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.

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.

Objective To provides reasonable and feasible suggestions for radiological protection to interventional staff by measuring the dose level in different auxiliary protective facilities at the standing position of interventional staff.Methods According to the characteristics of DSA equipment,451P ionization chamber tourimeter was used to measure the ambient Dose Equivalent rate at different heights of interventional staff with using different auxiliary protective equipment.The effect of radiological protection was compared between different auxiliary protective facilities.Results The dose level of double-tube exposure is much bigger than that of the single-tube exposure.The shielding effect of using a lead semen for the first surgeon is better than the second surgeon.The using of a lead screen in double-tube exposure can reduce the dose of 31％ ～ 99％ for the first surgeon and reduce the dose of 12％ ～90％ for the second surgeon.The using of a lead screen in single-tube exposure can reduce the dose of the first surgeon 4％ ～ 65％ of the dose,and reduce the 2％ ～ 30％ of the dose for the second surgeon.The dose of head,chest and abdomen of interventional staff can be significantly reduced through improving the existing auxiliary protective facilities,but the protective effect to the foot is not obvious.Conclusion The using of lead screens and improving the auxiliary protective equipment can shield the X-rays of interventional staff in varying degrees,it can protect interventional staff and reduce the radiation dose level.

Objective To calculate effective dose based on the dose-area Product (DAP) measured in dental cone beam computed tomograhic (CBCT) scanning and using a conversion coefficient.Methods The method of the DAP was used to calculate the effective dose from KODAK 9500 dental CBCT scanner with fields of view (FOV) of 16 cm×15 cm and 12 cmu×8 cm.The DAP-values (mGy · cm2) were measured using a transmission ionization chamber connected to an electrometer (Doseguard 100,RTI Electronics AB,Sweden) and the chamber was placed directly on the exit of the X-ray tube.All measurements were repeated three times and averaged on each FOV data.The conversion coefficient of 0.080 μSv/mGy · cm2 was used to estimate the effective dose on the basis of DAP values,which was quoted from a literature.Results DAP values were found between the two FAOs to vary from 512 to 1 083 mGy · cm2,and the effective doses calculated with 0.080 μSv/mGy · cm2were 41 to 87 μSv.The effective doses given in this paper was lower than those reported in other literatures.Conclusions DAP measurement was found to be well defined and easy-to-use method of determining effective dose for some CBCT Units.However,determination of specific conversion coefficient in the CBCT must be further developed.

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.

Objective To study the relationship between the nominal beam width and CTDI measurement efficiency of wide beam multi-slice spiral CT to provide data support for improving the specification for quality control testing of CT in China.Methods Dose measurements were performed on a 128 detector row CT scanner.The effect of beam widths on CTDI100 and CTDI300 was assessed for acquisitions from 5 mm to 80 mm.The CTDI100 is based on application of the readily available 150 mm long CT dose body phantoms and the 100 mm pencil ionization chamber.CTDI300 is supported by measurements with ex-tended 450 mm CT dose body phantom and a 300 mm long pencil CT ionization chamber.CTDI300 was used instead of CTDI∞ to calculate the CTDI measurement efficiency.An amended CTDI100.NT according to IEC and IAEA publications was calculated and compared with CTDI300.Results The CTDI100 measurement efficiency decreased with the increase of beam widths.The ratio of CTDI100 to CTDI300 was 0.62 from 5 am,at a beam width of 80 am,the measurement efficiency dropped to 0.56.Through the IEC and IAEA correction formula,the ratio of amended CTDI100,NT to CTDI∞ can be maintained at a relatively constant level.Conclusion The widely used CT dose index CTDI100 is lack of accuracy in evaluating the CT dose of widebeam multi-slice spiral CT.The correction formula can characterize the dose level of wide beam multi-slice spiral CT to a constant ratio.On how to accurately express and measure the dose of wide beam CT by a simple way,the international community is still on the road.

Objective To understand the recent progress of the application of Cone beam computed tomography(CBCT) in medical practice.Methods This article adopts a inductive and analytical method according to CBCT medical application range through literature review.Results This article provides performance comparisons between the CBCT and MDCT scanners and classifications for CBCT in use of medicine and evaluation of dose ranges for patients in the CBCT scanning.Finally,this article gives some problems on radiological protection in CBCT application of our country.Conclusion The use of CBCT spans has a wide range of clinical specialties and a large range for patient dose in our country.Authors provide a suggestion on making national radiological protection action plant in appropriate use of CBCT.

Objective To report estimated radiation dose to the eye lens of the interventionalist from five procedures.Methods The radiation doses to the eye lens for five interventional radiology fluoroscopic systems were measured by using OSLs (Optically Stimulated Luminescence)dosimetry calibrated in Hp (0.07).For the eyes,the OSLs are positioned to the right,left and middle sids.Meanwhile,fluoroscopy times,accumulated doses,and DAPs (Dose-Area Product) et.al were recorded for statistical analysis.Results The annual eye lens doses estimated for the operator with the highest workload according to the measurements and the system's log book were 15.12 mSv in CA(Coronary Angiography),11.59 mSv in PTCA (Percutaneous Transluminal Coronary Angioplasty) and PCI (Percutaneous Coronary Intervention),8.64 mSv in Cerebral aneurysm,36.10 mSv in Pacemaker Therapy,12.78 mSv in Radiofrequency ablation.In Pacemaker Therapy the dose of equivalent of eye lens was the highest in he five procedures.The eye lens doses were different in different procedures,fluoroscopy times,accumulated doses and DAPs.Conclusion The eye lens dose of operators in Pacemaker Therapy will receive an annual equivalence dose of more than 20 mSv as recommended by the ICRP provided by the current study.Attention should be paid to the protection of the eyes of operators.

Objective:To investigate and analyze the status of quality control of medical X-ray diagnostic equipment in Shigatse, and propose recommendations for quality improvement. Methods: Applying quality control tests to all the medical X-ray diagnostic equipment in the sampled hospitals and analyzing the results by statistic method.Results: The qualification rates of equipment for fluoroscopy, radiography and computed tomography are 80%, 40% and 50%, respectively. The qualification rates is 57.1% in all of different levels of the hospitals. Conclusion: The status of quality control of medical X-ray diagnostic equipment in Shigatse is grasped. Both of the testing of quality control and the training of the technician should be strengthened in the future, all over Tibet Autonomous Region.

目的 通过调查全国15个省市不同级别医疗机构乳腺X射线摄影曝光参数并测量计算受检者乳腺平均剂量,分析我国乳腺X射线摄影中受检者压迫后乳房厚度分布及乳腺受照剂量水平,为建立适合我国成年女性受检者乳腺X射线摄影的剂量指导水平提供依据.方法 按照《医用辐射危害评价与控制技术研究》实施方案的要求,调查临床实际乳腺摄影受检者的年龄、乳房压迫厚度、曝光参数、摄影体位等相关信息,通过手动曝光测量该条件下乳房压迫厚度处的入射空气比释动能(Ka,i),计算受检者的乳腺平均剂量(AGD).结果 共在全国15个省的149家医院调查了4372例乳腺X射线摄影体位,273台不同类型乳腺X射线摄影设备,包括屏片乳腺X射线摄影、计算机乳腺X射线摄影(乳腺CR)和直接数字乳腺X射线摄影(乳腺DR)设备,对于这三种类型的设备,头尾(CC)位投照时受检者AGD的平均值分别为1.21,1.77,1.61 mGy,AGD的75％位分别为1.36,2.22,1.81 mGy;斜侧(MLO)位时受检者AGD平均值分别为1.02,1.78,1.66 mGy,AGD的75％位分别为1.23,2.46,1.81 mGy.CC位和MLO位时乳房压迫厚度的中位数分别为4.2和4.5 cm.结论 不同类型乳腺X射线摄影设备中,屏片乳腺X射线摄影设备致受检者的乳腺平均剂量最低,其次是乳腺DR设备,乳腺CR设备致患者剂量最高.

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 refit a old movable screen fluoroscopy unit in to a new fluoroscopy unit based on image intensifier in order to improve image quality and reduce radiation dose. Methods:A SIEMENS image intensifier (type X1611,Φ210mm), WAT-120N+CCD and display units replaced a old fluorescent screen unit. According to WS76-2011and GBZ130-2013 national standards, performance comparisons between the old and new fluoroscopy unit were made to use quality control test devices and radiation dosemeters, including low and high contrast revolutions, brightness, entrance surface air kerma rate and ambient dose equivalent rate. Results:The new fluoroscopy unit has become more quality than the old fluoroscopy unit, such as low contrast revolution improved from 7 mm (4%)to 3 mm (4%), high contrast revolution from 0.8 lp/mm to 1.2 lp/mm, brightness increased 255 times. In addition, the entrance surface air kerma rate of patient and the ambient dose equivalent rate for operating position decreased 54.2%and 82%respectively. Conclusion:It was a good approach to use image intensifier instead of fluorescent screen for some small rural hospitals because some small hospitals lack the special fund to purchase modern X-ray radiography units.

Objective: To establish methods of specification of testing of quality control in direct digital radiography (DDR) system and a sets of scientific assessment standard. Methods:Based on conducted abroad literature search and referenced information from some manufacturers, it is established a sets of DDR performance measurements and assessment standards. Results: It is total 17 units of DDR from different manufacturers, including 7 foreign products and 10 home products . Each of DDR includes 13items of test parameter in which were all ested 5 units from abroad products (71%) and 6 units from home products (60%). There are 3 test paramenters with poorer pass rates, such as image retention is 64.7%pass rates, response uniformity are 76.5%pass rates and scaling errors are 76.5%pass rates. Conclusion:The 13 test paramenter with DDR were make an appropriate for the methods of measurements and the standards of assessment. A primary problem is the lack of one or several test paramenters for some of manufacturers. It was recommended them to improve this situation.

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.

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 investigate the difference of image quality between automatic exposure control (AEC) and manual exposure in CR digital mammography, and to observe the effect of image post-processing on improvement of image quality and dose reduction. Methods: CDMAM 3.4 phantom and TORMAM phantom were selected and exposed in a CR system in 5 different phantom thickness. Under each thickness there were 4 dose levels (once automatic and 3 times manual exposures, which corresponded to 80%, 60% and 40% dose). Three observers interpreted all the images. Each image was scored twice with unprocessed images and post-processed image. The differences of image quality were compared between 3 lower dose images and 100% dose image. Results: The results of image quality figure (IQF) of CDMAM phantom showed the image quality of post-processed images were higher than unprocessed images. Part of the lower dose images exceeded AEC dose image in image quality through post-processing. The dose decreased from 20% to 60% through image post-processing in different equivalent breast thickness. From the results of TORMAM phantom, for the detection of filament details and circular details, the scores increased after post-processing (P<0.001). However for the partical details, the effect of image post-processing on image quality was not obvious (P=0.74). Conclusion: In CR digital mammography, the image quality can be improved through image post-processing. Radiation dosage can decrease through the image post-processing without reduce of image quality.

Based on a high dose rate afterloading radiotherapy,the γ radiation level at inner entrance of the maze and the first transition in inner entrance of the maze as well as the outer entrance of the maze were calculated,and the influence of source's location to the distribution of radiation level in the maze was analyzed through a monte-carlo code,whose reliability was tested by comparing with the results measured on-site.Results show that the radiation level in the maze strongly depends on the location of radioactive source in the treat room,and reach to a relatively lower level when the source locates at the east of treat room and close to the maze wall which can be recommended as an optimized location for source when executing the therapy.

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 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.

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.