Photon-counting detectors for digital radiography and X-Ray computed tomography
We report on the adaption of new particle physics gas proportional microdetectors filled with a xenon/methane gas mixture at high pressure as image receptors for medical x-ray imaging. Currently in radiology, all detectors used clinically merely integrate the energy deposited by the beam. The next generation of detectors for digital radiography and computed tomography (CT) will obtain extra information by counting individual photons and measuring their energy. This will enable (i) implementation of single exposure dual-energy radiography, (ii) for CT, reconstruction of images free of spectral artefacts, and (iii) for the same quantum efficiency, reduced image noise compared with images obtained by energy integration. The new gas microdetectors can measure individual photon energies at radiological fluence rates and have high spatial resolution. Prototype systems in our laboratory have demonstrated a limiting spatial resolution of 7.0 lp mm-1 for a 30 kV x-ray spectrum and 11.9 1p mm-1 for 50 kV. The energy resolution at 4 atm was 10% at 17.7 keV and 8% at 59.6 keV. The counting rate ability for unfiltered 30 kV x rays was > 2 x 106 mm-2 s1 at 3 atm of Xeimethane corresponding to an exposure rate > 25 mR s-1. Future systems in which the readout anodes are parallel to the photon direction will be capable of even higher rates.
|Conference||SPIE Regional Meeting on Optoelectronics, Photonics, and Imaging, Opto-Canada 2002|
Johns, P, Dubeau, J. (Jacques), Gobbi, D.G. (David G.), Li, M. (Mei), & Dixit, M.S. (Madhu S.). (2002). Photon-counting detectors for digital radiography and X-Ray computed tomography. In Proceedings of SPIE - The International Society for Optical Engineering (pp. 367–369). doi:10.1117/12.2283929