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 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: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 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 investigate the urinary iodine and thyroid volume of children aged 8 to 10 years in Linhai City Zhejiang Province, and evaluate the iodine nutrition level of children so as to provide a basis for formulating intervention measures to eliminate iodine deficiency disorders.Methods:In 2019, a systematic sampling method was adopted to select 1 township (street) central primary school in each of the 5 areas in the east, west, south, north, and middle of Linhai City. At least 40 children aged 8 to 10 years were selected from each of the central primary schools in each township (street) to collect family edible salt samples and one-time urine samples during the day for salt iodine and urinary iodine testing, respectively, as well as thyroid B-ultrasound examination.Results:A total of 215 salt samples were collected. The median salt iodine was 21.0 mg/kg, the coverage rate of iodized salt was 57.2% (123/215), the qualified rate of iodized salt was 91.9% (113/123), and the consumption rate of qualified iodized salt was 52.6% (113/215). A total of 215 urine samples were collected. The median urinary iodine was 166.0 μg/L, and the proportion of urinary iodine < 50 μg/L accounted for 5.1% (11/215). A total of 215 children were examined, and the goiter rate was 4.7% (10/215).Conclusion:The overall iodine nutrition level of children aged 8 to 10 years in Linhai City is at an appropriate level (100-199 μg/L), and the goiter rate is within the standard limit for the elimination of iodine deficiency disorders (5%), but the coverage rate of iodized salt and the consumption rate of qualified iodized salt are seriously low.

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.

Objective:To discuss the design details of accelerator room for a novel enclosed O-ring linac Halcyon, and to optimize its protection and layout.Methods:According to the optimization principle of radiation protection and the requirements of national radiation protection standards, and the structural characteristics of Halcyon accelerator, the differences between conventional and this novel accelerator rooms were analyzed by discussing the space layout of the machine room, shielding calculation, electrical facilities, purifying ventilation, temperature and humidity control and other factors.Results:The Halcyon machine had a compact structure, a closed ring frame design and a main beam shielding device, which could greatly reduce the radiation protection pressure while improving the space utilization rate of the machine room. The optimized design layout of the machine room could eliminate hidden dangers, avoid design defects, and prevent adverse consequences caused by design errors.Conclusions:The overall structure of Halcyon accelerator is different from that of conventional accelerators. The design details should be taken into full consideration to ensure the optimization of radiation protection, lay a good foundation for subsequent installation, debugging and operation of the equipment and create a good treatment environment for patients and medical staff.

Objective To analyze the failure and processing methods of helical tomotherapy multileaf collimator (MLC) and summarize relevant maintenance experience,aiming to accurately identify the faulty parts,shorten the downtime and enhance the work time.Methods The failure data of the helical tomotherapy MLC system in the past 48 months were analyzed to identify the common faulty parts,causes and processing methods.Results During the previous 48 months,the MLC failure occurred for 20 times,11 times for air compressor failure,4 times for position verification board failure,twice for leaf driver failure,twice for cushion valve failure and once for the slip of leaf position verification rod.The MLC failure was significantly correlated with the humidity of high-pressure gas.The work time of machine exerted significant effect upon the service time of MLC parts.Conclusions The structure of the helical tomotherapy MLC system is complex.The high-intensity work increases the failure rate.The humidity of high-pressure gas affects the normal operation of the MLC equipment.The faulty parts can be identified,the downtime can be reduced and the work time can be enhanced by summarizing the experience of MLC maintenance.

Objective To study the effect of leaf movement speed on the setup error of multileaf collimator (MLC) in RapidArc mode,and to improve quality assurance and verify the reliability of RapidArc.Methods Referring to the PicketFenceStatic_M120.dcm and PicketFenceRA_Ml20.dcm files,the Tilt tests with different adjacent leaf speed were designed and setup errors of MLC were obtained by analyzing electronic portal imaging device images.Results In the Tilt tests,the setup errors gradually increased from gapl 1 to gapS0 in both static gantry mode and RapidArc mode.With a gantry angle of 270°,gap41 had the maximum setup error of-0.55 mm.In the RapidArc mode,gap46 had the maximum setup error of-0.67 mm.The deviation of gap width was no greater than 15％ in any mode.There was no significant difference in deviation pattern of gap width between four modes with different gantry angles.The same gaps in different stripes showed a consistent trend in gap width.The RapidArc mode had a larger variation in percentage deviation of gap width than the static gantry mode.Conclusions The setup error increases with the increase in the speed of MLC leaf.The variation in the leaf speed has no significant impact on the gap width.There is no correlation between the leaf speed and the deviation of gap width.Four different gantry angles give similar deviation patterns of gap width,suggesting that the deviation of gap width is related to the leaf rather than the gantry angle.The RapidArc mode has a greater impact on the gap width than the fixed gantry mode.