CyberKnife® and Gamma Knife® Radiosurgery – What are they and what are the differences?

The objective of these radiosurgery treatments is to deliver a lethal dose of radiationEnergy in the form of waves or particles, including radio waves, X-rays and gamma rays. to only the tumourAn abnormal swelling. without affecting surrounding healthy tissueA group of cells with a similar structure and a specialised function., and there are different ways in which this can be achieved.

CyberKnife® and Gamma Knife® are similar in many respects and so totalhealth asked Ian Sabin to explain the differences:

With regard to the differences between CyberKnife® (CK) and Gamma Knife® (GK) - CyberKnife® uses a former car building robot to move a LINAC radiotherapyThe treatment of disease using radiation. machine around the body in a series of arcs, allowing the multiple beams of radiotherapy to come together at the point of treatment 'focussing' the radiotherapy in this way.  It does not need a frame to be fitted to the head and can treat anywhere in the body.

CK is relatively new and there is not yet the volume of patient experience that we have for GK.

The Gamma Knife® uses a number of fixed radiotherapy sources (192 in the latest 'Perfexion') which converge at a single point and the target is placed at this point.  It can only treat lesions in the head and neck and requires a frame to be fixed to the patient to achieve the accuracy required for treatment.

Many CK treatments are split into fractions, perhaps 5, and may last longer than GK - partly due to any movement of the patient 'locking out' the equipment, whereas almost all GK treatments are performed in a single day, lasting only perhaps 30 to 60 minutes.

The CK uses electrically generated radiotherapy through the LINAC (linear accelerator) which has a significant down time for servicing; the GK sources of radiation are constantly decaying, giving off radioactivity. This leads to a decline in the potency of the GK sources over time and the need to renew the sources every 5 years or so - there is, however, very little machine 'down time'.

Finally, all GK users and many physicists consider that GK to be more accurate than CK - this is disputed by the CK manufacturers - but if I had an acoustic neuromaA rare, non-cancerous tumour arising from the cells surrounding the auditory nerve. I would have it treated with GK and not CK for this reason.

It should be noted that there are other varieties of LINAC systems which can be used for radiosurgery, including the Varian, this also sometimes requires a frame to be fitted to the head.