Corresponding magnetic resonance imaging (MRI) and diffuse opticalspectroscopic imaging (DOSI). Images were taken at baseline and end ofneoadjuvant chemotherapy in the contralateral normal breast of a premenopausalpatient. The yellow outlines in the MRI images depict the result of thesegmentation algorithm for fibroglandular tissue in the shown slices. The DOSImaps depict measured parameters as a function of position (tick mark separationequals 1 cm). The illustrated maps are from an 8- × 6-cm area from theupper-inner region of the left breast. The areolar region has more water,outlined by the semicircle. The decreased density after chemotherapy is clearlyvisible in both MRI and DOSI. MRI shows 30.4% reduction in fibroglandulartissue volume, and DOSI shows 24.4% reduction in tissue water. ctHHb,deoxyhemoglobin concentration; TOI, tissue optical index.