Apparatus and method for enhanced early photon detection in optical projection tomography
A system and method for optical tomography including illuminating an object with pulsing stimulus light and pulsing the stimulus light at a repetition frequency having a pulse period that is greater than a dead-time of a detector. Coordinating the pulse with the dead-time of the detector allows for higher powered light source and improves early photon detection.
1. A method for detecting early photons in optical projection tomography, comprising:
providing a pulsing stimulus light and a detector;
generating a first pulse of the stimulus light at and through a light scattering object;
detecting only a first excitation or emission photon that arrives at a detector for the first pulse of the stimulus light, wherein additional photons of the first pulse arrive at the detector during a first dead-time of the detector;
reactivating the detector after completion of the first pulse through the light scattering object, thereby correlating the timing of the first pulse with the first dead-time of the detector;
generating a subsequent pulse of the stimulus light through the light scattering object after the first pulse and upon the reactivation of the detector;
detecting only a next first excitation or emission photon that arrives at a detector for the subsequent pulse of the stimulus light, wherein additional photons of the subsequent pulse arrive at the detector during a subsequent dead-time of the detector; and
reactivating the detector after completion of the subsequent pulse through the light scattering object, thereby correlating the timing of the subsequent pulse with the subsequent dead-time of the detector.
2. The method of claim 1 , wherein the pulsing stimulus light provides a detector photon capture rate of greater than 20%.
3. The method of claim 2 , wherein the pulsing stimulus light provides a detector photon capture rate of at least 75%.
4. The method of claim 1 , further comprising pulsing the stimulus light at a repetition frequency that is less than the inverse of a dead-time of the detector.
5. The method of claim 1 , wherein the detector is a single photon counting photodetector.
6. The method of claim 1 , further comprising time-stamping each detected photon.
7. The method of claim 1 , further comprising providing a telecentric scanning lens adapted to scan a surface of the tissue.
8. The method of claim 7 , wherein the scanning lens is positioned opposite an excitation spot to collect light in a parallel geometry.
9. The method of claim 1 , further comprising administering a fluorophore contrast agent to the light scattering object, and forming a digital image of the light scattering object from a plurality of detected first excitations.
10. The method of claim 1 , wherein the detector comprises a multichannel photodetector adapted to capture data with the light scattering object illuminated at each of a plurality of discrete points in succession, and further comprising machine readable code including instructions for reconstructing a three dimensional model of a fluorophore distribution in the light scattering object from the data.
11. The method of claim 1 , further comprising time-stamping detected photon events using time-correlated photon counting.