[A multileaf collimator: additional quality assurance in a GE linear accelerator].

Background: In comparison to a conventional collimator, a multileaf collimator demands a great deal of quality assurance procedures due to its large number of leaves. A concept for daily quality assurance is presented, mainly concerning the positioning accuracy of the leaves.

Material And Methods: Two leaf configurations including maximal opening as well as overtravel of single leaves, at a maximal opening of the jaws, are transmitted online in daily exchange from our record- and verify system to the linac. Aiming at a special test phantom a visual control of the positioning accuracy is performed. The leaf positioning is documented by an electronic portal imaging system and is compared with a reference shot by superposition of a grid.

Results: This method of quality assurance offers a fast and effective possibility to guarantee the proper function of the whole system by simulating the routine treatment situation.

Conclusions: Compared to a conventional collimator only a slightly greater workload is needed for quality assurance of a multileaf collimator.