1. A computer-implemented method for quantifying liver function in a patient, the method executed by one or more processors programmed to perform the method, the method comprising: obtaining, at one or more processors, one or more three-dimensional (3-D) images of a patient's liver, the one or more 3-D images collected using magnetic resonance imaging (MRI), positron emission tomography (PET), or single-photon emission computed tomography (SPECT); for each of the one or more 3-D images: analyzing, by the one or more processors, the 3-D image to identify a plurality of contrast concentration parameters collected over time; generating, by the one or more processors, a linear liver pharmacokinetic model using the plurality of contrast concentration parameters collected over time; calculating, by the one or more processors, a contrast uptake rate metric for liver cells and a fractional distribution volume for blood based on the linear liver pharmacokinetic model, wherein the contrast uptake rate metric is indicative of liver function in the patient; and displaying, by the one or more processors, an indication of the contrast uptake rate metric to provide an assessment of the liver function in the patient to a healthcare professional.