in one aspect , the invention relates to a probe . the probe includes a sheath , a flexible , bi - directionally rotatable , optical subsystem positioned within the sheath , the optical subsystem comprising a transmission fiber , the optical subsystem capable of transmitting and collecting light of a predetermined range of wavelengths along a first beam having a predetermined beam size . the probe also includes an ultrasound subsystem , the ultrasound subsystem positioned within the sheath and adapted to propagate energy of a predetermined range of frequencies along a second beam having a second predetermined beam size , wherein a portion of the first and second beams overlap a region during a scan .