Gamma Knife or Gamma Unit is a highly accurate and reliable device.
The used irradiation system: The GK is, in terms of technology, jointly with the planning system, two most typical elements of the procedure and it requires a shallow description.
The GK has two essential parts:
The irradiation system:
The secondary collimator (left) moves to be fixed to the emptying semi-sphere where the radioactive sources are contained.
Gamma Unit diagram (right) showing the secondary collimator movement (to which the patient is submitted) to the sphere containing the sources.
Patient’s positioning system:
The patient’s brain area that is going to be irradiated must be placed extremely precisely in the centre of the radiating semi-sphere. The procedure involves the patient placing on a stretcher and holds his/her head to the secondary collimator by a stereotactic head frame.
Usually, the volumes to deliver beam radiation are not spherical. In those cases the patient must be moved so, that all the tumor volume is properly irradiated. The classic method (which sometimes will be necessary to apply) implies to release the patient and place him again manually in his new irradiating position.
The C model includes, as an amazing innovation, a robot (the APS) which safely and accurately moves the patient reducing human mistakes and implying a shorter treatment times and, therefore, a greater comfort for the patient.
On the whole, the movements are so slow that allow several patients snoozing during the treatment.
The patient is place inside the semi-sphere, so that the point on which the radiation concentrates matches with the brain area intended to be irradiated.
The rest of the brain supports as much a very small part (and of course tolerable) of the received dosage into the target.
The irradiated area is really tiny and almost spherical, however the shape of inter cerebral lesions often differs significantly to the spherical, so the patient’s position must be modified, in order to irradiate a near area to the above one. Thus, in a set of stages (overall, from 5 to 15) all the lesion size is covered with an extraordinary accuracy in all its volume.
With this system two main advantages are gained: The first one is that inside the lesion may remain small volumes in which the radiation delivery, by the two irradiated areas superposition, increases the desired action. The second one is that the dosage drop outside the lesion tends to become sharper as we use less basic volumes of irradiation.
Our Experience Our experience is reinforced with the one of other groups, which, using the same means, works in the rest of the world.
Average of the treated different pathologies with GK in our hospital.
Since 1993, more than 5.300 (June 2011) treatments from diverse pathologies have been performed with Gamma Knife radiosurgery in our hospital. This technology is applied in other centres, from the most renowned in the world: Karolinska University Hospital (Stockolm), Mayo Clinic, Pitssburg University, Munich, etc. Our results are proven, undoubtedly, with the ones of the series performed in the above mentioned centres through the close contact supported between the diverse Units of Gamma Knife by the personal visits, annual and biannual meetings, carried out in this regard.
The experience of more than 155 GK around the world means more than 200.000 performed treatments from 1986.
In 1993, we performed the first treatments with the second generation device (model B) which, in that moment was the equipment No 43 of the world. In year 2000 this model was changed to model C (our device is the No 11 of the world with this same specifications) improved with the automatic positioning system from April 2001. Finally in 2007, the machinery was completely renewed, the most cutting edge model since the moment (2011) called PERFEXION. It is outstanding its safety for the patient as it is a full automatic procedure and the beam dosage outside the head is lower (from 10 to 100 times lower to other procedures).
For further information please go to site Elekta in the Radiosurgery Spanish Society or click here aquí.