Radiosurgery of the Brain with the Gamma Knife® “Icon”

the Gamma Knive Icon 

In October 2016 a Gamma Knife® type Icon was installed in the NKI by Elekta. The Gamma Knife is a high precision stereotactic radiosurgery instrument. It offers an alternative to traditional brain surgery and whole brain radiation therapy for the treatment of complex, difficult brain conditions. At the heart of the machine is a helmet shaped radiation collimator that contains up to 192 Co-60 radiation sources. The new "Icon" type is built for image guided treatment  with a Cone Beam CT accessory attached.

High accuracy conformal radiosurgery

During treatment the patient is on the treatment couch with the head positioned in the centre of the helmet collimator. In treatment planning any combination from up to 192 radiation sources in positions around the brain can be chosen. Each individual C0-60 source projects a narrow beam that is precisely focussed at a fixed point in the helmet assembly. The resulting dose distribution is highly conformal to the delineated target,  sparing healthy tissues.

The position of the head is fixed by a minimal invasive frame attached to it or by a mask. The treatment couch is adjusted with high accuracy  to position the focal point of the radiation beams in the planned position.  In the NKI the treatment is administered by a multidisciplinary team of physicians, involving radiation oncologists, neurosurgeons, neurologists and radiologists.

gamma knive helm collimator


Fig.1  Drawing of the helm-collimator with fixation frame.  Copyright Technische Universität München


No radiation sources during commissioning.

The 192 radiation sources will be installed at a later date. The Gamma Knife team in the radiotherapy division of the NKI will first test all aspects of patient positioning and imaging and prepare for clinical use.

Cone Beam CT in combination with Gamma Knife.

The Gamma Knife in the NKI is equipped with a Cone Beam CT scanner. Prior to each radiation treatment the position of the brain in the helmet collimator is verified on CT images with high accuracy to assure a prcise treatment. A research group in the NKI is already involved in the development of Cone Beam CT imaging that is used worldwide on linear accelerators for isocentric Megavolt radiotherapy. The optimisation of CBCT on the Gamma Knife is intended research. The NKI aims to give the optimum treatment in a patient friendly way and to spare healthy brain tissue and reduce side effects.

Gamma Knive Icon hersenscan


fig.2 Example of dose distribution.

First treatment expected in 2017.

The NKI is the second centre in the Netherlands that can offer this treatment.  Since 2002 the Gamma Knife Centre in Tilburg (NL) is treating patients. The Gamma Knife Centre and NKI have a cooperation to ensure a smooth and successful installation and start in Amsterdam.

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