Isocentric technique

An isocentric technique is where all beams used in a radiation treatment have a common focus point, a.k.a. the isocentre.

Working

Linac movements: gantry rotation, collimator twist, bed swing.

The movements of the linear particle accelerator (or linac) are threefold:

1. the gantry rotates (like a big crane arm)
2. the collimator twists in the head of the gantry
3. the bed swings around in the floor

All of these movements in the modern linac occur around an axis that runs through the isocentre. In this way, if the centre of the target area in the patient's body is moved to coincide with the isocentre, then all motions of the machine will remain centred on the target. This way, non-target areas will only receive short durations of radiation, reducing damage to them, while the target area receives constant radiation.