Radiosurgery

GammaKnife®

The Development of Radiosurgery

CyberKnife uses a miniature linear accelerator mounted upon a highly flexible, robotically controlled arm to deliver precisely controlled beams of radiation from many different angles to minimise impact on surrounding tissue and focus on the tumour, AVM or other target.

How cases are assessed

CyberKnife treatments

Choose a CyberKnife centre

Complex shapes and difficult, inoperable locations next to nerves or blood vessels can be treated but the fine radiation beam employed means that CyberKnife is less well suited to treating multiple or large tumours. It can sometimes be used in these cases however if the tumours are first reduced, either by chemotherapy or surgery.

The first radiosurgical device was developed in the 1950s, leading to the GammaKnife. This is used for intracranial lesions, delivering precisely targeted gamma rays from a Cobalt-60 source through a helmet-shaped device with 201 separate holes and the beams converge on the lesion to be treated. Although effective it is necessary to screw an external metal frame to the patient's skull to ensure accurate targeting.

It can be difficult to treat targets on the periphery of the brain and it cannot be used for fractionated radiosurgery, which can be beneficial for larger tumours or lesions located near nerves and other sensitive structures. Whilst GammaKnife has a long and successful track record and is subject to continual improvements it cannot be used on other parts of the body.

Modified Linear Accelerator Systems

Linear accelerators (linacs) were developed in the mid 1980s and do not require or generate any radioactive material. By modifying the conventional linear accelerators that are commonplace in many large hospitals and using specialised software it is possible to do many types of brain radiosurgery. Dedicated linac systems tend to be more carefully calibrated for spatial accuracy and optimised for radiosurgical efficiency. When treating brain tumours with linac radiosurgery, a metal head frame is still attached to the patient's skull and used to target the radiation beam.

Shaped Beam Systems

IMRT or Intensity Modulated Radiation Therapy uses computer-controlled "beam-shaping" to give improved accuracy and it can be used on most areas of the body. Using sophisticated planning software a multi-leaf collimator, which is attached to most modern medical linear accelerators, dynamically reshapes the outline and intensity of the radiation field during treatment. This fits the radiation to a target much better than conventional radiation therapy can and reduces injury to neighbouring healthy tissue.

It is not as spatially precise as radiosurgery however, so treatment is typically administered over 20-30 sessions. For brain tumours an intrusive head frame is required and it does not offer the accuracy of GammaKnife or CyberKnife. Away from the head accuracy is degraded as the patient moves, e.g. through breathing.

CyberKnife®

The position of the tumour is tracked between doses, allowing CyberKnife to compensate for small body movements. For brain and spine tumours the patient's own bone structure is used to provide markers, so avoiding the need for intrusive frames. For other areas of the body small metal markers (fiducials) are placed first.

CyberKnife < Radiosurgery

What is CyberKnife? How CyberKnife works The advantages of CyberKnife Clinical acceptance

Web sites in 30 countries

Click map for details

MHL CyberKnife Service
cyberknifeservice.com