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More than 10 years experience of beam monitoring with the Gantry 1 spot scanning proton therapy facility at PSI
Author(s) -
Lin Shixiong,
Boehringer Terence,
Coray Adolf,
Grossmann Martin,
Pedroni Eros
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3244034
Subject(s) - ionization chamber , dosimetry , proton therapy , beam (structure) , detector , faraday cup , optics , pencil beam scanning , quality assurance , laser beam quality , beamline , deflection (physics) , dose profile , materials science , medical physics , physics , nuclear medicine , ion beam , ionization , engineering , medicine , laser beams , ion , laser , operations management , external quality assessment , quantum mechanics
Purpose: The beam monitoring equipments developed for the first PSI spot scanning proton therapy facility, Gantry 1, have been successfully used for more than 10 years. The purpose of this article is to summarize the author's experience in the beam monitoring technique for dynamic proton scanning. Methods: The spot dose delivery and verification use two independent beam monitoring and computer systems. In this article, the detector construction, electronic system, dosimetry, and quality assurance results are described in detail. The beam flux monitor is calibrated with a Faraday cup. The beam position monitoring is realized by measuring the magnetic fields of deflection magnets with Hall probes before applying the spot and by checking the beam position and width with an ionization strip chamber after the spot delivery. Results: The results of thimble ionization chamber dosimetry measurements are reproducible (with a mean deviation of less than 1% and a standard deviation of 1%). The resolution in the beam position measurement is of the order of a tenth of a millimeter. The tolerance of the beam position delivery and monitoring during scanning is less than 1.5 mm. Conclusions: The experiences gained with the successful operation of Gantry 1 represent a unique and solid background for the development of a new system, Gantry 2, in order to perform new advanced scanning techniques.