AbstractID: 8125 Title: Design optimization of an ionization-type multielement detector for megavoltage
photons using the Monte Carlo method
An efficient ionization-type multielement detector for megavoltage photons was
investigated. The incoming photons produce high-energy electrons in the metal array,
which defines the gas cavities. These electrons deposit their energy in the gas. A design
optimization of such a detector can be done with the Monte Carlo method. For the
simulations, only the central element of an array was irradiated and the deposited energy
in the gas was scored for each element. This approach allows the determination of the
primary and crosstalk signal. The optimal length of the detector in the direction of the
beam as well as the significance of the collecting electrodes were investigated. The
studies have shown that most of the long-range crosstalk originates from Compton
scattered photons. It was also shown that the attenuation of the photon beam in the metal
is not necessarily a good measure for the optimal length of the detector. The calculation
of the primary/crosstalk signal distribution in a given element along the direction of the
beam might be a better approach. The amount of primary signal can significantly be
reduced by the presence of collecting electrodes depending on the dimensions and shape
of the collecting electrodes. This work illustrates that Monte Carlo studies can aid in
finding a design, which results in a maximally efficient detector.
This work was partially funded by TomoTherapy, Inc.