At present,precise radiotherapy has been widely used through the development with many years,but the existing technique still is limited by the limitation of tolerance dose of normal tissues,which cannot achieve the optimal goal of treating tumor.Flash radiotherapy(Flash-RT)is one kind of radiotherapy technique that uses the beam with ultra-high dose rate(UHDR)to conduct irradiation,which can furthest treat tumors while significantly reduce radiation injury of normal tissues.But until now,the biological mechanism,key physical parameters and triggering mechanism of Flash-RT are still unclear,and its principle and clinical translational application are still in the stage of research.This review clarified the technological advance and clinical translational application of Flash-RT research through summarized the relevant research of Flash-RT.

The Flash radiotherapy(Flash-RT),which is the key breakthrough in the basic field of radiotherapy technique,which is expected to cause a new major transformation in the field of radiotherapy.In this paper,we reviewed the latest research advances of the application and the mechanism exploration of Flash-RT in tumor treatment.Current studies have found that both the Flash-RT with electron beams and photon and the Flash-RT with proton can reduce injury of normal tissue than radiotherapy with conventional dose-rate,but the relevant mechanisms are not yet clearly understood,which includes but not limited to oxygen depletion,DNA damage,cellular senescence,apoptosis and immune response.The difference of Flash-RT injury between tumor tissue and normal tissue further reduces the limitations of radiotherapy,and reduces the adverse reaction and complication compared with conventional radiotherapy,which has wide application prospects.

Radiotherapy is an important means to treat lung cancer,but it is easy to cause lung injury and reduce the quality of life of patients.Flash radiotherapy(FLASH-RT)has attracted attention due to its extremely short radiation duration and high dose rate,which can reduce toxicity of normal tissue while ensures treatment intensity of tumor.Whether Flash-RT can reduce radiation-induced lung injury has become an important research topic in recent years.Based on the literature analysis method,this review systematically assessed the effects and mechanisms of Flash-RT and radiotherapy with conventional dose rate on lung injury through searching relevant literatures at home and abroad,so as to provide scientific basis for the treatment of patients with lung cancer by reviewing the comparisons about the effects and mechanisms between Flash-RT and radiotherapy with conventional dose rate on lung injury.Compared with radiotherapy with conventional radiation rate,Flash-RT can significantly reduce lung injury and improve quality of life of patients.It is still demanded to explore the Flash-RT mechanism in future,so as to develop the Flash-RT instrument that is suitable for different tumors and to conduct larger-scale clinical researches.

Objective:To study and design one kind of flash radiotherapy(Flash-RT)equipment with ultra-high dose rate,which can be used in the mechanism research of Flash-RT with ultra-high dose rate.Methods:Based on the technique roadmap of high-power petal accelerator,the Flash-RT equipment can realize the requirement of Flash-RT for ultra-high dose rate and multiple irradiation angles.The corresponding design and research work were carried out on the basis of the overall design of the equipment,the main components and characteristics,the dynamics design of beam,the construction of movable and preliminary experimental platform,etc.Result:The dose rate of the designed equipment can reach to 100 Gy/s at a distance of 0.8 meters from the target point,which is easy to realize the radiotherapy method with multi angles.Conclusion:The designed X-ray equipment based on the technique roadmap of high-power petal accelerator can realize the research for the mechanism of medical Flash-RT equipment with ultra-high dose rate.

The protection effect of flash-radiotherapy(Flash-RT)with super-high dose on normal tissue has obtained wide attention in therapeutic radiology since it was found in 2014 year.The increasing research demand of Flash-RT with super-high dose-rate proposed new challenge for the existing radiotherapy equipment.Based on the demands of FLASH-RT research and clinical application,this review analyzed the proposed new requirement of Flash-RT for equipment,and introduce current scientific facilities with the experimental ability of X-ray FLASH-RT,as well as the situation of the specialized FLASH-RT equipment which were developing.The research of Flash-RT mechanism need the existing equipment with high-energy X-ray source develop toward high power,while the clinical application of Flash-RT demand these transient high-power devices should possess a series of radiotherapy techniques such as multi angle irradiation,conformal radiotherapy and others.Currently,China's X-ray FLASH-RT research is at the forefront of the world,which is expected to achieve the first breakthrough of high-end medical equipment in the X-ray Flash RT field.

Objective:To calibrate the absorbed doses of the configured ray water with different gears of energies in accelerator based onof International Atomic Energy Agency(IAEA)277 and 381 reports,so as to ensure the accuracy of the output dose of the linear accelerator during clinical radiotherapy.Methods:Elekta Infinity linear accelerator was used in this study,and the photon beam energies were respectively 6MV flattening filter(FF)mode and 6MV flattening filter free(FFF)mode.The electron beam energies were respectively 4,6,8,10,12 and 15MeV.According to the IAEA TRS277 and TRS381 reports,the calibrations of output doses in photon and electron beam waters were performed respectively by using the PTW dosimeter,PTW30013 finger type of ionization chamber and PTW34001 parallel plate ionization chamber.The error of each step was analyzed,and the accuracies of the calibrations of using different standards for the output waters of linear accelerator were compared.Results:The output amounts of photon beams of FF mode and FFF mode of 6MV at the maximum dose point in water were respectively 1.003 and 1.008cGy/MU.The output amounts of the energy of each gear of electron beams of 4,6,8,10,12 and 15MeV at the maximum dose point in water were respectively 1.003,1.002,0.998,0.999,1.000 and 1.003 cGy/MU.The calibration of the output of each gear of energy rays at the maximum dose point in water was 1cCy corresponded to 1MU,which error was less than 1%.Conclusion:The calibration for the output dose amount of accelerator in water on the basis of IAEA TRS277 and trs381 can ensure the accuracy of the output dose of the accelerator.

Objective:To investigate the dosimetry effect of rotational errors of multi-channel cylinder vaginal applicator of intravaginal irradiation after surgery of endometrial cancer.Methods:A total of 18 patients who underwent surgery of endometrial cancer at Peking Union Medical College Hospital from June to December 2022 were selected.The plans of patients who adopted the treatment of multi-channel cylinder applicator of vagina were retrospectively analyzed,which maintained the same retained mode with clinical plan.The applicator was rotated clockwise by 22.5? and 45.0?,respectively,simulating the rotational errors that occurred in placing the applicator among clinical inter-fractions.And then,the changes of dosimetry of target area and organs at risk(OAR)under two kinds of rotation amplitudes were further analyzed.Results:When the applicator was rotated as 22.5?,the minimum doses to 90%volumes of CTV by 2.03%than that of clinical plan,which was significantly different(t=5.86,P<0.05),and the maximal doses to 2cc of OARs of bladder and rectum respectively increased 2.35%and 2.71%,and the differences of them were statistically significant(t=-3.49,-2.40,P<0.05),respectively.When the applicator was rotated as 45?,the D90 of the target area decreased by 5.75%than that of clinical plan,which was statistically significant(t=14.07,P<0.05).The D2cc values of the bladder and rectum increased respectively by 6.50%and 9.49%than that of clinical plan,which were statistically significant(t=-7.72,-6.9,P<0.05).The differences of the exposed doses of sigmoid colon and small intestine after the applicator was rotated by 22.5? and 45.0? between the plan and original plan were respectively less,which were not statistical significance.Conclusion:The multi-channel cylinder applicator can provide individualized dose distribution in intravaginal irradiation.However,attention should be paid to the placement of the applicator when patients undergo inter-fractional treatment,in order to avoid deviations in the angular alignment from the original plan.This can impact the dosages of the target area and OARs.

Objective:To study the feasibility and value of applying organ dose modulation technique in computed tomography(CT)scanning on eyes.Methods:A total of 330 patients who admitted to Beijing Friendship Hospital affiliated with Capital Medical University from August 2021 to August 2023 and underwent CT examination on eyes were selected.They were divided into modulation group,conventional group and low-dose group based on the control methods of tube current in scanning.The modulation group used organ dose modulation technique with intelligent automatic tube current of 70-150 mA,and the conventional dose group used a fixed tube current of 100 mA,and the low-dose group used a fixed tube current of 70 mA.The differences in radiation dose and CT imaging quality among 3 groups were compared.Results:The dose length product(DLP),volume CT dose index(CTDIvol)and effective dose(ED)of cross-sectional scan of the modulation group were respectively 62.37,12.83 and 0.143 mSv,which were significantly lower than 115.23,18.93 and 0.265mSv of conventional dose group,respectively,with statistically significant(F=2544.944,6009.596,2544.944,P<0.05).The DLP,CTDIvol and ED of coronary scan of the modulation group were 68.19,13.15 and 0.156,respectively,which were significantly lower than 122.41,19.20 and 0.282 mSv of the conventional dose group,respectively,with statistically significant(F=1232.413,3813.940,1232.413,P<0.05).The excellent rates of cross-sectional scans among the modulation group,conventional group and lower-dose group were respectively 98.83%,86.15%and 47.69%,and the difference among three groups was statistically significant(x2=53.908,P<0.05).The excellent rates of image qualities of the modulation group,conventional group and low-dose group were respectively 96.61%,80.70%and 48.28%,and the difference among three groups was statistically significant(x2=20.992,P<0.05).Conclusion:The application of organ dose modulation technique in CT scanning on eyes can significantly reduce radiation dose on patient under ensures imaging quality can meet diagnostic needs when undergoes cross-sectional and coronal scans,which has higher clinical feasibility and application value.

Objective:To study the feasibility of magnetic resonance imaging(MRI)technique with amide proton transfer(APT)in predicting the prognosis of cerebral stroke.Methods:A total of 71 patients with acute cerebral stroke who admitted to the Nanjing First Hospital,Nanjing Medical University from September 2022 to May 2023 were selected.All of them underwent the test of National Institute of Health Stroke Scale(NIHSS),and received the MRI examination with chemical exchange saturation transfer(CEST).According to the modified Rankin scale(mRS)values of 1-month follow-up,they were divided into favorable recovery group(mRS<2,44 cases)and poor group(mRS≥2,27 cases).The asymmetric magnetization transfer ratio(MTRasym)image(APT)was obtained by analyzing data with special software.And then,the difference(△APTw)of APT values between ischemic zone and contralateral normal tissue was further calculated.The △APTw values of two groups were compared and analyzed,and the Pearson correlation analysis was adopted to analyze the correlation among △APTw,NIHSS and mRS.The receiver operating characteristics(ROC)curve was drawn,and the area under curve(AUC)of ROC curve was calculated.Results:There were significant positive correlations among △APTw,NIHSS and mRS scores(R2=0.659,0.522,P<0.001),and the differences of △APTW,NIHSS and mRS scores between the favorable recovery group and poor group were significant(t=5.73,6.36,13.92,P<0.05),respectively.The AUC value was 0.886,and the sensitivity and specificity of prediction were respectively 77.8%and 95.5%.The positive and negative predictive values were respectively 91.3%and 87.5%.Conclusion:APT imaging technique has feasibility in predicting the prognosis of acute cerebral ischemic stroke.

Objective:To investigate the application value of digital X-ray radiotherapy and single photon emission computed tomography(SPECT)radionuclide bone imaging in the diagnosis of intertrochanteric fracture of femur.Methods:A total of 70 patients who were diagnosed as intertrochanteric fracture of femur in Shijiazhuang People's hospital from January 2017 to December 2020 were selected,and they were divided into study group and control group according to random number method,with 35 cases in each group.Digital X-ray radiography combined with SPECT radionuclide bone imaging was used in the study group,and digital X-ray radiography was used in the control group.And then,the accuracy of the diagnostic results between the two groups were compared.Results:The radiographic examination indicated that 31 cases(88.6%)of 35 cases in the study group were confirmed,and 24 cases(68.6%)of 35 cases in the control group were confirmed.The diagnostic accuracy rate of the study group was significantly higher than that of the control group,and the difference was statistically significant(x2=4.158,P<0.05).The preoperative imaging diagnosis indicated that diagnosed number of fracture blocks in the study group was(3.57±0.50),which was significantly higher than that(2.67±0.40)in the control group,and the difference of that between two groups was statistically significant(t=8.315,P<0.05).In the actual intraoperative examining for bone continuity,5 cases were continuity and 30 cases were non-continuity.In the bone stability,13 cases were stability and 22 cases were non-stability.The study group was closer to intraoperative bone continuity and bone stability,and the differences of them between two groups were statistically significant(x2=12.857,4.644,P<0.05),respectively.Conclusion:The combination of digital X-ray radiography and SPECT radionuclide bone imaging has higher diagnostic value for intertrochanteric fracture of femur,which can provide important reference for clinical diagnosis.