Radiosurgical treatment using the Perfexion™ Gamma Knife and the Axesse linear accelerator are carried out either as an out-patient procedure or during a brief stay in hospital. It is not necessary to fast before being treated. Once the detailed preparatory consultation has taken place and the patient has been informed, an appointment can be made and the radiosurgical treatment carried out at our centre. The procedure is highly efficient and therefore gentle and non-invasive, delivering such an effective dose of radiation to the diseased area that a single session is generally sufficient. The treatment itself is completely painless, silent and lasts between 30 and 120 minutes, depending on the application.
Treatment with the Gamma Knife
Demonstration of Gamma Knife treatment
(Presentation film produced by the manufacturer, ELEKTA)
The 192 cobalt-60 radiation sources are shielded so that it is safe to enter the4 treatment room when irradiation is not being carried out. A focussing system forms a fine beam from each source, and all of the individual beams are superimposed on one another at the focal point. So each individual beam contributes approximately 0.5% to the overall dose necessary to deactivate the disease focus.
The first step in the treatment involves fitting frame to the patient's head to achieve accuracy down to fractions of a millimetre.
Attaching a frame is a very common procedure in neurosurgery and is used when a sample is being removed for a biopsy, for example.
The patient is given a local anaesthetic at the attachment points and the procedure does not hurt. The frame provides an exact reference so that the target area can be pinpointed with the aid of imaging procedures.
Devices for digital imaging
The location of the diseased tissue is determined precisely using the best possible imaging procedures immediately before treatment.
This ensures that the treatment can take account of recent developments of the disease. We make use of the considerable experience of the neuroradiologists at the neighbouring Helios Hospital, which means that the most advanced imaging infrastructure is available to us. For certain diseases, examination with computed tomography may be indicated in addition to MRI (magnetic resonance imaging).
If images of blood vessels are required, digital subtraction angiography (DSA) is performed in conjunction with the hospital neuroradiological department.
All the image data are transferred to the Gamma Knife planning system by the most up-to-date computer technology (PACS, etc.).
Planning the treatment
The doctor uses the image data to define the physical location of the diseased tissue.
All the image data that have been recorded using the stereotactic frame as a reference can be overlaid exactly.
Other image data sets can also be added once they have been matched to the references from the frame (e.g. PET examination).
This is necessary to ensure the best possible definition of the diseased site. Then the doctor plans the radiation treatment so that the target area receives exactly the dose of radiation that allows it to be successfully deactivated and, at the same time, preserves as far as possible the surrounding healthy tissue and nearby structures at risk.
After the irradiation has been planned, the actual radiosurgical treatment can go ahead. Normally, the patient is manoeuvred into the irradiation device and repositioned several times. Each time, a pre-determined point is irradiated for a certain length of time. Each target point (isocentre) is irradiated in turn until the entire area has been treated. On average, one treatment lasts for one to two hours. You may listen to music during this time if you wish.
The treatment can be interrupted at any time to provide a break. The stereotactic frame is removed immediately after treatment has been completed and the attachment points are covered with plasters. Normally the hair begins to grow back after a couple of days. The attachments points usually heal without any marks or scarring.