Document Detail

Dual energy x-ray absorptiometry: the effects of beam hardening on bone density measurements.
MedLine Citation:
PMID:  1584146     Owner:  NLM     Status:  MEDLINE    
X-ray tubes have superseded radionuclide sources for dual photon absorptiometry of the spine and hip. However, the use of a polyenergetic spectrum is a potential source of error for x-ray absorptiometers since beam hardening may result in a nonlinear measurement scale for bone mineral density (BMD). A quantitative study of the effects of beam hardening on measurements made with a commercial dual energy x-ray scanner has been performed. Bone was represented by layers of aluminum of linearly increasing thickness which were scanned under water thicknesses ranging from 0 to 25 cm to represent different body thicknesses of soft tissue. Beam hardening had two effects on measured BMD: (i) at a constant true BMD, measured BMD varied with water thickness; (ii) at a constant water thickness, the BMD scale was not precisely linear. For conditions appropriate to spine and hip studies (BMD) values in the range 0.7 to 1.4 g/cm2 and body thickness between 15 and 25 cm) the maximum deviation of measured BMD from a linear scale was 0.023 g/cm2, while the root-mean-square deviation (0.01 g/cm2) was comparable to the measurement precision for a spine or femoral neck scan (about 1%). The largest departures from linearity were found to occur at the thinnest water thicknesses for BMD values in the range 0.2 to 0.6 g/cm2. The effect of scale nonlinearity on the results of longitudinal studies was examined: for a spine scan at 20-cm body thickness, measured changes in BMD slightly overestimated the true change and implied an error of 0.15%/year for a measurement of a true rate of loss of 3% year in a postmenopausal woman.
G M Blake; D B McKeeney; S C Chhaya; P J Ryan; I Fogelman
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Medical physics     Volume:  19     ISSN:  0094-2405     ISO Abbreviation:  Med Phys     Publication Date:    1992 Mar-Apr
Date Detail:
Created Date:  1992-06-12     Completed Date:  1992-06-12     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0425746     Medline TA:  Med Phys     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  459-65     Citation Subset:  IM    
Department of Nuclear Medicine, Guy's Hospital, London, United Kingdom.
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MeSH Terms
Absorptiometry, Photon*
Bone Density*
Models, Structural

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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