Gamma-ray imaging using a Fresnel zone plate aperture, multiwire proportional chamber detector, and computer reconstruction

The use of the multiwire proportional chamber in a Fresnel zone plate coded aperture gamma-ray imaging system is described. Image reconstruction is by computer using the fast Fourier transform algorithm. Criteria for design parameters of the imaging system are established. A calculation of the signal/noise ratio of images reconstructed from computer-generated on-axis zone plate holograms gives values, for larger numbers of gamma-ray events, which are somewhat smaller than theoretical values based on a shot-noise formula. The use of a positive and a negative zone plate combination is shown to eliminate the large background usually associated with on-axis zone plate imaging.