[Use of a two-dimensional ionization chamber array for quality assurance in medical linear accelerators]

Two-dimensional dosimetry measurements are an important tool of Quality Assurance in modern radiotherapy techniques, such as the Intensity Modulated Radiation Therapy (IMRT). Common procedures are usually based on the use of films or semiconductor arrays as dosimeters. This paper presents our experience with a two-dimensional ionization-chamber array. The methods presented here allow the daily use of the array for a constancy check of the accelerator. It is also shown that the position of the individual leafs of the multi-leaf collimator (MLC) can be verified to within +/- 1 mm of their calibration. A procedure for the measurements is described and discussed.