| The material dependent x-ray scattering properties of tissues are determined by their scattering form factors, measured as a function of the momentum transfer argument, x. Incoherent scattering form factors, Finc, are calculable for all values of x while coherent scattering form factors, Fcoh, cannot be calculated except at large C because of their dependence on long range order. As a result, measuring Fcoh is very important to the developing field of x-ray scatter imaging.;An angle-dispersive technique is developed that uses a polychromatic x-ray beam and a large area, energy-insensitive detector. It is shown that Fcoh can be measured in this system if the incident x-ray spectrum is known. The problem is ill-conditioned for typical x-ray spectra and two numerical methods of dealing with the poor conditioning are explored. It is shown that these techniques work best with K-edge filters to limit the spectral width and that the accuracy degrades for strongly ordered materials. Measurements of width Fcoh for water samples are made using 50, 70 and 92 kVp spectra. The average absolute relative difference in Fcoh between our results and the literature for water is approximately 10-15%. Similar measurements for fat samples were made and found to be qualitatively similar to results in the literature, although there is very large variation between the literature values in this case. The angle-dispersive measurement is limited to low resolution measurements of the coherent scattering form factor although it is more accessible than traditional measurements because of the relatively commonplace equipment requirements.;An energy-dispersive technique is also developed that uses a polychromatic x-ray beam and an energy-sensitive detector. It is shown that F coh can be measured directly by computing the ratio of two spectra: one, measured at a given scattering angle and the other, the direct transmission spectrum with no scattering. Experiments were constructed on this principle and used to measure Fcoh for water, fat and several types of plastics. A 121 kVp x-ray spectrum and seven different scattering angles between 1.75° and 15° were used, resulting in a measurable range of x between 0.5 and 9.5 nm-1. These are the first measurements of coherent scattering form factors made without the need for a scaling factor.;Resolution in x varies between 10% at small scattering angles and 2% for larger scattering angles. Accuracy in F coh is shown to be strongly dependent on the precision of the experimental geometry and varies between 5% and 15%. The average absolute relative difference between repeated measurements was ∼ 5%.;Previous measurements of Fcoh, based on crystallographic techniques, have shown significant variability, as these methods are not optimal for amorphous materials. Two methods of measuring F coh, designed with amorphous materials in mind, are developed in this thesis.;The agreement between the energy-dispersive and angle-dispersive techniques is shown to be quite good, considering the low resolution of the angle-dispersive measurement. The average absolute relative difference in F coh between the angle-dispersive measurement with a 70 kVp spectrum and the energy-dispersive measurement was ∼ 12%. |
