Reduction of positron range effects by the application of a magnetic field: For use with positron emission tomography.

Abstract

The process of positron emission tomography has become a valuable medical research tool. This procedure involves the administration of a radiopharmaceutical labelled with a positron-emitting isotope to a living organism. Upon the emission and subsequent annihilation of a positron, the gamma rays produced are detected to create an image of metabolic activity within the subject. Many factors such as Compton scattering and photoelectric absorption of the gamma rays tend to limit the quality of these images. Another important limitation is the non-negligible distance the positron travels prior to annihilation. This phenomenon leads to the misplacement of data in the final image. A method for reducing this effect utilizing a magnetic field has been tested and evaluated. The application of a magnetic field constrains the positrons to travel in helical paths instead of their relatively straight courses. Thus, the effective distance the positrons travel from their point of emission is reduced. Results indicate that this technique is successful in reducing the blurring caused in PET images by positron range. The results also indicate that the amount of resolution improvement depends upon the choice of positron emitter and scanner resolution. Reduction of this blurring helps to produce clearer PET images which can allow for more precise localization of tumors, in addition to better measurement of metabolic rate constants. The use of a magnetic field to reduce the range of positrons will lead to more useful images produced by positron emission tomography.