  X-ray detectors made of crystalline silicon have several advantages including
low dark currents, fast charge collection and high energy resolution. For
high-energy x-rays, however, silicon suffers from its low atomic number, which
might result in low detection efficiency, as well as low energy and spatial
resolution due to Compton scattering. We have used a monte-carlo model to
investigate the feasibility of a detector for pediatric CT with 30 to 40 mm of
silicon using x-ray spectra ranging from 80 to 140 kVp. A detection efficiency
of 0.74 was found at 80 kVp, provided the noise threshold could be set low.
Scattered photons were efficiently blocked by a thin metal shielding between
the detector units, and Compton scattering in the detector could be well
separated from photo absorption at 80 kVp. Hence, the detector is feasible at
low acceleration voltages, which is also suitable for pediatric imaging. We
conclude that silicon detectors may be an alternative to other designs for this
special case.
