OBJECTIVE: To analyze the time characteristics of the Ethos online adaptive radiotherapy (OART) process in clinical practice and provide guidance for the comprehensive optimization of each stage of adaptive radiotherapy. METHODS: The study involved 61 patients with cervical, rectal, gastric, lung, esophageal, and breast cancers who underwent Ethos OART. The mean ± standard deviation of segmental time, total time, and target volume for these patients were tracked. The time characteristics for different cancer types were evaluated, and the average time for target and organ at risk (OAR) modifications was compared with the average target volume for each cancer type. RESULTS: Cervical cancer born the longest total treatment time, while breast cancer had the shortest. For all cancer types except breast cancer, the modification time for target and OAR was the most time-consuming segment. The average time for target and OAR modifications aligned with the trend of the average target volume. CONCLUSION The total treatment time for various cancers ranges from 15 to 35 minutes, indicating room for improvement.
Humans ; Radiotherapy Planning, Computer-Assisted/methods* ; Neoplasms/radiotherapy* ; Female

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 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 compare and study the improvement of different iterative reconstruction(IR)algorithms of the tomotherapy(TOMO)Radixact system on the image quality of megavoltage computed tomography(MVCT)imaging system,and the influence of that on the precision of automatic registration,and to explore the reconstruction algorithm that is suitable for clinical application.Methods:Using the MVCT imaging system to respectively scan the Tomo-Phantom HE phantom and the Catphan 604 phantom,and to analyze three groups of images were generated by three kinds of reconstruction algorithms,which included the Standard(STD)algorithm,IR General(IR-G)algorithm and IR Soft Tissue(IR-ST)algorithm,in MVCT image.The noise index(NI),uniformity index(UI)of image,modulation transfer function(MTF),low contrast visibility(LCV)index and contrast-to-noise ratio(CNR)of three groups of images were calculated respectively.The Lucy phantom was used to test the accuracy of automatic registration algorithm.The registration data of four dimensions,included left-right(X-axis),head-foot(Y-axis),vertical(Z-axis)and free rotation(Roll)around the Y-axis,were used to conduct verification analysis for the influences of them on the precision of automatic registration.Results:The NI values of IR-G and IR-ST reconstruction algorithms were respectively 39.58±0.10 and 14.62±0.26,which were better than 39.58±0.10 of STD algorithm,and the UI values of them were respectively 19.87±0.83 and 15.84±2.51,which were better than 24.51±1.81 of STD algorithm,and LCV values of them were respectively 2.50±0.03 and 1.74±0.11,which were better than 3.67±0.04 of STD algorithm.All of them appeared significant increase,but the resolution with high contrast of MTF were respectively 0.23 and 0.21,which were lower than 0.32 of STD.The overall image quality of the IR algorithms was superior to that of the STD algorithm.In the accuracy test of the automatic registration algorithm,the registration precisions of IR-G and IR-ST algorithms on Y-axis were respectively(0.360±0.142)mm and(0.245±0.050)mm,which were significantly higher than 0.145±0.136 of STD algorithm,and the differences of them were significant(Z=6.0,15.0,P<0.05).The differences of registration precisions of other directions were not significant(P>0.05).Conclusion:The IR algorithm has advantages in terms of noise,uniformity and resolution with low-contrast,however,it shows reduction on resolution with high-contrast.This reduction of resolution with high-contrast do not lead to the decrease of the precision of automatic registration.

Objective:To quantitatively analyze the differences in image quality and generated synthetic-computed tomography(sCT)between cone beam CT(CBCT)and iteration CBCT(iCBCT),which based on filtered back projection(FBP)and iterative reconstruction(IR)techniques of Varian Ethos adaption system.Methods:Using the special Catphan604 phantom of the test of CT image quality,five times of scanning series of CBCT and iCBCT were respectively performed based on thoracic and abdominal scanning protocols,so as to obtain four sets of images,and each set of image included the CBCT image,the composited sCT and iCBCT images based on CBCT,the composited sCT bases on iCBCT.The noise power spectrum(NPS),image uniformity(UI),modulation transfer function(MTF),low-contrast visibility(LCV)and contrast-to-noise ratio(CNR)of them were analyzed.Additionally,a retrospective analysis was conducted on images of six patients who underwent clinical radiotherapy,and the images of them were obtained by using thoracic and abdominal scanning protocols.The sCT images,which were generated by deformable registrations on the basis of CBCT and iCBCT,were analyzed,and they were compared with located CT images,and their mean absolute error(MAE)and root mean square error(RMSE)were further quantitatively analyzed.Results:Compared to CBCT,iCBCT significantly reduced NPS(thoracic images reduced by 0.08,abdominal images reduced by 0.06).The UI values of thoracic images and abdominal images of iCBCT were respectively 0.37 and 0.28,and those of CBCT were respectively 0.65 and 0.39.The LCV values of thoracic images and abdominal images of iCBCT were respectively 0.67 and 0.56,and those of CBCT were respectively 0.93 and 0.90.The MTF50％were 0.28 lp/mm except abdominal image of iCBCT was 0.29 lp/mm.The resolution rate of high contrast between iCBCT and CBCT was basic consistency.The differences of similarity analysis of the generated sCT and located CT bases on CBCT and iCBCT was no significant(P＞0.05).Conclusion:The image quality of iCBCT is superior to conventional CBCT.The accuracy of CT value of generated sCT bases on CBCT and iCBCT can meet requirement,and both of them can be used in the dose calculation of adaptive radiotherapy.