gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

The Design of a Multi-Layer Ionization Chamber for Proton Therapy

Meeting Abstract

  • T. Mertens - Dosimetry, IBA GmbH, Schwarzenbruck, Germany
  • B. Marchand - Particle Therapy, IBA, Louvain-la-Neuve, Belgium
  • F. Friedl - Dosimetry, IBA GmbH, Schwarzenbruck, Germany
  • V. Breev - Particle Therapy, IBA, Louvain-la-Neuve, Belgium
  • G. Mathot - Particle Therapy, IBA, Louvain-la-Neuve, Belgium
  • C. Brusasco - Particle Therapy, IBA, Louvain-la-Neuve, Belgium
  • S. de Neuter - Particle Therapy, IBA, Louvain-la-Neuve, Belgium

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog136

DOI: 10.3205/09ptcog136, URN: urn:nbn:de:0183-09ptcog1367

Published: September 24, 2009

© 2009 Mertens et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Background: Active beam delivery modalities, such as Uniform Scanning, are nowadays becoming more-and-more available for Proton Therapy centers. Efficient installation and commissioning procedures for these modalities is of paramount importance. Historically water phantom based systems have been intensively used for measurements performed with passive beam delivery methods like Single & Double Scattering. This approach turns out to be particularly cumbersome and time consuming for scanned beam measurements.

Material and methods: In order to provide a solution to this situation, a Multi-Layer Ionization Chamber (MLIC) system presented under the trading name ZeBra has been developed. The system consists of a stack of 180 independent parallel plane plate chambers separated by an 1 mm air gap offering a native resolution of 2 mm. The PCB material constituting the chambers has been designed in order to obtain a water equivalent device. The device is able to measure fully or partially modulated depth dose distributions up to 33 gr/cm2 for both passive and active delivery modalities. A dedicated electrometer based on Tera ASICS technology has been developed providing a charge quantum resolution of 100fC and a sampling time down to 10 ms. The application is driven by the OmniPro Incline software which allows the user to proceed with measurements and analysis of the depth dose profiles. The main Dosimetry properties of the dose distribution like range or modulation are extracted from the measurement data and available for further reporting and analysis purposes.

Results: The system's detector response has been fully characterized using both passive and active beam deliveries. Measurements over time show that the device is very stable, the device is shown to be linear with applied dose rates between 0.5 Gy/min and 15 Gy/min. Both stability and linearity have variations of the response lower than 1%.

Excellent agreement between measurements performed with a standard water tank and the MLIC have been found. The differences in terms of range measurements are smaller than 0.5 mm and less than 1 mm in terms of modulation. Details about the performance of the system will be presented and discussed.

Conclusion: The use of the ZeBra MLIC system in combination with its dedicated analysis software is providing a fast and accurate solution when performing calibration, commissioning and QA for scanned beam based proton systems The system is currently in the FDA approval process and patent pending.