AbstractID: 7848 Title: Digital vs. Film-Screen Mammography: Radiation Dose and SNR
The purpose of this study was to compare the performance of two different fullfield, digital mammography units to their corresponding film-screen units. The
average glandular dose and the signal-to-noise ratio (SNR) were determined for a
range of phantom thickness.
The GE Senographe 2000-D digital mammography unit was compared to a GE
DMR Plus film-screen unit. A Lorad Contour 2000 CCD unit was compared to a
Lorad M-IV Platinum film-screen unit. These data were also compared to the GE
units. Plastic BR-12, which simulates 50% adipose breast tissue, was used to
measure the typical radiation levels for the dose calculations. Uniform acrylic
sheets were used to measure SNR for various radiation dose levels.
Dependent upon the selection of exposure parameters, the digital units delivered
similar average glandular doses to the film-screen units. However, in certain modes,
the radiation levels were lower due to the utilization of higher kVp’s, filtration and
other factors. For the digital systems, the SNR increases with the square root of the
mAs. The dynamic range of digital systems is greater than film-screen units, which
influences the low contrast visualizations. Each imaging modality has certain
inherent advantages and disadvantages. Film-screen systems have better spatial
resolution. Digital mammography has wider dynamic range and variable displays.
It is important to note that low contrast visualization for digital systems is closely
tied to SNR and display features, which can be important in clinical applications.