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Objective To analyze the effect of the fixed-jaw technique on dosimetric parameters during dynamic intensity-modulated radiotherapy (DIMRT) planning. Methods Ten patients each with nasopharyngeal carcinoma, postoperative cervical cancer, and right breast cancer after radical surgery were selected for this study; all patients underwent DIMRT in our hospital in 2020. After administration at the prescribed dose, two methods were used to design the radiotherapy plan for each patient: split-field technique (SFT) and fixed-jaw technique (FJT). The two plans were compared for the differences in the dosimetric parameters and plan verification pass rate. Results Compared with SFT, FJT showed significant decreases (P <0.05) in the following parameters for patients with nasopharyngeal carcinoma, postoperative cervical cancer, and right breast cancer after radical surgery: number of radiation fields (down by 41.5%, 47.3%, and 34.9%, respectively, t = 7.954, 24.2, and 4.949, respectively), total number of monitor units (MUs) (down by 5.6%, 5.3%, and 13.5%, respectively, t = 3.211, 2.423, and 5.481, respectively), and actual beam-on time (down by 25.3%, 23.8%, and 13.6%, respectively, t = 5.814, 9.208, and 5.655, respectively). There were significant differences in some of the dosimetric parameters for all three types of cancer patients between the two plans (P <0.05). There were no significant differences in the plan verification pass rate (P >0.05). Conclusion FJT can reduce the total number of MUs and actual beam-on time while meeting the requirements for clinically prescribed doses in DIMRT planning.
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Objective:To investigate the role of three-dimensional dose distribution-based deep learning model in predicting distant metastasis of head and neck cancer.Methods:Radiotherapy and clinical follow-up data of 237 patients with head and neck cancer undergoing intensity-modulated radiotherapy (IMRT) from 4 different institutions were collected. Among them, 131 patients from HGJ and CHUS institutions were used as the training set, 65 patients from CHUM institution as the validation set, and 41 patients from HMR institution as the test set. Three-dimensional dose distribution and GTV contours of 131 patients in the training set were input into the DM-DOSE model for training and then validated with validation set data. Finally, the independent test set data were used for evaluation. The evaluation content included the area under receiver operating characteristic curve (AUC), balanced accuracy, sensitivity, specificity, concordance index and Kaplan-Meier survival curve analysis.Results:In terms of prognostic prediction of distant metastasis of head and neck cancer, the DM-DOSE model based on three-dimensional dose distribution and GTV contours achieved the optimal prognostic prediction performance, with an AUC of 0.924, and could significantly distinguish patients with high and low risk of distant metastasis (log-rank test, P<0.001). Conclusion:Three-dimensional dose distribution has good predictive value for distant metastasis in head and neck cancer patients treated with IMRT, and the constructed prediction model can effectively predict distant metastasis.
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Objective:To investigate the dosimetric effects of prone immobilization devices combined with a belly board (PIDBBs) in the intensity-modulated radiotherapy (IMRT) for gynecologic cancers.Methods:A total of 20 patients with cervical or endometrial cancer treated with radiotherapy in the Third Affiliated Hospital of Sun Yat-sen University from August 2020 to June 2021 were retrospectively analyzed. Two sets of body contours were outlined for each patient. One set of body contours did not contain the immobilization devices, and the other contour set included the immobilization devices. For each patient, doses were calculated for the two sets of contours using the same 7-field IMRT plan and were recorded as Plan without and Plan with. The dosimetric difference caused by the immobilization devices was assessed by comparing the parameter values in the dose-volume histograms (DVHs) and by plan subtraction. The Gafchromic EBT3 film and anthropomorphic phantom were used to verify the calculated doses. Results:The target coverage and average dose of Plan with were lower than those of Plan without. Specifically, the V50 Gy, V49 Gy, and Dmean of planning target volume (PTV) decreased by 19.75%, 7.99%, and 2.54% ( t = 8.96, 10.49, 22.09, P < 0.01), respectively. The V40 Gy, V30 Gy, V20 Gy, V15 Gy, and Dmean of skins increased by 51.79%, 51.05%, 45.72%, 33.63% and 10.80% ( t = -2.54, -5.63, -15.57, -24.06, -13.88, P < 0.01), respectively. Doses to other organs at risk (OARs) showed no significant differences. As indicated by the EBT3 measurements, the doses to skins of the abdomen and pelvis on the anthropomorphic phantom increased by approximately 37.24% ( t = 10.86, P<0.01). Conclusions:Although PIDBBs can effectively reduce the low dose to the small intestine, the radiation attenuation caused by them can reduce the PTV coverage of radiotherapy plans and increase the doses to abdominal and pelvic skins sharply, especially for patients requiring irradiation of the groin and perineum.
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Objective:To establish a three-dimensional (3D) U-net-based deep learning model, and to predict the 3D dose distribution in CT-guided cervical cancer brachytherapy by using the established model.Methods:The brachytherapy plans of 114 cervical cancer cases with a prescription dose of 6 Gy for each case were studied. These cases were divided into training, validation, and testing groups, including 84, 11, and 19 patients, respectively. A total of 500 epochs of training were performed by using a 3D U-net model. Then, the dosimetric parameters of the testing groups were individually evaluated, including the mean dose deviation (MDD) and mean absolute dose deviation (MADD) at the voxel level, the Dice similarity coefficient (DSC) of the volumes enclosed by isodose surfaces, the conformal index (CI) of the prescription dose, the D90 and average dose Dmean delivered to high-risk clinical target volumes (HR-CTVs), and the D1 cm 3 and D2 cm 3 delivered to bladders, recta, intestines, and colons, respectively. Results:The overall MDD and MADD of the 3D dose matrix from 19 cases of the testing group were (-0.01 ± 0.03) and (0.04 ± 0.01) Gy, respectively. The CI of the prescription dose was 0.70 ± 0.04. The DSC of 50%-150% prescription dose was 0.89-0.94. The mean deviation of D90 and Dmean to HR-CTVs were 2.22% and -4.30%, respectively. The maximum deviations of the D1 cm 3 and D2 cm 3 to bladders, recta, intestines, and colons were 2.46% and 2.58%, respectively. The 3D U-net deep learning model took 2.5 s on average to predict a patient′s dose. Conclusions:In this study, a 3D U-net-based deep learning model for predicting 3D dose distribution in the treatment of cervical cancer was established, thus laying a foundation for the automatic design of cervical cancer brachytherapy.
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Objective:To develop a spot scanning carbon ion beam model based on Monte Carlo code FLUKA and verify the accuracy of physical dose.Methods:A geometric model of the treatment nozzle was established in FLUKA. Various parameters such as monoenergy nominal energy, Gaussian energy spectrum distribution, initial spot size, and beam angular distribution in the model were adjusted to match the reference data of integral depth dose (IDD) and in-air spot size measuremed experimentally. Carbon ion beam plans were generated by using the treatment planning system (TPS). The difference in output dose distribution between FLUKA and TPS was compared by the gamma analysis.Results:The differences in Bragg peak width, beam range, and distal falloff width extracted from the IDD curve between the FLUKA model and measured vaues were less than 0.1 mm, with the maximum difference in spot sizes of 0.17 mm. Under the criterion of 2 mm/2% in all the simulations, 2D- and 3D-γ pass rates were all above 95%.Conclusions:An accurate spot scanning carbon beam model was developed based on the Monte Carlo code FLUKA. It has the potential to be used for not only the verification of clinical treatment plans, but also the development of new ion beam therapy equipment and the calculation of biologically effective dose.
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Objective:Topredict the three-dimensional dose distribution of regions of interest (ROI) with brachytherapy for cervical cancer based on U-Net fully convolutional network, and evaluate the accuracy of prediction model.Methods:First, 100 cases of cervical cancer intracavity combined with interstitial implantation were selected as the entire research data set, and divided into the training set ( n=72), validation set ( n=8), and test set ( n=20). Then the U-Net was used to construct two models based on whether the uterine tandem and the implantation needles were included as the distinguishing factors. Finally, dose distribution of 20 cases in the test set were predicted using the trained model, and comparative analysis was performed. The performance of the model was jointly evaluated by , and the mean absolute deviation (MAD). Results:Compared with the model without the uterine tandem and the implantation needles, the of the rectum was increased by (16.83±1.82) cGy ( P<0.05), and the or of the other ROI were not different significantly (all P>0.05). The MAD of the high-risk clinical target volume, rectum, sigmoid, small bowel, and bladder was increased by (11.96±3.78) cGy, (11.43±0.54) cGy, (24.08±1.65) cGy, (17.04±7.17) cGy and (9.52±4.35) cGy, respectively (all P<0.05). The MAD of the intermediate-risk clinical target volume was decreased by (120.85±29.78) cGy ( P<0.05). The mean value of MAD for all ROI was decreased by (7.8±53) cGy ( P<0.05), which was closer to the actual plan. Conclusions:U-Net fully convolutional network can be used to predict three-dimensional dose distribution of patients with cervical cancer undergoing brachytherapy. Combining the uterine tube with the implantation needles as the input parameters yields more accurate predictions than a single use of the ROI structure as the input.
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Objective:To assess the three-dimensional dose distribution in radiotherapy plans using the structural similarity index(SSIM), compare the performance of SSIM with commonly used quality assessment indices, and develop a SSIM-based quality assessment method of multiple prescribed doses.Methods:The SSIM was introduced to providea quality score of various voxels by comparing actual and ideal three-dimensional dose data and combining the spatial location information of the voxels. Then the average value in a region of interest (ROI) was calculated as the quality score of the region. Fifty-three cases of cervical cancer were selected to analyze the correlation of the SSIM with the uniformity index (HI), conformity index (CI) of the dose distribution in various ROIs and to explore the capability of the SSIM to reflect the uniformity and conformity of dose distribution.Two types of quality defects were individually introduced into two of 53 radiotherapy plans. Then the two plans were compared with normal plans to characterize the response of the SSIM.Results:There was no correlation between HI and SSIM in positive lymph nodes(PGTVnd) due to the decrease in the HI sensitivity, while there was a significant negative correlation between them in regions where PGTVnd was removed from the planning target volume(PTV, R=-0.86, P<0.01). Meanwhile, there was a significant positive correlation between CI and SSIM in PGTVnd ( R=0.83, P<0.01). Therefore, the SSIM can be used to identify the artificial design defects in plans by determining abnormal dose gradients. Conclusions:Apart from reducing the defects of previous assessment parameters, the SSIM has the capability to assess the quality of radiotherapy plans by combining the uniformity and conformity of dose distribution and can provide accurate feedback on the spatial locations of quality defects.
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Objective:To investigate the impacts of the composition and physical density of tissue on the dose distribution of implanted 125I seeds, in order to provide references for the clinical dose calculation and assessment of implanted radioactive particles. Methods:The OncoSeed 6711 physical model of 125I seeds was established using thes of twareegs_brachy and was validated through the calculation of dose rate constant and the radial dose function [ g( r)] in water. Then, based on the element composition and physical density of different types of tissue, the g( r) and absorbed dose ratein water, prostate, breast, muscle, and bone were calculated. Results:The calculated dose rate constant (0.950 cGy·h -1·U -1) and g( r)in water approached the values in related literature. The absorbed dose in bone was 6.042 times than that in water at a distance of 0.05 cm from the implanted source. The difference between the absorbed doses in breast and water was more than 10% at a distance of less than 1.7 cm from the implanted source. The difference between the absorbed doses in prostate/muscle and water was less than 5% at the same radial location. Conclusions:The dose distribution of 125I seeds in some types of human tissue is significantly different from that in water, which should be carefully considered in clinical dose calculation.
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Objective:To estimate the physical dose of an over exposed person working for industrial radiography.Methods:The main exposure parameters were obtained. The exposure duration was 8 min. The exposure pattern was external exposure by isotropic point radioactive source. The radioactive activity was 2.183 TBq. In the present calculation, the Chinese reference adult voxel phantom was used, and the Monte Carlo simulation was performed using the program based on the secondary development of Geant4 to obtain the absorbed dose of each part of the victim.Results:The dose distribution in the victim′s hands was obtained. The doses to most areas of the palm were 2-10 Gy, and the doses to the fingers were 10-20 Gy. The equivalent doses to 23 tissues or organs of the exposed person were estimated to be in the range of 0.012-0.207 Gy.Conclusions:The physical dose estimation method could evaluate rapidly the local dose distribution of the victim′s key exposed body parts, and thus provide an important reference for medical treatment.
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Virtual monochromatic images (VMI) that reconstructed on dual-energy computed tomography (DECT) have further application prospects in radiotherapy, and there is still a lack of clinical dose verification. In this study, GE Revolution CT scanner was used to perform conventional imaging and gemstone spectral imaging on the simulated head and body phantom. The CT images were imported to radiotherapy treatment planning system (TPS), and the same treatment plans were transplanted to compare the CT value and the dose distribution. The results show that the VMI can be imported into TPS for CT value-relative electron density conversion and dose calculation. Compared to conventional images, the VMI varies from 70 to 140 keV, has little difference in dose distribution of 6 MV photon treatment plan.
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Electrons , Phantoms, Imaging , Tomography Scanners, X-Ray Computed , Tomography, X-Ray ComputedABSTRACT
Resumen En el presente trabajo se muestran los resultados obtenidos durante los estudios dosimétricos de las etapas de calificación operacional y del comportamiento funcional de la instalación de irradiación semindustrial de Cuba después de su remodelación y recarga, así como el proceso de radioesterilización de un producto de uso médico.
Abstract The present work shows the results obtained during the dosimetric studies of the operational qualification stages and the functional behavior of the semi-industrial irradiation facility in Cuba after its remodeling and recharging, as well as the radio-sterilization process of a product for medical use.
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Objective To study a method for verifying the doses to PTV and OAR as well as the 2D dose distribution arising from IMRT through using radiochromic films and TLDs.Methods Totally 7 medical electronic linear accelerators from Varian,Siemens and Elekta were selected.The polystyrene phantom provided by IAEA was conducted with CT scan.After irradiation with 6 MV X-rays,the TLDs and films were returned to the secondary standard dosimetry laboratory of China CDC for measurement and estimation.Results According to the IAEA requirements,the relative deviations between TLD-measured and TPS-planned values for PTV and OAR doses were both within ±7.0％.For PTV,the measured relative deviations for 5 accelerators were in the range of-4.0％ to 3.4％,consistent with the IAEA requirements,whereas the values for the other 2 accelerators were in the range of-7.0％ to 10.6％,not consistent with the requirements.For OAR,the values for 4 accelerators were in the range of-5.6％ to 3.3％,consistent with the IAEA requirements,whereas the values for the other 3 accelerators were in the range of-20.8％ to 11.5％,not meeting the requirements.As required by the IAEA,the 2D dose distribution 3 mm/3％ pass rate should be higher than 90％.The measured values for 5 accelerators were in the range of 91.8％ to 98.5％,consistent with the requirements,whereas the values measured for the other 2 were 45.0％ and 77.0％ respectively,not meeting the requirements.Conclusions It is feasible for using TLDs and radiochromic films to verify the doses to PTV and OAR and the 2D dose distribution in IMRT.This method should be applied to not only quality verification but also hospital internal audit to the extent possible.
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Objective To use TLDs and radiochromic films to verify the prescribed doses to both planned target volume (PTV) and organ at risk (OAR) and the 2D dose distribution in IMRT.Methods Eight accelerators of different models were selected in Henan province.The polystyrene phantom provided by IAEA was scanned using CT scanners and then the scanned images were transmitted to treatment planning system (TPS) for prescribing respectively the doses to PTV and OAR.IMRT was performed with phantom exposed to a 6 MV X-rays.The irradiated TLDs and films were delivered for measurement and estimation at Secondary Standard Dosimetry Laboratory at National Institute for Radiological Protection,Chinese Center for Disease Control and Prevention.Results According to IAEA requirements,the relative deviations of the TLD-measured and TPS-planned values were within ±7.0％ for the prescribed doses to PTV and OAR.The measured results for PTV have shown that the relative deviation of TLD-measured and TPS-planned values were within-0.3％ to 6.9％ for 8 accelerators,all consistent with the IAEA requirements.For OAR,the relative deviations of TLD-measured and TPS-planned were within-7.0％ to 0.3％ for 6 accelerators,consistent with the requirements,whereas those for other 2 accelerators were within-10.8％ to-8.4％,not up to the requirements.IAEA required that,for 2D dose distribution,the pass rate of 3 mm/3％ be ≥ 90％.The measured values for 7 accelerators were from 90.2％ to 99.9％,consistent with the requirements,whereas that for another one was 70.0％,not meeting the requirement.Conclusions The method to verify,using radiochromic film and TLD,the prescribed doses to PTV and OAR and the pass rate of 2D dose distribution is simple and reliable.It is an important step to implement quality control for IMRT and can provide effective support for medical or third-party service institution to verify clinically prescribed dose.
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Objective To study a method to measure the doses to planned target volume (PTV) and organ at risk (OAR) and 2D dose distribution in IMRT by using TLD and radiochromic film for a verification purpose.Methods Totally 7 different types of medical linear accelerators were selected from seven hospitals in Hubei province.A polystyrene phantom provided by IAEA was CT scanned and then the scanned images were returned to the Treatment Planning System (TPS) for determining the prescribed doses to PTS and OAR and the corresponding MU.After the phantom was irradiated with 6 MV X-ray,the TLDs and films were transmitted to the secondary standard dosimetry laboratory of China CDC for measurement and estimation.Results The IAEA required the relative deviations between TLD-measured and TPS-planned doses to OAR and PTV be within ±7.0％.For PTV,the measured-to-planned deviation values for 7 accelerator were within-5.4％ to 6.5％,all consistent with the IAEA requirements.For OAR,the values for 5 accelerators were within-2.2％ to 6.7％,not consistent the requirements,whereas the values for the other 2 were-8.6％ and 8.2％ respectively,beyond the required values.The IAEA required that the 2D dose distribution 3 mm/3％ pass rate be higher than 90％.The measured values for 7 accelerators were in the range of 90.3％-98.9％,all consistent with the requirements.Conclusions It is feasible scientifically and easy to operate in practice for using TLD and film to carry out dose verification in IMRT.It would be advisable to apply this method to quality verification in IMRT in medical institutions to the extent possible.
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Objective To validate the method for measuring the TPV and OAR doses and 2D dose distribution in IMRT through using TLD and radiochromic film.Methods Eight medical linear accelerators (Valian,Elekta,Siemens) were selected.The polystyrene phantom provided by IAEA was CT scanned and the image obtained was transferred to TPS for formulation of treatment plan,prescription of PTV and OAR doses and calculation of corresponding monitoring unit (MU),IMRT was performed on the phantom using 6 MV X-ray.Irradiated TLDs and films were measured and evaluated at the Secondary Standard Dosimetry Laboratory at the Radiation Safety Institute of Chinese Center for Disease Control and Prevention.Results According to IAEA requirement,the relative deviations between TLD-measured and TPS-planned doses were within ±7.0％ for the prescribed PTV and OAR doses.As measured result,the PTV values for 8 accelerators were in the range of 0.6％ to 5.9％,consistent with the IAEA requirements,whereas the OAT values for 8 accelerators were within-0.6％ to 7.0％,consistent the requirements.As IAEA required,the 2D dose distribution passing rate of 3 mm/3％ should be higher than 90％.The filmmeasured and TPS-planned values for 8 accelerators were within 90.2％ to 100.0％,consistent with the requirements.Conclusions TLD and radiochromic film are feasible in validating the PTV and OAR doses and the 2D dose distribution pass rate in IMRT.This method can be widely used in quality audit and internal verification in IMRT in medical institutiions on a large scale.
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Objective To develop the methodology for using TLD and radiochromic film to measure the planned target volume (PTV) and organ at risk (OAR) doses and 2D dose distribution in IMRT,in order to provide technical guidance on the dose quality audit in IMRT at home.Methods China has participated in the research project launched by the international multi-radiotherapy centre (IMRC).IMRT polystyrene phantom provided by IAEA was scanned by CT scanner and then the scanned images were transmitted to TPS to outline prescribed dose to PTV and to OAR.The former was limited to 400 cGy while the latter limited to 200 cGy.IMRT was implemented with the phantom irradiated using 6 MV X-ray.The irradiated TLDs and films were sent to IAEA dosimerty laboratory for measurement and calculation.Jiangsu,Sichuan,Hubei and Henan provinces were selected to engage with this study for their variety of accelerators and highly skilled physicists.The procedures used were the same as in the IMRC and the irradiated TLDs and films were required to send to external audit group for measurement and calculation.Results According to IAEA requirement,the relative deviations of the TLD-measured and TPS planned doses are within ±7.0％ for PTV and OAR.The China's research results at the IMRC have shown that the relative deviation of TLD-measured and TPS-planned values for the upper and lower PTV were-0.2％ and 0.8％,respectively,consistent with the IAEA requirement,and the values for upper and lower OAR were -0.6％ and-1.0％,respectively,consistent with the requirement.As the results have shown in four provinces,the relative deviations of the TLD-measured and TPS-planned were within 0 to 10.6％ for upper and lower PTV and-0.6％ to 20.9％ for upper and lower OAR.According to IAEA requirement,the passing rate should be greater than 90％ for 3 mm /3％ for 2D dose distribution.China's result at the IMRC is 100％,being excellent.The four provinces' results have shown that 2D dose distribution pass rate of 3 mm/3％ was in the range of 45.0％-100.0％.Conclusions The uses of TLD in quality audit for PTV and OAR doses and the radiochromic film in 2D dose distribution pass rate in IMRT are characterized by scientific feasibility,strong operability,easy-to-mail and data realibility.They are can be applied to quality assurance and audit in medical institutions in the country to on a large scale.
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Objective@#To study a method for verifying the doses to PTV and OAR as well as the 2D dose distribution arising from IMRT through using radiochromic films and TLDs.@*Methods@#Totally 7 medical electronic linear accelerators from Varian, Siemens and Elekta were selected. The polystyrene phantom provided by IAEA was conducted with CT scan. After irradiation with 6 MV X-rays, the TLDs and films were returned to the secondary standard dosimetry laboratory of China CDC for measurement and estimation.@*Results@#According to the IAEA requirements, the relative deviations between TLD-measured and TPS-planned values for PTV and OAR doses were both within ±7.0%. For PTV, the measured relative deviations for 5 accelerators were in the range of -4.0% to 3.4%, consistent with the IAEA requirements, whereas the values for the other 2 accelerators were in the range of -7.0% to 10.6%, not consistent with the requirements. For OAR, the values for 4 accelerators were in the range of -5.6% to 3.3%, consistent with the IAEA requirements, whereas the values for the other 3 accelerators were in the range of -20.8% to 11.5%, not meeting the requirements. As required by the IAEA, the 2D dose distribution 3 mm/3% pass rate should be higher than 90%. The measured values for 5 accelerators were in the range of 91.8% to 98.5%, consistent with the requirements, whereas the values measured for the other 2 were 45.0% and 77.0% respectively, not meeting the requirements.@*Conclusions@#It is feasible for using TLDs and radiochromic films to verify the doses to PTV and OAR and the 2D dose distribution in IMRT. This method should be applied to not only quality verification but also hospital internal audit to the extent possible.
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Objective@#To use TLDs and radiochromic films to verify the prescribed doses to both planned target volume (PTV) and organ at risk (OAR) and the 2D dose distribution in IMRT.@*Methods@#Eight accelerators of different models were selected in Henan province. The polystyrene phantom provided by IAEA was scanned using CT scanners and then the scanned images were transmitted to treatment planning system (TPS) for prescribing respectively the doses to PTV and OAR. IMRT was performed with phantom exposed to a 6 MV X-rays. The irradiated TLDs and films were delivered for measurement and estimation at Secondary Standard Dosimetry Laboratory at National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention.@*Results@#According to IAEA requirements, the relative deviations of the TLD-measured and TPS-planned values were within ±7.0% for the prescribed doses to PTV and OAR. The measured results for PTV have shown that the relative deviation of TLD-measured and TPS-planned values were within -0.3% to 6.9% for 8 accelerators, all consistent with the IAEA requirements. For OAR, the relative deviations of TLD-measured and TPS-planned were within -7.0% to 0.3% for 6 accelerators, consistent with the requirements, whereas those for other 2 accelerators were within -10.8% to -8.4%, not up to the requirements. IAEA required that, for 2D dose distribution, the pass rate of 3 mm/3% be ≥90%. The measured values for 7 accelerators were from 90.2% to 99.9%, consistent with the requirements, whereas that for another one was 70.0%, not meeting the requirement.@*Conclusions@#The method to verify, using radiochromic film and TLD, the prescribed doses to PTV and OAR and the pass rate of 2D dose distribution is simple and reliable. It is an important step to implement quality control for IMRT and can provide effective support for medical or third-party service institution to verify clinically prescribed dose.
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Objective@#To study a method to measure the doses to planned target volume (PTV) and organ at risk (OAR) and 2D dose distribution in IMRT by using TLD and radiochromic film for a verification purpose.@*Methods@#Totally 7 different types of medical linear accelerators were selected from seven hospitals in Hubei province. A polystyrene phantom provided by IAEA was CT scanned and then the scanned images were returned to the Treatment Planning System (TPS) for determining the prescribed doses to PTS and OAR and the corresponding MU. After the phantom was irradiated with 6 MV X-ray, the TLDs and films were transmitted to the secondary standard dosimetry laboratory of China CDC for measurement and estimation.@*Results@#The IAEA required the relative deviations between TLD-measured and TPS-planned doses to OAR and PTV be within ±7.0%. For PTV, the measured-to-planned deviation values for 7 accelerator were within -5.4% to 6.5%, all consistent with the IAEA requirements. For OAR, the values for 5 accelerators were within -2.2% to 6.7%, not consistent the requirements, whereas the values for the other 2 were -8.6% and 8.2% respectively, beyond the required values. The IAEA required that the 2D dose distribution 3 mm/3% pass rate be higher than 90%. The measured values for 7 accelerators were in the range of 90.3%-98.9%, all consistent with the requirements.@*Conclusions@#It is feasible scientifically and easy to operate in practice for using TLD and film to carry out dose verification in IMRT. It would be advisable to apply this method to quality verification in IMRT in medical institutions to the extent possible.
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Objective@#To validate the method for measuring the TPV and OAR doses and 2D dose distribution in IMRT through using TLD and radiochromic film.@*Methods@#Eight medical linear accelerators (Valian, Elekta, Siemens) were selected. The polystyrene phantom provided by IAEA was CT scanned and the image obtained was transferred to TPS for formulation of treatment plan, prescription of PTV and OAR doses and calculation of corresponding monitoring unit (MU), IMRT was performed on the phantom using 6 MV X-ray. Irradiated TLDs and films were measured and evaluated at the Secondary Standard Dosimetry Laboratory at the Radiation Safety Institute of Chinese Center for Disease Control and Prevention.@*Results@#According to IAEA requirement, the relative deviations between TLD-measured and TPS-planned doses were within ±7.0% for the prescribed PTV and OAR doses. As measured result, the PTV values for 8 accelerators were in the range of 0.6% to 5.9%, consistent with the IAEA requirements, whereas the OAT values for 8 accelerators were within -0.6% to 7.0%, consistent the requirements. As IAEA required, the 2D dose distribution passing rate of 3 mm/3% should be higher than 90%. The film-measured and TPS-planned values for 8 accelerators were within 90.2% to 100.0%, consistent with the requirements.@*Conclusions@#TLD and radiochromic film are feasible in validating the PTV and OAR doses and the 2D dose distribution pass rate in IMRT. This method can be widely used in quality audit and internal verification in IMRT in medical institutiions on a large scale.