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Title: Fundamental x-ray interaction limits in diagnostic imaging detectors: Spatial resolution

The practice of diagnostic x-ray imaging has been transformed with the emergence of digital detector technology. Although digital systems offer many practical advantages over conventional film-based systems, their spatial resolution performance can be a limitation. The authors present a Monte Carlo study to determine fundamental resolution limits caused by x-ray interactions in four converter materials: Amorphous silicon (a-Si), amorphous selenium, cesium iodide, and lead iodide. The ''x-ray interaction'' modulation transfer function (MTF) was determined for each material and compared in terms of the 50% MTF spatial frequency and Wagner's effective aperture for incident photon energies between 10 and 150 keV and various converter thicknesses. Several conclusions can be drawn from their Monte Carlo study. (i) In low-Z (a-Si) converters, reabsorption of Compton scatter x rays limits spatial resolution with a sharp MTF drop at very low spatial frequencies (<0.3 cycles/mm), especially above 60 keV; while in high-Z materials, reabsorption of characteristic x rays plays a dominant role, resulting in a mid-frequency (1-5 cycles/mm) MTF drop. (ii) Coherent scatter plays a minor role in the x-ray interaction MTF. (iii) The spread of energy due to secondary electron (e.g., photoelectrons) transport is significant only at very high spatial frequencies. (iv) Unlike themore » spread of optical light in phosphors, the spread of absorbed energy from x-ray interactions does not significantly degrade spatial resolution as converter thickness is increased. (v) The effective aperture results reported here represent fundamental spatial resolution limits of the materials tested and serve as target benchmarks for the design and development of future digital x-ray detectors.« less
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [2]
  1. Imaging Research Laboratories, Robarts Research Institute, P.O. Box 5015, London, Ontario N6A 5K8 (Canada)
  2. (Canada) and Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 3K7 (Canada)
  3. (Canada) and London Regional Cancer Program, London Health Sciences Centre, London, Ontario N6A 4L6 (Canada)
  4. (Canada)
Publication Date:
OSTI Identifier:
21120850
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 35; Journal Issue: 7; Other Information: DOI: 10.1118/1.2924219; (c) 2008 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BIOMEDICAL RADIOGRAPHY; CESIUM IODIDES; COMPTON EFFECT; DIGITAL SYSTEMS; IMAGE PROCESSING; IMAGES; LEAD IODIDES; MONTE CARLO METHOD; SEMICONDUCTOR MATERIALS; SPATIAL RESOLUTION; TRANSFER FUNCTIONS; X RADIATION