Nondestructive analysis of urinary calculi using micro computed tomography

Abstract

BackgroundMicro computed tomography (micro CT) has been shown to provide exceptionally high quality imaging of the fine structural detail within urinary calculi. We tested the idea that micro CT might also be used to identify the mineral composition of urinary stones non-destructively.MethodsMicro CT x-ray attenuation values were measured for mineral that was positively identified by infrared microspectroscopy (FT-IR). To do this, human urinary stones were sectioned with a diamond wire saw. The cut surface was explored by FT-IR and regions of pure mineral were evaluated by micro CT to correlate x-ray attenuation values with mineral content. Additionally, intact stones were imaged with micro CT to visualize internal morphology and map the distribution of specific mineral components in 3-D.ResultsMicro CT images taken just beneath the cut surface of urinary stones showed excellent resolution of structural detail that could be correlated with structure visible in the optical image mode of FT-IR. Regions of pure mineral were not difficult to find by FT-IR for most stones and such regions could be localized on micro CT images of the cut surface. This was not true, however, for two brushite stones tested; in these, brushite was closely intermixed with calcium oxalate. Micro CT x-ray attenuation values were collected for six minerals that could be found in regions that appeared to be pure, including uric acid (3515 – 4995 micro CT attenuation units, AU), struvite (7242 – 7969 AU), cystine (8619 – 9921 AU), calcium oxalate dihydrate (13815 – 15797 AU), calcium oxalate monohydrate (16297 – 18449 AU), and hydroxyapatite (21144 – 23121 AU). These AU values did not overlap. Analysis of intact stones showed excellent resolution of structural detail and could discriminate multiple mineral types within heterogeneous stones.ConclusionsMicro CT gives excellent structural detail of urinary stones, and these results demonstrate the feasibility of identifying and localizing most of the common mineral types found in urinary calculi using laboratory CT.

CT visible internal stone structure, but not Hounsfield unit value, of calcium oxalate monohydrate (COM) calculi predicts lithotripsy fragility in vitro

“…The present study is a refinement of this approach, utilizing the powerful ability of CT to display the internal structure of urinary stones [18,20]. The results demonstrate that COM stones that show visible structure on CT are more fragile to SW's than COM stones that appear to be homogeneous in their structure (Figure 3).…”

“…Each stone was scanned with a Scanco mCT20 micro CT system (voxel size from 18 to 34 μm) to verify composition [20] (found to be 98±4% pure COM, mean ±s.d., for 47 stones) and also for assessment of heterogeneity (presence of pronounced lobulation, voids, or apatite inclusions) by four blinded observers (method described below). Stones were weighed dry, and a mean diameter of each stone was calculated from the stone volume found by micro CT, assuming a spherical shape for the stone.…”

Noninvasive Differentiation of Uric Acid versus Non–Uric Acid Kidney Stones Using Dual-Energy CT

“…After the completion of the experiment, the stones were dried, and evaluation of the internal structure of all stones was performed using micro CT. Each stone was scanned on a Scanco mCT20 micro-CT system (Scanco Medical AG, Bassersdorf, Switzerland) with 18-μm isotropic voxel size and assessed for stone composition, as previously described (17). The goal of this additional characterization was to find out if any of the stones previously identified by infrared spectroscopy as "pure" showed evidence of a mixed composition.…”

“…The goal of this additional characterization was to find out if any of the stones previously identified by infrared spectroscopy as "pure" showed evidence of a mixed composition. Examples of micro-CT sections of the stones used in this study are shown in Fig 4. For the stones with mixed composition, the volume content of each mineral component was estimated using ImageJ (a public domain image processing program) by thresholding the stone images at levels appropriate for the individual minerals (17). Stones were analyzed by micro-CT blindly; that is, the micro-CT analyses were completed without knowledge of the infrared spectroscopy data.…”

A Review of Pathological Biomineral Analysis Techniques and Classification Schemes

“…The micro computed tomography (micro CT) as a potential method for the analysis of urinary stone composition and morphology in a nondestructive manner at very high resolution (Zarse et al, 2004). Micro CT, which has seen considerable use as a research tool in bone biology (Ruegsegger et al, 1996), has the ability to reconstruct 2-D and 3-D images of urinary stones that allow the 3-D image of the stone to be cut and viewed in multiple planes with voxel sizes of 8-34 μm.…”