An ideal steel breakthrough converging channels Cap skull

In the 1970s, the Swedish neurosurgeon Lars Leksell was a great intuition: use radioactive radiation to destroy brain tumors without opening the skull. The scalpel gamma, or "Gamma Knife", he invented then, introduced radio-surgery in the neurological field. Thirty years later, a new stage has to be taken with the development of the second generation of this machine, with the prototype was delivered to hôpital de la Timone in Marseille.

Do not risk to irradiate the cells on the path of a single beam pointing to the tumor, the Swedish imagined converge at a point shooting of dozens of low-intensity ionizing radiation which, taken in isolation, are not likely to cause damage.

Refine the settings

To adjust the fire, the skull of the patient, which were located the tumour on sections of imaging 3D (scanner, MRI...), is stalled in a framework. Calibrated edges correspond to the coordinates of space of the brain as the neurosurgeon sees them on his computer screen. Previously, he calculated the best path to resolve the necessary radiation dose to the diseased area. An ideal steel breakthrough converging channels Cap skull. She comes to follow in a whipped more large containing Cobalt 60 ionizing sources.

In the first version of the machine, a wizard had to manually adjust the frame with a precision of the order of the eyes. "Manipulations were very long and difficult," admits Professor Jean Regis, which the Department of neurosurgery at the Timone hospital was the first equipped with France in 1992. Automation module was added since to more finely adjust the ballistic contact, and options have been added to track the progress of medical imaging. "It was becoming urgent to integrate these technologies because the original version showed its limits," continues the doctor.

Message received by Elekta, owner of the patent, which brought in 2002 College international neurosurgeons and medical physicists, floor on the development of the new generation of Gamma Knife. "It emerged a unanimous recommendation: a tool which is exactly the same on the screen and on the operating table", reported John Regis, who participated in this specification.

Three dimensions

To achieve this level of accuracy, Elekta had to completely redesign its machine. Let's start with Robotics. Nine companies Swiss, German, Japanese, American, Italian, working in precision industries, have worked on the new system of positioning of the patient. The robotic shelf moves in three dimensions with more than a tenth of a millimetre precision. In deporting the bed all Robotics, the area could be enlarged by 300, as result, increased opportunities for intervention, "including tumors of the cervical cord or the base of the skull that are usually difficult to operate", explained Jean Régis.

Elekta engineers brought the same care in the design of a new collimator of fire: a hollow cone tungsten replacing two demi-sphères who had the double disadvantage of being difficult to handle (350 kilograms each) and dive time patient in a slightly radioactive environment. Its principle: 192 fixed shooting collimators of different diameters are divided into eight sectors on the cone. At the back, cobalt-60 sources, operated by jacks, come position themselves before the selected guns. "It is an accurate ballistic to split doses according to the shape of the area to treat", shows Denis Porcheron, the medical physicist responsible for the maintenance of the machine, manipulating it with a single click of mouse. The realization of this piece, one of the largest tungsten machined to date, requested there yet the collaboration of a dozen of companies. Including Motala Verskad, who designs trees of propeller for tankers, and Aerotech, a manufacturer of fighter aircraft landing gear. This mechanics is a gem of accuracy can do drag parts combining different metal without lubricant, this component is prohibited in the ionizing atmosphere where it would be polymerized. As a result, quality in principle, since, according to the manufacturer, the device is guaranteed for twenty-five years of use without intervention.