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    The consequences of fixed-pattern noise and image movement on electronic portal images.

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    Authors
    Kirby, Mike C
    Affiliation
    North Western Medical Physics Department, Christie Hospital, Manchester, UK.
    Issue Date
    1996-11
    
    Metadata
    Show full item record
    Abstract
    Fixed-pattern noise in electronic portal images (EPIs) is normally eliminated by dividing raw image data by an open-field calibration image (OFCI). However, for successful elimination, there must be exact registration between the two image sets. Any movement within the imaging system, such as that which occurs with gantry angle, will result in misregistration and a subsequent increase in noise. This paper describes, both qualitatively, by way of example, and quantitatively, by way of variance analysis, the consequences of misregistration and its effects on image quality. Our results show that image quality is found to degrade significantly with change in gantry angle, when a single OFCI is used, with a loss of low-contrast, fine detail. Variance is observed to increase over 2.5-fold. A simple solution of using multiple OFCIs is described, along with a technique for optimizing the number of images required, and the gantry angles at which they are acquired. When five OFCIs are used, the variance changes with gantry angle are limited to less than 20%. These changes are observed in both long and very short exposures (5 MU or 1 s).
    Citation
    The consequences of fixed-pattern noise and image movement on electronic portal images. 1996, 41 (11):2345-56 Phys Med Biol
    Journal
    Physics in Medicine and Biology
    URI
    http://hdl.handle.net/10541/95142
    DOI
    10.1088/0031-9155/41/11/007
    PubMed ID
    8938030
    Type
    Article
    Language
    en
    ISSN
    0031-9155
    ae974a485f413a2113503eed53cd6c53
    10.1088/0031-9155/41/11/007
    Scopus Count
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