Abstract
Purpose
Several studies on the dosimetric properties of unflattened photon beams have shown some advantages for radiotherapy. In this study, the effect of removing the flattening filter from an 18-MV photon beam was investigated using the Monte Carlo method.
Materials and methods
The 18-MV photon beam of an Elekta SL25 linear accelerator was simulated using the MCNP4C Monte Carlo (MC) code. Beam dosimetric features, including central axis absorbed doses, beam profiles, and photon energy spectra, were calculated for flattened and unflattened 18-MV photon beams.
Results
A 4.24-fold increase in the dose rate was seen for the unflattened beam with a field size of 10 × 10 cm2. A decrease in the out-of-field dose up to 30% was seen for the unflattened beam. For the unflattened beam, photon energy spectra were softer, and the mean energies of the spectra were higher for a smaller field size.
Conclusion
Our study showed that the increase in dose rate and lower out-of-field dose can be possible advantages for an unflattened 18-MV beam.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Mesbahi A, Mehnati P, Keshtkar A, Farajollahi A. Dosimetric properties of a flattening filter-free 6-MV photon beam: a Monte Carlo study. Radiat Med 2007;25:315–324.
Mesbahi A. Dosimetric characteristics of unflattened 6MV photon beams of a clinical linear accelerator: a Monte Carlo study. Appl Radiat Isot 2007;65:1029–1036.
Vassiliev ON, Titt U, Ponisch F, Kry SF, Mohan R, Gillin MT. Dosimetric properties of photon beams from a flattening filter free clinical accelerator. Phys Med Biol 2006;51:1907–1917.
Bayouth JE, Kaiser HS, Smith MC, Pennington EC, Anderson KM, Ryken TC, et al. Image-guided stereotactic radiosurgery using a specially designed high-dose-rate linac. Med Dosim 2007;32:134–141.
Fu W, Dai J, Hu Y, Han D, Song Y. Delivery time comparison for intensity-modulated radiation therapy with/without flattening filter: a planning study. Phys Med Biol 2004;49:1535–1547.
Mesbahi A, Fix M, Allahverdi M, Grein E, Garaati H. Monte Carlo calculation of Varian 2300C/D Linac photon beam characteristics: a comparison between MCNP4C, GEANT3 and measurements. Appl Radiat Isot 2005;62:469–477.
Mesbahi A, Reilly AJ, Thwaites DI. Development and commissioning of a Monte Carlo photon beam model for Varian Clinac 2100EX linear accelerator. Appl Radiat Isot 2006;64:656–662.
Vassiliev ON, Titt U, Kry SF, Ponisch F, Gillin MT, Mohan R. Monte Carlo study of photon fields from a flattening filter-free clinical accelerator. Med Phys 2006;33:820–827.
Briesmeister JF. MCNP—a general Monte Carlo N-particle transport code, version 4C. Report LA-13709-M. Los Alamos, NM: Los Alamos National Laboratory; 2000.
Ponisch F, Titt U, Vassiliev ON, Kry SF, Mohan R. Properties of unflattened photon beams shaped by a multileaf collimator. Med Phys 2006;33:1738–17346.
Verhaegen F, Seuntjens J. Monte Carlo modeling of external radiotherapy photon beams. Phys Med Biol 2003;48:R107–64.
Titt U, Vassiliev ON, Ponisch F, Dong L, Liu H, Mohan R. A flattening filter free photon treatment concept evaluation with Monte Carlo. Med Phys 2006;33:1595–1602.
Author information
Authors and Affiliations
Corresponding author
About this article
Cite this article
Mesbahi, A., Nejad, F.S. Monte Carlo study on a flattening filter-free 18-MV photon beam of a medical linear accelerator. Radiat Med 26, 331–336 (2008). https://doi.org/10.1007/s11604-008-0234-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11604-008-0234-y