Virtual pet detector and quasi-pixelated readout scheme for pet

Patent metadata

Field	Value
Publication number	US-11119227-B2
Application number	US-201615209842-A
Country	US
Kind code	B2
Filing date	Jul 14, 2016
Priority date	May 16, 2007
Publication date	Sep 14, 2021
Grant date	Sep 14, 2021

Abstract

When designing detector arrays for diagnostic imaging devices, such as PET or SPECT devices, a virtual detector, or pixel, combines scintillator crystals with photodetectors in ratios that deviate from the conventional 1:1 ratio. For instance, multiple photodetectors can be glued to a single crystal to create a virtual pixel which can be software-based or hardware-based. Light energy and time stamp information for a gamma ray hit on the crystal can be calculated using a virtualizer processor or using a trigger line network and time-to-digital converter logic. Additionally or alternatively, multiple crystals can be associated with each of a plurality of photodetectors. A gamma ray hit on a specific crystal is then determined by a table lookup of adjacent photodetectors that register equal light intensities, and the crystal common to such photodetectors is identified as the location of the hit.

First claim

Having thus described the preferred embodiments, the invention is now claimed to be:

1. A virtual pixel array for a diagnostic imaging system, including:
a virtual pixel comprising at least one scintillator crystal;
a plurality of photodetectors optically and directly coupled to the at least one scintillator crystal, which generate output signals in response to scintillations in the crystal, wherein the plurality of photodetectors includes 4 photodetectors arranged in a 2×2 array; and
a virtualizer that processes the output signals associated with a gamma ray hit on the scintillator crystal as detected by the plurality of photodetectors and calculates a tune stamp for the gamma ray hit, wherein the calculated timestamp represents an earliest times amp associated with the gamma ray hit, independent of the energy of the hit;
a plurality of scintillator crystals, including the at east one scintillator crystal, arranged in a rectangular grid;
a plurality of the 2×2 arrays of photodetectors optically and directly coupled to the scintillator crystals in an offset relationship such that within a given in each 2×2 array, at least one of the scintillator crystals is optically and directly coupled to only one photodetector, one of the scintillator crystals is optically and directly coupled to four of the photodetectors, and at least two of the scintillator crystals are optically and directly coupled to two of the photodetectors;
wherein the scintillator crystals have a pitch of approximately one half a pitch of the photodetectors to which they are directly coupled.

2. The virtual pixel array according to claim 1 , wherein the length of each side of each scintillator crystal is approximately the length of each side of each photodetector, such that each array of photodetectors is associated with at least nine scintillator crystals.

3. A method of identifying a scintillator crystal in the virtual pixel array of claim 1 , including:
detecting light registration from a gamma ray at a first photodetector;
determining whether at least a second photodetector, adjacent to the first photodetector, has registered an amount of light equal to the amount of light registered at the first photodetector;
performing a table lookup of photodetectors registering substantially equal amounts of light; and
identifying a scintillator crystal overlapping all photodetectors registering the substantially equal amount of light as the scintillator crystal that was hit by the gamma ray.

4. The virtual pixel array according to claim 1 , further including:
one or more of:
at least one 4×4 array of photodetectors optically coupled to the scintillator crystals in an offset relationship; and
at least one 1×1 array of photodetectors optically coupled to the scintillator crystals in an offset relationship.

5. A method of calculating a time stamp for a virtual pixel, including:
arranging a plurality of scintillator crystals, including at least one scintillator crystal, in a rectangular grid;
optically and directly coupling a plurality of 2×2 arrays of photodetectors to the scintillator crystals in an offset relationship such that in each 2×2 array, at least one of the scintillator crystals is optically coupled to only one photodetector, one of the scintillator crystals is optically coupled to four of the photodetectors, and at least two of the scintillator crystals are optically coupled to two of the photodetectors receiving a gamma ray hit on at least one scintillator crystal of the virtual pixel;
evaluating output signals from each of a plurality of photodetectors optically coupled to the at least one scintillator crystal to determine an energy and a photodetector time stamp for each photodetector associated with the gamma ray hit;
calculating a total energy of the gamma ray hit by combining the energies detected by the plurality of photodetectors associated with the gamma ray hit; and
calculating a time stamp for the gamma ray hit as a function of the photodetector time stamp registered by at least one photodetector in the plurality of photodetectors, wherein the calculated timestamp represents an earliest timestamp associated with the gamma ray hit, independent of the energy of the hit;
wherein the scintillator crystals have a pitch that is approximately one half of a pitch of the photodetectors to which they are coupled.

6. The method according to claim 5 , wherein the length of each side of each scintillator crystal is approximately ½ the length of each side of each photodetector, such that each array of photodetectors is associated with at least nine scintillator crystals.

7. The method according to claim 5 , further comprising:
detecting light registration from a gamma ray at a first photodetector;
determining whether at least a second photodetector, adjacent to the first photodetector, has registered an amount of light equal to the amount of light registered at the first photodetector;
performing a table lookup of photodetectors registering substantially equal amounts of light; and
identifying a scintillator crystal overlapping all photodetectors registering the substantially equal amount of light as the scintillator crystal that was hit by the gamma ray.

8. The method according to claim 5 , further including:
one or more of:
optically coupling at least one 4×4 array of photodetectors to the scintillator crystals in an offset relationship; and
optically coupling at least one 1×1 array of photodetectors to the scintillator crystals in an offset relationship.

9. A detector array for a diagnostic imaging device, including:
a plurality of photodetectors arranged in an array;
a plurality of scintillator crystals arranged in an array and optically and directly coupled to the plurality of photodetectors, the photodetector array and the scintillator array being offset from each other such that each 2×2 array of photodetectors is coupled to nine whole scintillator crystals and one or more partial scintillator crystals, and wherein each of the nine whole scintillator crystals is coupled to one, two, or four photodetectors; and
a processor that identifies a scintillator crystal that has been hit by a gamma ray based on an output signal generated by one or more of the plurality of photodetectors optically coupled to the scintillator crystal hit by the gamma ray, and calculates a timestamp that represents an earliest timestamp associated with the gamma ray hit, independent of the energy of the hit;
wherein the scintillator crystals have a pitch that is one half of a pitch of the photodetectors to which they are coupled.

10. The detector array according to claim 9 , wherein the length of each side of each scintillator crystal is approximately ½ the length of each side of each photodetector.

11. The detector array according to claim 9 , further including:
a plurality of the scintillator crystals arranged in a rectangular grid;
a plurality of 2×2 arrays of photodetectors optically coupled to the scintillator crystals in an offset relationship such that in each 2×2 array, at least one of the scintillator crystals is optically coupled to only one photodetector, one of the scintillator crystals is optically coupled to four of the photodetectors, and at least two of the scintillator crystals are optically coupled to two of the photodetectors.

12. A method of identifying a scintillator crystal in the detector array of claim 9 , including:
detecting light registration from a gamma ray at a first photodetector;
determining whether at least a second photodetector, adjacent to the first photodetector, has registered an amount of light equal to the amount of light registered at the first photodetec

Assignees

• Koninklijke Philips Nv

Inventors

• Frach Thomas
• Thon Andreas

Classifications

• G01T1/1644 Primary

  using an array of optically separate scintillation elements permitting direct location of scintillations (G01T1/1645 takes precedence) · CPC title

• G01T1/20184

  Detector read-out circuitry, e.g. for clearing of traps, compensating for traps or compensating for direct hits · CPC title

• G01T1/2985

  In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis); (using external radiation sources A61B6/02) · CPC title

• A61B6/037

  Emission tomography · CPC title

• G01T1/1642

  using a scintillation crystal and position sensing photodetector arrays, e.g. ANGER cameras · CPC title