A　novel　MRI-guided　near-infrared　spectroscopic　tomographic　imaging　system　(NIRST)　has　been　developed　for　breast　cancer　detection.　NIRST　imaging　for　an　entire　breast　can　be　simultaneously　carried　out　during　MRI　scanning　in　less　than　4　minutes.　Reconstructed　phantom　images　showed　clear　contrast　of　a　20　mm　inclusion　to　the　background,　and　the　total　hemoglobin　(HbT)　and　water　concentration　values　estimated　from　the　reconstructed　images　of　a　normal　subject　were　in　the　same　range　as　those　obtained　in　our　previous　imaging　studies.　©　2023　SPIE.