Latest development of operational quantities and their impact / 中国辐射卫生

@#With the utilization of more types of radiation with a wider energy range, the application scope of the currently valid operational quantities is limited due to some conceptual defects, so a new group of operational quantities was proposed recently by the International Commission on Radiation Units and Measurements. The unification of protection quantities and operational ones is achieved in conceptual and physical sense. However, to achieve the comprehensive application of these new operational quantities in China, such preliminary work should be done as computational model construction and built-in of a calibration system in monitoring equipment, which depends on the collaborative development of multi-parties.

Research progress on new operational quantities and the effects in area dose monitoring / 中国辐射卫生

@#Operational quantities, which are used to estimate protection quantities in the field of radiation protection, are important in area monitoring. The current operational quantities show certain limitations as the particle types and energy ranges are expanded. The International Commission on Radiation Units and Measurements Report 95 proposed a new system of operational quantities, where the definitions and phantoms of the operational quantities are consistent with the protection quantities, enabling better estimation of the protection quantities over wider ranges of particle types and energies. This paper focuses on the effects of the new recommended operational quantity system in area monitoring from the aspects of phantom application, conversion coefficient updating, and monitor design and calibration.

Investigation and analysis on entrance surface dose of patients in radiography procedures in China / 中华放射医学与防护杂志

Objective To investigate the entrance surface dose to the examined patients in radiography using digital and screen-film system in hospitals at different levels in 15 provinces and municipalities in China,in order to provide data for developing diagnostic reference level of radiography suitable for our national physical characteristics.Methods According to the requirements of the Technical Study on Medical Radiation Hazard Assessment and Control,the examined patients aged 20-70 years were selected,with body weight ranging from 55 to 80 kg for male and 50 to 70 kg for female.TLDs were used to measure the entrance surface dose to adult patients in radiography.No less than 10 examined patients were required at each body position,with examined locations including head (PA,LAT),chest (PA,LAT),abdomen (AP),pelvis (AP),lumbar (AP,LAT),and thoracic vertebra (AP,LAT).Results A total of 19 975 individuals undergoing radiography and 1 813 radiographic equipment of different types including screen-film radiography,computed radiography (CR) and digital radiography (DR),were investigated in 342 hospitals in 15 provinces and municipalities throughout the country.For these three types of equipment,the average entrance surface dose to the examined were 1.75,1.9,and 1.15 mGy in head (PA),1.69,1.46and 1.03 mGy in head (LAT),0.75,0.65 and 0.36 mGy in chest (PA),1.81,1.26 and 0.88 mGy in chest (LAT),4.37,3.77 and 2.15 mGy in abdomen (AP),3.73,3.56 and 2.75 mGy in pelvis (AP),5.49,5.84 and 4.17 mGy in lumbar (AP),12.01,9.37 and 6.82 mGy in lumbar (LAT),4.53,3.65 and 2.49 mGy in thoracic vertebra (AP),and 6.91,6.43 and 4.15 Gy in thoracic vertebra (LAT).Conclusions Entrance surface dose caused by radiography examination varies dependent on different exposure locations.Entrance surface doses caused by digital radiography are all lower than by screen-film radiography;those caused by digital radiography are lower than by computed radiography,except for thoracic vertebra (AP).In all examinations,no difference of statistical significance is found between CR and screen-film radiography in entrance surface dose.

Investigation and analysis on the dose of the subjects in CT scanning in China / 中华放射医学与防护杂志

Objective To investigate the CT scanning parameters in hospitals at different levels in 15 provinces and cities in China and the doses to patients undergoing CT examination,in order to provide the basis for establishing CT diagnostic reference level suitable for our country.Methods As required in the implementation program for Technical Study on Medical Radiation Hazard Assessment and Control,the information on the patients examined and the CT scanning parameters in clinical practices were investigated.The CT dose index (CTDI100,CTDIW,CTDIVOL) of CT scanner was measured by using the CT ionization chamber.The dose length product (DLP) was calculated on the basis of the scan length of the patients examined.Results A total of 6 524 CT scanning procedures and 483 different types of CT scanning equipment were surveyed in 166 hospitals in 15 provinces in China.For head,chest,abdomen,and lumbar vertebrae,the average weighted CTDIW were 43,15,19 and 25 mGy,respectively,and the third quartile of CTDIw were 50,19,23 and 32 mGy,respectively.The average DLP were 540,397,503 and 376 mGy· cm,respectively.The third quartile of DLP were 659,525,632 and 479 mGy· cm respectively.Conclusions Through this survey,the doses to CT-examined patients in some provinces were basicly ascertained.The third quartile of doses to four body parts of the examined patients are different from the diagnostic reference level given in publications in other countries and regions.It is important to establish the CT diagnostic reference level suitable for our CT-examined patients according to Chinese national physical characteristics and therefor to promote the optimization of medical radiation protection in CT examination.

Assessment of radiation dose in dual energy X-ray absorptiometry scanner / 中华放射医学与防护杂志

Objective To evaluate the radiation dose from a dual energy X-ray absorptiometry (DXA) study. Methods A Radcal multifunctional dosimeter (1800 cc ionization chamber, USA) was used, for purpose of comparison, to measure the entrance surface doses (ESD) from Norland XR-800 DXA ( pencil beam scan, 100/46. 8 kVp, 1. 3 mA) and from Hologic Discovery A DXA ( fan beam scan, 140/100 kVp, 5. 0 mA) . Ambient dose equivalent rate at 1 m away from studied phantom center and at 1 m above floor was measured using the US 451P ionizaion chamber survey meter ( Fluke, USA). Results The ESD measured using a Radcal dosimeter for Norland XR-800 DXA was 0. 43 μGy in high speed mode and 0. 73 μGy in standard mode ( AP spine ) , 1. 93 μGy ( hip ) , 0. 40 μGy ( wrist ) and 1. 06 μGy ( mandible) . The ESD measured for Hologic Discovery A DXA was 65. 6 μGy ( AP spine) and 63. 9 μGy ( hip) . The ESD measured for Norland XR-800 at different scan types and scan speeds was <2 μGy while Hologic Discovery A DXA showed a result of <66 μGy ( AP spine and hip scan ) , which were both consistent with the data given in their own respective operational manual. A comparison of DXA scanners with fan beam and pencil beam indicated that ambient equivalent dose rate, measured with 451P survey meter, from fan beam scan was 65 times that from pencil beam scan. Conclusions Compared with other medical X-ray studies, the ESD to the phantom undergoing a DXA study is relatively low. DXA pencil beam scan doses to lumbar spine and hip were about 1/153-1/33 of those from DXA fan beam scan. Pencil beam scan dose to DXA staff was negligible and fan beam scan dose to DXA staff was lower than the personal dose limits of 20 mSv per year.

Evaluation performance of calibration apparatus for dosimeters used in X-ray mammography / 中华放射医学与防护杂志

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.

Comparison of dosimetric characteristics of two radiochromic films (XR-RV3 and EDR2) / 中华放射医学与防护杂志

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.

Peak skin dose measurements in two cardiac interventional procedures using radiochromic film / 中华放射医学与防护杂志

Objective To measure the peak skin dose (PSD) in two cardiovascular interventional procedures,including coronary angiography (CA) and percutaneous transluminal coronary angioplasty (PTCA) using radiochromic film.Methods Gafchromic XR-RV3 film was selected to measure PSD in two hospitals.The films were placed on the table underneath the patient during interventional surgery.The kV,mA,fluoroscopy time,dose-area product (DAP),and cumulative dose at reference point and other relevant information were recorded for all cases.Using the Epson V750 flatbed scanner for scanning and analyzing film,FilmQA software was chosen to analyze the pixel value of red,green and blue color channels.The PSD was determined using red channel data.The correlation and linear regression analysis between PSD and device-displayed parameters was carried out.Results PSD were measured using XR-RV3 film for 26 CA and 19 CA + PTCA procedures.For CA procedures,maximum fluoroscopy time,cumulative dose and DAP were 17.62 min,1 498.50 mGy and 109.68 Gy · cm2,respectively.The maximum PSD was 361.20 mGy.However,for CA + PTCA procedures,maximum fluoroscopy time,cumulative dose and DAP were 64.48 min,6 976.20 mGy and 5 336.00 Gy· cm2,respectively.One patient with CA + PTCA procedures was found to have received the PSD value more than 2 Gy,up to 2 195.70 mGy.DAP was found to be a good indicator (R2 =0.815,P ＜0.05) of PSD for CA procedure,and correlated with cumulative dose (R2 =0.916,P ＜ 0.05) for CA + PTCA procedures.Conclusions The PSD value of some patients in cardiac interventional procedures would exceed 2 Gy,the threshold of deterministic effects recommended by ICRP.The dose-related parameters value showed on DSA device can only used to estimate PSD roughly.Using XR-RV3 film accurate measurement of the PSD in interventional projects is a very fast and effective method.

Research of angular dependence of mammographic dosimeters / 中华放射医学与防护杂志

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.

Human reliability in high dose rate afterloading radiotherapy based on FMECA / 中华放射医学与防护杂志

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.

Study on application of human cognition reliability model in human error in emergency response against the source blockage of high dose rate afterloading unit / 中华放射医学与防护杂志

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.

Development of measurement method using TLD for workers occupation personally exposed to 125Ⅰ seed source in the implant / 中华放射医学与防护杂志

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.

Failure mode, effects and criticality analysis research on human factors in clinical PET application / 中华放射医学与防护杂志

Objective To identify the steps with potentially higher risk through the analysis of human factors in clinical PET application so as to provide the efficient measures to reduce the risk of potential exposures.Methods The basic data were obtained through field investigation, questionnaire,failure mode, risk identification, FMECA and expert's evaluation, with statistical analysis made.Comparison was made of the relative risk values of automatic encapsulation equipment and manual encapsulation ones.Results The 10 steps with potentially higher risks were identified through analyzing human factors of clinical PET application, of which 8 occurred in the phase of chemical synthesis.The measures to control risk were addressed for the steps with higher risk.The results show that the relative risk value of the clinical process with automatic encapsulation equipment was 2.28 ± 0.99 and the one with manual encapsulation equipment was 3.20 ± 2.01 ( t = 2.56, P ＜ 0.05 ), with the latter being 76% of the former.Conclusions Failure mode and FMECA are effective in risk evaluation of clinical PET application, which can provide important basis for risk control.

Energy dependence of three passive solid detectors on low energy X-ray / 中华放射医学与防护杂志

Objective To assess the feasibility of ESD measurements in the mammography by the comparative study of energy dependence of the three passive solid detectors on low energy X-ray.Methods Two thermoluminescent TL) detectors ( LiF(Mg,Ti) and LiF( Mg,Cu, P) and one optically stimulated luminescence (OSL) detector( Al2O3: C ) were irradiated for the same air kerma by ten kinds of beam quality between 25-40 kV in a Mo/Mo low energy X-ray generator,respectively. Results The energy dependences of TL and OSL were 25% and 11% between 25-40 kV, respectively. Conclusions considerable potential for OSL detector can be used in routine quality control and ESD measurements in the mammography.

Comparison of the energy response for several dosimeters used in mammography / 中华放射医学与防护杂志

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.