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

Abstract

Published paper AbstractPurpose: 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 V 95% ) 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 V 95% . The AAA also predicted small increases in the mean dose to the normal lung and the V 20 . 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.3

National dosimetric audit network finds discrepancies in AAA lung inhomogeneity corrections

“…Bragg et al [29] compared predicted and measured dose distributions with ion chamber and film measurements in homogeneous and inhomogeneous phantoms, with simple and complex fields. The effect of inhomogeneities was investigated using a range of phantoms constructed of water, bone and lung substitute materials.…”

Radiotherapy Treatment Plans With RapidArc for Prostate Cancer Involving Seminal Vesicles and Lymph Nodes

“…The anisotropic Analytical Algorithm (AAA, version 8.6) dose calculation algorithm was used (14). The total prescription dose was 75.6 Gy with a daily dose of 1.8 Gy.…”

Functional image-based radiotherapy planning for non-small cell lung cancer: A simulation study

“…Following optimisation, forward dose calculation was performed for each plan to generate an accurate dose distribution, using the eclipse anisotropic analytical algorithm (AAA) with inhomogeneity correction [21]. All plans were designed for delivery using 6 MV photons, to a prescribed CHART dose of 54 Gy in 36 fractions [22].…”