1.1 - Movements Of The Linac
Modern linear accelerators typically have three movements:
- The gantry rotates around a central point (the isocentre), which is always the same distance from the treatment head. The gantry can typically rotate just over 180o in each direction from the neutral position.
- The collimator or treatment head can rotate around the axis which passes from the isocentre to the target. This rotation is usually about 180o in each direction as well
- For linear accelerators with dynamic wedges, the jaws which create the wedge are usually limited to a single pair; therefore wedging may only be performed along one axis. To wedge in the other axis, the collimator must be rotated.
- The treatment couch in most linear accelerators can move in six directions - up, down, left, right, forwards and backwards.
- The treatment couch in modern linear accelerators is also capable of rotating 90o in each direction from the neutral position.
- These movements are important when junctioning of fields is required.