0.05).However the MMP-2 and pro MMP-2 concentrations were still higher 30 d after implantation(13 935?2 167,15 628?1 739 INT?mm~2 vs 11 568?2 219,13 649?1 894 INT?mm~2,P

Objective To evaluate whether eight kinds of dosimeters satisfy the clinical mammography dose measurement through the comparison of energy response.Methods According to GB/T 19629-2005,the energy responses of eight available mammography dosimeters were determined for ten standard radiation qualities in the range 25-40 kVp at the SSDL using a refrence-class dosimeter.Results Except 2000S,the energy response factors of all the other dosimeters were consistent within ±5%.Conclusions The energy response of ionizing chamber type is better than other types of dosimeters.

Objective To fulfill the requirements for uncertainty of the calibration apparatus for dosimeters used in X-ray mammography through setting standard radiation quality at the SSDL and developing calibration procedures.Methods According to IEC 61267-2005 and IAEA TRS No 457 to recommend RQR-M and RQA-M series standard radiation quality,the calibration apparatus was evaluated for long term stability of the radiation field over 8 years from 2006 to 2014,including 10 response quantities,such as field homogeneity,change rate of mean air kerma and scatter radiation contributions and so on.In addition,the reference dose instrument was traced back to the PSDL of PTB in Germany by post during 2008 and 2012.Results The field homogeneity (φ 40 mm) relative error was ± 1.4％.The long term stability of the calibration apparatus was less than ± 2％ (limits of variation).The scatter radiation contributions at their points of test were below 0.12％.The calibration factors traced to PTB were 0.999-1.000.As a result of the calibration apparatus,the expanded uncertainty was ± 3％ (k =2,95％ confidence interval).Conclusions The calibration apparatus may meet the requirements of IEC 61267-2005 and IAEA TRS No 457 and has obtained the license of metrology from national regulatory authority.The laboratory now performs very well to calibrate dosimeters used in X-ray mammography.

Objective To study the method of measuring air kerma strength of afterloading units with 192Ir source by using well type ionization chamber.MethodsThe air kerma strength of 30 afterloading units with 192Ir source was measured using 2000A electrometer and 1000 plus well type ionization chamber,and apparent activity of the source was calculated with the air kerma strength and apparent activity conversion factor.The measured activity of the source was compared with the original value of the source provided by the manufacturer,and the relevant deviation should be within ± 5%.Results Theair kerma strength of afterloding units with 192Ir sources was tested.The relevant deviation of the measured activity and the original value was within -0.1%-4.4%.Conclusions The measurement method with a well type ionization chamber is convenient and highly accurate which can be used for the test of quality control in hospitals.

Objective To study the angular dependence of four different mammographic dosimeters to monoenergetic X-ray beams and observe the variation tendency in angular dependence to different energy X-rays and to discuss the evaluation of average glandular dose(AGD)in digital breast tomosynthesis(DBT)system.Methods One ionization chamber and three semiconductor dosimeters were exposed by four kinds of beam quality.The signal of each dosimeter was tested over an angular range of 0° to 90°.The dosimeters were exposed for three times at each selected angular position.The measurement at each angle was normalized to the appropriate measurement at perpendicular incidence.Results The responses from all the dosimeters had a maximum at 0° and decreased with increasing angles.When the radiation incidence angle was 10°,the angular dependence were 0.99,0.99,0.96 and 0.96 for dosimeters A,B,C and D,respectively.And the angular dependence decreased to 0.96,1.00,0.78 and 0.52 when the incidence angle was up to 25°.For semiconductor dosimeters,no signal was recorded when incidence angle was beyond 45°.For ionization chamber,the magnitude of the angular dependence generally decreased with increasing energy.Conclusions All of the dosimeters will underestimate the dose if used in DBT.In order to minimize the error due to the rotation angle of X-ray tube,correction factor of mammography dosimeter should be used for the measurement of AGD in DBT systems.

Objective To study the dosimetric characteristics of two different radiochromic films used to estimate peak skin dose(PSD) of patients.The characteristics of these two films were investigated and compared after exposure to ionizing radiation in the diagnostic energy range,including post-exposure gray growth,sensitivity,energy dependence and dose response.Methods GafChromic XR-RV3 film and KODAK EDR2 film were exposed to air kerma 800 mGy free-in-air using five X-ray beam qualities (60,80,100,120 and 140 kVp) in a SSDL.The measurement for each energy was normalized to 80 kV to analyze energy dependence of films.The films were calibrated to different dose level (0.025-10 Gy) onphantom by 80 kV X-rays.The response curve were plotted to analyze sensitivity and dose response.The films were scanned with Epson V750 commercial flatbed scanner.Color channel analysis was performed.Results The post-exposure gray growth of XR-RV3 film was found to be fairly stable.The change were 2％,4％,6％ at 24 h,72 h and 6 weeks after exposure respectively.EDR2 film was found to be more sensitivity than XR-RV3 film in low dose.The energy response of the XR-RV3 film and EDR2 film were within 9％ and 23％ over the clinical diagnostic x-ray energies,respectively.In the dose range of 0.025-10 Gy,for the XR-RV3 film,the red channel with the dose response curve was most obvious.For EDR2 film,the pixel value of three color channels was coincident.The EDR2 film appeared to be saturated when receiving doses greater than 500 mGy.Conclusions The XR-RV3 film is superior to EDR2 film in gray growth,energy dependence,dose-response and other aspects.This film is very suitable for measuring and analyzing PSD of patients in interventional radiology procedures.

Objective To put forward reasonable and feasible recommendations against the procedure with relative high risk during the high dose rate (HDR) afterloading radiotherapy,so as to enhance its clinical application safety,through studying the human reliability in the process of carrying out the HDR afterloading radiotherapy.Methods Basic data were collected by on-site investigation and process analysis as well as expert evaluation.Failure mode,effect and criticality analysis (FMECA) employed to study the human reliability in the execution of HDR afierloading radiotherapy.Results The FMECA model of human reliability for HDR afterloading radiotherapy was established,through which 25 procedures with relative high risk index were found,accounting for 14.1％ of total 177 procedures.Conclusions FMECA method in human reliability study for HDR afterloading radiotherapy is feasible.The countermeasures are put forward to reduce the human error,so as to provide important basis for enhancing clinical application safety of HDR afterloading radiotherapy.

Objective To explore the method for measuring and calculating both absorbed dose and effective dose received in organ and tissues of occupational workers by using TLDs for the implantation of 125Ⅰ seed sources.Methods The experiments with 60Co γ-rays were carried out for the stability.A group of TLD chips was exposed to 125Ⅰ seed sources to establish standard dose curve for air kerma.During the 125Ⅰ seed implantation, the TLD chips were pasted to 13 locations like thyroid inside and outside the lead aprons worn by occupational workers to measure average absorbed dose and calculate the absorbed doses and effectives to organs and tissues.Results For 3 cases of prostate cancers with implantation of 125Ⅰ seeds, the worker's organs and tissues received the absorbed dose 0.02 -3.80 μ Gy and effective dose 0.06- 1.81 μSv outside lead aprons and the highest absorbed dose 2.35 μ Gy and effective 0.02 μSv inside lead aprons, respectively, with more than 65.9% of rays shielded.For 3 cases of brain cancers with implantation of 125Ⅰ seeds, the workers received the absorbed dose 0.23 - 11.31 μGy and effective dose 0.88 - 4.07 μSv outside lead aprons and the highest absorbed dose 2.22 μ Gy and effective dose 0.09 μSv inside lead aprons, respectively, with more than 54.5% of rays shielded.For 3 cases of lung cancers with implantation of 125Ⅰ seeds, the workers received the absorbed dose 0.03 - 14.78 μGy and effective dose 0.35 -7.59 μSv outside lead aprons and the highest absorbed dose 4.09 μGy and effective 0.22 μSv inside lead aprons, respectively, with more than 58.4% of rays shielded.For 2 cases of mediastinum cancers with implantation of 125Ⅰseeds, the workers received the absorbed dose 0.06 - 74.91 μGy and effective dose 0.83 - 17.96 μSv outside lead aprons and the highest absorbed dose 10.29 μGy and effective 0.5 μSv inside lead aprons, respectively, with more than 85% of rays shielded.For one case of ovary cancer with implantation of 125Ⅰ seeds, the worker received the absorbed dose 0.09 - 14.29 μGy and effective dose 2.40 - 4.50 μSv outside lead aprons and the highest absorbed dose 7.77 μGy and effective 0.12 μSv inside lead aprons, respectively, with more than 34% of rays shielded.For one case of eye cancer with implantation of 125Ⅰ seeds, the workers received the absorbed dose 2.2 -39.84 μGy and effective dose 4.48 - 10.06 μSv outside aprons and the highest absorbed dose 5.19 μGy and effective 0.16 μSv inside aprons, respectively, with more than 54.6 % of rays shielded.Conclusions The method of using TLDs to measure the doses to the occupational workers in the course of the implantation of 125Ⅰ seed sources is simple and easy to operate.It would be an effective approach to protecting medical workers in the case of brachytherapy.

Objective To put forward reasonable and feasible recommendations aiming at enhancing the application safety of afterloading unit, through studying the human reliability in the emergency response against the source blockage of afterloading unit.Methods Based on the human cognition reliability model, ten operation errors during the emergency response against the source blockage of afterloading unit were analyzed and permissible time widow of emergency response operation were determined.The human error probability was calculated with the execution time of emergency response operation obtained through simulation, observation and recording.Results The operation action, relevant permissible time window and execution time were obtained with the corresponding human error probabilities in the range 0.04 - 0.27.Conclusions The human error model in emergency response against the source blockage of afterloading unit based on HCRmodel is feasible, and provides important reference basis to reduce the occurrence of potential exposure and mitigate the consequence of potential exposure.

Objective To carry out the quality control testing and evaluation for three digital mammography systems.Methods The performance of three digital mammography systems was assessed by applying methods recommended in the European guidelines for quality assurance in breast cancer screening and diagnosis and Chinese specification for testing of quality control in X-ray mammography.The performance of X-ray generator of three digital mammography systems were tested and evaluated.CDMAM 3.4 phantom with four different thickness(30,40,50,60 mm) were exposured in DR,PCM,and CR system,respectively.The average glandular dose (AGD) value was measured and image quality figure (IQF) analysis was performed in each thickness.Results The X-ray machine performance of DR and CR was in accordance with existing standard,however the standard was inappropriate to evaluate part of X-ray machine performance of PCM system.The AGDs for system DR were 1.20,1.42,1.75 and 2.20 mGy for 30,40,50 and 60 mm PMMA thickness,respectively.The respective AGDs for system PCM and CR were 0.82,1.19,1.33,1.70 mGy and 0.59,0.88,1.47,2.19 mGy.For the same phantom thickness sequence,the IQFs were 21.36,21.57,27.25 and 30.58 for system DR,28.02,29.10,35.90,and 41.24 for system PCM,whereas they were 39.78,39.30,43.85 and 48.08 for system CR.Conclusions The AGDs of all three systems were in accordance with the values recommended in European guideline.The AGD and IQF could provide an effective way for performance assessment and constancy checks for digital mammography systems.