Fig. 3
From: Characteristics of non-coplanar IMRT in the presence of target-embedded organs at risk
Beam port constellation. Shown are the beam entrance ports (smaller circles) and exit ports (larger circles) on a spherical phantom for a ball shaped target (for simplicity). Beam arrangements for the techniques (a) Q4π, non-coplanar, quasi-isotropic; (b) 2P, split into two planes; (c) Co coplanar; (d) Co + 1 coplanar plus additional orthogonal beam. Always the cases with highest beam numbers are depicted (b, c: 15; a, d: 16); green: entrance port of the [gantry 0°; table 0°] beam. White arrow: table axis for standard orientation of the beam set