Improving Kidney Stone Treatment through Materials Chemistry
Robinson, John
2024
Abstract
As pathogenic bioinorganic composites, the formation and destruction of kidney stones is of fundamental and practical interest for materials chemists. The prevalence of urinary calculi has increased in industrialized societies over the past 50 years and today about 1 in 10 people will experience at least one kidney stone in their lifetime. The increase in prevalence has been correlated with dietary changes and the increase in related medical problems like obesity and diabetes. Kidney stones are treated surgically using various forms of lithotripsy with near-infrared, laser-based lithotripsy becoming increasingly favored over older mechanical methods. Despite the common application of near-infrared laser ablation to stone destruction, the mechanisms of laser lithotripsy are poorly understood quantitatively. This dissertation begins with a focus on quantitative measurement of photothermal properties related to kidney stone decomposition in Chapter 2, particularly the absorption coefficients of kidney stone minerals. To achieve these measurements, new methods for growth of large single crystals of kidney stone minerals were developed. Absorption in the near-infrared region was determined to primarily result from the excitation of the combination vibrational modes of water molecules found within crystal lattices. Peak near-infrared absorption for kidney stone minerals typically occurs in the range of 1.9-2.0 µm aligning well with existing near-infrared laser systems. Chapter 3 is devoted to understanding kidney stone growth and destruction requiring an understanding of kidney stone structure. Sample preparation techniques were developed to allow Raman imaging of kidney stone cross-sections and fragments. Sub-micrometer spatial resolutions were achieved in Raman chemical maps revealing previously unobserved features like ≈1 µm thick rings of calcium oxalate monohydrate in uric acid stones that may prevent effective treatment by dissolution. In brushite stones, calcium oxalate crystals were shown to be localized to regions of brushite crystals with specific morphology and may be an indicator of higher stone recurrence risk. Such structural insights become important when designing new artificial kidney stone models for use in urology research. Many lithotripsy studies have utilized gypsum-based plasters for artificial stone models though gypsum itself does not form kidney stones. Chapter 4 describes new brushite-based plasters developed for use as artificial kidney stone models. These have superior composition and ablation performance compared to gypsum plasters and allowed new studies of the stone ablation process. It was determined that fragmentation of stones occurs on <100 µs time scales, much shorter than the laser pulse length of some lithotripsy systems. Such insights can be use by medical device engineers to improve lithotripter performance.Deep Blue DOI
Subjects
kidney stone disease laser lithotripsy Raman imaging urology near infrared spectroscopy crystallization
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