Here's a link to the inventors of the CyberKnife:
http://cancer.stanfordhospital.com/forPatients/services/cyberknife/default

The newer generation of the device are a robotic arm with a miniaturized linear accelerator.

It is actually quite different from the GammaKnife and certainly more versatle.

The original Gamma Knife was a huge contraption and they bolted a device to your head that resembled a collander that provided the beam entry ports. The design limited it to mainly brain tumors.

See http://www.ucsf.edu/gammakf/

I don't believe that anyone here has had Gamma or Cyber Knife treatment specifically for head & neck cancer although some have had the procedure for brain metastesis.