1. A method for simultaneously generating spectral images and spatial images of a subject using a magnetic resonance imaging (MRI) system, the steps of the method comprising: arranging a subject having received a dose of a hyperpolarized molecular imaging agent within a magnetic resonance imaging (MRI) system; acquiring MR image data from the subject according to a k-space sampling trajectory that spatially oversamples to encode both spatial frequency information and spectral frequency information in the oversampled points; and reconstructing the MR image data into spatial and spectral images using a priori knowledge of an expected chemical species associated with the molecular imaging agent and a model-based reconstruction technique.