Theoretical and experimental investigation of dose enhancement due to charge storage in electron-irradiated phantoms

Journal Article · Thu Nov 01 04:00:00 EST 1984 · Med. Phys.; (United States)

DOI:https://doi.org/10.1118/1.595569· OSTI ID:6103269

Rawlinson, J A; Bielajew, A F; Munro, P; Galbraith, D M

Recent measurements have shown that significant errors in radiation dosimetry can arise by the use of insulating plastic phantoms which have been exposed to electron beams. The effect has been attributed to the generation of large electric fields in the phantom by charge storage causing alteration of electron trajectories and an increase in the measured dose. In this report, we examine this hypothesis theoretically by calculating the change in response to radiation of an ion chamber in a cylindrical cavity in an electron-irradiated polymethylmethacrylate phantom. The electric field distribution is determined using a model which allows for charge leakage by radiation-induced conductivity, and the dose in the cavity is determined by a Monte Carlo simulation using the EGS (electron gamma shower) code modified to account for electron trajectories in the electric field. The theoretical results are shown to agree well with new and previously published experimental dose enhancement data. The agreement is taken as confirmation of the reported explanation of the effect. The use of conducting phantoms in radiation dosimetry is advocated.

• Research Organization: Physics Division, Ontario Cancer Institute, Toronto M4X 1K9, Canada
• OSTI ID: 6103269
• Journal Information: Med. Phys.; (United States), Journal Name: Med. Phys.; (United States) Vol. 11:6; ISSN MPHYA
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
655003* -- Medical Physics-- Dosimetry
BEAMS
DIELECTRIC MATERIALS
ELECTRICAL EQUIPMENT
ELECTRICAL INSULATORS
ELECTRON BEAMS
EQUIPMENT
LEPTON BEAMS
MATERIALS
MOCKUP
PARTICLE BEAMS
PETROCHEMICALS
PETROLEUM PRODUCTS
PHANTOMS
PHYSICAL RADIATION EFFECTS
PLASTICS
RADIATION DOSE DISTRIBUTIONS
RADIATION EFFECTS
STRUCTURAL MODELS
SYNTHETIC MATERIALS