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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
5
|
| pubmed:dateCreated |
1992-1-9
|
| pubmed:abstractText |
Two methods of dual-photon absorptiometry (DPA) utilizing an x-ray tube instead of a radionuclide source have recently been introduced. In one method kVp switching is employed and two transmitted intensities at each pixel are determined. In the other method, K-edge filtration combined with a single kVp spectrum is used, but photons in two energy windows are counted. We present a theoretical analysis of the two methods, focusing on a figure of merit which is essentially the exposure efficiency (the precision for a given entrance exposure) and tube loading. We also compare their exposure efficiencies to theoretical limits that no DPA system can exceed. Our study indicates that the K-edge-filtered method is more exposure efficient by about a factor of 2. The switched-kVp method requires less heat units per scan by about a factor of 3. A hybrid K-edge switched-kVp method is suggested which achieves the same exposure efficiency as the K-edge-filtered method at lesser tube loading. Our theoretical model is based on published x-ray spectra and attenuation coefficients and is in good agreement with other simulation work. It is of interest that a point source of Gd-153 would be even more exposure efficient, achieving about 90% of the theoretical limit. However, in practice, the Gd source is of finite size and limited strength, and consequently the radionuclide method cannot achieve as good a precision as either x-ray method in similar scan times.
|
| pubmed:grant | |
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:status |
MEDLINE
|
| pubmed:issn |
0094-2405
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
18
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
978-84
|
| pubmed:dateRevised |
2007-11-14
|
| pubmed:meshHeading | |
| pubmed:articleTitle |
Bone mineral densitometry with x-ray and radionuclide sources: a theoretical comparison.
|
| pubmed:affiliation |
Department of Radiology, University of Alabama Hospitals and Clinics, University of Alabama, Birmingham 35294.
|
| pubmed:publicationType |
Journal Article,
Comparative Study,
Research Support, U.S. Gov't, P.H.S.
|