Use of the EM algorithm for maximum likelihood estimation in electron microscope autoradiography

Abstract

In this paper we describe a new method for the analysis of electron microscope auto-radiographs. It uses a Poisson model to describe the autoradiographic grain distribution, and the method of maximum likelihood to estimate the radioactive intensities. An iterative procedure is derived from the EM algorithm to produce maximum likelihood estimates. The procedure leads to simple iterative calculations and a complete treatment of edge effects. The resulting method of analysis enables data from the whole area of autoradio-graph plates to be utilized without the need for any form of windowing to guard against edge effects. It also facilitates inference about the precision of estimated intensities and about comparisons between intensities. The estimation procedures are illustrated with real autoradiograph data from a study of rabbit blood plasma.