Dose profile measurement system for clinical proton fields

Abstract

A beam profile measurement detector is a tool to efficiently verify dose distributions created with active methods of a clinical proton beam delivery. A Multi-Pad Ionization Chamber (MPIC) has 128 ionization chambers arranged in one plane and measure lateral profiles in fields up to 38 cm in diameter. The MPIC pads have a 5 mm pitch for fields up to 20 cm in diameter and a 7 mm pitch for larger fields, providing an accuracy of field size determination of about 0.5 mm. The Multi-Layer Ionization Chamber (MLIC) detector contains 122 small-volume ionization chambers stacked at a 1.82 mm step (water-equivalent) for depth-dose profile measurements. The MLIC detector can measure profiles up to 20 cm in depth, and determine the 80% distal dose fall-off with about 0.1 mm precision. Both detectors can be connected to the same set of electronics modules, which form the detectors' data acquisition system. The detectors operate in proton fields produced with active methods of beam delivery such as uniform scanning and energy stacking. The MPIC and MLIC detectors can be used for dosimetric characterization of clinical proton fields.

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