Article

Helical computed tomography accurately reports urinary stone composition using attenuation values: in vitro verification using high-resolution micro-computed tomography calibrated to fourier transform infrared microspectroscopy.

Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120, USA.
Urology (impact factor: 2.43). 06/2004; 63(5):828-33. DOI:10.1016/j.urology.2003.11.038 pp.828-33
Source: PubMed

ABSTRACT To assess the ability of helical computed tomography (CT) to differentiate regions of known mineral composition in typical, heterogeneous urinary stones. Interest is substantial in the urologic community in using radiologic imaging to determine accurately the composition of urinary calculi. Recent advances in CT make this a viable prospect, but the heterogeneity of most stones is a complicating factor.
The ability of micro-CT (a high-resolution laboratory instrument) to identify the mineral composition of stones was confirmed by calibrating micro-CT attenuation values to pure mineral regions of sliced stones using infrared microspectroscopy. Intact human urinary stones were then analyzed by micro-CT, and regions-of-interest of pure mineral were correlated with identical regions-of-interest from quad slice multi-detector row helical CT images. With helical CT, narrow slice widths were used to decrease volume-averaging errors, and bone windows were used so that internal stone structure was visible.
When stones were imaged using helical CT at narrow slice widths, mineral-specific regions-of-interest yielded nonoverlapping attenuation values for uric acid (566 to 632 Hounsfield units [HU]), struvite (862 to 944 HU), calcium oxalate (1416 to 1938 HU), and hydroxyapatite (2150 to 2461 HU).
High resolution helical CT yields unique attenuation values for common types of stone mineral, but proper windowing is required to localize regions of homogeneity. The results of this in vitro study suggest that high-resolution helical CT may be able to identify stone composition at patient diagnosis.

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Keywords

632 Hounsfield units [HU]
 
calcium oxalate
 
complicating factor
 
differentiate regions
 
helical computed tomography
 
helical CT
 
heterogeneous urinary stones
 
high-resolution helical CT
 
Intact human urinary stones
 
internal stone structure
 
localize regions
 
mineral composition
 
patient diagnosis
 
proper windowing
 
pure mineral regions
 
quad slice multi-detector row helical CT images
 
sliced stones
 
stone composition
 
urologic community
 
vitro study
 

Chad A Zarse