| Helical CT of urinary calculi: effect of stone composition, stone size, and scan collimation. | |
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MedLine Citation:
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PMID: 10915668 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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OBJECTIVE: Helical CT has become the preferred methodology for identifying urinary calculi. However, the ability to predict stone composition, which influences patient treatment, depends on the accurate measurement of the radiographic attenuation of stones. We studied the effects of stone composition, stone size, and scan collimation width on the measurement of attenuation in vitro. MATERIALS AND METHODS: One hundred twenty-seven human urinary calculi of known composition and size were scanned at 120 kVp, 240 mA, and a 1:1 pitch at different collimations. A model, based on the physics of helical CT, was used to predict the effect of scan collimation width and stone size on measured attenuation. RESULTS: At a 1-mm collimation, stone groups could be differentiated by attenuation: the attenuation of uric acid was less than that of cystine or struvite, which overlapped; these were less than the attenuation of calcium oxalate monohydrate, which was in turn lower than that of brushite and hydroxyapatite, which overlapped and showed the highest values. At a wider collimation, attenuation was lower and the ability to differentiate stone composition was lost. Attenuation also decreased with smaller stones. At a 10-mm collimation, some uric acid stones (<approximately 6 mm) and other stones (< approximately 4 mm) had very low attenuation, so low that they could remain undetected on helical CT. The model predicted well the degree that attenuation was affected by stone size and collimation width. CONCLUSION: Stone composition and stone size, relative to CT collimation, independently influenced CT attenuation. The effect of stone size and collimation generally conformed to the model's predictions. We determined that small stones with low attenuation can be overlooked on helical CT. |
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Authors:
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K C Saw; J A McAteer; A G Monga; G T Chua; J E Lingeman; J C Williams |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: AJR. American journal of roentgenology Volume: 175 ISSN: 0361-803X ISO Abbreviation: AJR Am J Roentgenol Publication Date: 2000 Aug |
Date Detail:
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Created Date: 2000-08-23 Completed Date: 2000-08-23 Revised Date: 2008-02-15 |
Medline Journal Info:
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Nlm Unique ID: 7708173 Medline TA: AJR Am J Roentgenol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 329-32 Citation Subset: AIM; IM |
Affiliation:
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Methodist Hospital Institute for Kidney Stone Disease, Indianapolis, IN 46202, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Humans Tomography, X-Ray Computed* / methods Urinary Calculi / chemistry*, pathology, radiography* |
| Grant Support | |
ID/Acronym/Agency:
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P01 DK43881/DK/NIDDK NIH HHS |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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