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. Author manuscript; available in PMC: 2011 Jun 21.
Published in final edited form as: Phys Med Biol. 2010 May 18;55(12):3299–3316. doi: 10.1088/0031-9155/55/12/003

Figure 1.

Figure 1

The geometries of three kV imaging systems chosen in this study as representative of those commonly used for IGRT: (a) the CyberKnife system has a dual orthogonal kV imaging system in the coplanar plane, (b) the ExacTrac system has a dual kV imaging system in the non-coplanar plane with the angular separation of 60° and (c) linac for IGRT has a single gantry-mounted kV imaging system in the coplanar plane. (d) The rotation transforms from the patient coordinate system (x, y, z) to the imager coordinate system (x′, y′, z′). Rotation of ϕ around the z-axis and the following rotation of θ around the y-axis transforms the patient coordinates into the imager coordinate frame. Note that the source-to-axis distance and source-to-imager distance are not shown in the actual scale (for simplicity), but are included in the calculations.