title: High transparency coded apertures in planar nuclear medicine imaging.
abstract: Coded apertures provide an alternative to the collimators of nuclear medicine imaging, and advances in the field have lessened the artifacts that are associated with the near-field geometry. Thickness of the aperture material, however, results in a decoded image with thickness artifacts, and constrains both image resolution and the available manufacturing techniques. Thus in theory, thin apertures are clearly desirable, but high transparency leads to a loss of contrast in the recorded data. Coupled with the quantization effects of detectors, this leads to significant noise in the decoded image. This noise must be dependent on the bit-depth of the gamma camera. If there are a sufficient number of measurable values, high transparency need not adversely affect the signal-to-noise ratio. This novel hypothesis is tested by means of a ray-tracing computer simulator. The simulation results presented in the paper show that replacing a highly opaque coded aperture with a highly transparent aperture, simulated with an 8-bit gamma camera, worsens the root-mean-square error measurement. However, when simulated with a 16-bit gamma camera, a highly transparent coded aperture significantly reduces both thickness artifacts and the root-mean-square error measurement.
authors.affiliation: Biomedical Engineering Research Group, School of Electrical and Information Engineering, University of the Witwatersrand, Johannesburg, Private Bag 3, WITS 2050, South Africa. d.starfield@ee.wits.ac.za
authors.forename: David M
authors.initials: DM
authors.lastname: Starfield
authors.forename: David M
authors.initials: DM
authors.lastname: Rubin
authors.forename: Tshilidzi
authors.initials: T
authors.lastname: Marwala
mesh_terms: D003198:Computer Simulation; D005720:Gamma Rays; D007091:Image Processing, Computer-Assisted; D008962:Models, Theoretical; D009683:Nuclear Medicine / Q000379:methods*; D019047:Phantoms, Imaging; D014054:Tomography / Q000379:methods*