1. One or more non-transitory computer readable media comprising computer instructions configured to cause one or more computer processors to perform actions comprising: accessing a plurality of electronic magnetic resonance imaging (MRI) images of an area that includes a region of interest in an intervertebral disc of a spine; for each of the plurality of electronic MRI images: processing the electronic MRI image to emphasize pixels associated with two opposite borders between the intervertebral disc and two superiorly and inferiorly adjacent vertebral bodies, respectively; identifying a population of pixels in the electronic MRI image associated with the borders; and fitting a two dimensional rectilinear shape inside a cross-section of the region of interest in the intervertebral disc and between the borders shown by the electronic MRI image based on the population of pixels; and generating world coordinates that define a three dimensional selected volume comprising a voxel that fits inside of the region of interest in the intervertebral disc and excludes the two superiorly and inferiorly adjacent vertebral bodies associated with the borders based on one or more of the two dimensional rectilinear shapes; wherein the one or more non-transitory computer readable media are configured to be used with a magnetic resonance spectroscopy (MRS) system in communication with the one or more computer processors, and the MRS system is configured to provide an MRS spectrum of chemical constituents within the voxel.