Abstract:
:In critical organ in vivo x-ray dosimetry, the relative contaminating electron contribution to the total dose and total detector response outside the field will be different to the corresponding contributions at the central axis detector calibration position, mainly due to the effects of shielding in the linear accelerator head on the electron and x-ray energy spectrum. To investigate these contributions, the electron energy response of a Scanditronix PFD diode was measured using electrons with mean energies from 0.45 to 14.6 MeV, and the Monte Carlo code MCNP-4C was used to calculate the electron energy spectra on the central axis, and at 1 and 10 cm outside the edge of a 4 x 4, 10 x 10 and a 15 x 15 cm(2) 6 MV x-ray field. The electron contribution to the total dose varied from about 8% on the central axis of the smallest field to about 76% at 10 cm outside the edge of the largest field. The electron contribution to the total diode response varied from about 7-8% on the central axis of all three fields to about 58% at 10 cm outside the edge of the smallest field. The results indicated that a near surface x-ray dose measurement with a diode outside the treatment field has to be interpreted with caution and requires knowledge of the relative electron contribution specific to the measurement position and field size.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Edwards CR,Mountford PJ,Moloney AJdoi
10.1088/0031-9155/51/24/013subject
Has Abstractpub_date
2006-12-21 00:00:00pages
6471-82issue
24eissn
0031-9155issn
1361-6560pii
S0031-9155(06)26645-4journal_volume
51pub_type
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