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dc.contributor.advisor Dobbins, James T en_US
dc.contributor.author Schnell, EA
dc.contributor.author Samei, E
dc.contributor.author Dobbins, JT
dc.coverage.spatial United States
dc.date.accessioned 2010-05-13T17:50:46Z
dc.date.issued 2012-03
dc.identifier http://www.ncbi.nlm.nih.gov/pubmed/22380382
dc.identifier.citation Med Phys, 2012, 39 (3), pp. 1495 - 1504
dc.identifier.issn 0094-2405
dc.identifier.uri http://hdl.handle.net/10161/2503
dc.description Thesis en_US
dc.description.abstract PURPOSE: The purpose of this work is to improve the noise power spectrum (NPS), and thus the detective quantum efficiency (DQE), of computed radiography (CR) images by correcting for spatial gain variations specific to individual imaging plates. CR devices have not traditionally employed gain-map corrections, unlike the case with flat-panel detectors, because of the multiplicity of plates used with each reader. The lack of gain-map correction has limited the DQE(f) at higher exposures with CR. This current work describes a feasible solution to generating plate-specific gain maps. METHODS: Ten high-exposure open field images were taken with an RQA5 spectrum, using a sixth generation CR plate suspended in air without a cassette. Image values were converted to exposure, the plates registered using fiducial dots on the plate, the ten images averaged, and then high-pass filtered to remove low frequency contributions from field inhomogeneity. A gain-map was then produced by converting all pixel values in the average into fractions with mean of one. The resultant gain-map of the plate was used to normalize subsequent single images to correct for spatial gain fluctuation. To validate performance, the normalized NPS (NNPS) for all images was calculated both with and without the gain-map correction. Variations in the quality of correction due to exposure levels, beam voltage/spectrum, CR reader used, and registration were investigated. RESULTS: The NNPS with plate-specific gain-map correction showed improvement over the noncorrected case over the range of frequencies from 0.15 to 2.5 mm(-1). At high exposure (40 mR), NNPS was 50%-90% better with gain-map correction than without. A small further improvement in NNPS was seen from carefully registering the gain-map with subsequent images using small fiducial dots, because of slight misregistration during scanning. Further improvement was seen in the NNPS from scaling the gain map about the mean to account for different beam spectra. CONCLUSIONS: This study demonstrates that a simple gain-map can be used to correct for the fixed-pattern noise in a given plate and thus improve the DQE of CR imaging. Such a method could easily be implemented by manufacturers because each plate has a unique bar code and the gain-map for all plates associated with a reader could be stored for future retrieval. These experiments indicated that an improvement in NPS (and hence, DQE) is possible, depending on exposure level, over a wide range of frequencies with this technique.
dc.format.extent 1495 - 1504
dc.format.mimetype application/pdf
dc.language ENG
dc.language.iso en_US
dc.relation.ispartof Med Phys
dc.relation.isversionof 10.1118/1.3685580
dc.subject Calibration
dc.subject Radiographic Image Enhancement
dc.title Plate-specific gain map correction for the improvement of detective quantum efficiency in computed radiography.
dc.type Journal Article
dc.department Medical Physics en_US
duke.embargo.months 6 en_US
dc.date.accessible 2010-05-18T05:00:37Z
pubs.author-url http://www.ncbi.nlm.nih.gov/pubmed/22380382
pubs.issue 3
pubs.organisational-group /Duke
pubs.organisational-group /Duke/Pratt School of Engineering
pubs.organisational-group /Duke/Pratt School of Engineering/Biomedical Engineering
pubs.organisational-group /Duke/School of Medicine
pubs.organisational-group /Duke/School of Medicine/Clinical Science Departments
pubs.organisational-group /Duke/School of Medicine/Clinical Science Departments/Radiology
pubs.organisational-group /Duke/School of Medicine/Institutes and Centers
pubs.organisational-group /Duke/School of Medicine/Institutes and Centers/Duke Cancer Institute
pubs.organisational-group /Duke/Trinity College of Arts & Sciences
pubs.organisational-group /Duke/Trinity College of Arts & Sciences/Physics
pubs.publication-status Published
pubs.volume 39

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