Resultsįor all fluence based techniques in cases A and C, plan quality increased considerably if more irradiation directions were used. The overall plan quality, PTV coverage, and OAR sparing are evaluated. A selection of plans is optimized with direct machine parameter optimization (DMPO) allowing 120 and 64 segments. The orientation of the beam sets is systematically changed dose distributions resulting from optimal fluence are explored. The number of beam directions varies from 9 to 16. Several IMRT techniques are used for the planning study: a) non-coplanar quasi-isotropic b) two sets of equidistant coplanar beams, half of beams incident in a plane perpendicular to the principal plane c) coplanar equidistant (reference) d) coplanar plus one orthogonal beam. The OAR shapes are spherically symmetric (A), cylindrical (B), and bended (C). The authors focus on OARs embedded in the PTV. The planning study applies to generalized organ at risk (OAR) – planning target volume (PTV) geometries. The aim is to analyze characteristics and to study the potentials of non-coplanar intensity modulated radiation therapy (IMRT) techniques.
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June 2023
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