Rotating Gamma Institute Debrecen, Hungary
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GammaART 6000TM - Rotating System for Radiosurgery

The Rotating Gamma TechnolgyTM uses 30 individual radioactive sources of Co-60 isotopes for radiosurgical procedures. Each source can deliver up to 200 Ci at the initial loading. The sources are located in a sector of about 60 degrees of a hemisphere and rotate in concentric circles around the treated area. The need for heavy helmets used in other designs have been eliminated. In a rotating arrangement the radiation arrives from a larger solid angle that results in less radiation damage to the healthy tissues surrounding the target area.

The GammaART-6000TM rotating gamma system at work at the Debrecen center uses a set of secondary collimators arranged on a rotating hemisphere. Beam shaping collimation of the gamma radiation is done by the synchronous rotation of the source and collimator hemispheres eliminating the need for the use of heavy helmets for the same purpose. The technology helps the work of the physicians and shortens the treatment preparation time.

The mechanical accuracy of the system is based on a so called stereotactic localization procedure. As a first step a localization frame is attached to the skull with the use of four sterile positioning screws. In the second step a tomographic image is taken with the frame rigidly attached to the patients head. This allows the highly accurate determination of the position of the treated structure with respect to the localization frame. The images are automatically transferred to the gamma center through the computer network of the university. A high performance graphical workstation allows the careful analysis of the images and the planning of the treatment using the Explored4D planning system.

In the final phase of the procedure the localization headframe is firmly and precisely attached to the GammaART-6000 machine based on the X,Y, and Z and angle coordinates determined by the planning system. The attachment can be a manual positioning where every set of coordinates are set by the neurosurgeon using the precision localization scales of the headframe and the machine, or it can based on the Automatic Positioning System (APS) that can robotically change the patient's position in between the different regions to be treated. The accuracy of the localization procedure is better than 0.5 mm in both cases. The overall accuracy of the process including the imaging and planning uncertainties is better than 1mm. This is the best achievable accuracy available for radiosurgery in any kind of devices currently available.

Some dry facts about the machine:

– Total weight: 21,000 kg
– Length, width, height: 485,3 cm, 169,6 cm, 169,8 cm
– Total intensity of the Co-60 isotopes at the initial loading: : 6,000 Ci +-10%, (30 sources)
– Dose rate at the isocenter: larger than 3 Gy/min
– Dimensions of the isocenter (80% to 20% dose drop): <10 mm or the size of the collimator
– Mechanical accuracy: +/- 0.1 mm
– Radiation blocking sector: "turns off" the radiation
– Isocenter dose rate in the blocked positionn: <2% of the total dose rate
– Accuracy of mechanical focusing: +/- 0.5 mm
– Accuracy of the rotating: +/- 0.3 mm
– Available secondary collimator sizes: 4, 8, 14, 18 mm
– Total weight on the treatment couch: maximum 200 kg
– Rotation speed: 2-4 RPM