  Statistical event reconstruction techniques can give better results for gamma
cameras than the traditional centroid method. However, implementation of such
techniques requires detailed knowledge of the PMT light response functions.
Here we describe an iterative technique which allows to obtain the response
functions from flood irradiation data without imposing strict requirements on
the spatial uniformity of the event distribution. A successful application of
the technique for medical gamma cameras is demonstrated using both simulated
and experimental data. We show that this technique can be used for monitoring
of the photomultiplier gain variations. An implementation of the iterative
reconstruction technique capable of operating in real-time is also presented.
