We are examining the feasibility of performing digital mammography by combining a storage-phosphor image receptor with a highly efficient x-ray system. The image receptor consists of Fuji series HR-V high resolution imaging plates and a Fuji 9000 reader. The x-ray system was developed using multiparameter optimization techniques, with the goal of reducing patient dose as much as possible while retaining acceptable imaging performance. We have measured sensitometric properties, modulation transfer function (MTF), and noise power spectrum (NPS) of the Fuji plates with low-energy x-ray spectra. We have used the measurements, along with information about the x-ray system, to estimate signal-to-noise ratios (SNRs) for objects in a contrastdetail (C-D) phantom. We present the results of our measurements on the Fuji plates, comparisons of calculated and observed C-D diagrams for this system and a conventional system, and comparisons of phantom images and doses for this system to images and doses for a conventional system. We conclude that digital mammography with the system studied is at least feasible since phantom image quality is comparable to that of a conventional system at dose levels that are somewhat lower.

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Microcalcifications can be identified on mammograms in approximately 50-55 % of breast cancer cases. Three factors affect the ability to use the presence of microcalcifications as a sign of cancer. They must be seen (conspicuity), their shape must be assessed (to differentiate benign and malignancy associated shapes) and they should be countable since the greater the number of clustered calcifications, the more likely they are malignancy associated. Concern has been expressed that digital systems with their inherently worse resolution would not allow adequate shape information to be captured. Using a 100 micron pixel size storage phosphor system we randomly selected 20 cases, 10 benign and 10 showing malignancy on biopsy and asked four radiologists to assess the calcifications present comparing the original screen film and the digital images and using the screen film biopsy specimen radiograph as ground truth. The preferences were mixed with some radiologists preferring screen film and others the digital images. Whatever their preferences, the radiologists were unable to use the shape criteria to distinguish benign and malignant cases in this case sample.