Method and apparatus to facilitate crystal identification in a pet detector

1. A method for creating a look-up table for determining a crystal of interaction in a gamma ray detector, the method comprising:

arranging a mask configured to cover a subset of crystals of a plurality of crystals in a scintillation array so as to block exposure of the subset of crystals to gamma rays, the mask being aligned on the scintillation array in a first position to cover a first set of crystals;

exposing the scintillation array to gamma rays having a predetermined energy;

collecting a first set of data from at least one photosensor positioned to receive light generated by the scintillation array;

realigning the mask in a second position on the scintillation array to cover a second subset of crystals of the plurality of crystals, the second subset of crystals being different than the first subset of crystals;

repeating the exposing step with the mask aligned on the scintillation array in the second position;

collecting a second set of data from the at least one photosensor with the mask aligned on the scintillation array in the second position;

creating a first flood histogram from the first set of collected data and creating a second flood histogram from the second set of collected data;

superimposing the first flood histogram with the second flood histogram to create a superimposed flood histogram; and

generating a look-up table by assigning regions of the superimposed flood histogram to corresponding crystals of the plurality of crystals.

2. The method of claim 1 , wherein the mask is configured to block gamma rays having an energy level of 511 keV or greater.

3. The method of claim 1 , wherein the mask is a lattice structure that does not cover two consecutively positioned crystals in the scintillation array.

4. The method of claim 1 , wherein the mask is a block structure that covers at least two consecutively positioned crystals in the scintillation array.

5. The method of claim 1 , wherein the mask covers only edge crystals in the scintillation array.

6. A method for creating a look-up table for determining a crystal of interaction in a gamma ray detector, the method comprising:

arranging a mask configured to cover a subset of crystals of a plurality of crystals in a scintillation array so as to block exposure of the subset of crystals to gamma rays, the mask being aligned on the scintillation array in a first position to cover a first set of crystals;

exposing the scintillation array to gamma rays having a predetermined energy;

collecting a first set of data from at least one photosensor positioned to receive light generated by the scintillation array;

removing the mask from the scintillation array;

repeating the exposing step with the mask removed from the scintillation array to expose each crystal in the plurality of crystals to the generated gamma rays;

collecting a second set of data from the at least one photosensor without the mask aligned on the scintillation array;

creating a first flood histogram from the first set of collected data and creating a second flood histogram from the second set of collected data;

subtracting the first flood histogram from the second flood histogram to create a modified flood histogram; and

generating a look-up table by assigning regions of the first flood histogram and the modified flood histogram to corresponding crystals of the plurality of crystals.

7. The method of claim 6 , wherein the mask is configured to block gamma rays having an energy level of 511 keV or greater.

8. The method of claim 6 , wherein the mask is a lattice structure that does not cover two consecutively positioned crystals in the scintillation array.

9. The method of claim 6 , wherein the mask is a block structure that covers at least two consecutively positioned crystals in the scintillation array.

10. The method of claim 6 , wherein the mask covers only edge crystals in the scintillation array.

11. A Positron Emission Tomography (PET) system for crystal identification, the system comprising:

a scintillation array including a plurality of crystals;

a mask configured to cover a subset of crystals of the plurality of crystals so as to block exposure of the subset of crystals to gamma rays;

at least one photosensor positioned to receive light generated by the scintillation array; and

a processor configured to

collect a first set of data from the at least one photosensor in response to exposure of the scintillation array to gamma rays when the mask is arranged on the scintillation array in a first position to cover a first subset of crystals;

collect a second set of data from the at least one photosensor in response to exposure of the scintillation array to gamma rays when the mask is arranged on the scintillation array in a second position to cover a second subset of crystals being different than the first subset of crystals;

create a first flood histogram from the first set of collected data and create a second flood histogram from the second set of collected data;

superimpose the first flood histogram with the second flood histogram to create a superimposed flood histogram; and

generate a look-up table by assigning regions of the superimposed flood histogram to corresponding crystals of the plurality of crystals.

12. The system of claim 11 , wherein the mask is configured to block gamma rays having an energy level of 511 keV or greater.

13. The system of claim 11 , wherein the mask is a lattice structure that does not cover two consecutively positioned crystals in the scintillation array.

14. The system of claim 11 , wherein the mask is a block structure that covers at least two consecutively positioned crystals in the scintillation array.

15. The system of claim 11 , wherein the mask covers only edge crystals in the scintillation array.

16. A Positron Emission Tomography (PET) system for crystal identification, the system comprising:

a scintillation array including a plurality of crystals;

a mask configured to cover a subset of crystals of the plurality of crystals so as to block exposure of the subset of crystals to gamma rays;

at least one photosensor positioned to receive light generated by the scintillation array; and

a processor configured to

collect a first set of data from the at least one photosensor in response to exposure of the scintillation array to gamma rays when the mask is arranged on the scintillation array in a first position to cover a first subset of crystals;

collect a second set of data from the at least one photosensor in response to exposure of the scintillation array when the mask is removed from the scintillation array;

create a first flood histogram from the first set of collected data;

create a second flood histogram from the second set of collected data;

subtract the first flood histogram from the second flood histogram to create a modified flood histogram; and

generate a look-up table by assigning regions of the first flood histogram and the modified flood histogram to corresponding crystals of the plurality of crystals.

17. The system of claim 16 , wherein the mask is configured to block gamma rays having an energy level of 511 keV or greater.

18. The system of claim 16 , wherein the mask is a lattice structure that does not cover two consecutively positioned crystals in the scintillation array.

19. The system of claim 16 , wherein the mask is a block structure that covers at least two consecutively positioned crystals in the scintillation array.

20. The system of claim 16 , wherein the mask covers only edge crystals in the scintillation array.