Apparatus and methods for evaluating operation of pixelated detectors

• US 8,158,951 B2
• Filed: 02/03/2009
• Issued: 04/17/2012
• Est. Priority Date: 02/03/2009
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Bal, Girish, Jansen, Floribertus Heukensfeldt, Zak, Osnat, Berlad, Gideon, Hefetz, Yaron, Dolinsky, Sergei, Yanoff, Brian D., Tkaczyk, John Eric, Du, Yanfeng, Manjeshwar, Ravindra Mohan, Asma, Evren, Hua, Qian
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US12/365,100
• Publication Number:
  US 20100193697A1
• Time in Patent Office: 1,169 Days
• Field of Search: 250/370.09
• US Class Current: 250/370.09
• CPC Class Codes: G01T 1/247 Detector read-out circuitry for processing gain or off-set correction H04N
• CPC Class Codes: G01T 1/249 specially adapted for use in SPECT or PET SPECT imaging G01T1/1642; PET imaging G01T1/2985; detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects G01V5/20

Abstract

An apparatus and methods for evaluating the operation of pixelated detectors are provided. The method includes obtaining data values for each of a plurality of pixels of a pixelated detector and determining a data consistency metric for each of the plurality of detector pixels. The method further includes identifying, using the determined data consistency metric, any detector pixels that exceed an acceptance criterion as noisy pixels.

Claims

1. A method for identifying noisy pixels in a pixelated detector, the method comprising:

obtaining data values for each of a plurality of pixels of a pixelated detector;

determining a data consistency metric for each of the plurality of detector pixels;

identifying, using the determined data consistency metric, any detector pixels that exceed an acceptance criterion as noisy pixels; and

confirming an identified detector pixel when an energy spectrum for the identified pixel is not consistent with a measured gamma radiation, wherein the energy spectrum of each detector pixel is compared to that of adjacent good pixels or that of the entire detector.

2. A method in accordance with claim 1 wherein the acceptance criterion is based on a statistical deviation.

3. A method in accordance with claim 2 wherein the statistical deviation comprises at least one of a mean and a standard deviation.

4. A method in accordance with claim 1 further wherein the identifying is performed iteratively and further comprising performing a re-projection after each iteration of a reconstructed image and the reprojected data is used with or without smoothing.

5. A method in accordance with claim 1 further comprising determining a time at which any detector pixels exceed the acceptance criterion based on a plurality of timing bins in which the data values are sorted.

6. A method in accordance with claim 5 further comprising flagging the detector pixels exceeding the acceptance criterion.

7. A method in accordance with claim 6 further comprising initializing the identified detector pixels to zero at the time at which any pixel exceeds the acceptance criterion or exclude data from identified pixels from reconstruction.

8. A method in accordance with claim 6 further comprising correcting the identified detector pixels at the time at which any pixel exceeds the acceptance criterion by decreasing the bias voltage on that particular pixel.

9. A method in accordance with claim 6 further comprising estimating a value for the identified detector pixels at the time at which any pixel exceeds the acceptance criterion.

10. A method in accordance with claim 9 wherein the estimating comprises extrapolating values from detector pixels adjacent to the identified pixel.

11. A method in accordance with claim 9 wherein the estimating comprises interpolating values from detector pixels adjacent to the identified pixel.

12. A method in accordance with claim 1 further comprising excluding the data from the identified detector pixels during a subsequent iteration of an image reconstruction process.

13. A method in accordance with claim 12 further comprising re-projecting the reconstructed image with an initialized pixels.

14. A method in accordance with claim 12 further comprising assigning different values to the identified detector pixels after determining the values of the identified pixels after a plurality of iterations.

15. A method in accordance with claim 1 further comprising disabling detector pixels that exceed the acceptance criterion a predetermined number of times.

16. A method in accordance with claim 1 further comprising identifying the detector pixels after a number of image reconstruction processes.

17. A method in accordance with claim 1 wherein identifying the detector pixels comprises comparing one or more pixels of the plurality of pixels with one or more pixels in a vicinity thereof to determine a consistency metric value.

18. A method in accordance with claim 1 wherein the pixelated detector comprises a pixelated photon detector.

19. A method in accordance with claim 1 wherein the identifying is performed during a pre-imaging process and based on a geometry of an emission and detection process.

20. A method in accordance with claim 1 wherein the data values are obtained when no radiation source is operating.

21. A method in accordance with claim 1 further comprising using a radiation source and reconstructing an image to identify noisy detector pixels.

22. A method in accordance with claim 21 further comprising determining a difference in detector pixel counts for each of the plurality of pixels.

23. A method in accordance with claim 22 further comprising reconstructing an image and reprojecting the reconstructed image to determine a difference between the data values and the reprojected image.

24. A method in accordance with claim 23 further comprising determining whether the difference is within a predetermined threshold.

25. A method in accordance with claim 24 further comprising sub-dividing a measured projection based on one of time and spatial subsets to reconstruct an image.

26. A method in accordance with claim 25 further comprising identifying noisy detector pixels based on individual subsets or a combination of subsets.

27. A method for dynamically detecting and disabling noisy pixels in a pixelated detector, the method comprising:

using at least one statistical measure to identify a detector pixel that is not operating properly; and

correcting the identified detector pixel wherein the correcting comprises permanently disabling detector pixels that are identified more than a threshold amount of times as not operating properly.

28. A method in accordance with claim 27 wherein the correcting is performed only during a time period in which the detector pixel was not operating properly.

29. A method in accordance with claim 27 wherein the correcting comprises extrapolating non-identified detector pixels to identified pixels.

30. A method in accordance with claim 27 wherein the correcting comprises interpolating non-identified detector pixels to identified pixels.

31. A diagnostic imaging system comprising:

at least one pixelated detector including a plurality of pixels and configured to acquire photon data; and

a detector processor configured to identify any of the plurality of detector pixels for which the detected number of photons exceeds a statistical acceptance criterion as compared to other detector pixels of the plurality of pixels to determine noisy pixels, wherein an identified detector pixel is confirmed when an energy spectrum for the identified pixel is not consistent with a measured gamma radiation, and wherein the energy spectrum of each detector pixel is compared to that of adjacent good pixels or that of the entire detector.

32. A diagnostic imaging system in accordance with claim 31 wherein the processor is configured to determine noisy detector pixels one of prior to an image acquisition process, during an image acquisition process, during a pre-processing stage and during an image reconstruction process.

33. A diagnostic imaging system in accordance with claim 31 wherein the processor is configured to flag the identified detector pixels.

34. A diagnostic imaging system in accordance with claim 33 wherein the processor is configured to one of disable, remove or correct the flagged detector pixel.