Study of the response of plastic scintillation detectors in small-field 6 MV photon beams by Monte Carlo simulations.

Purpose: To investigate the response of plastic scintillation detectors (PSDs) in a 6 MV photon beam of various field sizes using Monte Carlo simulations.

Methods: Three PSDs were simulated: A BC-400 and a BCF-12, each attached to a plastic-core optical fiber, and a BC-400 attached to an air-core optical fiber. PSD response was calculated as the detector dose per unit water dose for field sizes ranging from 10 x 10 down to 0.

Monte Carlo study of the energy and angular dependence of the response of plastic scintillation detectors in photon beams.

Purpose: By using Monte Carlo simulations, the authors investigated the energy and angular dependence of the response of plastic scintillation detectors (PSDs) in photon beams.

Methods: Three PSDs were modeled in this study: A plastic scintillator (BC-400) and a scintillating fiber (BCF-12), both attached by a plastic-core optical fiber stem, and a plastic scintillator (BC-400) attached by an air-core optical fiber stem with a silica tube coated with silver. The authors then calculated, with low statistical uncertainty, the energy and angular dependences of the PSDs' responses in a water phantom.

Replacement correction factors for plane-parallel ion chambers in electron beams.

Purpose: Plane-parallel chambers are recommended by dosimetry protocols for measurements in (especially low-energy) electron beams. In dosimetry protocols, the replacement correction factor P(repl) is assumed unity for "well-guarded" plane-parallel chambers in electron beams when the front face of the cavity is the effective point of measurement. There is experimental evidence that ion chambers which are not well-guarded (e.

Monte Carlo study of si diode response in electron beams.

Silicon semiconductor diodes measure almost the same depth-dose distributions in both photon and electron beams as those measured by ion chambers. A recent study in ion chamber dosimetry has suggested that the wall correction factor for a parallel-plate ion chamber in electron beams changes with depth by as much as 6%. To investigate diode detector response with respect to depth, a silicon diode model is constructed and the water/silicon dose ratio at various depths in electron beams is calculated using EGSnrc.

Estimation of the focal spot size and shape for a medical linear accelerator by Monte Carlo simulation.

The focal spot size and shape of a medical linac are important parameters that determine the dose profiles, especially in the penumbral region. A relationship between the focal spot size and the dose profile penumbra has been studied and established from simulation results of the EGSnrc Monte Carlo code. A simple method is proposed to estimate the size and the shape of a linac's focal spot from the measured dose profile data.