System and method of X-ray detection with a sensor

• US 8,119,990 B2
• Filed: 10/26/2009
• Issued: 02/21/2012
• Est. Priority Date: 10/27/2008
• Status: Active Grant

• Current Assignee: Dental Imaging Technologies Corporation (Envista Holdings Corporation)
• Original Assignee: Imaging Sciences International LLC
• Inventors: Zeller, Uwe
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): Sung, Christine
• Application Number:
  US12/605,624
• Publication Number:
  US 20100102241A1
• Time in Patent Office: 848 Days
• Field of Search: 250/370.09
• US Class Current: 250/370.09
• CPC Class Codes: A61B 6/4233 using matrix detectors
• CPC Class Codes: A61B 6/508 for non-human patients
• CPC Class Codes: A61B 6/51 for dentistry
• CPC Class Codes: G01T 1/17 Circuit arrangements not adapted to a particular type of detector pulse-selection circuits H03K, G01R
• CPC Class Codes: G01T 1/2928 using solid state detectors
• CPC Class Codes: G03B 42/042 for dental applications radiation diagnosis specially adapted for dentistry A61B6/51; individual packages for X-ray film G03C3/003
• CPC Class Codes: H01L 27/146 Imager structures
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30

Abstract

A system and method for automatic detection of x-rays at an x-ray sensor. A source emits x-ray radiation towards an x-ray sensor, and the x-ray sensor automatically detects the x-ray radiation. The x-ray sensor automatically detects x-ray radiation by evaluating a time series and determining that a voltage threshold is crossed a certain amount of time earlier than the average time it takes the voltage threshold to be crossed from dark current and other noise.

Claims

1. A method of automatically detecting x-ray radiation with an x-ray sensor, the method comprising:

resetting a pixel array by removing stored charge from the pixel array;

determining an average dark current trigger time;

measuring an elapsed time since resetting of the pixel array;

performing a comparison based upon the elapsed time and the average dark current trigger time;

determining that a threshold has been crossed, crossing of the threshold indicating that a predetermined amount of charge has been stored on at least a portion of the pixel array;

determining that x-ray radiation has been received at the at least a portion of the pixel array based on the comparison; and

upon determining that x-ray radiation has been received, outputting data from the pixel array to be used to generate an x-ray image.

2. The method of claim 1, wherein performing the comparison includes comparing a difference between the elapsed time and the average dark current trigger time with at least one of

a predetermined value, and

a product of a fine tuning variable and a standard deviation of the average dark current trigger time.

3. The method of claim 2, wherein x-ray radiation is determined to have been received at the at least a portion of the pixel array if the difference is greater than the at least one of the predetermined value or the standard deviation.

4. The method of claim 1, wherein the average dark current trigger time is based on iteratively calculating an elapsed time between a reset of the pixel array and a determination that the threshold has been crossed due to dark current.

5. The method of claim 1, wherein the average dark current trigger time indicates a temperature of the x-ray sensor.

6. The method of claim 5, further comprising generating an error condition if the temperature of the x-ray sensor indicated by the average dark current trigger time exceeds a predetermined level.

7. The method of claim 1, wherein the threshold is a predetermined voltage level, and wherein the predetermined amount of charge stored on the at least a portion of the pixel array causes a voltage potential at a diode to drop below the threshold.

8. The method of claim 1, further comprising

performing a second comparison using the elapsed time and the average dark current trigger time,

wherein performing the second comparison includes comparing a difference between the elapsed time and the average dark current trigger time with a first value,

and wherein performing the second comparison includes comparing the difference with a second value and comparing a second difference between a previous elapsed time and a previous average dark current trigger time with the second value.

9. The method of claim 8, wherein x-ray radiation is determined to have been received at the at least a portion of the pixel array if

the difference is greater than the first value, or

both the difference and the second difference are greater than the second value.

10. The method of claim 9, further comprising concluding 1) a high dose rate occurred if the difference is greater than the first value and 2) a low dose rate occurred if both the difference and the second difference are greater than the second value, wherein the first value is greater than the second value.

11. The method of claim 1, further comprising

determining that x-ray radiation is no longer being received, and

reducing an integration time for a subsequent x-ray radiation exposure based on a duration of x-ray radiation received at the at least a portion of the pixel array.

12. An x-ray sensor that automatically detects receipt of x-rays, the x-ray sensor including a processor, a pixel array, and a memory, the processor configured to:

reset the pixel array by removing stored charge from the pixel array;

determine an average dark current trigger time;

measure an elapsed time since resetting of the pixel array;

perform a comparison based upon the elapsed time and the average dark current trigger time;

determine that a threshold has been crossed, crossing of the threshold indicating that a predetermined amount of charge has been stored on at least a portion of the pixel array;

determine that x-ray radiation has been received at the at least a portion of the pixel array based on the comparison; and

upon determining that x-ray radiation has been received, output data from the pixel array to be used to generate an x-ray image.

13. The x-ray sensor of claim 12, wherein the processor is further configured to perform the comparison by comparing a difference between the elapsed time and the average dark current trigger time with at least one of

a predetermined value, and

a product of a fine tuning variable and a standard deviation of the average dark current trigger time.

14. The x-ray sensor of claim 13, wherein x-ray radiation is determined to have been received at the at least a portion of the pixel array if the difference is greater than the at least one of the predetermined value or the standard deviation.

15. The x-ray sensor of claim 12, wherein the average dark current trigger time is based on iteratively calculating an elapsed time between a reset of the pixel array and a determination that the threshold has been crossed due to dark current.

16. The x-ray sensor of claim 12, wherein the average dark current trigger time indicates a temperature of the x-ray sensor.

17. The x-ray sensor of claim 16, wherein the processor is further configured to generate an error condition if the temperature of the x-ray sensor indicated by the average dark current trigger time exceeds a predetermined level.

18. The x-ray sensor of claim 12, wherein the threshold is a predetermined voltage level, and wherein the predetermined amount of charge stored on the at least a portion of the pixel array causes a voltage potential at a diode to drop below the threshold.

19. The x-ray sensor of claim 12, wherein the processor is further configured to

perform a second comparison using the elapsed time and the average dark current trigger time,

wherein performing the second comparison includes comparing a difference between the elapsed time and the average dark current trigger time with a first value, and

wherein performing the second comparison includes comparing the difference with a second value and comparing a second difference between a previous elapsed time and a previous average dark current trigger time with the second value.

20. The x-ray sensor of claim 19, wherein x-ray radiation is determined to have been received at the at least a portion of the pixel array if

the difference is greater than the first value, or

both the difference and the second difference are greater than the second value.

21. The x-ray sensor of claim 20, wherein the processor is further configured to conclude 1) a high dose rate occurred if the difference is greater than the first value and 2) a low dose rate occurred if both the difference and the second difference are greater than the second value, and wherein the first value is greater than the second value.

22. The x-ray sensor of claim 12, wherein the processor is further configured to

determine that x-ray radiation is no longer being received, and

reduce an integration time for a subsequent x-ray radiation exposure based on a duration of x-ray radiation received at the at least a portion of the pixel array.