ABSTRACT
Objective To investigate optimal radiation dose for digital radiography by researching the correlation between radiation dose and image quality of high kV chest radiography.Methods The kV of chest radiography was setted on 120 kV while mAs was changed.The chest radiography phantom and the contrast detail phantom CDRAD2.0 were exposed by DR with different mAs from 1 to 25 mAs.The entrance doses were measured for all exposures and the images were read independently by 5 observers on a higher resolution monitor of diagnosis work station.The image quality figure (IQF) was measured for each image.Comparison of the mean IQFs with different exposure doses were conducted in order to determined which was the optimal exposure condition for high kV radiography.The image quality of normal adult using different mAs,4 and 10 mAs for high KV chest radiography was compared.Results When the mAs was increased from 1 to 25 mAs,the entrance doses varied from 0.067 to 1.468 mGy.With the entrance doses increasing,the value of IQF was decreased (F =31.00,P ＜ 0.05).The values of IQF were statistically different between 1 and 4 mAs(F =15.3,P ＜0.05),and between 10 and 25 mAs(F =9.74,P ＜0.05).At 4 and 10 mAs with the entrance dose 0.250 and 0.606 mGy,the synthesis score of chest high kV radiography from two kinds of exposure dose was (24.8 ± 1.64),(25.8 ± 2.05),with no statistically significant difference.Conclusions For digital radiography,increasing radiation dose can improve image information.The optimal entrance dose of high kV chest radiography for standard body was about 0.250 mGy.
ABSTRACT
Objective To study the relationship between the selection of tube tension in digitalchest radiograph and image quality.Methods When tube current was fixed at 4 mAs, the choice of X-ray tube voltage changed from 60 to 120 kV.CDRAD2.0 contrast details phantom and normal human chest were exposed by X-ray system with 7 kinds of tube voltage (the difference between tube voltage was 10 kV) ,and the X-ray incidental dose of phantom surface was measured.Five radiologists with 3 years working experience evaluated the image quality on monitor and calculated the image quality factor (IQF) and image reading score.Statistics analysis was then performed by using ANOVA test and t test.According to the results, the optimum tube voltage range was determined.Results (1) The incidental dose of phantom surface increased with the higher tube voltage.(2)When the tube voltage was changed from 60 kV to 120 kV, the IQF value observed in CDRAD2.0 phantom image on monitor was 75.0±10.4,57.1±6.4,52.7±2.5,47.9±4.5, 46.0±3.8,46.0±2.8,45.2±3.5 ,there was significant statistical differences between groups(F=19.10, P<0.01).(3)The integrated score of the chest image quality in the tube voltage 90 kV and 120 kV were 12.4±0.9 and 13.0±0.7, respectively, and there was no statistical difference between two groups(t= 1.500,P>0.05).Conclusions (1)With the increase of tube tension,the display capacity of display device gradually strengthened.When the tube tension exceeded 90 kV, the increase of image quality on monitor was not evident.(2) With proper radiation dose, the value of tube tension in digital X-ray chest photograph was about 90 kV.
ABSTRACT
Objective To explore the relationship between image quality and different exposure intensity of digital radiography(DR).Methods Using a contrast-detail phantom Cdrad 2.0,observers evaluated images on the monitots when exposure parameters were 90 kV and mAs ranged from 0.5 to 16.0 mAs.Then calculate image quality figure(IQF),and ANOVA was used to analyze the difference of IQF under different radiation dose in 8 subjects.Results (1)When exposure parameters were 90 kV and mAs altered from 0.5 to 8.0 mAs.the IQF observed on the monitor was reduced,and the minimal value was 38.54±2.82.When mAs changing from 8.0 to 16.0 mAs.IQF observed on the monitor was increased,and the maximum was 44.33±2.35.(2)Under the different exposure condition,the difference of IQF values were statistically significant(F=60.35,P＜0.01).Conclusions With the increased exposure intensity,the image quality on monitor increased.When mAs was 8.0 mAs,image quality was the optimum When mAs was more than 8.0 mAs,the image quality on monitor reduced.
ABSTRACT
Objective To test and analyse the characteristics of double three field iono chamber developed by ourselves. Methods We tested the time characteristic, dose rate characteristic and X ray quality characteristic by using direct test method, and current characteristic, voltage characteristic and thickness characteristic of double three field iono chamber by using photograph test method with NERO 6000B test meter, RF 500 mA X ray equipment and so on. The results were analysed. Results The time characteristic and dose rate characteristic had satisfied linear scales(the return coefficients of linety scales were R =0.999 61 and R = 0.998 88 respectively). The X ray quality characteristic was steady (the maximum output variation was ? max ≤?5%). The good characteristics of current, voltage and thickness were found(the maximum variations of film density were ?D max ≤?0.01, ?D max ≤?0.15 and ?D max ≤?0.06 respectively). The excellent repeat was showed (repeating error of exposure time and dose were ?T max ≤?0.004 s and ?X max ≤0.01?10 -5 C/kg). Conclusion The performace of the new Iono chamber is excellent and steady, so it has practical value.
ABSTRACT
Objective To compare and analyze the performance indexes and the imaging quality of the home and imported X-ray machines through testing their partial imaging performance parameters. Methods By separate sampling from 10 home and 10 imported X-ray machines, the parameters including tube current, time of exposure, machine total exposure, and repeatability were tested, and the imaging performance was evaluated according to the national standard. Results All the performance indexes met the standard of GB4505-84. The first sampling tests showed the maximum changing coefficient of imaging performance repeatability of the home X-ray machines was ?max1=0.025,while that of the imported X-ray machine was ?max1=0.016. In the second sampling tests, the maximum changing coefficients of the two were ?max2=0.048 and ?max2=0.022, respectively. Conclusion The 2 years′ follow-up tests indicate that there is no significant difference between the above-mentioned parameters of the elaborately adjusted home X-ray machines and imported ones, but the home X-ray machines are no better than the imported X-ray machines in stability and consistency.
ABSTRACT
Objective To design an automatic exposure control circuit for X ray equipment to improve the performance of equipment and the quality of film. Methods The device acted in series control. During exposuring process,the X ray reaching the film through patient body was measured by ray sensor. After it was treated with integration, amplification and contrast management,the signal of X ray quantity drived the device to cut off exposure circuit, so that the exposure time was automatic any controlled. Results The effect of the device has been proved by its application in several hospitals. Conclusion The device is simple and effective and has practical value.
ABSTRACT
This paper introduces the digital stopwatch designed by our lab for teaching and experiment of medical imaging specialty.Its design idea,principle and configuration are discussed in detail.