Analytical expressions have been written for image quality in mammography. Multiparameter optimizations have been conducted to find mammography systems providing the lowest patient dose for a given image quality. The optimizations are subject to constraints imposed by technology, such as power limits on the tube focal spot, absorption efficiency related to detector resolution, and others. The optimizations permit system geometry, kVp, filtration, detector resolution, focal spot size, and grid characteristics to vary simultaneously and self-consistently subject to the constraints. A system configuration approaching a factor of 3 dose reduction has been found without assuming radical technological advances. The system satisfies image quality constraints for both large and small targets and would be possible to implement clinically. The sensitivity of the results to the assumptions made in the modeling has been investigated.

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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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