Sci‐YIS Fri ‐ 10: Tomographic composition analysis of intact urinary calculi by x‐ray coherent scatter

Abstract

Knowledge of urinary stone composition and structure provides important insights in guiding treatment and preventing recurrence. No present method can successfully provide information relating structure and composition of intact stones. We are developing a tomographic technique that uses measures of coherently scattered diagnostic x rays to yield stone composition and structure. Coherent‐scatter (CS) properties depend on molecular structure and are, therefore, sensitive to material composition. For powdered, amorphous or polycrystalline materials with no significant parallel crystal orientation, CS patterns are azimuthally symmetric. In materials with preferred crystallite orientation, such as urinary stones, bright spots appear in their CS patterns. This may compromise a composition analysis based on comparing CS measurements from urinary calculi to a library of CS signatures from powdered chemicals. We show that a tomographic reconstruction of CS measurements (CSCT) effectively eliminates bright spots and yields CS patterns equivalent to powders. This allows for direct comparison with a powdered chemical reference library and provides more accurate material identification. Validation was achieved using an aluminium rod phantom, which exhibits bright spots much like calculi. CSCT composition analysis was performed on intact stones deemed chemically pure by infrared spectroscopy. Computed tomographic reconstruction of CS signals allowed the generation of composition maps, showing the distribution of components. These images provide strong evidence that current laboratory techniques risk missing critical stone components in their analysis due to inadequate sampling. This supports the development of CS analysis as a stone analysis technique both in the laboratory and possibly in situ.