Abstract：
:The relationship between the pixel value and exit dose was investigated for a new commercially available amorphous silicon electronic portal imaging device. The pixel to dose mapping function was established to be linear for detector distances between 116.5 cm to 150 cm from the source, radiation field sizes from 5 x 5 cm2 to 20 x 20 cm2 and beam energies of 6 to 18 MV. Coefficients in the mapping function were found to be dependent on beam energy and field size. Open and wedged field profiles measured with the device showed agreement to a maximum of 5% and 8%, respectively, as compared to film. A comparison of relative transmission measurements between the EPID and ion chamber indicate a maximum deviation of 6% and 2% at 6 and 18 MV, respectively, for an attenuator thickness of 21 cm and SDD > or = 130 cm. It was found that accuracies of better than 1% could be obtained if detector position and field size specific fitting parameters were used to generate unique mapping functions for each configuration.
journal_name
Med Physjournal_title
Medical physicsauthors
Grein EE,Lee R,Luchka Kdoi
10.1118/1.1508108subject
Has Abstractpub_date
2002-10-01 00:00:00pages
2262-8issue
10eissn
0094-2405issn
2473-4209journal_volume
29pub_type
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