by Cox proportional hazards model.Results:Among 290 keloids, 52 keloids (17.9%) relapsed in 3 to 42 months from the end of radiotherapy (median 12 months). The main side effects were hyperpigmentation and local incisional extension. Univariate analysis showed that local incisional color darker than skin, pruritus, pain and young age were associated with recurrence. Multivariate analysis indicated that local incisional color darker than skin and pain were the independent prognostic factors for scar recurrence. Recurrence, hyperpigmentation and local incisional extension were the main reasons for patients′ dissatisfaction.Conclusions:Postoperative electronic radiation can achieve satisfactory efficacy in the treatment of refractory keloids. Local incisional color darker than skin and pain are the independent prognostic factors of keloid recurrence. Patient self-assessment results are not fully consistent with the objective clinical outcomes and recurrence status.