Time-domain method and apparatus for determining the depth and concentration of a fluorophore in a turbid medium
View Patent ↗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.
1. An apparatus for determining depth and concentration of a fluorophore in a turbid medium comprised within an object, said apparatus comprising:
a light source, optically coupled to a source channel and said object, to inject light in said object at a desired point and excitation wavelength;
at least one detector channel, optically coupled to a photon detector and said object, in a back reflection geometry relative to said source channel, to acquire at least one temporal point spread function from a desired point of said object;
a means for spatially positioning said object relative to said channels;
a depth calculator for calculating the depth of the fluorophore on the basis of a time t max corresponding to a maximum of the temporal point spread function; and
a concentration calculator for calculating the concentration of the fluorophore based on the depth and on an intensity of the temporal point spread function.
2. The apparatus as claimed in claim 1 wherein said source and detector channels are in a configuration selected from contact and free-space optic.
3. The apparatus as claimed in claim 1 wherein said channels comprise optical coupling means selected from, mirrors, optic fibers.
4. The apparatus as claimed in claim 1 wherein said channels are mounted in a fixed position relative to one another.
5. The apparatus as claimed in claim 1 wherein said channels are mounted on a gantry that is moveable relative to said object.
6. The apparatus as claimed in claim 1 wherein said channels are independently moveable.
7. The apparatus as claimed in claim 1 wherein said object is placed on a platform transparent to an emission wavelength.
8. The apparatus as claimed in claim 7 wherein said platform is moveable relative to said channels.
9. The apparatus as claimed in claim 1 wherein said light source is a multiwavelength light source.
10. The apparatus as claimed in claim 1 wherein detection is effected using a plurality of source/detector configurations.
11. The apparatus as claimed in claim 1 comprising a plurality of detector channels.
12. The apparatus as claimed in claim 1 comprising a plurality of source channels.
13. The apparatus as claimed in claim 1 further comprising wavelength selection means between said source and said object for selecting one or more excitation wavelength.
14. The apparatus as claimed in claim 1 further comprising wavelength selection means between said object and said detector for selecting one or more emission wavelengths.
15. The apparatus as claimed in claim 1 wherein said detector in a trans-illumination geometry operates in time domain, frequency domain or continuous wave mode.
16. The apparatus as claimed in claim 1 further including a second detector channel in a trans-illumination geometry relative to said source channel, to measure an emission intensity of said fluorophore.
17. The apparatus as claimed in claim 1 , wherein a relative concentration of the fluorophore is calculated as:
Conc
.
Re
lative
=
Id
2
ⅇ
2
d
μ
α
/
D
where:
Conc. Relatlive is the relative concentration of the fluorophore;
I is the intensity of the temporal point spread function;
d is the depth of the fluorophore;
μ a is an optical absorption coefficient of the turbid medium; and
D is an optical diffusion coefficient of the turbid medium.