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Objective:To evaluate the usability of Gafchromic HD-V2 film for dose dosimetry in the ultra-high dose-rate (UD) electron beam from a modified medical linac, and to investigate the response between the energy and dose-rate dependence to the film.Methods:The HD-V2 film was utilized to measure the average dose-rate of the UD electron beam. The measured result was compared with those by advanced Markus chamber and alanine pellets. And characteristics of the UD electron beam were also measured by HD-V2 film. Energy dependence of HD-V2 film at three beam energies (6 MV X-ray, 9 MeV and 16 MeV electron beam) was investigated by obtaining and comparing the calibration curves based on the clinical linear accelerator in the dose range of 10-300 Gy. The dose-rate dependence of HD-V2 film was also studied by varying the dose rate among 0.03 Gy/s, 0.06 Gy/s and 0.1 Gy/s, and range of 100-200 Gy/s.Results:The measured average maximum dose-rate of 9 MeV UD electron beam at source skin distance (SSD) 100 cm was approximately 121 Gy/s using HD-V2 film, consistent with the results by advanced Markus chamber and alanine pellets. The measured percentage depth dose (PDD) curve parameters of the UD electron beam were similar to the conventional 9 MeV beam. The off-axis dose distribution of the UD electron beam showed the highest central axis, and the dose was gradually decreased with the increase of off-axis distance. The energy dependence of HD-V2 film had no dependency of 6 MV and 9, 16 MeV while measuring the dose in the range from 20 to 300 Gy. The HD-V2 film had no significant dose-rate dependency at the dose rate of 0.03 Gy/s, 0.06 Gy/s and 0.1 Gy/s for the clinical linear accelerator. Likewise, there was also no dose-rate dependence in the range 100-200 Gy/s in the modified machine.Conclusion:HD-V2 film is suitable for measuring ultra-high dose rate electron beam, independent of energy and dose rate.
RESUMO
Objective:To build a systemic and automatic importing scheme for importing CT images and structures into the treatment planning systems (TPSs) of Eclipse and Monaco.Methods:Based on two TPSs of Eclipse and Monaco, the files of CT images and structures were automatically transported from OAR auto-delineation system to the importing directory of these two TPSs using batch script in Windows system. Following the standard importing procedures of these two TPSs, the automatically importing script of CT images and structures were developed using the application of UiBot. Finally, the CT images and structures were imported into these two TPSs opportunely.Results:By comparing the importing time using script and manual methods, the script not only achieved auto-importing CT images and structures into TPSs, but also yielded almost the same efficiency to manual method. The number of imaging layers in most patients was between 130 and 180, and the average manual and automatic importing time within this interval was 76 s and 75 s.Conclusions:Automatic scripts can be developed by using the automation function of UiBot combined with the actual problems of radiotherapy and repeated workflow. The efficiency of radiotherapy work can be significantly improved. Manual and time costs can be saved. It provides a novel alternative for the automation of radiotherapy procedures.
RESUMO
Objective:To validate the accuracy of physical model of in-vivo 3D dose verification based on electronic portal imaging device (EPID) using the phantom and preliminarily analyze the clinical application.Methods:Two phantoms (uniform and non-uniform phantoms) were involved in this study. The system of in-vivo 3D dose verification based on EPID was employed to acquire the images of square fields (SF) and combined fields of intensity-modulated radiotherapy (CFIMRT). The physical model of different media was constructed using the system. The factor of γ passing rate under different dose/distance criteria was statistically compared. For clinical cases, the dose-volume histograms were adopted to analyze the dose distribution of target volume and organs at risk (OARs).Results:For the SF in the uniform phantom, the average γ passing rate (3%/3 mm) was (97.49±1.11)%, and (94.06±5.11)% for the SF in the non-uniform phantom ( P>0.05). No statistical significance was noted in IMRT using different delivery methods (all P>0.05). For clinical cases, the average γ passing rate (3%/2 mm) was (97.96±1.84)% in the pre-treatment dose verification, and (90.51±6.96)%(3%/3 mm) for the in-vivo 3D dose verification. For clinical cases, significant dose deviation was observed in OARs with small size and large volume changes. Conclusion:The in-vivo 3D dose verification model based on EPID can be effectively applied in inter-fraction dose verification, providing technical support for adaptive radiotherapy in clinical practice.
RESUMO
Objective:Based on the AAPM-TG218 report, the dose verification of intensity-modulated radiotherapy (IMRT) plans were classified to understand the current status, establish the process and determine the limits of dose verification in our hospital.Methods:Different combinations of tumor locations, accelerators, treatment planning systems and verification devices in our hospital were verified and compared to determine the tolerance limits and action limits of each combination. The measurement requirement was adopted according to the AAPM-TG218 report, and 80 cases were selected for each measurement. The measurement procedures were implemented based upon the AAPM-TG218 report and clinical experience of our hospital.Results:The clinical action limits of IMRT plans in our hospital could meet the recommended range of the AAPM-TG218 report, and the tolerance limits were slightly lower than the AAPM-TG218 report′s recommendation (93.94% for 3%/2 mm). The measurement of verification devices was related to the sensitivity. The tolerance limits measured by EPID were higher than ArcCHECK, especially when the dose/distance requirements were more stringent (94.12% and 92.03% for 3%/2 mm, P=0.074; 86.82% and 74.61% for 2%/2 mm, P=0.017). Conclusion:Through the AAPM-TG218 report, the work flow of IMRT dose verification and the limit range are established in our hospital, providing guidance for subsequent clinical dosimetric measurement.