Determination of ion recombination and polarity effect correction factors for a plane-parallel ionization Bragg Peak chamber under proton and carbon ion pencil beams.

Determination of ion recombination and polarity effect correction factors for a plane-parallel ionization Bragg Peak chamber under proton and carbon ion pencil beams.
Phys Med Biol. 2019 Mar 07;:
Authors: Mirandola A, Magro G, Maestri D, Mairani A, Mastella E, Molinelli S, Russo S, Vai A, Ciocca M
Abstract
Within the dosimetric characterization of particle beams, laterally-integrated depth-dose-distributions (IDDs) are measured and provided to the treatment planning system (TPS) for beam modeling or used as a benchmark for Monte Carlo (MC) simulations. The purpose of this work is the evaluation, in terms of ion recombination and polarity effect, of the dosimetric correction to be applied to proton and carbon ion curves as a function of linear energy transfer (LET).
 LET was calculated with a MC code for selected IDDs. Several regions of Bragg Peak (BP) curve were investigated. The charge was measured with the plane-parallel BP-ionization chamber mounted in the Peakfinder as a field detector, by delivering a fixed number of particles at the maximum flux. The dose rate dependence was evaluated for different flux levels. The chamber was connected to an electrometer and exposed to un-scanned pencil beams. For each measurement the chamber was supplied with {±400, +200, +100} V. Recombination and polarity correction factors were then calculated as a function of depth and LET in water. Three energies representative of the clinical ...

Source: Physics in Medicine and Biology - March 6, 2019 Category: Physics Authors: Mirandola A, Magro G, Maestri D, Mairani A, Mastella E, Molinelli S, Russo S, Vai A, Ciocca M Tags: Phys Med Biol Source Type: research