Comparison of anode/filter combinations in digital mammography with respect to the average glandular dose.
OBJECTIVE
To investigate the average glandular dose (AGD) applied for clinical digital mammograms acquired with the anode/filter combinations molybdenum/molybdenum (Mo/Mo), molybdenum/rhodium (Mo/Rh), and tungsten/rhodium (W/Rh).


METHODS
Using the method of Dance, the AGD was evaluated from the exposure data of 4867 digital mammograms at two sites equipped with a full-field digital mammography (FFDM) system based on an amorphous selenium detector. 1793 images were acquired and analyzed with Mo/Mo, 643 with Mo/Rh, and 2431 with W/Rh.


RESULTS
In the Mo/Mo cases the mean compressed breast thickness was 46 +/- 10 mm with an average AGD of 2.29 +/- 1.31 mGy. For the Mo/Rh cases with a mean compressed thickness of 64 +/- 9 mm, we obtained 2.76 +/- 1.31 mGy. The W/Rh cases with a mean compressed thickness of 52 +/- 13 mm resulted in 1.26 +/- 0.44 mGy. The image quality was assessed as normal and adequate for diagnostic purposes in all cases.


CONCLUSIONS
Applying a W/Rh beam quality permits the reduction of the patient dose by approximately 50 % when using an FFDM system based on amorphous selenium. The dose reduction becomes larger as the breast thickness increases. The results are in agreement with simulations and phantom studies known from the literature.
Uhlenbrock
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Radiologie, Gemeinschaftspraxis für Radiologie und Nuklearmedizin, Erlangen.
Mertelmeier
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D000368:Aged; D001940:Breast / Q000528:radiation effects*; D005260:Female; D005374:Filtration / Q000295:instrumentation*; D006801:Humans; D008327:Mammography / Q000295:instrumentation*; D008875:Middle Aged; D008982:Molybdenum; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000295:instrumentation*; D011874:Radiometry / Q000295:instrumentation*; D012238:Rhodium; D012643:Selenium; D012680:Sensitivity and Specificity; D014414:Tungsten
D008982:Molybdenum; D012238:Rhodium; D012643:Selenium; D014414:Tungsten