Inhomogeneity correction and the analytic anisotropic algorithm

Abstract

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

Clinical dosimetric impact of Acuros XB and analytical anisotropic algorithm (AAA) on real lung cancer treatment plans : review

“…2 A number of studies have shown the limitation of photon dose calculation algorithms such as analytical anisotropic algorithm (AAA), collapsed cone convolution (CCC) algorithm, and pencil beam convolution (PBC) algorithm when complex geometry with inhomogeneity is involved along the photon beam path. [3][4][5][6][7][8][9][10][11][12] Both the AAA and CCC are based on the superposition/convolution method, which calculates the dose by superposition of dose kernels of primary and scatter components that are derived from the Monte Carlo (MC). The tissue inhomogeneity correction in superposition/convolution method such as in the AAA is done both in the beamlet direction and lateral directions.…”

Dosimetric Comparison of Anisotropic Analytical Algorithm and Acuros XB in Stereotactic Body Radiotherapy and Effect of Calculation Grid Size

“…[1][2][3][4][5][6][7][8][9][10][11][12] Particularly, it has been observed that in the transition from tissue to air, dose is incorrectly calculated near two mediums. Varian (Varian Medical Systems, Palo Alto, CA) has introduced a new dose calculation algorithm called Acuros XB (AXB), a computational algorithm for clinical use.…”

“…[10] The functional forms that form the basic physical quantities initiate a process by adding device properties to the account. This often leads to a noticeable reduction in the computation required for such algorithms.…”

Irradiation of lung and esophagus tumors: A comparison of dose distributions calculated by anisotropic analytical algorithm and pencil beam convolution algorithm, a retrospective dosimetric study

“…9 The dose from the adjacent pencil beams is left out in the calculation leading to inconsistencies in dose determination of large tumors in homogeneities. 10 The development of a superposition-convolution method known as AAA, has been shown to be more than accurate than PBC in photon dose calculations. 11,12 Because the AAA algorithm takes into account lateral scattering it calculates photon beams interactions in regions of complex tissue heterogeneities better.…”