Caracterización de un sistema de imagen portal basado en silicio amorfo para la medida de distribuciones de dosis absorbida
- Pérez Moreno, J.M.
- Fernández Letón, Pedro
- Zucca Aparicio, D.
- García Ruiz Zorrilla, Juan
- Miñambres Moro, A.
ISSN: 1576-6632
Year of publication: 2011
Volume: 12
Issue: 2
Pages: 85-96
Type: Article
More publications in: Revista de Física Médica
Abstract
We have developed a method for using a portal imaging device based on amorphous silicon (EPID) for the dosimetric verification of intensity modulated radiotherapy (IMRT) treatments using 6 MV beams. The images obtained using the imaging system are deconvolved with a kernel for radiation and scattering of light generated in the EPID. This kernel has an analytical form and has been experimentally determined. The fluence thus obtained is convolved with a dose deposition kernel, also modeled analytically in a empirical way. The result is an absorbed dose distribution in water at 5 cm depth. The difference between the measured dose using portal imaging device and ionization chamber is -0.3±0.9 % in open fields, with a maximum deviation of 1.5% in a 20 cm × 20 cm field with 60° virtual wedge. The degree of agreement between dose distributions measured with the EPID and ionization chamber array is satisfactory, exceeding all cases evaluated 95% of points with c<1 using 3%, 3 mm criteria for gamma analysis.