1. An MRS preprocessing system for preprocessing raw MRS spectrum data comprising: one or more processors; and a plurality of modules configured to be executed by the one or more processors, the plurality of modules comprising: a normalization module to normalize the raw MRS spectrum data to generate normalized MRS spectrum data, wherein the raw MRS spectrum data comprise a summary of signals produced by a plurality of types of a tissue comprising normal and abnormal types of the tissue, at a range of nuclear magnetic resonance frequencies; a recalibration module to shift each of the nuclear magnetic resonance frequencies representing a particular biomarker to a reference nuclear magnetic resonance frequency representing the particular biomarker to generate a recalibrated MRS spectrum data; a variance-weighting module to scale the recalibrated MRS spectrum data by using a plurality of weighting constants to generate a weighted MRS spectrum data, wherein each of the plurality of weighting constants corresponds to a particular nuclear magnetic resonance frequency, wherein each of the plurality of weighting constants at a particular magnetic resonance frequency represents an average relative standard deviation taken from an average of raw MRS spectrum data associated with the plurality of tissue types at the particular nuclear magnetic resonance frequency, and wherein scaling the recalibrated MRS spectrum data comprises dividing each of the summary of signals from the recalibrated MRS spectrum data at the particular nuclear magnetic resonance frequency by one of the plurality of weighting constants corresponding to that same particular nuclear magnetic resonance frequency; and a renormalization module to renormalize the weighted MRS spectrum data to generate a preprocessed MRS spectrum data.