The CyberKnife, an acronym for the stereotactic radiosurgery platform, represents an image-guided stereotactic radiotherapy technique. This technology precisely delivers ionizing radiation to tissues, effectively damaging tumor cells, and is suitable for radiotherapy of both intracranial and extracranial tumors. This article reports the first performance of CyberKnife by radiotherapy at Peking Union Medical College Hospital, including a patient with uncontrolled pituitary adenoma after surgery and radiotherapy, and another patient with vertebral metastasis following targeted therapy for lung adenocarcinoma. The application of CyberKnife technology in radiotherapy has achieved highly accurate dose delivery, enabling targeted irradiation of tumor lesions while minimizing damage to surrounding normal tissues, thereby yielding relatively ideal clinical outcomes.

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 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 evaluate the robustness of fully automated adaptive planning for Ethos online adaptive radiotherapy (ART) based on the intelligent optimization engine (IOE).Methods:Clinical data of 11 stage ⅠB cervical cancer patients admitted to Peking Union Medical College Hospital between June 2021 and June 2022 were retrospectively analyzed. Original planning images and iterative cone-beam computed tomography (iCBCT) images of each radiotherapy treatment were acquired, and all patient data were imported into the Ethos simulator. IOE-based 9-field automatic plan generation was performed for 11 patients using Ethos, and the generated plans were sent to online adaptive radiotherapy simulation to obtain each online adaptive radiotherapy plan (273 fractions in total) and complete the simulated treatment. For comparison, manual plan design was performed based on the images and contoured structures used for online adaptive radiotherapy planning, and the manually plans created with evenly divided 9 fields. Dosimetric parameters, plan complexity parameters, and Mobius quality assurance (QA) pass rates were collected to compare and evaluate the robustness of the online adaptive radiotherapy plan in terms of organs at risk (OAR), target volume dosimetric parameters, and plan complexity by using paired t-test or rank sum test. Results:The online adaptive plan of cervical cancer had comparable planning target volume (PTV) coverage compared to the manual plan. For the clinical target volume (CTV) D 99%, online adaptive plan was significantly higher than the manual plan [(45.93±0.36) vs. (45.32±0.31) Gy, P<0.001]. For hot dose area, the maximum point dose (PTV D max) of adaptive plan was significantly higher than the manual plan [(49.89±1.25) vs. (48.48±0.77) Gy, P<0.001], but the PTV D 1% of adaptive plan was significantly lower than the manual plan [(47.22±0.29) vs. (47.59±0.48) Gy, P<0.001]. There was no statistical difference in the conformal index ( P=0.967). And there was significant difference in the homogeneity index, with same medians and less dispersion in adaptive plan ( P<0.001). For OAR dose, bladder D mean, rectal V 40 Gy, small intestine D mean of adaptive plan was slightly higher than that of the manual plan; the rectal D mean, small intestine D 2 cm3 of the adaptive plan was slightly lower than that of manual plan; dosimetric parameters of right and left femoral heads, spinal cord and bone marrow of the adaptive plan were better than those of manual plan. The adaptive plan had more monitor units (MU) than the manual plan, but the complexity of the adaptive plan was significantly lower than that of the manual plan (0.135±0.012 vs. 0.151±0.015, P<0.001). For Mobius γ pass rate (5%/3 mm), both adaptive and manual plans met clinical requirements. Conclusion:Ethos cervical cancer online adaptive plan, which is based on the IOE engine, demonstrates good robustness and ensures the quality of online adaptive plans generated for each treatment fraction.

Objective:To evaluate the automatic optimization performance and clinical feasibility of the intelligent optimization engine (IOE) in the Ethos online adaptive radiotherapy platform.Methods:Clinical data of 11 patients with postoperative cervical cancer treated with Halcyon accelerator were retrospectively analyzed. Manual planning was performed for all patients using the 4 full arc volumetric modulated arc therapy (VMAT) (Manual-4Arc) in Eclipse, with a prescription dose of 45 Gy/25F. Patient images and structures were imported into the Ethos simulator, and appropriate clinical goals were added based on clinical requirements. The target coverage was normalized to 95%. Automatic plan generation was conducted using IOE, resulting in 7, 9, and 12 field intensity modulated radiotherapy (IMRT) plans (IMRT-7F、IMRT-9F、IMRT-12F), as well as 2 and 3 arc VMAT plans (VMAT-2Arc、VMAT-3Arc). Dosimetric index comparisons were made between the Manual-4Arc plans and the 5 groups of IOE-generated plans through one-way analysis of variance. Based on the analysis results, Turky post hoc multiple comparisons were performed to evaluate the automatic optimization performance of IOE.Results:In terms of the high dose area, the IMRT-12F plans showed the lowest D 1% for the planning target volume (PTV), and there were significant differences compared to the Manual-4Arc plans ( P=0.004). Regarding target coverage, all groups produced clinical target volume (CTV) plans that met the clinical requirements. Although the Ethos online adaptive plans were normalized during planning, the PTV coverage was slightly insufficient. For organs at risk (OAR) close to the target, such as the bladder, there were significant differences in V 30 Gy, V 40 Gy, and D mean among the 6 groups of plans. The dose ranking for the bladder was generally as follows: IMRT-12F

Objective:The purpose of this study is to test and assess the model of modeling data of TaiChi accelerator in the Raystation Treatment Planning System(RayStation system)according to the test method and item of TG119 report of American Association Physicians Medicine(AAPM).Methods:The intensity-modulated radiation therapy(IMRT)and volumetric-modulated arc therapy(VMAT)plans of the test cases of different clinical situations,which included the simulated multi target region,prostate target region,head and neck target region,easy type C-shape target region plan and difficult type C-shape target region plan,were designed according to the AAPM TG119 report in the treatment planning system.The deviations of the doses of point and area of the two kinds of plans were measured,and the measured results were compared and analyzed with the recommended standards of AAPM TG119 report.The IBA CC13 ionization chamber and the ArcCHECK matrix ionization chamber were used respectively to verify the point dose and area dose,and the assessment standard was γ passing rate under 3%3mm.The confidence interval was adopted to judge the consistency between the measured dose and the calculated dose.Results:The accuracies of plan dose target,point dose deviation and area dose distribution of tested cases could meet the requirement of the TGl19 report.The deviations of mean doses for the high-dose points of IMRT plan and VMAT plan of tested cases were respectively(0.39±1.02)%and(1.27±0.64)%,and the confidence intervals of them were respectively 2.39%and 2.52%.The average dose deviations of low doses of organ at risk(OAR)of IMRT plan and VMAT plan were respectively(0.53±1.73)%and(0.88±1.11)%,and the confidence intervals were respectively 3.92%and 3.06%.The average γ passing rate under 3%/3mm of IMRT plan and VMAT plan were respectively(99.52±0.366)%and(99.86±0.136)%,and the confidence intervals of them were respectively 1.196%and 0.406%.Conclusion:The TaiChi accelerator performance and the accuracy of Raystation system 6MV FFF model fitting can meet the standard of TG119 report,and the subsequent standards of the quality control of equipment and patients were established according to these tested results,which would provide reference for the improvement of the performance of subsequent accelerator.

Objective To explore and establish accurate detection quality control method of source positioning and timer precision for afterloading equipment. Methods The source positioning detection device was made of hd camera,EBT3 disposable film and steel rule,collecting source in each resident point for video images and film. Accurate measurement of radioactive source positioning and timer accuracy, including the timing absolute error and linear error through analysis of image sampling rate. After the film grayscale distribution analysis,comparison between film gray peak position and the measurement of resident point geometry,got the stay point source physics and radiation center deviation. Results Radioactive source physics and radiation center deviation was (-0.33± 0. 10) mm;For all default dwell time,timer average absolute deviation was (0.22±0. 02) s,linear fitting result was y=x-0. 226,R2=1,timing linear error was-0. 01％ Conclusions established detection means through the video images and film exposure quantitative analysis for accurately determination of source positioning,dwell time and source radiation center precision. After experimental testing the machine precision satisfied the requirement of clinical use.

Objective To measure the irradiation doses from the image beam line (IBL) of Artiste linac under the 2Dplanar,MV CBCT,6 MV 2Dplanar and Somatom CT modes to select an appropriate image-guided mode combined with the irradiation sites. Methods The head, chest and pelvic phantom doses from the IBL under the 2Dplanar,MV CBCT and 6 MV 2Dplanar modes were measured by using IBA Dose 1 electrometer and FC65 ionization chamber.The irradiation doses of Somatom CT scans of the head, chest and pelvis were measured using IBA Dosimax plus A system and the measurement results were analyzed. Results In the head and neck, the average irradiation dose was 16. 60 mGy under IBL 2Dplanar mode, 58. 73 mGy under IBL MV CBCT mode, 19. 83 mGy under 6 MV 2Dplanar mode and 7-9 mGy under Somatom CT. In the chest, the average irradiation dose was 14. 08 mGy under IBL 2Dplanar mode, 49. 17 mGy under MV CBCT mode, 18. 97 mGy under 6 MV 2Dplanar mode and 9-11 mGy under Somatom CT mode.In the pelvis, the average irradiation dose was 13. 36 mGy under IBL 2Dplanar mode, 45. 65 mGy under MV CBCT mode, 17. 52 mGy under 6 MV 2Dplanar mode and 12-15 mGy under Somatom CT mode. Conclusions In the head and neck, the image quality under IBL 2Dplanar mode is recommended, which is qualified for image registration standards. Somatom CT mode is suitable for the chest. In the pelvic region, IBL 2DPlanar mode can be applied when the intestinal cavity and bladder are well filled, and MV CBCT mode can be chosen if they are poorly filled.

Objective To investigate whether the accelerator image beam line (IBL) full scan and extend field of view(EFOV) scan mode megavoltage cone beam CT(MV CBCT) images can be used for dose calculation in adaptive radiotherapy.Methods The large aperture CT and MV CBCT were used to scan the CIRS 062M electron density modules,the CT value was established to electron density curves in the Pinnacle treatment planning system.Also,CT and MV CBCT were used to scan the head and neck,chest,abdomen and pelvis phantom.The intensity modulated radiotherapy(IMRT) plans were made with CT images and transplanted to MV CBCT images.The dose of targets and organs with their electron density curves was calculated,and two type IMRT plans with different CT images were compared.Results The dose distribution of head and neck phantom was acceptable,compared with the reference plan,the difference was within 3 ％.The dose distribution of chest and.pelvis was significantly reduced from reference plans,and the difference was 5％ and 10％ separately.This difference was beyond the scope of clinical acceptance.Conclusions MV CBCT images of accelerator IBL full scan mode in patients with head and neck site scan could be used for dose calculation in adaptive radiotherapy,chest and pelvic sites in EFOV mode scanning MV CBCT images could only be used for image guidance.

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.