A semianalytic model to investigate the potential applications of x‐ray scatter imaging

Abstract

Although x-ray scatter is generally regarded as a nuisance that reduces radiographic contrast (C) and the signal-to-noise ratio (SNR) in conventional images, many technologies have been devised to extract useful information from the scattered x rays. A systematic approach, however, for analyzing the potential applications of x-ray scatter imaging has been lacking. Therefore, we have formulated a simple but useful semianalytic model to investigate C and SNR in scatter images. Our model considers the imaging of a target object against a background material of the same dimensions when both are situated within a water phantom. We have selected biological materials (liver, fat, bone, muscle, blood, and brain matter) for which intermolecular form factors for coherent scattering were available. Analytic relationships between C and SNR were derived, and evaluated numerically as the target object thickness (0.01-40 mm) and photon energy (10-200 keV) were systematically varied. The fundamental limits of scatter imaging were assessed via calculations that assumed that all first-order scatter exiting the phantom, over 4 pi steradians, formed the signal. Calculations for a restricted detector solid angle were then performed. For the task of imaging white brain matter versus blood in a 15 cm thick water phantom, the maximum SNR, over all energies, for images based on the detection of all forward scatter within the angular range 2 degrees-12 degrees is greater than that of primary images for target object thicknesses < or = 23 mm. Use of the backscattered x rays within the range 158 degrees-178 degrees to image objects 3 cm below the surface of a 25 cm thick water phantom allows the liver to be distinguished from fat with a SNR superior to that of primary imaging when the objects are < or = 22 mm thick. Our analysis confirms the usefulness of scattered x rays, and provides simple methods for determining the regimes of medical interest in which x-ray scatter imaging could outperform conventional imaging.

Analysis of spectral blur effects in x‐ray scatter imaging

“…The existence of the Cϭ0 locus was shown in our previous work ͓see in Ref. 13, Fig. 11͑c͒ ͑bone/muscle, backscatter͔͒.…”

“…13, a reduction in SNR will occur due to the multiple scatter in the water phantom. There will probably not be much difference between monoenergetic and polyenergetic beams.…”

A method to estimate the fractional fat volume within a ROI of a breast biopsy for WAXS applications: Animal tissue evaluation

“…The coherent form factors F used in the calculations were those measured by Poletti et al 35 The incoherent scattering functions S were calculated using S of atoms from Hubbell et al 36 and the sum rule. 37 The compositions used were those from Poletti et al 35 The attenuation coefficients for fib and fat were taken from Johns and Yaffe. 31 The µ sc (fib) curves obtained via the subtraction model for the three sample configurations are shown in Fig.…”

<title>Fundamental information content accessible with medical x-ray scatter imaging</title>

“…The analytic expressions for contrast C and SNR are given in Ref. 10. In all four imaging models, SNR o C. For the total-scatter model, the radiographic contrast is given by where p is the total linear attenuation coefficient of mat erial I (i I for target , i b for background ) Ilie variables = aCoh and i' = p aC are the partial linear attenuation coefficients, respect i velv, for coherent an( I incoherent processes, where p° is the electron density (per unit.…”