Blurring and MTF determination of a radiotherapy EPID using the edge spread function

Author

Franco, L. ; Gómez, F. ; Iglesias, A. ; Pardo, J. ; Pena, J. ; Lobato, R. ; Mosquera, J. ; Pombar, M. ; Sendón, J.R. ; Ledo, F. ; Yáñez, A.

Author_Institution

Particle Phys. Dept., Santiago de Compostela Univ., Spain

Volume

4

fYear

2004

fDate

16-22 Oct. 2004

Firstpage

2639

Abstract

We present a method based in the study of the edge spread function (ESF) obtained by using a solid metallic block image to measure the resolution of a radiotherapy EPID. With this simple method it is possible to determine the effective focal spot size of a LINAC, the intrinsic unsharpness of the portal imaging device and also its MTF response, which it is not usually tested in routine quality controls since an specific phantom is needed. Results for the spatial resolution are compared to those calculated with a bar phantom of the same material. This procedure can be implemented in the routine EPID quality control in the clinical practice. Measurements were made with the Beamview TI EPID of a Siemens Primus linac. A focal spot size of 1.057 and 1.484 mm (X, Y directions) and a f₅₀ at isocenter of 0.272 and 0.304 lp/mm (X,Y directions) were obtained.

Keywords

biological effects of radiation; linear accelerators; particle beam diagnostics; phantoms; radiation therapy; 1.057 mm; 1.484 mm; MTF response; Siemens Primus linac; edge spread function; effective focal spot size; electronic portal imaging device; phantom; radiotherapy; solid metallic block image; Hospitals; Image resolution; Imaging phantoms; Linear particle accelerator; Optical imaging; Pixel; Portals; Quality control; Solids; Testing;

fLanguage

English

Publisher

ieee

Conference_Titel

Nuclear Science Symposium Conference Record, 2004 IEEE

ISSN

1082-3654

Print_ISBN

0-7803-8700-7

Type

conf

DOI

10.1109/NSSMIC.2004.1462793

Filename

1462793