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Commissioning of photon beams of a flattening filter-free linear accelerator and the accuracy of beam modeling using an anisotropic analytical algorithm


Hrbacek, J; Lang, S; Klöck, S (2011). Commissioning of photon beams of a flattening filter-free linear accelerator and the accuracy of beam modeling using an anisotropic analytical algorithm. International Journal of Radiation Oncology, Biology, Physics, 80(4):1228-1237.

Abstract

PURPOSE:

To investigate dosimetric characteristics of a new linear accelerator designed to deliver flattened, as well as flattening filter-free (FFF), beams. To evaluate the accuracy of beam modeling under physical conditions using an anisotropic analytical algorithm.
METHODS AND MATERIALS:

Dosimetric data including depth dose curves, profiles, surface dose, penumbra, out-of-field dose, output, total and scatter factors were examined for four beams (X6, X6FFF, X10, and X10FFF) of Varian's TrueBeam machine. Beams modeled by anisotropic analytical algorithm were compared with measured dataset.
RESULTS:

FFF beams have lower mean energy (tissue-phantom ratio at the depths of 20 and 10 cm (TPR 20/10): X6, 0.667; X6FFF, 0.631; X10, 0.738; X10FFF, 0.692); maximum dose is located closer to the surface; and surface dose increases by 10%. FFF profiles have sharper but faster diverging penumbra. For small fields and shallow depths, dose outside a field is lower for FFF beams; however, the advantage fades with increasing phantom scatter. Output increases 2.26 times for X6FFF and 4.03 times for X10FFF and is less variable with field size; collimator exchange effect is reduced. A good agreement between modeled and measured data is observed. Criteria of 2% depth-dose and 2-mm distance-to-agreement are always met.
CONCLUSION:

Reference dosimetric characteristics of TrueBeam photon bundles were obtained, and successful modeling of the beams was achieved.

Copyright © 2011 Elsevier Inc. All rights reserved.

Abstract

PURPOSE:

To investigate dosimetric characteristics of a new linear accelerator designed to deliver flattened, as well as flattening filter-free (FFF), beams. To evaluate the accuracy of beam modeling under physical conditions using an anisotropic analytical algorithm.
METHODS AND MATERIALS:

Dosimetric data including depth dose curves, profiles, surface dose, penumbra, out-of-field dose, output, total and scatter factors were examined for four beams (X6, X6FFF, X10, and X10FFF) of Varian's TrueBeam machine. Beams modeled by anisotropic analytical algorithm were compared with measured dataset.
RESULTS:

FFF beams have lower mean energy (tissue-phantom ratio at the depths of 20 and 10 cm (TPR 20/10): X6, 0.667; X6FFF, 0.631; X10, 0.738; X10FFF, 0.692); maximum dose is located closer to the surface; and surface dose increases by 10%. FFF profiles have sharper but faster diverging penumbra. For small fields and shallow depths, dose outside a field is lower for FFF beams; however, the advantage fades with increasing phantom scatter. Output increases 2.26 times for X6FFF and 4.03 times for X10FFF and is less variable with field size; collimator exchange effect is reduced. A good agreement between modeled and measured data is observed. Criteria of 2% depth-dose and 2-mm distance-to-agreement are always met.
CONCLUSION:

Reference dosimetric characteristics of TrueBeam photon bundles were obtained, and successful modeling of the beams was achieved.

Copyright © 2011 Elsevier Inc. All rights reserved.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Clinic for Radiation Oncology
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:2011
Deposited On:28 Feb 2012 16:19
Last Modified:07 Dec 2017 13:14
Publisher:Elsevier
ISSN:1879-355X
Publisher DOI:https://doi.org/10.1016/j.ijrobp.2010.09.050
PubMed ID:21129855

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