1. A motion tracking system for tracking and compensating for motion of a patient during a medical imaging scan, the motion tracking system comprising: an optical marker configured to be attached to the patient, wherein the optical marker comprises a plurality of optically visible landmarks, the plurality of optically visible landmarks defining a plurality of reference points; a plurality of optical detectors, wherein each of the plurality of optical detectors is positioned to view the optical marker along a different line of sight; a marker location filter for determining locations of marker reference points, the marker location filter configured to: receive a digital image from each of the plurality of optical detectors, wherein each digital image represents a view along a different line of sight; determine, for each digital image, whether the digital image includes a view of the optical marker; and for each digital image that includes a view of the optical marker, determine positions of the plurality of reference points in the digital image; a patient orientation filter for estimating a three-dimensional pose of the patient, the patient orientation filter configured to: calculate a plurality of baseline attributes related to the plurality of reference points, the plurality of baseline attributes calculated based on the determined positions of the plurality of reference points; and estimate iteratively the three-dimensional pose of the patient, until a measure of error is within a threshold amount, the measure of error calculated based on the plurality of baseline attributes as compared to a plurality of comparison attributes, the plurality of comparison attributes calculated by assuming the object is in an estimated pose; and one or more computers configured to operate the marker location filter and patient orientation filter, wherein the one or more computers comprises a computer processor and an electronic storage medium.