6X acuros algorithm validation in the presence of inhomogeneities for VMAT treatment planning.

Aim: To validate the Acuros®XB (AXB) dose calculation algorithm for a 6 MV beam from the Varian TrueBeam treatment units.

Background: Currently Anisotropic Analytic Algorithm (AAA) is clinically used on authors' department but AXB could replace it for VMAT treatments in regions where inhomogeneities and free air are present.

Materials And Methods: Two steps are followed in the validation process of a new dose calculation algorithm.

Experimental investigation of the response of an a-Si EPID to an unflattened photon beam from an Elekta Precise linear accelerator.

The characteristics of an Elekta amorphous silicon (a-Si) electronic portal imaging device (EPID) in response to a 6 MV photon beam generated without a flattening filter, an unflattened beam, have been determined. The characteristics were then compared to those for a conventional photon beam generated with a flattening filter in the beam, a flattened beam, in order to determine the suitability of an a-Si EPID for transit dosimetry. The response of the EPID to the unflattened beam increased by 7.