Virtual PET detector and quasi-pixelated readout scheme for PET

Patent metadata

Field	Value
Publication number	US-9423511-B2
Application number	US-60007208-A
Country	US
Kind code	B2
Filing date	Apr 29, 2008
Priority date	May 16, 2007
Publication date	Aug 23, 2016
Grant date	Aug 23, 2016

Abstract

When designing detector arrays for diagnostic imaging devices, such as PET or SPECT devices, a virtual detector, or pixel, combines scintillator crystals ( 10, 20, 40 ) with photodetectors ( 12 ) 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 ( 10, 20, 40 ) 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 ( 54 ) can be associated with each of a plurality of photodetectors ( 52 ). A gamma ray hit on a specific crystal is then determined by a table lookup of adjacent photodetectors ( 52 ) that register equal light intensities, and the crystal ( 54 ) common to such photodetectors ( 52 ) 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 a scintillator crystal and a plurality of photodetectors optically coupled to the scintillator crystal, which generate output signals in response to scintillations in the crystal, wherein the photodetectors are smaller than the crystal to which they are coupled; 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 time stamp for the gamma ray hit.

2. The system according to claim 1 , wherein the virtual pixel is a software-based virtual pixel and the virtualizer employs an algorithm that calculates the time stamp.

3. The system according to claim 2 , wherein the virtualizer calculates the time stamp as an energy-weighted sum of a partial photodetector time stamp from the output signals of each of the plurality of photodetectors.

4. The system according to claim 2 , wherein the virtualizer calculates the time stamp as a function of the output signal of a photodetector registering a highest energy level relative to other photodetectors in the virtual pixel.

5. The system according to claim 2 , wherein the virtualizer calculates the time stamp as a function of an earliest photodetector time stamp registered by a photodetector in the virtual pixel.

6. The system according to claim 1 , wherein the virtual pixel is a hardware-based virtual pixel, and includes a network that connects a trigger line from each of the plurality of photodetectors to a time-to-digital converter.

7. The system according to claim 6 , further including a selector/multiplexer that selects time stamp data from all photodetector time stamps received over the network for forwarding to at least one output buffer.

8. The system according to claim 1 , wherein the virtual pixel array is disposed in a diagnostic imaging device and the virtualizer includes:
a routine for evaluating energies and time stamps associated with a plurality of photodetectors in the virtual pixel in response to a gamma ray hit;
a routine for calculating total energy associated with the gamma ray hit; and
a routine for calculating a time stamp for the gamma ray hit.

9. The system according to claim 1 , wherein the plurality of photodetectors includes 4 photodetectors arranged in a 2×2 array.

10. A method of calculating a time stamp for a virtual pixel, including:
receiving a gamma ray hit on a scintillator crystal of the virtual pixel;
evaluating output signals from each of a plurality of photodetectors optically coupled to the scintillator crystal to determine an energy and a photodetector time stamp for each photodetector associated with the gamma ray hit, wherein the photodetectors are smaller than the scintillator crystal to which they are optically coupled;
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.

11. The method according to claim 10 , further including calculating the time stamp for the gamma ray hit as an energy-weighted sum of a partial photodetector time stamp from each of the plurality of photodetectors associated with the gamma ray hit.

12. The method according to claim 10 , further including calculating the time stamp as a function of a photodetector time stamp of a photodetector registering a highest energy level relative to other photodetectors in the virtual pixel.

13. The method according to claim 10 , further including calculating the time stamp as a function of an earliest photodetector time stamp registered by a photodetector in the virtual pixel.

14. The method according to claim 10 , further including calculating the time stamp as a function of partial time stamps received at a time-to-digital converter via a network connection a trigger line from each of the plurality of photodetectors.

15. A reconfigurable pixel array, including:
an array of photodetectors;
an array of scintillator crystals in which the crystals are any of a plurality of selectable sizes; and
a processor that processes the output signals associated with a gamma ray hit on one of the scintillator crystals as detected by a respective portion of the array of photodetectors to calculate a time stamp for the gamma ray hit;
wherein the photodetectors are smaller than the scintillation scintillator crystals to which they are attached.

16. The pixel array according to claim 15 , wherein the array size is selectable.

Assignees

• Frach Thomas
• Thon Andreas
• Koninklijke Philips Nv

Inventors

• Frach Thomas
• Thon Andreas

Classifications

• A61B6/037

  Emission tomography · CPC title

• G01T1/1644 Primary

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

• G01T1/1642 Primary

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