The
Laser Induced
Fluorescence Attenuation
Spectroscopy (LIFAS) method and apparatus preferably include a source adapted to emit
radiation that is directed at a
sample volume in a sample to produce return light from the sample, such return light including modulated return light resulting from modulation by the sample, a first sensor, displaced by a first distance from the
sample volume for monitoring the return light and generating a first
signal indicative of the intensity of return light, a second sensor, displaced by a second distance from the
sample volume, for monitoring the return light and generating a second
signal indicative of the intensity of return light, and a processor associated with the first sensor and the second sensor and adapted to process the first and second signals so as to determine the modulation of the sample. The methods and devices of the inventions are particularly well-suited for determining the
wavelength-dependent attenuation of a sample and using the attenuation to restore the intrinsic
laser induced
fluorescence of the sample. In turn, the attenuation and intrinsic
laser induced
fluorescence can be used to determined a characteristic of interest, such as the ischemic or hypoxic condition of
biological tissue.