Application of X-Ray Diffraction to Material Analysis and Medical Imaging

Powder diffraction is commonly used to determine the structures of both inorganic and organic materials. The angle and intensity of the diffraction (also called coherent scatter) peak depends on the nanostructure of the material. When no x-ray optic is used, the peak width broadens, and hence the resolution worsens, as the sample area is increased. However, a small sample area gives low diffracted signal intensity, particularly for thin films and for organic materials, which have low diffraction cross sections. X-ray optics can be used in x-ray powder diffraction to increase the diffraction intensity, thus decreasing exposure times. For a small sample area, highly focused beams will provide the greatest intensity increase, but focused beams will also broaden the diffraction peaks. For some kinds of optics, this again degrades the resolution. However, because of the clean, symmetric, near-Gaussian peaks produced by polycapillary optics, the location of the center of the diffraction peak can be obtained with high precision even with broad peak widths.;In this work, a rotating anode x-ray source and a microfocus x-ray source were used for powder diffraction measurements with collimating and focusing optics. The diffraction peak center locations, widths and intensities were measured. A simple geometrical calculation to predict resolution and intensity was developed and was in good agreement with the measurement.;Because diffraction from tissue depends on its structure, x-ray diffraction could potentially be used in screening for breast cancer. Cancer tissue and normal tissue have different structures, and therefore different diffraction angles. However, conventional diffraction measurements use a pencil x-ray beam, which is not compatible with mammography. A slot beam geometry was developed to obtain diffraction from a breast tissue sample. A high ratio grid was used to select the signal from the cancer phantom (surrogate). The whole setup was compatible with conventional screening mammography. Contrast optimization was studied using a series of measurements and simulations.;For samples consisting of normal breast tissue and a breast cancer phantom, the coherent scatter from the cancer phantom can be clearly observed. Coherent scatter analysis is promising for inclusion in screening mammography.