Treatment
201 “Shots” and One Hit
Radiosurgical treatment using the Gamma Knife is 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 Gamma Knife treatment carried out. The procedure is highly efficient and therefore gentle and non-invasive, and it delivers such an effective dose of radiation to the diseased area that a single session is sufficient in most cases. The treatment itself is silent and completely painless and lasts between 30 minutes and two hours, depending on the application.
Demonstration of Gamma Knife treatment
Irradiation Unit
The 201 radiation sources are shielded so that it is safe to enter the treatment room when irradiation is not being carried out. A focussing system forms a fine beam from each source, and all the individual beams are superimposed on one another at the focal point. So each individual beam contributes 0.5% to the overall dose necessary to deactivate the diseased tissue.
Stereotactic Frame
The first step in the treatment involves fitting a frame to the patient’s head. This is necessary 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 so that the procedure does not hurt. The frame provides an exact reference so that the target area can be pinpointed with the aid of the 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 great experience of the neuroradiologists at the neighbouring Helios hospital, which means that the most advanced imaging infrastructure is available to us. For certain diseases, an additional examination with computed tomograpy may be indicated in addition to MRI (magnetic resonance imaging).
If images of blood vessels are required, digital subtraction angiography (DSA) is performed in co-operation with the neuroradiological department in the hospital.
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 irradiation treatment so that the target area receives exactly the dose of radiation that allows it to be successfully deactivated and at the same time as far as possible preserves 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 last 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 and the attachment points usually heal without any marks or scarring.
Aftercare
The radiosurgical treatment does not remove the diseased tissue, but instead deactivates it or kills it off. It is therefore necessary to check on the success of the treatment and find out whether any side-effects have occurred. New MRI imaging allows doctors to measure the volumes of the tumours accurately and to gauge how far malformations of blood vessels have closed off.
Whereas brain metastases generally shrink after six weeks, benign tumours need longer. Angiomas can take several years to close. Therefore we arrange check-ups with you at intervals of six weeks to one year, depending on the disease.
In addition to assessment of the MR images, there is also always a neurological examination. Of course you have the opportunity to discuss the results and the continuing procedure with us in detail at any time. Because most of our patients are treated by several specialists, we consider it very important that we should be informed of the treatments you are receiving from other doctors.
If, contrary to expectation, the treatment is ineffective, or new tumours occur, the therapeutic options will be discussed with you again. If side-effects occur, we clarify whether they require treatment and if necessary we start the preparations immediately.
The treatment data and the information from the follow-up examinations are kept anonymous, which means that it is impossible see which patient the data are from, and entered into a database. We have a large body of data relevant to treatment and with scientific evaluation we can improve the Gamma Knife method.
