Fluid analysis of positrons in soft matter

Abstract

Improvements to Positron Emission Tomography (PET) technology depend to a large extent on obtaining a better understanding of positron transport processes in soft condensed matter. The most economically computational, physically tenable method of carrying out such an investigation is the fluid approach, in which the Boltzmann kinetic equation is replaced by a hierarchy of low order, velocity moment equations, in which collision terms are approximated by extending 'momentum transfer theory' to allow for coherent scattering arising from the structure of the medium. We show how these fluid equations furnish structure-modifed versions of well known semi-empirical relations linking transport coefficients, and give numerical calculations for simple models.