Correlation study of effect of additional filter on radiation dose and image quality in digital mammography

Objective To explore the effect of different additional filters on radiation dose and image quality in digital mammography.Methods Hologic company's Selenia digital mammography machine and the post-processing workstations and 5 M high resolution medical monitor were used in this study.Mammography phantoms with the thickness from 1.6 cm to 8.6 cm were used to simulate human breast tissue.The same exposure conditions,pressure,compression thickness,the anode were employed with the additional filters of Mo and Rh under the automatic and manual exposure mode.The image kV,mAs,pressure,filter,average glandular dose (AGD),entrance surface dose (ESD),signal-to-noise ratio (SNR),contrast-to-noise ratio (CNR) and image score according to ACR criteria were recorded for the two additional filters.Paired sample t test was performed to compare the indices of Mo and Rh groups by using SPSS 17.0.Results AGD and ESD of Rh and Mo group were both higher with the increase of the thickness of all the phantoms.AGD,ESD and their increased value of Rh filter(1.484 ± 1.041,7.969 ± 7.633,0.423 ± 0.190 and 3.057 ± 2.139) were lower than those of Mo filter(1.915 ± 1.301,12.516 ± 11.632,0.539 ±0.246 and 4.731 ± 3.294),in all the phantoms with different thickness (t values were 4.614,3.209,3.396 and 3.605,P ＜0.05).SNR,CNR,and image score of Rh and Mo group both decreased with the increase of the thickness of all the phantoms.There were no statistical difference (P ＞ 0.05).Conclusions Compared with Mo filter,Rh filter could reduce the radiation dose,and this advantage is more obvious in the thicker phantom when the same image quality is required. Key words: Mammography;  Radiation dosage;  Comparative study