ANNIHILATION DENSITY DISTRIBUTION CALCULATIONS FOR MEDICALLY IMPORTANT POSITRON EMITTERS

The effect of positron range on the image-plane resolution of tomographic images is evaluated through calculations based on a model which employs beta-decay energy spectra and an empirical range formula. Predicted range distribution functions are compared with published measurements for three medically important positron emitters; C-11, Ga-68, and Rb-82. The effect of tomographic slice thickness on point-source annihilation distribution functions is also demonstrated. Line-spread functions are calculated using the model, for the above isotopes as well as for F-18, O-15, and N-13. Image-plane resolution predictions are made for high-resolution positron cameras for various positron emitting isotopes with end-point energies up to 4 Mev.