Detector geometry, spatial sampling, and more fundamentally, positron range and noncollinearity of annihilation photon emission define Positron Emission Tomography (PET) spatial resolution. In this paper, a strong magnetic field is used to constrain positron travel transverse to the field. Measurement of the spread function from a 500 microns diameter 68Ga impregnated resin bead shows a squeezing of the full width at half maximum (FWHM) by a factor of 1.0, 1.22, 1.42, and 2.05, at 0, 4.0, 5.0, and 9.4 Tesla, respectively. The full width at tenth maximum (FWTM) decreases by a factor of 1.0, 1.73, 2.09, and 3.20, at 0, 4.0, 5.0, and 9.0 Tesla, respectively. Acquiring a PET image in a magnetic field should significantly reduce resolution loss due to positron range.