AbstractID: 7530 Title: Characterization of High-Sensitivity, Isotropic p-MOSFET
Dosimeters and a New Tissue-Equivalent Plastic for Use in Pediatric Anthropomorphic
Phantoms
MOSFET dosimeters are a very useful tool for dose measurement in diagnostic applications. Therefore, it
is necessary to know quantitatively fundamental ways in which the MOSFET behaves. A major research
area at the University of Florida is to determine doses to pediatric patients during diagnostic procedures
using tomographic phantoms. Thus, the behavior of the MOSFETs as depth in tissue is varied is also
valuable to know, as is how dose is deposited at different depths in the tissue-equivalent plastics used to
construct the phantoms. The sensitivity of MOSFET dosimeters as a function of tube potential was
examined, as well as the angular response of the MOSFETs during rotations axially and normal-to-axially
in a tissue-equivalent cylinder. MOSFET sensitivity exhibited little variation for tube potentials between
40 and 120 kVp. MOSFET angular response exhibited a very small dependence on the orientation of the
MOSFET. However, during normal-to-axial rotation, at an end-on orientation with respect to the beam
(90º) and at the opposite orientation (180º), the MOSFET exhibited a sharp difference in response. In
addition, MOSFET response as a function of depth in soft tissue was studied, along with the dose
deposition characteristics of STES-3N, a tissue-equivalent plastic. This was done using one cm blocks of
plastic stacked sequentially on either an ion chamber or MOSFET dosimeters. Comparisons between
experimentally determined tissue doses and tissue doses measured using MCNP simulations of the same
experimental setup are also presented.
Work supported by the National Institute for Child Health & Human Development, Grant ROI HD3893201