Design of a QA method to characterize submillimeter-sized PBS beam properties using a two-dimensional ionization chamber array.

Design of a QA method to characterize submillimeter-sized PBS beam properties using a two-dimensional ionization chamber array.
Phys Med Biol. 2018 Apr 12;:
Authors: Lin Y, Bentefour EH, Flanz JB, Kooy HM, Clasie BM
Abstract
Pencil beam scanning (PBS) periodic quality assurance (QA) programs ensure the beam delivered to patients is within technical specifications. Two critical specifications for PBS delivery are the beam width and position. The aim of this study is to investigate whether a 2-dimensional ionization chamber array, such as the MatriXX detector (IBA Dosimetry, Schwarzenbruck, Germany), can be used to characterize submillimeter-sized PBS beam properties. The motivation is to use standard equipment, which may have pixel spacing coarser than the pencil beam size, and simplify QA workflow. 
 The MatriXX pixels are cylindrical in shape with 4.5 mm diameter and are spaced 7.62 mm from center to center. Two major effects limit the ability of using the MatriXX to measure the spot position and width accurately. The first effect is that too few pixels sample the Gaussian shaped pencil beam profile and the second effect is volume averaging of the Gaussian profile over the pixel sensitive volumes. We designed a method that overcomes both limitations and hence enables the use of the MatriXX to characterize sub-millimeter-sized PBS beam properties. This method uses a cross-like irradiation pattern that is designed to increase ...

Source: Physics in Medicine and Biology - April 12, 2018 Category: Physics Authors: Lin Y, Bentefour EH, Flanz JB, Kooy HM, Clasie BM Tags: Phys Med Biol Source Type: research