Investigation of optimum exposure dose for chest imaging using CR and amorphous silocon DR system

Objective To compare the difference of entrance dose between CR and amorphous silocon DR system in chest imaging, and to discuss their optimum exposure dose. Methods For CR and DR, different entrance dose was measured by dosimeter in chest phantom. The value of IQFinv was analyzed by CDRAD2. 0 software. Image quality difference between CR and DR was assessed by group t-test. The relationship between image quality and entrance dose was tested by using Pearson correlation analysis. The best IQFinv values in CR and DR system were achieved via ROC curve analysis, and the exposure dose was then calculated. Results There were direct correlation values between entrance dose and the value of IQFinv in CR and DR system, respectively( r =0. 893 ,0. 848 ,P < 0. 01 ) . The linear regression equation for DR was IQFinv =0. 0050 +3. 359, and for CR was IQFinv =0. 005D + I. 651 , where D was entrance dose. The difference of IQFinv value between CR and DR was significant(t = 5. 455 ,P < 0. 05). The best IQFinv value of the two groups from ROC analysis was 3.55. Conclusions With the entrance dose increased, the detection ability of contrast-detail was elevated in the two digital radiography systems. With equal entrance dose, the detection ability of DR in contrast-detail was superior to CR. With equal image quality, DR obviously decreased the radiation dose to the patients. Key words: Digital radiography; Image quality; Exposure dose; Quality control