Transit dosimetry in IMRT with an a-Si EPID in direct detection configuration

M. Sabet, Pejman Rowshanfarzad, P. Vial, F.W. Menk, P.B. Greer

    Research output: Contribution to journalArticlepeer-review

    10 Citations (Scopus)


    In this study an amorphous silicon electronic portal imaging device (a-Si EPID) converted to direct detection configuration was investigated as a transit dosimeter for intensity modulated radiation therapy (IMRT). After calibration to dose and correction for a background offset signal, the EPID-measured absolute IMRT transit doses for 29 fields were compared to a MatriXX two-dimensional array of ionization chambers (as reference) using Gamma evaluation (3%, 3mm). The MatriXX was first evaluated as reference for transit dosimetry. The accuracy of EPID measurements was also investigated by comparison of point dose measurements by an ionization chamber on the central axis with slab and anthropomorphic phantoms in a range of simple to complex fields. The uncertainty in ionization chamber measurements in IMRT fields was also investigated by its displacement from the central axis and comparison with the central axis measurements. Comparison of the absolute doses measured by the EPID and MatriXX with slab phantoms in IMRT fields showed that on average 96.4% and 97.5% of points had a Gamma index
    Original languageEnglish
    Pages (from-to)N295-N306
    JournalPhysics in Medicine and Biology
    Issue number15
    Publication statusPublished - 17 Jul 2012


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