X-ray forward-scatter imaging: experimental validation of model

Conference Paper · February 2000
DOI: 10.1109/IEMBS.2000.901531 · Source: IEEE Xplore
Conference: Engineering in Medicine and Biology Society, 2000. Proceedings of the 22nd Annual International Conference of the IEEE, Volume: 4


    X-ray scatter imaging is a novel tool under development which
    obtains diagnostic information from the photons scattered out of the
    patient. The authors have formulated a semianalytic model to quantify
    the information obtainable. Their predictions confirm the usefulness of
    scattered X-rays for various imaging tasks, even when polyenergetic
    beams are used. In this work, the authors experimentally validate their
    forward-scatter imaging model using 80 kV beams. The scatter signatures
    from plastic targets-polymethyl methacrylate (lucite), polycarbonate,
    polystyrene, polyethylene and nylon-were measured for target thicknesses
    d=0.5, 1, 2, 3, and 4 cm. The scattered field was sampled in 1°
    increments from 2° to 12° with a high-purity germanium detector
    (dΩ=1.61× 1°<sup>-4</sup> sr). The beam diameter at the
    front surface of the targets is ≅1.51 mm. The approximative
    dependence of scattering cross-section on angle was in good agreement
    with predictions. Comparisons of contrast (C) and signal-to-noise ratio
    (SNR) between experiment and theory were made by scaling and summing the
    detected numbers of counts so as to approximate an annular detector
    extending from 2° to 12° from the primary beam. For the task of
    imaging 2 cm thick lucite versus polycarbonate targets placed at the
    center of a 15-cm-diam spherical water phantom, the authors obtain
    C=0.28±0.1, and SNR/(K<sub>air</sub><sup>c</sup>)<sup>1/2</sup>
    (53±20) (mJ/kg)<sup>-1/2</sup>, where
    K<sub>air</sub><sup>c</sup>=air collision kerma. The corresponding
    prediction values are C=0.38, and SNR/
    (K<sub>air</sub><sup>c</sup>)<sup>1/2</sup> n=68 (mJ/kg)<sup>-1/2</sup>