Scanned-projection digital mammography.
The effectiveness of film-screen mammography is limited by tradeoffs between latitude and contrast, film granularity, and the need to increase dose when antiscatter methods are used. We are currently developing a scanned-projection digital mammography (SPDM) system to overcome these limitations. The system consists of a pair of scanning slits, a high-resolution x-ray image intensifier tube, a linear photodiode array, and a digital display. The detective quantum efficiency of the SPDM system at spatial frequencies up to 3 cycles/mm is similar to that of mammographic film-screen combinations, but is lower at high frequencies. For low-contrast objects as small as 0.1 mm in diameter, the signal-to-noise ratio is currently equal to that of optimally exposed mammographic film-screen images for equal dose to the breast and superior for regions which would be underexposed or overexposed on film. This is achieved by the use of a low-noise detector system, geometric magnification, and scatter elimination. Images of a contrast-detail phantom and excised breast tissue illustrate the superior contrast sensitivity of SPDM.
Nishikawa
R M
RM
Department of Medical Biophysics, University of Toronto, Ontario, Canada.
Mawdsley
G E
GE
Fenster
A
A
Yaffe
M J
MJ
D005260:Female; D006801:Humans; D008327:Mammography / Q000295:instrumentation*; D011856:Radiographic Image Enhancement / Q000295:instrumentation*; D014963:X-Ray Intensifying Screens