An optical system for quick and precise assessment of mechanical isocenter of accelerator.
Why it is soo needed?
Mechanical isocenter of linear accelators have to be verified regularly. There are several different techniques for determination of the isocenter of accelerators. The optical system for measurements of the accelerator isocenter has been designed. The aim of this work is to present the system optical system called NaviRation designed for making all mechanical tests of linear accelerator.
The system consists of two optical cameras mounted on a horizontal arm at a distance of 1 m from each other and from the marker set. The cameras are positioned at distance of about 1 meters from the isocenter of the accelerator. The marker set is placed sequentially on the arm of accelerator, on the top of the treatment table and on the collimator. During the rotation of the each part of the accelerator the position of the marker set captured by the cameras are transferred to the computer. With the specialized software the actual position of rotation axis (isocenter) is calculated. Finally the actual position of the axes of all three rotational parts of the accelerators are numerically and graphically presented.
The precision of our system obtained with the coordinate-measuring machine revield that the imprecision is smaller than 0.1 mm. We have perfomed all feasibility tests using two accelerator installed in the National Cancer Center in Warsaw with two Varian accelerators Clinac 2300 CD and Edge. Comparison of our measurements with the measurements carried out by the Varian service with the specialised micrometer system showed the conformity of both measurements. Our measurements were 10 times shorter than the measurements performer with the system used by other service.
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