AbstractID: 7147 Title: Evaluation of a computed radiography detector for digital
mammography
Several digital mammography detector systems are being considered as potential
replacements for conventional screen-film mammography, including computed
radiography. The quantitative evaluation of a photostimulable storage phosphor (PSP)
detector and computed radiography image reader (Fuji FCR5000) using a dedicated highresolution PSP imaging plate and mammography cassette is described in this work.
Quantitative indices include evaluation of the pre-sampled modulation transfer function
(MTF), the Noise Power Spectrum (NPS) and the Detective Quantum Efficiency (DQE).
Image data is linearized to incident exposure. The pre-sampled MTF data is obtained in
the scan and sub-scan directions of the image. A sequence of uniform exposures incident
on the detector (25 kVp, 4.0 cm Lucite filter, and 2.3, 5.0, 10.8, 19.5, 29.3, 39.6 58.6 78.1
mR exposures) are used for NPS analysis. The NPS estimates are determined from 256
averages of 64x64 image patches in each image set using 2-D Fourier transforms.
Results show that the DQE increases with increasing exposure up to about 5 mR,
reaching a maximum value of about 30%, and then decreases. Spatial resolution
matches the expected response according to sampling pitch. This investigation
demonstrates that the quantitative performance of computed radiography imaging plates
using a conventional CR reader is comparable in terms of DQE and incident exposure to
conventional mammography screen-film detectors at low spatial frequencies.
Improvements in spatial resolution and DQE are expected with the imminent introduction
of a dedicated CR mammography reader with 50 micron sampling pitch and double side
readout capabilities.