Utilizing MRI information to estimate F18-FDG distributions in rat flank tumors

This paper investigates the potential of magnetic resonance imaging (MRI) to improve the estimation of within-tumor variations in F18-FDG concentration. An image model is described for incorporating MRI images into positron emission tomography (PET) and single photon emission computed tomography (SPECT) radiotracer image reconstruction. The model promotes greater smoothing, of estimated radiotracer concentration, among nearby voxels that have more nearly similar MRI signals. R3230 mammary adenocarcinomas are grown on rat flanks. Autoradiography, histology, and T2-weighted MRI are used to demonstrate that the above image model accurately reflects true F18-FDG distributions in R3230 tumors. In vivo F18-FDG distributions are then reconstructed from PET projection data, with and without incorporating MRI. The F18-FDG images reconstructed with MRI show greater detail, and this additional detail is consistent with the results of the autoradiography and histology studies.