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

Preliminary characterization of the beam monitors for CNAO with the PSI clinical proton beam

Meeting Abstract

  • S. Giordanengo - Istituto Nazionale Fisica Nucleare, Torino, Italy
  • M. Donetti - Centro Nazionale Adroterapia Oncologica, Pavia, Italy
  • M. A. Garella - Centro Nazionale Adroterapia Oncologica, Pavia, Italy
  • C. Ansarinejad - University of Torino, Torino, Italy
  • C. Tomba - University of Torino, Torino, Italy
  • S. Lin - Paul Scherrer Institut, Villigen, Switzerland
  • A. Attili - Istituto Nazionale Fisica Nucleare, Torino, Italy
  • F. Bourhaleb - University of Torino, Torino, Italy
  • R. Cirio - University of Torino, Torino, Italy
  • F. Marchetto - Istituto Nazionale Fisica Nucleare, Torino, Italy
  • V. Monaco - University of Torino, Torino, Italy
  • E. Pedroni - Paul Scherrer Institut, Villigen, Switzerland
  • C. Peroni - University of Torino, Torino, Italy
  • G. Russo - University of Torino, Torino, Italy
  • R. Sacchi - University of Torino, Torino, Italy

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog069

DOI: 10.3205/09ptcog069, URN: urn:nbn:de:0183-09ptcog0695

Veröffentlicht: 24. September 2009

© 2009 Giordanengo et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Purpose: The beam monitors for CNAO (Centro Nazionale di Adroterapia Oncologica), developed and built in collaboration between INFN, Torino University and CNAO foundation, are ready to be installed on the CNAO nozzle. A basic debug of the detectors with X-rays was done and a more precise characterization with a clinical particle beam was necessary. Two sets of detectors have been tested at Paul Scherrer Institut (PSI) in Villigen (CH) with a clinical proton beam delivered with a dynamic spot scanning technique. The aim of the test was to check the reproducibility of the integrated charge per spot and the uniformity across the sensitive area for four monitor chambers segmented in strip, two segmented in pixel and four not segmented (integral) chambers.

The test results and some details on the readout system will be presented.

Methods and materials: Two complete monitor systems for the CNAO have been used. Each one is characterized by five ionization chambers arranged into two independent boxes. One integral chamber for intensity measurement and two orthogonal strip chambers mainly for beam position measurements are included in a box (box 1) while a second integral chamber and a pixel chamber compose another box (box 2).

The hardware elements of the data acquisition system was very similar to the final ones used for CNAO. Dedicated software was implemented to readout the five detectors at the same time with maximum frequency of 2 kHz, or synchronized with the spot in order to have a measure few microseconds before the particle arrival and few microseconds after.

The particle beam was the PSI clinical proton beam delivered at Gantry 1, daily used to treat patients.

Several measurements of a fix number of spots with the same dose and in the same central position where performed to verify the reproducibility of the detectors.

A uniform 10x10 cm2 field, 9 spots on a 3x3 grid of 0.5 cm pitch and a uniform line were operated several times to check the uniformity across the sensitive area.

Beam position and dimension have been analyzed through the strip and pixel chambers data and with different algorithms.

Results: The reproducibility in the integrated charge has been measured several times over 20 and 400 consecutive spots with 4 integral chambers, 4 strip chambers and 2 pixel chambers. It is better than 0.6% for 9 detectors; one integral chamber was not working properly.

The uniformity across the sensitive area is better than 1% for the integral and strip chambers and around 1.5% for the pixel chambers.

Some differences in charge collection have been observed between detectors which will be investigated.

Conclusions: A preliminary test with a dynamic proton beam to study the performances of the beam monitors of CNAO has been performed at PSI. The main goal was to verify reproducibility and uniformity of two sets of chambers which will be soon installed in the CNAO therapy treatment line.