Computed radiography (CR) has shown promise in digital mammographic sc
reening due to its good low spatial frequency MTF and its relatively w
ide exposure latitude. The CR image format has not gained acceptance c
linically because of reduced high spatial frequency resolution as comp
ared to film-screen images. X-ray capillary optics, aligned between th
e breast and CR phosphor imaging plate, will capture primary x-ray pho
tons almost exclusively. Due to the very small angle of acceptance, sc
attered photons angled more than about 1.6X10(-3) radians from primary
trajectory will not be accepted at the capillary optic entrance. The
virtual elimination of detected scatter means almost 100% of the possi
ble primary contrast should be visible in the image. In addition, the
image can be magnified without focal spot blurring. Effective resoluti
on of CR images can be increased by a factor equal to that magnificati
on. Clinical implementation of future capillary optics are expected to
be either in the form of a large, stationary, post-patient optic that
accepts primary from the entire breast or a fan-shaped optic that is
scanned across the breast. Measurements of a test capillary optic show
ed a reduction of scatter fraction to 0.018. Images of a lucite contra
st detail phantom revealed a corresponding increase in image contrast
when compared to anti-scatter grid and no grid methods. Spectral trans
mission measurements using a high-purity germanium detector showed goo
d primary transmission (45%-50%) in the mammographic energy range. The
MTF measurements of both stationary and scanned capillary optics show
ed improvement at the 5% MTF level to 8.4 mm(-1) for scanned optics an
d 9.2 mm(-1) for stationary optics representing a 68% and 84% respecti
ve increase over the CR MTF without magnification or capillary optics.
(C) 1996 American Association of Physicists in Medicine.