Conference Paper

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

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

ABSTRACT 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°-4 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/(Kairc)1/2
(53±20) (mJ/kg)-1/2, where
Kairc=air collision kerma. The corresponding
prediction values are C=0.38, and SNR/
(Kairc)1/2 n=68 (mJ/kg)-1/2

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