Dosimetry protocol for the forthcoming clinical trials in synchrotron stereotactic radiation therapy (SSRT)

Journal Article · Tue Mar 15 00:00:00 EDT 2011 · Medical Physics

DOI:https://doi.org/10.1118/1.3556561· OSTI ID:22096952

Prezado, Y.; Vautrin, M.; Martinez-Rovira, I. ^[1]; others, and

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1. ID17 Biomedical Beamline, European Synchrotron Radiation Facility (ESRF), 38043 Grenoble (France)

Purpose: An adequate dosimetry protocol for synchrotron radiation and the specific features of the ID17 Biomedical Beamline at the European Synchrotron Radiation Facility are essential for the preparation of the forthcoming clinical trials in the synchrotron stereotactic radiation therapy (SSRT). The main aim of this work is the definition of a suitable protocol based on standards of dose absorbed to water. It must allow measuring the absolute dose with an uncertainty within the recommended limits for patient treatment of 2%-5%. Methods: Absolute dosimetry is performed with a thimble ionization chamber (PTW semiflex 31002) whose center is positioned at 2 g cm{sup -2} equivalent depth in water. Since the available synchrotron beam at the ESRF Biomedical Beamline has a maximum height of 3 mm, a scanning method was employed to mimic a uniform exposition of the ionization chamber. The scanning method has been shown to be equivalent to a broad beam irradiation. Different correction factors have been assessed by using Monte Carlo simulations. Results: The absolute dose absorbed to water at 80 keV was measured in reference conditions with a 2% global uncertainty, within the recommended limits. The dose rate was determined to be in the range between 14 and 18 Gy/min, that is to say, a factor two to three times higher than the 6 Gy/min achievable in RapidArc or VMAT machines. The dose absorbed to water was also measured in a RW3 solid water phantom. This phantom is suitable for quality assurance purposes since less than 2% average difference with respect to the water phantom measurements was found. In addition, output factors were assessed for different field sizes. Conclusions: A dosimetry protocol adequate for the specific features of the SSRT technique has been developed. This protocol allows measuring the absolute dose absorbed to water with an accuracy of 2%. It is therefore satisfactory for patient treatment.

• OSTI ID: 22096952
• Journal Information: Medical Physics, Vol. 38, Issue 3; Other Information: (c) 2011 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
62 RADIOLOGY AND NUCLEAR MEDICINE
60 APPLIED LIFE SCIENCES
CLINICAL TRIALS
COMPUTERIZED SIMULATION
DOSE RATES
DOSIMETRY
EUROPEAN SYNCHROTRON RADIATION FACILITY
IONIZATION CHAMBERS
IRRADIATION
KEV RANGE 10-100
MONTE CARLO METHOD
PATIENTS
PHANTOMS
QUALITY ASSURANCE
RADIATION DOSES
RADIOTHERAPY
SYNCHROTRON RADIATION
SYNCHROTRONS
WATER