Open AccessInhomogeneity correction and the analytic anisotropic algorithm
Author(s) -
Robinson Don
Publication year - 2008
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1120/jacmp.v9i2.2786
Subject(s) - imaging phantom , algorithm , superposition principle , radiation treatment planning , range (aeronautics) , benchmark (surveying) , eclipse , computer science , convolution (computer science) , hounsfield scale , attenuation , physics , mathematics , computational physics , materials science , optics , mathematical analysis , artificial intelligence , computed tomography , geology , medicine , geodesy , astronomy , artificial neural network , composite material , radiology , radiation therapy
The ability of the analytic anisotropic algorithm (AAA), a superposition– convolution algorithm implemented in the Eclipse (Varian Medical Systems, Palo Alto, CA) treatment planning system (TPS), to accurately account for the presence of inhomogeneities in simple geometries is examined. The goal of 2% accuracy, as set out by the American Association of Physicists in Medicine Task Group 65, serves as a useful benchmark against which to evaluate the inhomogeneity correction capabilities of this treatment planning algorithm. A planar geometry phantom consisting of upper and lower layers of Solid Water (Gammex rmi, Middleton, WI) separated by a heterogeneity region of variable thickness, is modeled within the Eclipse TPS. Results obtained with the AAA are compared with experimental measurements. Seven different materials, spanning the range from air to aluminum, constitute the inhomogeneity layer. In general, the AAA overpredicts dose beyond low‐density regions and underpredicts dose distal to volumes of high density. In many cases, the deviation between the AAA and experimental results exceeds the Task Group 65 target of 2%. The source of these deviations appears to arise from an inability of the AAA to correctly account for altered attenuation along primary ray paths. PACS number: 87.53.Tf