Leksell Gamma Knife
I had the honor to visit a department with working Leksell gamma knife during my medical study in 2007. At that time, there used to be only 200 such machines in the world, but the number of the device steadily grows.
The device is basically a strong source of radioactive energy, which emits X-rays towards a specific target. A layman can imagine it as a very strong X-ray. The radiation emitted from the device is so powerful that it can destroy cells and the energy is used to destroy malignant tumors. Normally, brain affections including local tumors are treated by neurosurgeons, but some brain areas are practically inaccessible for the surgeons who could cause a severe brain damage in case of operation.
Surely you can think of a question - when the radiation of the gamma knife kills the tumor cells deep in the brain, how is that possible that it does not destroy normal brain cells? This is assured by the shape of the emitter. The gamma knife has shape of a large ring, which surrounds the patient's head and the perimeter of the ring consists of many emitters. Every emitter transmits a beam of relatively weak radiation. However, when all the beams meet in the desired area, their energy adds up and becomes lethal to the local cells. The surrounding structures are indeed also irradiated, but by much smaller and relatively harmless doses.
The patient's head is put into a metal structure, which is tightly fixed to the skull. This prevents the patient from moving his head during the procedure. With this construction around the head, the brain is examined by an imaging method to accurately evaluate the target lesion, its location and relationship to the deployed metal structure. The data are transmitted into the computer of the gamma knife. The device checks the lesion and targets its radioactive beams to concentrate within the lesion, thus destroying it with radiation. During the procedure, the patient lies in horizontal position and must not move with his head. As the head is still tightly fixed, this would not be possible even if the patient tried. The actual gamma knife radiation is completely painless and it usually takes from few minutes to few dozens of minutes.
As already mentioned above, the ideal target for the gamma knife are certain primary brain tumors, brain metastases of other tumors and some cerebral vascular malformations. These vascular malformations are clusters of abnormal blood vessels that can cause sudden bleeding into the brain.