Abstract
Objectives
To verify the dosimetric accuracy of treatment plans in high dose rate (HDR) brachytherapy
by using Gafchromic EBT2 film and to demonstrate the adequacy of dose calculations
of a commercial treatment planning system (TPS) in a heterogeneous medium.
Methods
Absorbed doses at chosen points in anatomically different tissue equivalent phantoms
were measured using Gafchromic EBT2 film. In one case, tandem ovoid brachytherapy
was performed in a homogeneous cervix phantom, whereas in the other, organ heterogeneities
were introduced in a phantom to replicate the upper thorax for esophageal brachytherapy
treatment. A commercially available TPS was used to perform treatment planning in
each case and the EBT2 films were irradiated with the HDR Ir-192 brachytherapy source.
Results
Film measurements in the cervix phantom were found to agree with the TPS calculated
values within 3% in the clinically relevant volume. In the thorax phantom, the presence
of surrounding heterogeneities was not seen to affect the dose distribution in the
volume being treated, whereas, a little dose perturbation was observed at the lung
surface. Doses to the spinal cord and to the sternum bone were overestimated and underestimated
by 14.6% and 16.5% respectively by the TPS relative to the film measurements. At the
trachea wall facing the esophagus, a dose reduction of 10% was noticed in the measurements.
Conclusions
The dose calculation accuracy of the TPS was confirmed in homogeneous medium, whereas,
it was proved inadequate to produce correct dosimetric results in conditions of tissue
heterogeneity.
Keywords
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Article info
Publication history
Published online: February 20, 2012
Accepted:
January 17,
2012
Received in revised form:
December 2,
2011
Received:
August 19,
2011
Identification
Copyright
© 2012 Associazione Italiana di Fisica Medica. Published by Elsevier Inc. All rights reserved.
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- In regard to: “Dosimetric verification of a high dose rate brachytherapy treatment planning system in homogeneous and heterogeneous media”Physica Medica: European Journal of Medical PhysicsVol. 30Issue 8
