ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
Objective:An investigation on the prevention and control measures taken by radiotherapy centers of various hospitals in Beijing during the COVID-19 pandemic was conducted. The experience was summarized to provide reference for further work.Methods:Electronic questionnaires were distributed to each radiotherapy center through members of the radiation oncology therapeutics branch of Beijing medical association and members of Society of Radiotherapy Specialists (Technicians) of Beijing Medical Doctors Association. Statistical analysis was performed based on the feedback results of electronic questionnaires.Results:All forty radiotherapy centers in Beijing returned the questionnaires by the end of April 10, 2020. Except for the suspension of treatment in one center due to COVID-19 pandemic, all radiotherapy centers have taken corresponding prevention and control measures and continued to carry out radiotherapy. No COVID-19 infection of patients or medical staffs occurred during this pandemic.Conclusions:During the COVID-19 pandemic, all radiotherapy centers attach great importance to optimizing the clinical process and adopt reasonable prevention and control measures. On the basis of efficient prevention and control measures, radiotherapy is delivered to fulfill the treatment demands of cancer patients.
ABSTRACT
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.
ABSTRACT
Objective To evaluate the anxiety and explore relevant risk factors in patients receiving radiotherapy and their relatives,aiming to provide evidence for improving the quality of life. Methods Before radiotherapy,the self-rating anxiety scale (SAS) was utilized to evaluate the anxiety of patients and their relatives. The incidence rate of anxiety was analyzed under the influence from different risk factors. Results A total of 646 participants (463 patients and 183 relatives) were included in this study. The average SAS scores of all participants,patients and family relatives were 41.52±10. 08,41.02±19. 37 and 42.79±11. 56, significantly higher than 37.23±12. 58 for the healthy population in China (P= 0. 000. 0.000,0. 000).For patients aged 11-30,31-50 and 51-90 years,the incidence rate of anxiety was 26％(7/ 26),11. 0％(20/ 182) and 19. 1％(47/ 246),respectively (P= 0. 026).The incidence rate of anxiety for patients with and without tumor recurrence was 27％ (13/ 48) and 15. 4％ (64/ 415) (P= 0. 040).Seventeen of 63 patients (27％) with metastases experienced anxiety,whereas 60 of 396 patients (15. 2％) without metastases suffered from anxiety (P= 0. 020).The incidence rate of anxiety in patients with three or more chronic diseases was 26％(19/ 74),significantly higher compared with 15. 0％(58/ 387) in those with less comorbidities (P= 0. 024). Multivariate binary logistic regression analysis demonstrated that three or more chronic diseases or serious diseases were high risk factors of anxiety (OR= 1. 92,95％CI:1. 03-3. 567). Conclusions Patients who receive radiotherapy and their relatives are prone to anxiety. Young age,tumor recurrence or metastasis and≥ three comorbidities or severe diseases are the high risk factors of anxiety. It is necessary to evaluate the anxiety of patients and their family relatives before radiotherapy and deliver psychological counseling.
ABSTRACT
Objective To investigate how to use the ArcCHECK to complete synchronization test in helical tomotherapy(HT). Methods According to the synchronization test suggested by AAPM TG148, three aspects should be tested.(1)Gantry angle consistency:ArcCHECK device in the long axis was perpendicular to the rotation plane using virtual isocenter positioning. A delivery sequence was defined with a slice width of 2.5 cm,a pitch of 0.1,and a minimum of 40 rotations. The control sinogram was set to open the middle two leaves(No. 32 and 33)at projections centered at 0°, 120°, and 240°.(2)Couch speed uniformity:The ArcCHECK was fixed on the treatment couch by positioning the long axis in the movement direction of couch. An irradiation was done with a static gantry in the 0° position, the collimation set to 1 cm,and all MLC leaves open. A couch travel distance of 20 cm was programmed using a clinically common couch speed(0.3-0.5 mm/s for 2.5 cm treatment slice width)in the course of irradiation.(3) Synchronization of couch translation and gantry rotation:In this test,a rotational irradiation was used with the nominal 1.0 cm beam and a pitch of 1 for 13 rotations. The control sonogram was set to open all the leaves for a half rotation on the second,seventh,and twelfth rotations. The initial collected data were used as the baseline data of parameters. The subsequent measurements were compared with the baseline data using the point to point absolute dose pass rates of DD(dose difference,1%). Results The gantry angle consistency could check the correct initial angles at the beginning of the treatment and the ability to reproduce the projection every rotation.There were six parallel and straight high-dose regions in ArcCHECK software.In the couch speed uniformity test,the relative dose in the long axis in the high-dose regions was changed less than 2%. In the synchronization test of couch translation and gantry rotation,three parallel high-dose regions with the same separation spacing were present in the ArcCHECK software. The synchronization tests were done twenty-eight times in the second,seventh, and twelfth irradiation rotations and the average pass rates were 93.2%±1.5%,93.7%±1.1%,and 93.5%±1.3%,respectively. Conclusions The ArcCHECK device is a suitable alternative method for performing the synchronization test in HT due to its lower workload and costs compared with the film.
ABSTRACT
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.
ABSTRACT
Objective To determine the peripheral dose ( PD) of a Trilogy accelerator under different conditions and the feasibility of PD measurement using the semiconductor diode ionization chamber. Methods In a solid water phantom, a CC13 air?filled ionization chamber and a semiconductor diode ionization chamber were used for PD measurements with different distances (13 measurement locations within 1?31 cm) , depth ( 3, 5, 15 cm) , field sizes ( 10, 20, 30 cm) , wedge ( W15, W45, VW15, VW45) , and beam energy (6, 18 MV). The relationship of PD with PDleakage and PDscat er was determined by removing the scatter phantom. Simulating the patients with cervical cancer undergoing radiotherapy, a CIRS phantom received volumetric modulated arc therapy ( VMAT) , step?shoot intensity?modulated radiotherapy ( IMRT) , and sliding?window IMRT to measure PDs of the breast, thyroid, and lens. All the data were normalized to the isocenter. Results PD was gradually reduced with the increase in distance ( 13?41% at 1 cm from the edge to 0?25% at 31 cm from the edge) . With a fixed distance from the edge of the radiation field, there was no significant difference in PD between different depths. A radiation field with a size of 30 cm had a PD about two?fold higher than that with a size of 10 cm. PD increased with the increase in the physical wedge angle and increased by 1% compared with the open field;PD decreased with the increase in the virtual wedge angle and decreased by 2?3% compared with the open field. PD decayed from 13?35% at 1 cm to 0?23% at 31 cm under 6 MV X?ray and from 11?06% at 1 cm to 0?20% at 31 cm under 18 MV X?ray. Dscat er was dominant in the regions close to the edge of radiation field and decreased from 62?45% at 1 cm to 5?71% at 25 cm. In all measurements under 6 MV X?ray, the maximum proportion difference between CC13 ionization chamber and diode ionization chamber was less than 1%. PDs of the breast, thyroid, and lens were 6?72, 2?90, and 2?37 mGy in VMAT mode, 7?39, 4?05, and 2?48 mGy in step?shoot IMRT mode, and 9?17, 4?61, and 3?21 mGy in sliding?window IMRT mode, respectively. Conclusions For the measurement of PDs, the CC13 air?filled ionization chamber and semiconductor diode ionization chamber have good consistency and feasibility under 6 MV X?ray. In clinical practice, the understanding of the relationship of PD with different radiation conditions helps to reduce the doses to organs at risk. Shielding and protective techniques can further reduce dose deposition.
ABSTRACT
Objective To study the dosimetric peculiarity of 3D intracavitary brachytherapy in the application of endometrial carcinoma comparing with traditional 2D plans. Method 39 3D brachytherapy treatment plans of 11 patients with endometrial carcinoma were retrospectively analyzed with re?planning 2D treatment plan, the dose volume histogram ( DVH) parameters such as the target dose volume parameters V150 and D90 , the 2?cc doses to organs such as bladder, small intestine, rectum and sigmoid and the total reference air kerma TRAK were analyzed. The differences between the two groups are compared by paired samples T test. Results For target with V<60 cm3 ,there is no statistically significant difference between 2D and 3D plans,the D90 is (551?17±90?33) cGy and (574?15±117?18) cGy,respectively (P=0?390). As the increase of target volume,the D90 came to be significantly different ( P=0?001) , high dose region V150 for 3D and 2D plans is (51?05±21?61) cm3 and (53?41±11?71) cm3, respectively (P=0?482). With the target volume larger than 60 cm3 ,compare to 2D plans, the 3D plan can increase the target coverage as well as OAR dose except for small intestine ( P=0?128) . In addition, with different plan mode,the BMI did not affect the crisis organ dose such as rectum, small intestine, bladder and sigmoid, the P value is 0?239, 0?198,0?744 and 0?834,respectively. Conclusions For endometrial carcinoma,compared with traditional two?dimensional plans,the 3D brachytherapy treatment plans can significantly improve the target coverage and avoiding overdose of organs, clinical curative effect and side effect still needs further observation.
ABSTRACT
Objective To compare the dosimetry characteristics of volumetric intensity-modulated arc therapy (VIMAT) and fixed field intensity-modulated radiation therapy (FF-IMRT) for cervix cancer.Methods CT images of 13 patients with cervix uteri cancer were transferred into Eclipse planning system.FF-IMRT and VIMAT plans were optimized on an Eclipse treatment planning system using beam data generated for Varian trilogy linear accelerator.Planning target volume (PTV) and organs at risk were evaluated with dose-volume histogram.To appraise the difference between the techniques,the paired t-test was applied.Results Compared with the FF-IMRT plans,PTV95％ coverage of VIMAT plan group increased (t =9.84,P =0.000),PTV110％ became lower (t =-3.72,P =0.003),Dmax decreased (t =-3.51,P=0.005),and CI became worser (t=5.39,P=0.000).PTV105％,Dmean,and HI had no difference (t =-0.02,-0.60,1.13,P =0.842,0.560,0.283).V30 of the bladder was reduced by about 10％ (t =-4.99,P =0.000),and Dmean and Dmax were 1.4 Gy and 1.5 Gy lower respectively (t =-3.65,-18.03,P =0.004,0.000) ;V40 of the rectum was reduced by about 10％ (t =-2.99,P =0.012),and Dmean and Dmax were reduced by 0.6 Gy,0.8 Gy respectively (t =-2.98,-4.05,P =0.013,0.002) ;V30,V40 and V50 of the small intestine were reduced by 16％,10％ and 11％ (t =-10.85,-4.74,-8.66,P =0.000,0.001,0.000),and Dmax was reduced by 0.8 Gy (t =-9.45,P =0.000) ; V30,V40 and V50 of the bone marrow were reduced by 26％,19％ and 16％ (t =-22.10,-10.19,-4.04,P =0.000,0.000,0.002),and Dmean reduced by 1.9 Gy (t =-16.21,P =0.000) ; D5 of the left and right femoral heads were reduced by 1.6 Gy and 2.7 Gy (t =-2.89,-6.22,P =0.015,0.000).Dmax of the caudate equine was reduced by 1.5 Gy (t=-4.80,P=0.001).V20,V30,V40 and V50 of the body were reduced by 18％,18％,4％ and3％(t=-7.52,-11.75,-6.26,-6.94,P=0.000,0.000,0.000,0.000).Dmean and Dmax of the body decreased by 1.0 Gy and 0.4 Gy (t=-3.72,-3.51,P=0.000,0.005).Average machine unit (MU) decreased by 57％ (t =-40.54,P =0.000).Conclusions cervical cancer Patients with VIMAT technology can get equivalent or superior dose distribution compared with the FF-IMRT technology.And VIMAT technology could reduce MU.But the efficacy needs further clinical evaluation
ABSTRACT
Objective To study the dosimetric comparison of split field and fixed jaw techniques for large IMRT target volumes in the rectum cancer.Methods CT images of fifteen patients with rectum malignancies and regional target volumes were transferred into Eclipse planning system.SFT plan and FJT plan were performed on an Eclipse TPS using beam data generated for linear accelerator.A standard beam arrangement consisting of seven coplanar fields was used in both techniques.Institutional dose-volume constraints used in rectum cancer were kept the same for both techniques.Target and organs at risk were evaluated.Results PTV95 in FJT plan coverage was lower (t =-2.24,P ＜ 0.05).Dmean in FJT plan was increased (t =2.54,P ＜ 0.05),but Dmax was not different.HI in FJT plan became inferior (t =3.09,P ＜0.05),while CI was not different.There was no difference in dose distribution among bladder,femoral head and cauda equina.The value of V5 of small intestine increased in FJT plan (t =4.76,P ＜0.05),and the values of V20 and V50 of bone marrow were better than those in SFT plan (t =-2.66,-3.36,P＜0.05),while Dmax was higher than that in SFT plan (t =3.30,P ＜ 0.05).The value of V20 of body was higher in FJT plan than that in SFT plan (t =2.48,P ＜0.05).The number of MU was significantly lower in FJT plan than that in SFT plan (t =-9.38,P ＜0.05).The average segments in FJT plan decreased by 39.4％ compared with SFT plan (t =-6.46,P ＜ 0.05).Verification rate in FJT plan group was better than that in SFT plan (t =10.46,P＜0.05),and the treatment time was shortened from 12 to 6 min.Conclusions Compared to SFT technique,patients with rectal cancer who were treated with FJT could get better dose of target and organs,which can meet the clinical treatment requirements.The technique could shorten the treatment time and reduce the treatment MU.It also could increase the number of patients to be treated,reduce their waiting time and reduce the difficulty of QA.