Study on correlation between exposure dose and image quality of X-ray chest radiography

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. (authors)