Objective To investigate the feasibility and efficiency of electronic portal imaging device for dosimetric verification of intensity-modulated radiation therapy.Methods 10 patients treated with intensity-modulated radiation therapy were verified using the electronic portal imaging device of aS1000 from Varian and MatriXX from IBA.The gamma pass rate and time needed was recorded and compared.Results The gamma pass rate at 3％/3 mm was 95.82％ (94.77％-96.86％) and 99.08％ (98.72％-99.45％) with aS1000 and MatriXX,respectively.The average time needed for dosimetric verification with aS1000 and MatriXX was 12.7 and 47.8 min,respectively.Conclusions The electronic portal imaging device of aS1000 has the potential as a tool for IMRT dosimetric verification.It is more convenient and efficient than MatriXX.

Objective To test the accuracy and reliability of Axesse accelerator for volumetric modulated arc therapy (VMAT).Methods The accuracy and reliability of Axesse accelerator for VMAT were tested in a stepwise manner, from the simple to the complex and from the part to the whole.For the parts of the system, the stability of dosimetric output and the position accuracy of multi-leaf collimator (MLC) were tested.For the process of the system, the variable VMAT dose rates and gantry speed modulation, the MLC speed and dose rate modulation, and dosimetric verification in patients were tested.Results Compared with fixed gantry irradiation, the variation in dosimetric output was below 1.0% for rotary irradiation including the slide rotary irradiation of the dynamic MLC.The MLC position error of 0.5 mm was visible using the electronic portal imaging system of Axesse, iViewGT 3.40.The MLC position accuracy was within 1 mm for fixed gantry irradiation and rotary irradiation.In the range of the dose rate applied in clinical practice, the testing results of variable VMAT dose rates and gantry speeds as well as variable dose rates and MLC speeds showed that the variation between different strip-field beam intensities was below 2.0%.Using a gamma criterion of 3 mm/3%, the pass rates in dosimetric verification of patients with cervical cancer, prostate cancer, and breast cancer were 96.52%, 95.72%, and 98.83%, respectively.Conclusions The Axesse system can precisely control MLC motion, variable dose rates, and gantry speeds in VMAT.The Axesse system is accurate and reliable for VMAT.

Objective To analyze the patient-specific dosimetric verification results of 2010 intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans from different treatment sites,and provide a reference for improving the patient-specific dosimetric verification program.Methods A total of 2 010 (965 IMRT and 1 045 VMAT) patient-specific dosimetric verification results were reviewed for isocenter dose difference and percentage of pixels passing planar dose γ analysis.All plans were designed with Eclipse planning system and delivered with Trilogy linear accelerator from February 2012 to February 2016.The dosimetric verification was performed with MatriXX array together with Muhicube phantom.Point dose difference larger than ± 3％ and/or γ pass rate (3％/ 3 mm) less than 90％ was defined as plan failure.Additional analysis was conducted for trends in difference of pass rates with treatment site and delivery technique (IMRT vs.VMAT).Results The mean isocenter difference between measured and calculated doses was-0.3％ ± 2.4％ for 2 010 plans.The mean percentage of pixels passing the γ criteria was 97.9％ ± 3.4％.88.2％ and 96.7％ of plans passed the point and planar dose verification,respectively.The γ pass rate was different among the treatment sites (F =3.09,P ＜ 0.05).The pass rate of point and planar dose difference was different among the treatment sites(x2 =40.93,39.15,P ＜0.05).There was no difference between IMRT and VMAT plans for both point dose and planar dose evaluation (P ＞ 0.05).Conclusions Most of IMRT and VMAT plans passed the tolerance criteria of ±3％ and 90％ for point and planar dose verification with MatriXX together with Multicube phantom,respectively.Both point and planar dose verification results varied among treatment sites,whereas no significant difference was found between IMRT and VMAT.

Objective To investigate the dosimetric effect of multi-leaf collimator (MLC)transmission on intensity-modulated radiation therapy (IMRT).Methods MLC transmission through theleaves and rounded ends were measured with ion chamber for Varian Trilogy linear accelerator with the X-ray of 6 MV and 10 MV.The intraleaf and interleaf transmission were also measured with the electronic portal imaging device of aS1000.10 tumor patients treated with IMRT were used to evaluate the MLC parameters modeling in the Eclipse treatment planning system.Results The average transmissions of Millennium MLC were 1.6％ and 1.8％ for 6 MV and 10 MV X-rays.The transmission increased with the field size and depth of measurement.The transmissions at off axis position were a little lower than those on the central axis.The intraleaf transmissions measured with aS1000 were 0.8％-1.2％ and 1.1％-1.6％,the interleaf transmission were 1.3％-1.9％ and 1.6％-2.5％ for 6 MV and 10 MV X-rays respectively.Modeling with the measured MLC parameters,the Eclipse treatment planning system could calculate the dose distribution accurately.The γ pass rate at 3％ 3 mm was above 95％,except for two patients with nasopharyngeal cancer with the pass rate of 93.6％ and 94.5％.Conclusions The transmissions through the MLC leaves and the leaf ends contribute to the dose throughout the target significantly for IMRT.MLC transmission varied with the field size,depth of measurement and off axis position.

Objective To evaluate four detectors for the off-axis ratio profile measurements of a CyberKnife system, and provide reference and suggestions for selecting and using the correct detectors. Methods Profiles were acquired by using four detectors, PTW-60017, PTW-60018, PTW-60019 and IBA-SFD, at different depths for different collimator sizes, with the detector stem being oriented both perpendicular and parallel to the central beam axis. The differences of profiles and the influence of detector orientation on measurement result were analyzed. Results All full width at half maximum ( FWHM) of field measured by four detectors in parallel orientation was larger than that in actual field size. The deviation was increased with the size of collimator and measurement depth, with the maximum deviation of 1. 9 mm. The maximum deviation of FWHM among four detectors was 0. 2 mm. The penumbra was the smallest for IBA-SFD, and the largest for PTW-60019. The maximum deviation of penumbra was 0. 3 mm. The IBA-SFD tended to over-respond in the out-of-field region when the collimator size was larger than 30 mm. Both FWHM and penumbra in perpendicular orientation were smaller than those in parallel orientation for PTW-60017, PTW-60018 and PTW-60019, especially at 5 mm collimator. However, the trend was opposite for IBA-SFD. With the increase of collimator aperture, the difference between the right and left penumbra acquired by four detectors was increased, with more obvious stem effects. Conclusions Similar profiles were acquired by four detectors, but the detector characteristics and effects of detector orientations should be considered.

Objective To compare five different detectors in output factor(OF)measurement for the CyberKnife(CK)system,and to select a suitable detector. Methods OFs for 12 different sizes of CK collimators were measured by EBT3films and 5 different commercially available detectors,consisting of diode detectors PTW 60017 and PTW 60018,ionizing chamber detectors PTW 31010 and PTW 30013,and diamond detector PTW 600019.OF was compared between different detectors and different measurement orientations. Results When the size of collimator was larger than 30 mm,the OF deviation among five detectors was less than 1%.When the size of collimator was smaller than 30 mm,however,the OF deviation among five detectors became large and obviously increased with the decrease in the size of collimator. With a OF deviation less than 2%,PTW 60019 achieved the best agreement with films. Compared with films,diode detectors gave slightly higher OFs,while ionizing chamber detectors gave much smaller OFs. The OF measurement was also affected by measurement orientation. PTW 60019 gave a smaller OF in the direction parallel to the central axis than in the direction perpendicular to the central axis of the radiation field,while PTW 31010 had an opposite result. Conclusions When the size of collimator is larger than 30 mm,PTW 31010,PTW 60017,PTW 60018,and PTW 60019 can be directly used for the OF measurement. When the size of collimator is smaller than 30 mm,correction is needed for the OF measurement using the above detectors. PTW 30013 is not suitable for the OF measurement in the small radiation field.

In recent years,the application of machine learning in the field of radiotherapy has been gradually increased along with the development of big data and artificial intelligence technology.Through the training of previous plans,machine learning can predict the results of plan quality and dose verification.It can also predict the multi-leaf collimator (MLC) positioning error and linear accelerator performance.In addition,machine learning can be applied in the quality assurance of intensity-modulated radiotherapy to improve the quality and efficiency of treatment plan and implementation,increase the benefits to the patients and reduce the risk.However,there are many problems,such as difficulty in the selection,extraction and calculation of characteristic value,requirement for large training sample size and insufficient prediction accuracy,which impede its clinical translation and application.In this article,research progress on the application of machine learning in the quality assurance of IMRT was reviewed.

Objective To evaluate the accuracy and reliability of the CyberKnife VSI system for stereotactic radiotherapy.Methods First,the mechanical accuracy of the robotic manipulator system,the repeatability of the Iris variable aperture collimator system,the couch position accuracy of the patient positioning system,the tacking precision of the target locating system and the dosimetric beam characteristics of the linac system for each subsystem of CyberKnife VSI system were tested.Finally,the total beam delivery precision of the CyberKnife VSI system was evaluated.Results The mean positioning deviations of the mechanical arm movement of the robotic manipulator system were less than 0.1 mm,and the maximum positioning deviation of single note was ≤ 0.29 mm.The repeatability of the aperture sizes for the Iris variable aperture collimator system was ≤ 0.28 mm.The couch position accuracy of the patient positioning system was＜0.2 mm and the tracking precision of the target locating system was less than 0.5°.The linac beam-laser beam axes coincidence between the Iris and fixed collimators was better than 0.4 mm.The 6-MV beam parameters,such as beam quality and profile,were found within the acceptance limits.The deviations of output reproducibility,linearity and constancy versus linac orientation were less than 1.0％.The transmission factors of two types of collimators were lower than 0.4％.End-to-end test demonstrated that the maximum deviation of the total delivery precision of CyberKnife VSI system was 0.87 mm.Conclusion The CyberKnife VSI system is accurate and reliable for stereotactic radiotherapy.

Objective:To investigate the effect of Halo-Vest on the dose distribution of different radiotherapy techniques for primary cervical spine malignant tumors.Methods:Ten patients with primary cervical spine malignancies who underwent radiotherapy after Halo-Vest surgery were retrospectively studied. The IMRT and VMAT plans were designed on the contoured CT images including Halo-Vest delineations using Monaco planning system. The IMRT and VMAT plans with the same field parameters were duplicated to the CT images without the Halo-Vest delineations, and the dose distribution was recalculated. The dose distribution of the target, organs at risk and normal tissues was analyzed and compared for the plans with and without the Halo-Vest delineation.Results:For most dosimetric parameters of VMAT plans, the mean deviations induced by the Halo-Vest were less than 1%, except for PGTV 107%. Without Halo-Vest delineation, the mean maximum dose of spinal cord and spinal cord-PRV increased by 0.38 Gy and 0.42 Gy ( Z=-2.803, -2.803, P<0.05), respectively. The mean Dmean of spinal cord and spinal cord PRV increased by 0.35 Gy and 0.37 Gy, respectively ( Z=-2.703, -2.701, P<0.05). The maximum deviation observed in the mean V5, V30, and Dmean of mucosa, thyroid, parotid gland, mandible, mandibular joint, and normal tissues was 0.74%. For IMRT plans, larger dosimetric deviations than VMAT plans were observed in PTV and PGTV, most of which were more than 1.0% and the maximum deviation was 4.55%. The absence of Halo-Vest delineation increased the mean maximum dose of spinal cord and spinal cord-PRV by 0.48 Gy and 0.59 Gy ( P>0.05), respectively. The mean Dmean of spinal cord and spinal cord PRV increased by 0.57 Gy and 0.59 Gy, respectively ( Z=-2.293, -2.293, P<0.05). The maximum deviation of other organs at risk was 1.98%. Conclusions:There are no clinically significant dose differences for VMAT planning with or without Halo-Vest delineation on the CT images. But the dosimetric impact of absent or partial Halo-Vest delineation on IMRT planning is relatively large and should be considered.

Objective To evaluate the dynamic efficacy of Invigorating Qi and Dissipating Depression Herbs in the treatment of depressive disorders and its effect on recurrence rate and suicidal thoughts.Methods The prospective cohort study was used to divide the patients into three cohorts according to the different exposure factors(treatment regimens):Western medicine group,integrated traditional Chinese and Western medicine group,and Invigorating Qi and Dissipating Depression Herbs group,and followed up for 2 years,and the treatment effects of each cohort at half a year,one year,one and a half years,and two years were observed respectively,and the evaluation indicators were Montgomery Depression Scale(MADRS),Hamilton Anxiety Scale(HAMA)and Social Deficit Screening Scale(SDSS)reduction rates,and endpoint events(relapse,suicidal ideation)incidence;By comparing the efficacy and endpoint event rate of the three cohorts,the effect of Invigorating Qi and Dissipating Depression Herbs on improving depressive disorders was evaluated.Results A total of 409 patients(67 in the Western medicine group,131 in the integrated traditional Chinese and Western medicine group,and 211 cases in the Invigorating Qi and Dissipating Depression Herbs group)were enrolled,and the rate of score reduction after treatment with MADRS,HAMA and SDSS increased compared with the pre-treatment treatment with the extension of the drug taking time.The difference between the MADRS and SDSS reduction rates in the Invigorating Qi and Dissipating Depression Herbs group on taking the drug for half a year and the SDSS reduction rate on one year of taking the drug were statistically significant compared with the Western medicine group,and there was no significant difference compared with the integrated Chinese and Western medicine group.On one and a half years and two years of medication,the integrated Chinese and Western medicine group had more advantages in MADRS reduction rate than the Invigorating Qi and Dissipating Depression Herbs group.The recurrence rates of depression in the three groups within 2 years were 20.9％,30.5％and 36.0％,and the difference was not statistically significant,and the length of taking medication was used as a protective factor by logistic regression analysis.The incidence rates of suicidal thoughts were 44.8％,19.1％and 17.5％,and the differences were statistically significant,and the exposure factors and income level were the protective factors by logistic regression analysis.Conclusion Invigorating Qi and Dissipating Depression Herbs can significantly improve the depressive state of patients,promote the recovery of social function,reduce the occurrence of long-term suicidal ideation,and appropriately extend the time of taking medicine can increase the long-term efficacy and reduce recurrence.