  We demonstrate determination of the location of the distal-end of a
fibre-optic device deep in tissue through the imaging of ballistic and snake
photons using a time resolved single-photon detector array. The fibre was
imaged with centimetre resolution, within clinically relevant settings and
models. This technique can overcome the limitations imposed by tissue
scattering in optically determining the in vivo location of fibre-optic medical
instruments.
