Urinary stone components can be characterized through their diffraction signatures using monoenergetic or polyenergetic x rays. Sharp characteristic diffraction peaks are observed under monoenergetic conditions, facilitating component separability in measurements of stones with mixed composition. This favors uniqueness of a materials analysis solution. However, these monoenergetic techniques are either impractical (as with synchrotron radiation) or impossible to perform in situ (as with conventional low energy diffractometry). Alternatively, our approach measures signals from x-ray diffraction, or coherent scatter (CS), for stones and their components using polyenergetic x rays from diagnostic equipment, allowing for in situ applications. Although the polyenergetic x-ray spectrum is the primary contributor to the angular broadening of diffraction peaks in our measured CS cross-sections, we show that it is possible to relate the polyenergetic and monoenergetic results through a “non-stationary” convolution operation. This requires the computation of a linear superposition integral of the monoenergetic cross-section with a function representative of the polyenergetic spectrum. Experimentally acquired diffractometry cross-sections of the seven major urinary stone components were subjected to this operation, revealing good agreement of diffraction features with CS. These results indicate that angular resolution is principally hindered by the energy spectrum in CS measurements. Nevertheless, distinct scatter patterns were observed using CS, suggesting that a strictly monoenergetic beam is not required for the depiction of pure stone components.
The formation and development of plaques in the arterial wall is a direct consequence of atherosclerosis. The composition of a plaque is of particular interest as it is thought to be an important indicator of vulnerability, or risk of rupture and thrombosis. Current diagnostic methods do not yet have the ability to fully characterize plaque composition. Coherent-scatter imaging, a technique being developed in our laboratory, produces images based on the low-angle scattering properties of tissue. As these properties depend on molecular structure, material-specific maps of the different components in a tissue can be created. Material-specific images were produced for an atherosclerotic carotid artery. The image distributions of fatty and calcified deposits agreed with visual examination of the specimen. Preliminary results indicate that fat and calcifications, two typical plaque constituents, can be identified and distinguished from the undiseased vessel wall using coherently scattered x rays.
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