The matRad coordinate system
<a name="LPS" /a>
matRad uses the LPS (Left, Posterior, Superior) coordinate system
where the x-axis points towards the left patient-side, the y-axis towards the posterior direction and the z-axis towards the superior direction (see image below).
3D points, e.g. the iso center in the plan struct or source and target points in the stf struct, directly follow the conventions of the LPS coordinate system: The first coordinate, e.g. pln.isoCenter(1) corresponds to the x coordinate, i.e., the coordinate in left-right direction. For the dose and ct cubes, however, which are stored as matlab 3D arrays, the second dimension corresponds to the x-coordinate, i.e., the coordinate in left-right direction, and the first dimension corresponds to the y-coordinate, i.e., the coordinate in posterior-anterior direction. We decided to make this permutation due to matlab's way to display two-dimensional matrices with the image command, which displays the first array dimension always along the vertical direction.
<a name="rotation" /a>
The rotation of the gantry (Φ) and the couch (θ) are defined in the following way:
- Gantry: Clockwise rotation around the z-axis
- Couch: Counter-clockwise rotation around the y-axis
simple gantry rotation:
simple couch rotation:
simultaneous couch and gantry rotation:
