Influence of photographic conditions in full field digital mammography on radiation dose and image quality in patients with dense breasts / 中华放射学杂志

ABSTRACT

Objective To investigate the radiation dose delivered to the patients with dense breasts and the influence of photographic conditions on image quality in full field digital mammography (FFDM).Methods (1) Clinical testwe analyzed the compression thickness of breasts,Target-filter(T-F),voltage current (kV),tube current (mAs),average glandular dose (AGD) and entrance surface dose (ESE) of 100 patients (a total of 370 images,277 images of Molybdenum-Rhodium(Mo-Rh)and 93 images of Wolfram-Rhodium (W-Rh)) who underwent examinations in mode of automatic exposure by FFDM with dense breasts.(2) Phantom experimentsplaced the Aluminium plate on different thickness of polymethyl methacrylate (PMMA) plates to simulate the dense breasts.68 mm phantom was used to simulate photographic condition of W-Rh and 58 mm to Mo-Rh.The two groups of dense phantom were exposed automatically and manually.The parameters were recorded for each exposure including the compression thickness of breasts,T-F,kV,mAs,AGD,ESE,the calculation of the ratio between ESE and AGD (ESE/AGD).The image quality figure inverse (IQFInv) was obtained by software.To the clinical test,used multiple factors of variance to analyze the influence of compression thickness and mAs on AGD and ESE,Pearson correlation and regression to analyze the influence of compression thickness on ESE/AGD.To the phantom experiments,used Pearson correlation to analyze the influence of kV and mAs on AGD,ESE and ESE/AGD,single factor of variance to analyze the influence of kV and mAs on IQFInv.Results (1) Clinical testto Mo-Rh and W-Rh,with the increase of compression thickness,ESE/AGD was increased significantly.Compression thickness had linear relationship with ESE/AGD.Pearson correlation coefficients of W-Rh and Mo-Rh were 0.956 and 0.980,respectively(P＜0.01).The effects of compression thickness and mAs on AGD and ESE were statistically significant (P＜0.05) in the two groups.(2)Phantom experimentsadjusted exposure parameters to the two dense phantoms of W-Rh and Mo-Rh.With the increase of mAs and kV,IQFInv was increased in W-Rh and Mo-Rh.Different mAs and kV were statistically significant (P＜0.05) on IQFInv,mAs and kV had positive correlation with ESE and AGD (P＜0.05),mAs and kV had different correlation with ESE/AGD in the two dense phantoms.Conclusions In mode of automatic exposure by FFDM,choosing W-Rh can achieve relatively high image quality and lower radiation dose.According to the results of phantom experiments,adjusting kV and mAs properly in manual exposure can reduce AGD and ESE effectively and ensure the quality of the image.