1.1 - Movements Of The Linac

Modern linear accelerators typically have three movements:

Gantry 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 180^o in each direction from the neutral position.

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Collimator Movements

• The collimator or treatment head can rotate around the axis which passes from the isocentre to the target. This rotation is usually about 180^o 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.

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Couch Movements

• 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 90^o in each direction from the neutral position.
  • These movements are important when junctioning of fields is required.

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Links

• Treatment Machines
  • 1 - The Linear Accelerator
  • 2 - Safety And Radiation Protection
  • 3 - Quality Assurance
  • 4 - Patient Setup
  • 5 - Treatment Verification
  • 6 - The Console
  • 8 - Early Tissue Toxicity
  • 9 - Waiting Lists, Fractionation and Triage