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ObjectiveTo reduce the effective dose and maintain the image quality by adjusting the image processing parameters in the lumbar spine examinations.Methods This study investigated the influence of image processing parameters on image quality of Philips DR system by evaluating image quality of CDRAD 2.0 phantom.The parameters include detail contrast enhancement,noise compensation,unsharp masking and unsharp masking kernel.The entrance surface dose of phantom was measured by solidose meter.A synthetical parameters optimization project was proposed by analyzing the results of the investigation.This project was also testified by phantoms.ResultsImportant effects were the main effects of DCE,unsharp masking and kernel at the clinically used tube potential of 70 kVp( F =91.45,373.79,429.88,P ＜ 0.05).These effects indicated an increase of the 1QF about 20 units with increasing unsharp masking,while an increase of DCE and kernel led to decrease of IQF about 10 and 21 units.When the tube potential was increased to 85 kV,keeping the settings of the process parameters unchanged,the IQF increased.The results showed statically significant difference ( t =5.31,P ＜ 0.05 ).ConclusionIt is possible to lower the effective dose to the patient by the use of a higher tube potential and maintain a good image quality,and it will have little influence on clinic diagnosis through the most optimal setting of the process parameters.
RESUMEN
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.