title: The response of a MOSFET, p-type semiconductor and LiF TLD to quasi-monoenergetic x-rays.
abstract: A metal oxide semiconductor field effect transistor (MOSFET), p-type semiconductor and a TLD can all be used for x-ray dosimetry, with each system having the common disadvantage of a response which is dependent upon the incident photon energy, particularly for energies < 1 MeV. A Pantak HF-320 quasi-monoenergetic x-ray unit was used to determine the response of two Thomson and Nielson TN-502RD MOSFETs, a Scanditronix EDP-10 semiconductor (build-up cap 10 mm: tissue equivalence), an EDD-5 semiconductor (build-up cap 4.5 mm: tissue equivalence) and an Lif:Mg:Ti TLD over the energy range 12-208 keV. The sensitivity of each detector was normalized to the value produced by exposure to 6 MV x-rays. The maximum relative sensitivities of the two MOSFET detectors were 4.19 +/- 0.25 and 4.44 +/- 0.26 respectively, occurring at an incident x-ray energy of 33 keV. The maximum relative sensitivity of the Scanditronix EDP-10 of 2.24 +/- 0.13 occurred at 65 keV, and for the EDD-5, it was 7.72 +/- 0.45 at 48 keV. The TLD produced a maximum relative sensitivity of 1.31 +/- 0.09 at 33 keV. Compared with available data based on heteroenergetic x-ray sources, these measurements have identified a more representative response for each detector to low-energy x-rays.
authors.affiliation: Department of Biomedical Engineering and Medical Physics, North Staffordshire Hospital (Royal Infirmary), Stoke-on-Trent, UK.
authors.forename: C R
authors.initials: CR
authors.lastname: Edwards
authors.forename: S
authors.initials: S
authors.lastname: Green
authors.forename: J E
authors.initials: JE
authors.lastname: Palethorpe
authors.forename: P J
authors.initials: PJ
authors.lastname: Mountford
mesh_terms: D004867:Equipment Design; D005459:Fluorides; D018020:Lithium Compounds; D008163:Luminescent Measurements; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000295:instrumentation* / Q000379:methods; D012680:Sensitivity and Specificity; D014965:X-Rays
chemical_list: D018020:Lithium Compounds; C027651:lithium fluoride; D005459:Fluorides