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

Abstract

Although scattered radiation is generally regarded as a nuisance in radiological imaging, many innovative imaging concepts that use the scattered field have been demonstrated. A systematic approach, however, for analyzing the medical applications of x-ray scatter imaging has been lacking. We have therefore formulated a simple semi-analytic model that consists of imaging a target object against a background material of the same dimensions when both are situated within a water phantom. The target and background objects have small cross-sectional areas (1.0 mm2) to allow the omission of self-attenuation and multiple scatter within the objects. The incident energy fluence is kept constant so that similar doses are delivered by the various photon beams. For imaging white brain matter versus gray brain matter in a 15 cm thick water phantom, the maximum signal-to-noise ratio, over all photon energies, for images obtained with the forward scatter between 2° -12°exceeds that of primary images for all object thicknesses 40 mm. The penalty in dose as a result of spectral blur is generally moderate. For example, using an 80 kV beam for the previous imaging task would require approximately a 24% dose increase relative to using a monoenergetic beam. A high-precision experimental apparatus has been assembled to validate our predictions.

An energy-dispersive technique to measure x-ray coherent scattering form factors of amorphous materials

“…X-ray scatter imaging is a new approach to x-ray instrumentation for medicine. Several groups have been investigating ways to make use of scattered x-radiation to extend the usefulness of x-ray imaging beyond conventional primary beam imaging (Brateman et al 1984, Arendtsz and Hussein 1995, Leclair and Johns 1998, 1999, Poletti et al 2002, Davidson et al 2005, Leclair et al 2006, Van Uytven et al 2007, Griffiths et al 2007, Elshemey and Elsharkawy 2009.…”

“…Previous work in our group has analysed the improvement in image quality possible through using scattered x rays (Leclair and Johns 1998). As an example, it was shown that to distinguish between a 1 mm target of gray matter versus water, the signal-to-noise ratio can be multiplied by about 14 by using the coherently-scattered photons as compared to the primary (Leclair and Johns 1999). This analysis was based on the available data for the scattering properties of the tissues in question.…”

Analysis of spectral blur effects in x‐ray scatter imaging

“…Results shown in Ref. 23, however, show that the general conclusions of Ref. 13 do not change if ⌿ 0 is fixed instead of ⌽ 0 .…”

Measurement of coherent x-ray scatter form factors for amorphous materials using diffractometers

“…A number of researchers have configured laboratory prototypes to demonstrate imaging using either backscatter (Towe andJacobs 1981, Herr et al 1994) or forward scatter (Harding et al 1985, Kleuker et al 1998, Westmore et al 1996, Batchelar and Cunningham 2002. We developed a semi-analytic model (Leclair and Johns 1998, 1999a, 1999b for analysing and comparing x-ray scatter imaging systems. Our calculations predict that for some imaging tasks, the contrast and signal-to-noise ratio achieved by collecting a portion of the scatter (in an annular cone) will be superior to that achieved by conventional primary imaging, for the same number of photons incident on the patient.…”