Fragility of Brushite Stones in Shock Wave Lithotripsy: Absence of Correlation with Computerized Tomography Visible Structure

Abstract

Purpose Brushite stones were imaged in vitro and then broken with shock wave (SW) lithotripsy (SWL) to assess whether stone fragility correlates with internal stone structure visible by helical computed tomography (helical CT). Materials and Methods 52 brushite stones were scanned by micro CT, weighed, hydrated, and placed within a radiological phantom. The stones were scanned using a Philips Brilliance iCT 256 system, and the images evaluated for visibility of internal structural features. The stones were then treated by SWL in vitro, and the number of SWs needed to break each stone to completion was recorded. Results The number of SWs to break each stone, normalized to stone weight, did not differ by Hounsfield unit value (P=0.84), or CT-visible structure that could be identified consistently by all observers (P =0.053). Fragility of stones was highly correlated with stone density and with brushite content (both P <0.001), with stones of nearly pure brushite requiring the most SWs to break. When all observations of CT-visible structure were used in analysis by logistic fit, CT-visible structure predicted increased stone fragility with an overall area under the receiver operating characteristic (ROC) curve of 0.64. Conclusions SWL fragility of brushite stones did not correlate with internal structure discernable using helical CT. However, fragility did correlate with stone density and increasing brushite mineral content, which is consistent with clinical experience with brushite stone patients. Thus, current technology in diagnostic CT does not provide a means to predict when brushite stones will break well using SW lithotripsy.

Therapy modifies cystine kidney stones at the macroscopic scale. Do such alterations exist at the mesoscopic and nanometre scale?

“…Such structural characterization on pathological calcifications can be performed either through various classical physical techniques (Evan et al, 2007;Rao et al, 2011;Bazin et al, 2006), such as scanning electron microscopy (SEM) (Grà cia-Garcia et al, 2011;Dessombz, Mé ria et al, 2011, micro-computerized tomography (Williams et al, 2012;Kaiser et al, 2011), Fourier transform infrared (FTIR) and Raman spectroscopy (Quy Dao & Daudon, 1997;Estepa & Daudon, 1998;Guerra-Lopez et al, 2008;Wilson et al, 2010), proton induced X-ray emission (Pineda-Vargas et al, 2009), and laser ablation methods (Stepankova et al, 2013), or through techniques specific to large instruments, such as micro X-ray fluorescence (Bazin et al, 2007), micro X-ray absorption spectroscopy Carpentier et al, 2010;Nguyen et al, 2011), micro FTIR spectroscopy or neutron scattering (Bazin, André et al, 2012).…”

The Need for Better Decision Tools in Managing Stone Disease

“…6,7 In this issue of The Journal Williams et al (page 996) built on this important work, now addressing the question of whether brushite stones demonstrate the same correlation between CT visible stone structure and stone fragility. 8 In contradistinction to what this investigative group found with cystine and calcium oxalate monohydrate stones, the internal structure of brushite stones did not help identify stones that would fragment more or less readily.…”

Robustness of Textural Features to Predict Stone Fragility Across Computed Tomography Acquisition and Reconstruction Parameters

“…A previous study examining stone fragility based on stone composition concluded that knowing the composition alone may not accurately predict the fragility (13). However, other studies examining homogeneity (14), surface roughness (15), and internal stone structures visible with CT (16,17) have demonstrated that internal and external stone morphological features show correlation with kidney stone fragility. A recent study was demonstrated that quantitative relationships exist between stone fragility and stone morphological features extracted from routine singleenergy CT (SECT) and dual-energy CT (DECT) scans (12).…”