Track counting and the blots

Track detectors are very useful devices for alpha particle dosimetry. Alpha particle tracks are registered on the detector's surface. The registered track density is proportional to the dose. When the dose is low the greatest effect on the total error of dose assessment has a Poisson distribution (random error). When the dose is high, the greatest contribution to the total error is the effect of track overlapping (systemic error). This paper describes how to solve the problem of overlapping tracks when a computer aided image analyser is used. The formulae presented in this paper were proven in the international calibration programme run by NRPB and EU.