Determination of imaging performance of a photostimulable phosphor system for digital mammography

Quantitative analysis of a prototype photostimulable phosphor system for digital mammography was performed. The pre-sampled MTF, noise power spectrum (NPS), noise equivalent quanta (NEQ), and detective quantum efficiency (DQE) were measured at 26 and 32 kVp to assess the imaging performance of a commercial computed radiography system dedicated for mammographic imaging. The pre-sampled MTF demonstrated 5% modulation at 8 lp/mm with a small dependence on kVp, and noise power estimates indicated x-ray quantum-limited spectral characteristics from 2 mR up to ∼30 mR incident exposure. Maintenance of x-ray information content up to ∼500,000 quanta/mm ² based upon NEQ measurements was demonstrated. DQE (0 mm ^-1) was 30-50%, DQE (2.5 mm ^-1) was 15-25%, and DQE (4 mm ^-1) was 5-15%, depending on kVp, incident exposure, and readout direction. A significant increase in DQE compared to previous CR mammography implementations was found. In addition to the quantitative measurements, qualitative experience suggests that CR mammography is essentially equivalent to mannnography screen-film detector systems.