Methods and apparatuses for determining the depth and concentration of fluorophores in a turbid medium are disclosed. The method advantageously provides for a rapid estimation of the depth of the fluorophore using characteristics of a temporal point spread function. The concentration of the fluorophore can be determined using the method of the present invention by combining a calculated depth of the fluorophore with a measurement of the intensity of the emitted fluorescence. The intensity can be accurately measured by the apparatus disclosed herein which combine back-reflection and trans-illumination geometries for the source of light injecting and detection.