DOT-MRI system in the clinical MR suite. The optical and electronic components of the DOT-MRI instrument are housed in an instrument rack on pneumatic wheels for easy transport to and from the MR suite. The rack contains all laser sources, the pulsed laser diode driver, all optical switches, the CW detection fiber imaging plate and CCD, PMTs and PMT control-units for TD detection, and TCSPC control instrumentation. When in use, the DOT instrument rack is brought to the control room of the MR suite at the Hospital of the University of Pennsylvania. The fiber bundles then pass into the MRI bore and are incorporated into the clinical breast biopsy RF coil, on which the subject can lie in a prone position to be simultaneously imaged by MRI and DOT.