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Objective:To evaluate the feasibility of the "task-based" teaching mode in dose measurement of tumor radiotherapy to develop the independent practical ability of students.Methods:Twenty-one undergraduate students majoring in radiotherapy dosimetry were randomly divided into experimental group ( n=11) and control group ( n=10). The "task-based" teaching mode based on independent learning, thinking and designing was used in the experimental group, while the traditional teaching mode based on the guidance of teachers was applied in the control group. Then the practical examination of students was carried out through the case of measuring the absorbed dose of accelerator electron beam. The practical ability of the two groups of students was scored and compared by the objective and comprehensive scoring criteria. Results:The scores of each practical step and total score in the experimental group were higher than those in the control group ( P<0.05). The average total scores of the two groups were (90.18±1.97) and (83.70±3.68), respectively. Conclusion:The "task-based" practice teaching mode can improve students' ability of completing radiotherapy dose measurement independently.
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Objective To investigate the dosimetric effect of accelerator gantry rotation angle errors, collimator and multileaf collimator ( MLC) leaf position errors on volumetric-modulated arc therapy ( VMAT) for cervical cancer. Methods A total of 10 patients with cervical cancer were selected. The plan. Trail file of each clinical plan was extracted from the Pinnacle3 V9. 2 planning system of USA Philips, then the operating parameters of tach control point were read and modified by Matlab programs, and thus the operating error of the accelerator was simulated. Results In this paper, it was discovered that systematic accelerator gantry rotation angle errors, systematic collimator position errors and systematic MLC shift errors which led to the maximum changes of the PTV dose limit were 0. 16％, 0. 46％ and 0. 57％, respectively, and the maximum changes of the dose limit of organs at risk ( OAR) were 0. 38％, -1. 32％ and -0. 44％, respectively. When the systematic MLC gap width errors were ± 0. 5, ± 1 and ± 2 mm, respectively, the maximum changes of PTV dose were 2. 11％, 3. 04％ and 6. 03％, respectively, while the maximum changes of the OAR average dose were 2. 17％, 3. 92％ and 7. 97％, respectively. Furthermore, the dose limits of PTV and OAR showed a strong linear correlation with MLC open or close errors(t=21. 201～90. 562,P<0. 05). If actual errors of each parameter of accelerator were introduced, the maximum changes of PTV and OAR dose limits were 0. 16％ and 1. 30％, respectively, and conformity index (CI) and homogeneity index (HI) were barely changed. Conclusions No significant effect was found for systematic accelerator gantry rotation angle errors, systematic collimator position errors and systematic MLC shift errors for cervical cancer VMAT patients. However, there is a high sensitivity to dose distribution for MLC open or close errors. Therefore, it is necessary to pay more attention on the quality control of the accelerator running in particular MLC position errors to ensure the therapeutic accuracy.
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Objective To evaluate the feasibility of an in-room automated volumetric arc therapy (VMAT) planning engine based on dose volume histogram (DVH) prediction model in RayStation treatment planning system.Methods A total of 4,0 VMAT plans of cervix cancer,planned by experts,were chosen to build DVH estimation model by principal component regression analytic method.An in-room automated VMAT planning program based on IroPython scripting language combined with DVH prediction model was performed in RayStation treatment planning system.The DVH estimation model was applied to Another 10 testing cases of cervical cancer and the feasibility was evaluated by comparing the automatic plans with manual plans.Results The predicted DVH of organs at risk showed a good fit with real DVH in the ten testing cases.There were no statistically significant differences between manual and automatic plans in PTV conformal index (CI) and homogeneity index (HI) (P ＞ O.05).V40 and V50 of bladder were significantly decreased by 4.3％ and 1.6％ in automatic plans (t =2.75,5.26,P ＜ 0.05).V30,V40 and Vs0 of rectum were also decreased by 6.8％,5.8 ％ and 2.1％ (t =2.26,3.55,5.19,P ＜ 0.05).Both left and right femoral heads were better spared in automatic plans with average doses decreased by 380 and 322 cGy(t =5.55,7.25,P ＜ 0.05).The time of creating a treatment plan was 36 min for automatic plan and 53 min for manual plan.Conclusions The fully automated VMAT treatment plan program can create a VMAT plan of cervix cancer with high efficiency and good quality.
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Objective To reduce the dose to organ at risk ( OAR) by script-based optimizing the gantry angles of tangential beams for forward-planned intensity-modulated breast radiotherapy ( fIMRT ) plans. Methods A total of 46 patients with breast cancer (26 in left and 20 in right) after conservative surgery who were treated with manually planned fIMRT were retrospectively re-planned using a script to place the tangential beams automatically. The script program was developed using Pinnacle3 scripting language as imbedded in the Pinnacle3 treatment planning system, and the Python scripting language. Dosimetric indices, including V20 of the ipsilateral lung, D1 of the contralateral breast and V10 of the heart were extracted by the script for plans of different gantry angles. Then the optimal tangential angles were selected by a penalty function. Results For the 26 left breast cancer cases, V20 of the ipsilateral lung for manual and script were (18.2 ±3.4)% and (18.1 ±3.4)%, respectively(P>0.05), while D1 of the contra-lateral breast(249. 2 ± 88. 4) cGy and (230. 4 ± 80. 2) cGy, respectively( t=2. 27, P<0. 05), V10 of the heart (13. 7 ± 5. 7)% and (13. 1 ± 5. 7)%(t=2. 82, P<0. 05). The V20 of the ipsilateral lung of the 20 right breast cancer cases were (19. 8 ± 3. 8)% and (19. 8 ± 3. 9)%, respectively(P>0. 05). The script plans achieved better V10 of the heart[(298. 0 ± 239. 7) cGy] than the manual plans[(340. 0 ± 286. 2) cGy] (t =2. 53, P <0. 05). Conclusions Compared with the manualmethod, the script can assess of the impact of tangential beam angles on the OAR dose, patient-specifically and quantitatively, hence make better trade-offs and improve the plan quality.
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Objective To reduce the dose to organ at risk ( OAR) by script-based optimizing the gantry angles of tangential beams for forward-planned intensity-modulated breast radiotherapy ( fIMRT ) plans. Methods A total of 46 patients with breast cancer (26 in left and 20 in right) after conservative surgery who were treated with manually planned fIMRT were retrospectively re-planned using a script to place the tangential beams automatically. The script program was developed using Pinnacle3 scripting language as imbedded in the Pinnacle3 treatment planning system, and the Python scripting language. Dosimetric indices, including V20 of the ipsilateral lung, D1 of the contralateral breast and V10 of the heart were extracted by the script for plans of different gantry angles. Then the optimal tangential angles were selected by a penalty function. Results For the 26 left breast cancer cases, V20 of the ipsilateral lung for manual and script were (18.2 ±3.4)% and (18.1 ±3.4)%, respectively(P>0.05), while D1 of the contra-lateral breast(249. 2 ± 88. 4) cGy and (230. 4 ± 80. 2) cGy, respectively( t=2. 27, P<0. 05), V10 of the heart (13. 7 ± 5. 7)% and (13. 1 ± 5. 7)%(t=2. 82, P<0. 05). The V20 of the ipsilateral lung of the 20 right breast cancer cases were (19. 8 ± 3. 8)% and (19. 8 ± 3. 9)%, respectively(P>0. 05). The script plans achieved better V10 of the heart[(298. 0 ± 239. 7) cGy] than the manual plans[(340. 0 ± 286. 2) cGy] (t =2. 53, P <0. 05). Conclusions Compared with the manualmethod, the script can assess of the impact of tangential beam angles on the OAR dose, patient-specifically and quantitatively, hence make better trade-offs and improve the plan quality.
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Intensity-modulated radiotherapy planning for nasopharyngeal carcinoma is very complex. The quality of plan is often closely linked to the experience of the treatment planner. In this study, 10 nasopharyngeal carcinoma patients at different stages were enrolled. Based on the scripting of Pinnacle 9. 2 treatment planning system, the computer program was used to set the basic parameters and objective parameters of the plans. At last, the nasopharyngeal carcinoma intensity-modulated radiotherapy plans were completed automatically. Then, the automatical and manual intensity-modulated radiotherapy plans were statistically compared and clinically evaluated. The results showed that there were no significant differences between those two kinds of plans with respect to the dosimetry parameters of most targets and organs at risk. The automatical nasopharyngeal carcinoma intensity-modulated radiotherapy plans can meet the requirements of clinical radiotherapy, significantly reduce planning time, and avoid the influence of human factors such as lack of experience to the quality of plan.
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Humans , Carcinoma , Feasibility Studies , Nasopharyngeal Neoplasms , Radiotherapy , Radiometry , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted , Radiotherapy, Intensity-ModulatedABSTRACT
Objective To verify the daily delivery accuracy of volumetric-modulated arc therapy (VMAT) and achieve the process quality control (PQC) of linac using statistical process control (SPC)technology.Methods The log files of all treatments were taken out from the linac system.An in-house software which created by Matlab 7.14 was used to analyze the daily parameters accuracy and the mechanism and dose delivery accuracy of the linac for each VMAT,and an daily evaluation report was automatically created for the linac.The stability of the linac and the deviation of the delivery accuracy for various cancer sites were also analyzed.To achieve the process quality control of hnac using SPC technology,the control limit of each parameter was calculated by Johnson alternation and the single value control charts were drawn.Results 76 patients mainly with nasopharyngeal carcinoma,cervical carcinoma,rectal cancer and laryngeal cancer,got the treatment daily with VMAT technology,and a total of 2 446 arcs were delivered by the linac in continuous 16 days.The gantry angle error,y and x collimator position error,MLC leaf position error and dose delivery error were 0.49°,0.09 mm,0.38 mm,0.31 mm,0.05 MU,respectively.Compare to the nasopharynx,uteri,rectal and larynx cancer,it can be seen that the variation factors of dose delivery and gantry angle errors for various cancer sites were higher,which was 8.10％ and 4.54％,respectively.Through the process quality control of the linac,it was found that all the parameters were in control.While some abnormal points arose (the error was greater than UCL),and the ratio of the gantry angle which was out of control (0.45％) was the highest in all parameters.Conclusions linac delivery accuracy could be monitored and verified during the whole VMAT treatment for each patient,and the daily running condition of linac could be monitored.Through the introduction of SPC technology and the control charts,the process quality control of linac in VMAT could be achieved.It is a financial and valid method for the daily quality assurance of linac.
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Objective To evaluate the characteristics and clinical suitability of the ArcCHECK diode array for volumetric-modulated arc therapy (VMAT) verification.Methods The intrinsic sensitivity,short and long term reproducibility,dose and dose rate dependence,dose per pulsed dependence,field sizes dependence and directional response of the diodes were measured.The results of the diodes were compared with the measurement results of an ionization chamber and calculated results of treatment planning system.Gamma index was used to analyze the dose difference between the calculation and measurement for random selected 211 verified VMAT plans.Results The ArcCHECK performed well for all tests except directional dependence,which varies from a minimum of-3.9％ (seen only when the beam was incident on the diode at 180°) to a maximum of 7.7％ (approximately at 255°).Average gamma analysis passing rates with 3 mm/3％ for 113 nasopharyngeal cancer,48 cervical cancer and 50 rectal cancer patients VMAT plans were 93.5％,95.7％ and 97.5％,respectively,statistical significance has been found between either two of the groups (t=-12.69-4.88,all P＜ 0.01).Conclusions With proposed calibration method,the ArcCHECK diode array is very suitable for VMAT pretreatment verification,the complexity of VMAT plan is the main factor affecting the passing rate.
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OBJECTIVE@#To better understand the embryonal rhabdomyosarcoma of nose and make correct decision for diagnosis and treatment.@*METHOD@#Thirteen patients with rhabdomyosarcoma in the nose were studied retrospectively and the related literature was reviewed.@*RESULT@#Male predilection for the disease was present. One patient was in stage I, four patients were in stage II, seven patients were in stage III and one patients was in stage IV. Nine patients were operated plus chemotherapy and radiotherapy, one was operated together with radiotherapy, one was treated by radiotherapy and chemotherapy and the other two were treated by operation alone. The survival rate of two years was 69.2% (9/13), survival rate of 3 years was 30.8% (5/13).@*CONCLUSION@#The pathological growth form of embryonal rhabdomyosarcoma in nose is often convert. If the diagnosis are under suspicion, pathological or immunohistochemical examination should be taken in time. Early diagnosis and combined therapy will make contribution to better prognosis. Surgery combined with radiotherapy and chemotherapy can improve the survival rate.
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Adolescent , Adult , Child , Female , Humans , Male , Young Adult , Neoplasm Staging , Nose Neoplasms , Diagnosis , Therapeutics , Prognosis , Retrospective Studies , Rhabdomyosarcoma, Embryonal , Diagnosis , TherapeuticsABSTRACT
Hot spots and cold spots always appear in the matched region of electron-photon fields. The degree of this kind of dose heterogeneity depends on the physical characteristic of a treatment unit and the energy of electrons. In this paper, a set of dosimetric parameters have been measured on electron rays and x rays for the Elekta Precise treatment unit and the Elekta Synergy treatment unit, respectively. The hot spots and cold spots in the region of perpendicular electron-photon matching fields have been analysed quantitatively. The method to extend penumbra for photon beam profiles was proposed for improving the dose uniformity in the matched regions. And the dose profiles in the matched regions for different treatment units were compared. The results showed that there were stronger hot spots and cold spots for treatment unit with smaller penumbra for photon beams either under the condition of unmodified photon beam profile or the condition of modified photon beam profile.