Objective:To investigate the influence of contrast-enhanced computed tomography(CECT)on dose calculation in magnetic resonance imaging(MRI)-guided online adaptive radiotherapy(oART)based on the electron density(ED)assignment method for rectal cancer.Methods:A retrospective analysis was conducted on the medical data of 15 patients with locally advanced rectal cancer at middle-low segments,who admitted to the Chinese PLA General Hospital between December 2023 and April 2025.All patients underwent both plain computed tomography(PCT)and CECT scans during location.The average HU and ED value of all organs that were extracted from PCT and CECT images in the treatment plan system were obtained,and the influences of contrast agent of intake on image characteristics of the structure of each organ(small intestine,femoral head,bladder)were analyzed.PCT was used as referred image to design reference plan(Pref).The synthetic CT(sCT)was simulated and generated on the basis of PCT and CECT,respectively.The beam flow field that was same with Pref was used to recalculate dose on sCT,and then,the online plan(PPCT)based on PCT,and the online plan(PCECT)based on CECT were obtained,respectively,which can simulate the online dose calculation of MRI-guided online adaptive radiotherapy(oART).The Pref was used as reference to compare dosimetric parameters for target region and organ at risk(OAR)through dose volume histogram(DVH)and planed evaluation indicators.Additionally,three dimension(3D)slicer software was used to perform γ analysis for the results of dose distribution,and explore the differences among PPCT,PCECT and Pref on dose distribution.Results:In terms of image characteristics,the HU values of soft-tissue organs(intestine,bladder,spinal cord,soft tissue)and planning target volume(PTV)in CECT were higher than those in PCT,and the differences of them were statistically significant(Zintestines=-2.188,Zbladder=-3.196,tspinal cord=-3.767,tsoft tissue=-10.083,tPTV=-4.693,P<0.05),while its influence was less on bone tissue.The statistical results of ED were consistent with those of HU.Regarding to dosimetric parameters,there was no statistically significant difference in target coverage rate between PPCT and Pref(P>0.05),and the D50%of the PPCT[(2724.25±19.91)cGy]was higher than that of the Pref[(2718.99±21.13)cGy],and the difference was statistically significant(t=-3.679,P=0.002).However,the target coverage rate of PCECT was 94.65(94.04,95.27)%,and the difference of that between PCECT and Pref was statistically significant(Z=-2.158,P=0.031).For OAR,the differences of Dmax value of the small intestine,and the V20 of the left femoral head between PPCT and Pref were significant(Z=-2.556,-2.529,P<0.05).The differences of the Dmax of small intestine,and the D50%of bladder between PCECT and Pref were significant(t=-4.821,2.171,P<0.05).The comparative γ passed rates of PPCT,PCECT and Pref under the standards of 3 mm/3%and 2 mm/2%were all above 95%,and the differences were not significant(P>0.05).Conclusions:The influence of CECT on dose calculation in MRI-guided oART based on ED assignment method for rectal cancer is relatively small,which can be directly used in the design of reference plan,but the maximum dose of radiation-sensitive organs such as the small intestine should be paid attention.

Objective:To assess performance advantages of voxel-less optimization(VoLO)algorithm of CyberKnife-based S7 treatment plan system for the optimization of stereotactic body radiation therapy(SBRT)for liver cancer.Methods:The case data of 20 patients with hepatocellular carcinoma from Chinese PLA General Hospital during June 2022 and April 2023 were retrospectively selected,which included 10 patients with large hepatocellular carcinoma and 10 patients with small hepatocellular carcinoma.All patients adopted respectively sequential optimization(SO)and VoLO to conduct optimization for plan.The optimized quality of plan and execution efficiency of two kinds of algorithms were assessed,and the influences of different tumor volumes also were considered.The planed quality assessment included dosimetric parameters of the target region and organ at risk(OAR).The assessment parameters of execution efficiency included the numbers of monitor units(MUs),nodes and beams,and estimated treatment time.Paired t-test method was adopted to analyze quality of plan and treatment efficiency.Results:On the aspect of the dose of target region,for small hepatocellular carcinoma,the conformity index(CI)value(1.08±0.05)of target region of VoLO algorithm was significantly better than(1.17±0.06)of SO algorithm(t=4.631,P<0.05).The gradient index(GI),coverage rate and dose by 95%(D95%)of VoLO algorithm were better than those of SO algorithm,while the differences were not significant(P>0.05).According to the defined standards of liver surgery,for large hepatocellular carcinoma,the differences in CI,GI,coverage rate and D95%of target region between two kinds of algorithms were significant(t=3.337,4.238,-3.359,-3.311,P<0.05),respectively.On the aspect of dosimetry for OAR,for the target region of large hepatocellular carcinoma,the differences of liver Dmean and D700 cm3 between two kinds of algorithms were significant(t=4.114,3.415,P<0.05).However,for small hepatocellular carcinoma,there was no significant statistical difference in dosimetry parameters of OAR between two kinds of algorithms(P>0.05).The execution efficiency of the plan of VoLO group was obviously higher than that of SO group,and the differences of MU number,node number,beam number and estimated treatment time between two groups were significant(t=12.661,4.423,5.024,9.487,P<0.05).Conclusion:The quality of VoLO plan is significantly better than that of SO,which has a significant improvement in execution efficiency of treatment.For the cases of large hepatocellular carcinoma with more complexity,the VoLO optimization shows better advantages on the aspect of dose on target region,and protection for normal liver.

Objective:To assess performance advantages of voxel-less optimization(VoLO)algorithm of CyberKnife-based S7 treatment plan system for the optimization of stereotactic body radiation therapy(SBRT)for liver cancer.Methods:The case data of 20 patients with hepatocellular carcinoma from Chinese PLA General Hospital during June 2022 and April 2023 were retrospectively selected,which included 10 patients with large hepatocellular carcinoma and 10 patients with small hepatocellular carcinoma.All patients adopted respectively sequential optimization(SO)and VoLO to conduct optimization for plan.The optimized quality of plan and execution efficiency of two kinds of algorithms were assessed,and the influences of different tumor volumes also were considered.The planed quality assessment included dosimetric parameters of the target region and organ at risk(OAR).The assessment parameters of execution efficiency included the numbers of monitor units(MUs),nodes and beams,and estimated treatment time.Paired t-test method was adopted to analyze quality of plan and treatment efficiency.Results:On the aspect of the dose of target region,for small hepatocellular carcinoma,the conformity index(CI)value(1.08±0.05)of target region of VoLO algorithm was significantly better than(1.17±0.06)of SO algorithm(t=4.631,P<0.05).The gradient index(GI),coverage rate and dose by 95%(D95%)of VoLO algorithm were better than those of SO algorithm,while the differences were not significant(P>0.05).According to the defined standards of liver surgery,for large hepatocellular carcinoma,the differences in CI,GI,coverage rate and D95%of target region between two kinds of algorithms were significant(t=3.337,4.238,-3.359,-3.311,P<0.05),respectively.On the aspect of dosimetry for OAR,for the target region of large hepatocellular carcinoma,the differences of liver Dmean and D700 cm3 between two kinds of algorithms were significant(t=4.114,3.415,P<0.05).However,for small hepatocellular carcinoma,there was no significant statistical difference in dosimetry parameters of OAR between two kinds of algorithms(P>0.05).The execution efficiency of the plan of VoLO group was obviously higher than that of SO group,and the differences of MU number,node number,beam number and estimated treatment time between two groups were significant(t=12.661,4.423,5.024,9.487,P<0.05).Conclusion:The quality of VoLO plan is significantly better than that of SO,which has a significant improvement in execution efficiency of treatment.For the cases of large hepatocellular carcinoma with more complexity,the VoLO optimization shows better advantages on the aspect of dose on target region,and protection for normal liver.

Objective:To investigate the influence of contrast-enhanced computed tomography(CECT)on dose calculation in magnetic resonance imaging(MRI)-guided online adaptive radiotherapy(oART)based on the electron density(ED)assignment method for rectal cancer.Methods:A retrospective analysis was conducted on the medical data of 15 patients with locally advanced rectal cancer at middle-low segments,who admitted to the Chinese PLA General Hospital between December 2023 and April 2025.All patients underwent both plain computed tomography(PCT)and CECT scans during location.The average HU and ED value of all organs that were extracted from PCT and CECT images in the treatment plan system were obtained,and the influences of contrast agent of intake on image characteristics of the structure of each organ(small intestine,femoral head,bladder)were analyzed.PCT was used as referred image to design reference plan(Pref).The synthetic CT(sCT)was simulated and generated on the basis of PCT and CECT,respectively.The beam flow field that was same with Pref was used to recalculate dose on sCT,and then,the online plan(PPCT)based on PCT,and the online plan(PCECT)based on CECT were obtained,respectively,which can simulate the online dose calculation of MRI-guided online adaptive radiotherapy(oART).The Pref was used as reference to compare dosimetric parameters for target region and organ at risk(OAR)through dose volume histogram(DVH)and planed evaluation indicators.Additionally,three dimension(3D)slicer software was used to perform γ analysis for the results of dose distribution,and explore the differences among PPCT,PCECT and Pref on dose distribution.Results:In terms of image characteristics,the HU values of soft-tissue organs(intestine,bladder,spinal cord,soft tissue)and planning target volume(PTV)in CECT were higher than those in PCT,and the differences of them were statistically significant(Zintestines=-2.188,Zbladder=-3.196,tspinal cord=-3.767,tsoft tissue=-10.083,tPTV=-4.693,P<0.05),while its influence was less on bone tissue.The statistical results of ED were consistent with those of HU.Regarding to dosimetric parameters,there was no statistically significant difference in target coverage rate between PPCT and Pref(P>0.05),and the D50%of the PPCT[(2724.25±19.91)cGy]was higher than that of the Pref[(2718.99±21.13)cGy],and the difference was statistically significant(t=-3.679,P=0.002).However,the target coverage rate of PCECT was 94.65(94.04,95.27)%,and the difference of that between PCECT and Pref was statistically significant(Z=-2.158,P=0.031).For OAR,the differences of Dmax value of the small intestine,and the V20 of the left femoral head between PPCT and Pref were significant(Z=-2.556,-2.529,P<0.05).The differences of the Dmax of small intestine,and the D50%of bladder between PCECT and Pref were significant(t=-4.821,2.171,P<0.05).The comparative γ passed rates of PPCT,PCECT and Pref under the standards of 3 mm/3%and 2 mm/2%were all above 95%,and the differences were not significant(P>0.05).Conclusions:The influence of CECT on dose calculation in MRI-guided oART based on ED assignment method for rectal cancer is relatively small,which can be directly used in the design of reference plan,but the maximum dose of radiation-sensitive organs such as the small intestine should be paid attention.

Objective To evaluate the application of three deep learning algorithms in automatic segmentation of clinical target volumes (CTVs) in high-dose-rate brachytherapy after surgery for endometrial carcinoma. Methods A dataset comprising computed tomography scans from 306 post-surgery patients with endometrial carcinoma was divided into three subsets: 246 cases for training, 30 cases for validation, and 30 cases for testing. Three deep convolutional neural network models, 3D U-Net, 3D Res U-Net, and V-Net, were compared for CTV segmentation. Several commonly used quantitative metrics were employed, i.e., Dice similarity coefficient, Hausdorff distance, 95th percentile of Hausdorff distance, and Intersection over Union. Results During the testing phase, CTV segmentation with 3D U-Net, 3D Res U-Net, and V-Net showed a mean Dice similarity coefficient of 0.90 ± 0.07, 0.95 ± 0.06, and 0.95 ± 0.06, a mean Hausdorff distance of 2.51 ± 1.70, 0.96 ± 1.01, and 0.98 ± 0.95 mm, a mean 95th percentile of Hausdorff distance of 1.33 ± 1.02, 0.65 ± 0.91, and 0.40 ± 0.72 mm, and a mean Intersection over Union of 0.85 ± 0.11, 0.91 ± 0.09, and 0.92 ± 0.09, respectively. Segmentation based on V-Net was similarly to that performed by experienced radiation oncologists. The CTV segmentation time was < 3.2 s, which could save the work time of clinicians. Conclusion V-Net is better than other models in CTV segmentation as indicated by quantitative metrics and clinician assessment. Additionally, the method is highly consistent with the ground truth, reducing inter-doctor variability and treatment time.

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.

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 evaluate the safety and clinical efficacy of hypofractionated radiotherapy (HFRT) at 36.5 Gy in 10 fractions for the chest wall and reginal lymph nodes following modified radical mastectomy for breast cancer.Methods:This was a prospective, single-arm, phase Ⅱ clinical study. A total of 85 patients who received HFRT at 36.5 Gy in 10 fractions to the chest wall ± supraclavicular region following modified radical mastectomy for locally advanced breast cancer from March 2014 to December 2015 were included. The primary endpoint was radiotherapy toxicities. The secondary endpoints were locoregional failure-free survival (LRFFS), disease-free survival (DFS), and overall survival (OS).Results:The median follow-up period was 98 (94.0-109.0) months. Radiotherapy toxicities were mild. The incidence rates of grade 1 acute cutaneous and pulmonary toxicities were 52.9% and 40%, and those of grade 1 late cutaneous, pulmonary, and cardiac toxicities and upper extremity edema were 10.6%, 29.4%, 2.4%, and 21.2%, respectively. Only 1 (1.2%) patient suffered from grade 2 radiation-induced brachial plexus injury. Of the 85 patients, one patient had regional recurrence (supraclavicular lymph nodes), six patients had distant metastasis, and six patients died of breast cancer. The 9-year LRFFS, DFS, and OS were 97.7%, 91.8%, and 92.8%, respectively.Conclusions:HFRT at 36.5 Gy in 10 fractions following modified radical mastectomy for breast cancer is associated with mild toxicities. A phase Ⅲ study is necessary for validating HFRT's clinical efficacy.

Based on the theory of engineering medicine,a consensus which takes the basic medical ethics of harm reduction as the starting point is proposed to addresses the current clinical problems of a wide variety of radiotherapy setup equipments and methods,large differences by principles,and inaccurate setup.The consensus is formed in two aspects.(1)Advocate coordination of multiple setup methods for joint setup;collect,compare,analyze and screen data on setup methods;determine the operational guidelines and methods for joint setup based on the principle of standardized and unified clinical consistency,with a view to achieving the clinical purpose of greatly ensuring the precision of radiotherapy setup and radiotherapy safety without relying on the golden standard.(2)Standardize the operational methods for tracing setup deviations,so that when the difference in setup leads to poor clinical consistency,the cause of deviation can be traced and the effectiveness of different setups can be screened.Based on the concept of engineering medicine,the consensus is expected to standardize the method of radiotherapy setup,realize accurate radiotherapy,improve treatment effect and show medical ethical care.

Based on the theory of engineering medicine,a consensus which takes the basic medical ethics of harm reduction as the starting point is proposed to addresses the current clinical problems of a wide variety of radiotherapy setup equipments and methods,large differences by principles,and inaccurate setup.The consensus is formed in two aspects.(1)Advocate coordination of multiple setup methods for joint setup;collect,compare,analyze and screen data on setup methods;determine the operational guidelines and methods for joint setup based on the principle of standardized and unified clinical consistency,with a view to achieving the clinical purpose of greatly ensuring the precision of radiotherapy setup and radiotherapy safety without relying on the golden standard.(2)Standardize the operational methods for tracing setup deviations,so that when the difference in setup leads to poor clinical consistency,the cause of deviation can be traced and the effectiveness of different setups can be screened.Based on the concept of engineering medicine,the consensus is expected to standardize the method of radiotherapy setup,realize accurate radiotherapy,improve treatment effect and show medical ethical care.