skip to main content

Title: Characterization of radiation beams used to determinate the correction factor for a CyberKnife® unit reference field using ionization chambers

This paper aimed to characterize a 6 MV x-ray beam from a Varian® iX linear accelerator in order to obtain the correction factors needed by the IAEA/AAPM new formalism{sup 1}. The experiments were performed in a liquid water phantom under different irradiation conditions: a) Calibration of the reference field of 10 cm × 10 cm at 90 cm SSD and 10 cm depth was carried out according to the TRS-398 protocol using three ionization chambers (IC) calibrated in different reference laboratory and b) Measurement of the absorbed dose rate at 70 cm SSD and 10 cm depth in a 10 cm × 10 cm and 5.4 cm × 5.4 cm fields was obtained in order to simulate the CyberKnife® conditions where maximum distance between the source and the detector is equal to 80 cm and the maximum field size is 6 cm diameter. Depending where the IC was calibrated, differences between 0.16% and 2.24% in the absorbed dose rate measured in the 10 cm × 10 cm field at 90 cm SSD were observed, while for the measurements at 70 cm SSD, differences between 1.27% and 3.88% were obtained. For the 5.4 cm × 5.4 cm field, the absorbed dosemore » measured with the three ICs varies between 1.37% and 3.52%. The increase in the difference on the absorbed dose when decreasing the SSD could possibly be associated to scattering radiation generated from the collimators and/or the energy dependence of the ionization chambers to low-energy radiation. The results presented in this work suggest the importance of simulating the CyberKnife® conditions using other linear accelerator for obtaining the correction factors as proposed by the IAEA/AAPM new formalism in order to measure the absorbed dose with acceptable accuracy.« less
Authors:
;  [1] ;  [2]
  1. Instituto de Física, Universidad Nacional Autónoma de México, D.F (Mexico)
  2. Hospital de Oncología, Centro Médico Nacional Siglo XXI, D.F (Mexico)
Publication Date:
OSTI Identifier:
22390522
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1626; Journal Issue: 1; Conference: 13. Mexican Symposium on Medical Physics, Leon, Guanajuato (Mexico), 15-16 Mar 2014; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 61 RADIATION PROTECTION AND DOSIMETRY; ABSORBED RADIATION DOSES; ACCURACY; CALIBRATION; COLLIMATORS; CORRECTIONS; ENERGY DEPENDENCE; GAMMA DOSIMETRY; IONIZATION CHAMBERS; IRRADIATION; LINEAR ACCELERATORS; LIQUIDS; PHANTOMS; PHOTON BEAMS