Evaluation of a full-scale gas microstrip detector for low-dose X-ray imaging

A new scanning slit digital radiography system based on a gas microstrip detector is presented. The EOS device, manufactured by Biospace Instruments, is equipped with two orthogonal xenon detectors and can produce dual-view full body scans at speeds up to 15cm/s. The detectors are operated at 6 atm and contain 1764 channels at a pitch of 254μm, with an avalanche signal amplification stage. The system can produce images with minimal dose requirements because of excellent scatter rejection and high quantum detection efficiency. Modulation transfer function (MTF) results for three beam qualities as well as comparisons with Monte Carlo simulations are reported. The resolution was found to be dependent on beam quality and on direction. In the horizontal direction, the measured MTF drops to half its full value at 1.0, 0.90 and 0.76mm-1 for beams having half value layers of 1.8, 3.4 and 5.1mm of Al. In the vertical direction, the corresponding values are 0.97, 0.95 and 0.92mm-1