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Clinical implications of the anisotropic analytical algorithm for IMRT treatment planning and verification

Bragg, C.M., Wingate, K. and Conway, J. (2008) Clinical implications of the anisotropic analytical algorithm for IMRT treatment planning and verification. Radiotherapy and Oncology, 86 (2). pp. 276-284. ISSN 0167-8140

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Abstract

PURPOSE: To determine the implications of the use of the Anisotropic Analytical Algorithm(AAA) for the production and dosimetric verification of IMRT plans for treatments of the prostate, parotid, nasopharynx and lung.

METHODS: 72 IMRT treatment plans produced using the Pencil Beam Convolution (PBC)algorithm were recalculated using the AAA and the dose distributions compared. 24 of the plans were delivered to inhomogeneous phantoms and verification measurements made using a pinpoint ionisation chamber. The agreement between the AAA and measurement was determined.

RESULTS: Small differences were seen in the prostate plans, with the AAA predicting slightly lower minimum PTV doses. In the parotid plans, there were small increases in the lens and contralateral parotid doses while the nasopharyngeal plans revealed a reduction in the volume of the PTV covered by the 95% isodose (the V95%) when the AAA was used. Large changes were seen in the lung plans, the AAA predicting reductions in the minimum PTV dose and large reductions in the V95%. The AAA also predicted small increases in the mean dose to the normal lung and the V20. In the verification measurements, all AAA calculations were within 3% or 3.5mm distance to agreement of the measured doses. Conclusions: The AAA should be used in preference to the PBC algorithm for treatments involving low density tissue but this may necessitate re-evaluation of plan acceptability criteria. Improvements to the Multi-Resolution Dose Calculation algorithm used in the inverse planning are required to reduce the convergence error in the presence of lung tissue. There was excellent agreement between the AAA and verification measurements for all sites.

Item Type: Article
Copyright, Publisher and Additional Information: © 2008 Elsevier B.V. This is an author produced version of a paper published in Radiotherapy And Oncology. Uploaded in accordance with the publisher's self-archiving policy.
Academic Units: The University of Sheffield > Faculty of Medicine, Dentistry and Health (Sheffield) > School of Medicine (Sheffield)
Depositing User: Sherpa Assistant
Date Deposited: 20 Mar 2008 12:04
Last Modified: 08 Feb 2013 16:55
Published Version: http://dx.doi.org/10.1016/j.radonc.2008.01.011
Status: Published
Publisher: Elsevier Ireland Ltd
Refereed: Yes
Identification Number: 10.1016/j.radonc.2008.01.011
URI: http://eprints.whiterose.ac.uk/id/eprint/3702

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