Three dimensional positron emission tomography (PET) plays an important role in cancer soil studies by enabling detection and localization of tumor cells. This thesis investigates the ClearPET measuring system. Central matter of interest is the reconstruction process. There is to be examined how accurate the ClearPET can reconstruct known interrelations between source activities. The optimization of this process is accomplished by normalizing the reconstruction image by means of a homogeneous phantom. In case of this experimental setup the phantom is a cylinder with a homogeneous activity distribution.:1 Introduction 2 Material and Methods 2.1 Measuring system 2.1.1 Measuring procedure 2.1.2 Cassettes 2.1.3 Homogeneous phantom 2.2 Physical background 2.2.1 Compton scattering 2.2.2 Attenuation coefficient 2.2.3 Types of radiation 2.2.4 Sodium-22 and related physical phenomena 2.3 Reconstruction process 2.3.1 Intensity and Beer’s law 2.3.2 Radon transform and its inverse 2.3.3 OSMAPOSL algorithm 2.4 Fourier rebinning algorithm 3 Experimental results 25 3.1 Reconstruction routine 3.2 Back projection of point sources 3.2.1 Full width half maximum analysis of the strong point source 3.2.2 Investigation of the statistical error 3.2.3 Validation of the maxima approach 3.3 Comparison of activities and quantification of spatial reconstruction behavior . 3.4 Normalization measurement 3.5 Sinogram 3.6 Reconstruction with the OSMAPOSL algorithm 3.7 Implementation of attenuation correction and multiple iterations of the OSMAPOSLalgorithm 4 Summary