Method and system for determining a source-to-image distance in a digital imaging system

• US 6,435,716 B1
• Filed: 05/23/2000
• Issued: 08/20/2002
• Est. Priority Date: 05/23/2000
• Status: Expired due to Fees

• Current Assignee: GE Medical Technology Services, Inc. (General Electric Company)
• Original Assignee: GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
• Inventors: Polkus, Vincent S., Omernick, Jon C., Boomgaarden, Jonathan C., Stetz, Robert M.
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): Dunn, Drew A.
• Application Number:
  US09/576,848
• Time in Patent Office: 819 Days
• Field of Search: 378/205, 378/207, 378/197, 378/193, 378/98.8, 378/162, 378/166
• US Class Current: 378/205
• CPC Class Codes: A61B 6/4233 using matrix detectors
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: A61B 6/588 Setting distance between source unit and detector unit

Abstract

A method is provided for determining source-to-image distance (SID) setpoints in a digital imaging system. SID setpoints are determined during a setup and calibration procedure which includes generating radiation beams while varying certain system parameters, such as the radiation source position, and detecting and determining the size of the radiation beams that impact on the digital detector. SID values and a separation gain constant can then be determined based on the calculated sizes of the detected radiation beams and the feedback signals which are representative of the various system parameters that were varied (e.g., source position, etc.) during the setup and calibration procedure. The separation gain constant and the calculated, empirical SID values can then be used to position the radiation source at any user-selected SID based on position sensor feedback signals. The procedure also provides for a calibrated readout of the SID, which can be displayed to a user of the imaging system.

Claims

1. A method for determining a source-to-image distance (SID) setpoint between a radiation source and a digital detector in a digital imaging system, the method comprising:

positioning the radiation source with respect to the digital detector at a first source position;

sensing the first source position and providing a first feedback signal representative thereof;

generating a first radiation beam with the radiation source, the first radiation beam having a beam angle;

detecting the first radiation beam on the detector;

determining a first size of a first impact area of the first radiation beam on the detector;

displacing the radiation source to a second source position;

determining an amount of the displacement;

sensing the second source position and providing a second feedback signal representative thereof;

generating a second radiation beam with the radiation source, the second radiation beam having substantially the same beam angle as the first radiation beam;

detecting the second radiation beam on the detector;

determining a second size of a second impact area of the second radiation beam on the detector;

determining a separation gain constant based on the determined amount of the displacement and the first and second feedback signals;

determining a separation distance between the radiation source and the digital detector based on the first and second sizes of the first and second impact areas and the determined amount of the displacement; and

utilizing the determined separation gain constant and the determined separation distance to position the radiation source at a selected SID.

2. The method as recited in claim 1, further comprising:

displaying indicia representative of the selected SID.

3. The method as recited in claim 1, further comprising:

continuously sensing positions of the radiation source; and

generating feedback signals representative thereof,

wherein utilizing the determined separation gain constant and the determined separation distance comprises determining a feedback signal value representative of a source position that corresponds to the selected SID.

4. The method as recited in claim 3, further comprising:

displacing the radiation source until a value of the generated feedback signal is substantially equal to the determined feedback signal value that corresponds to the selected SID.

5. The method as recited in claim 4, further comprising:

providing a command signal to initiate determination of the separation gain constant.

6. The method as recited in claim 5, wherein the command signal is provided from a location remote from the radiation source and the digital detector.

7. The method as recited in claim 5, wherein the command signal includes a control signal to position and displace the radiation source.

8. The method as recited in claim 1, wherein determining the first and second sizes of the first and second impact areas comprises:

detecting opposing lateral peripheral edges of the first impact area; and

detecting opposing lateral peripheral edges of the second impact area.

9. The method as recited in claim 8, wherein the digital detector comprises a plurality of rows and a plurality of columns which define an image matrix, and detecting opposing lateral peripheral edges of the first impact area comprises determining first and second rows of the image matrix which correspond to the opposing lateral peripheral edges.

10. The method as recited in claim 8, wherein determining the first and second sizes further comprises:

detecting opposing longitudinal peripheral edges of the first impact area; and

detecting opposing longitudinal peripheral edges of the second impact area.

11. The method as recited in claim 10, wherein the radiation source comprises an x-ray source.

12. A method for determining a separation distance between a radiation source and a digital detector positioned to detect an radiation beam generated by the radiation source, the method comprising:

generating a first radiation beam with the radiation source positioned at a first source position;

determining a first size of a first impact area of the first radiation beam detected on the detector;

varying a system parameter such that a second radiation beam generated by the radiation source has a second impact area on the detector, the second impact area having a second size that is different than the first size;

generating the second radiation beam;

determining the second size of the second impact area of the second radiation beam detected on the detector; and

calculating a first separation distance of the radiation source with respect to the detector based on the determined first and second sizes of the first and second impact areas and the variation of the system parameter.

13. The method as recited in claim 12, wherein the varied system parameter is a position of the radiation source, and varying the system parameter comprises displacing the radiation source to a second source position displaced from the first source position.

14. The method as recited in claim 13, further comprising:

providing a source position transducer to sense source position and to generate a feedback signal representative of the sensed source position.

15. The method as recited in claim 14, further comprising:

determining a separation gain constant based on the first and second sizes of the first and second impact areas and the feedback signals representative of the first and second source positions;

utilizing the separation gain constant and the calculated first separation distance to position the radiation source at a source position corresponding to a selected source-to-image distance (SID).

16. The method as recited in claim 15, wherein utilizing the separation gain constant and the calculated first separation distance to position the radiation source comprises:

determining a value of feedback signal corresponding to the selected SID; and

displacing the radiation source with respect to the detector until the feedback signal generated by the source position transducer is substantially the same as the determined value of feedback signal.

17. The method as recited in claim 16, wherein displacing the radiation source comprises:

providing a command from a remote location to displace the radiation source.

18. The method as recited in claim 12, wherein the first radiation beam has a first beam angle and the system parameter is varied such that the second radiation beam has a second beam angle, the second beam angle being different than The first beam angle of the first radiation beam.

19. The method as recited in claim 18, wherein the first and second radiation beams are generated at the first source position, the first source position corresponding to the calculated first separation distance, and the method further comprises:

providing a source position transducer to detect source position;

generating a feedback signal representative of the detected source position;

displacing the radiation source to a second source position displaced from the first source position;

determining an amount of the displacement;

generating a third radiation beam with the radiation source, the third radiation beam having a third beam angle that is substantially the same as the first beam angle;

determining a third size of a third impact area of the third radiation beam detected on the detector;

determining a separation gain constant based on the determined amount of the displacement and the feedback signals representative of the first and second source positions; and

determining a second separation distance between the radiation source and the digital detector based on the sizes of the first and third impact areas and the determined amount of the displacement.

20. The method as recited in claim 19, further comprising:

utilizing the separation gain constant and the determined second separation distance to position the radiation source at a selected SID.

21. The method as recited in claim 20, further comprising:

displaying indicia representative of the selected SID.

22. The method as recited in claim 12, wherein the radiation source comprises an x-ray source.

23. The method as recited in claim 12, wherein determining the sizes of the first and second impact areas comprises:

detecting opposing lateral peripheral edges of the first impact area; and

detecting opposing lateral peripheral edges of the second impact area.

24. The method as recited in claim 23, wherein the digital detector comprises a plurality of rows and a plurality of columns which define an image matrix, and detecting the opposing lateral peripheral edges of the first and second impact areas comprises:

determining a row of the image matrix which corresponds to each lateral peripheral edge.

25. The method as recited in claim 12, comprising:

generating a command to initiate computation of the separation distance.

26. The method as recited in claim 25, wherein the command comprises a control signal to vary the system parameter.

27. The method as recited in claim 25, wherein the command is generated from a location remote from the radiation source and the digital detector.

28. A digital imaging system, comprising:

a digital detector;

a radiation source to generate a radiation beam, the radiation source being displaced from the detector and configured to generate a first radiation beam having a first impact area of a first size when detected at the detector and a second radiation beam having a second impact area of a second size when detected at the detector;

a transducer to sense a system parameter and to generate a first feedback signal representative of the system parameter when the radiation source generates the first radiation beam and a second feedback signal representative of the system parameter when the radiation source generates the second radiation beam, wherein a variation of the system parameter causes the second size of the second impact area to be different than the first size of the first impact area; and

a processing module configured to;

determine the first size of the first impact area;

determine the second size of the second impact area; and

determine a first separation distance of the radiation source with respect to the detector based on the determined first and second sizes and the variation of the system parameter.

29. The system as recited in claim 28, wherein the system parameter is the position of the radiation source and the variation of the system parameter is a displacement of the radiation source with respect to the digital detector, wherein the radiation source is displaced from a first source position to a second source position and the first and second feedback signals are representative of the first and second source positions, respectively.

30. The system as recited in claim 29, wherein the processing module is configured to:

determine a separation gain constant based on the displacement of the radiation source and the first and second feedback signals.

31. The system as recited in claim 30, comprising:

a user interface to input commands and system parameters including a selected separation distance,

wherein the processing module is configured to;

utilize the separation gain constant and the determined first separation distance to determine a source position that corresponds to the selected separation distance.

32. The system as recited in claim 31, wherein the user interface is at a location remote from the detector and the source.

33. The system as recited in claim 28, wherein the digital detector comprises a plurality of rows and columns defining an image matrix, and the first size of the first impact area is determined by detecting a pair of rows which correspond to opposing peripheral edges of the first impact area, and the second size of the second impact area is determined by detecting a pair of rows which correspond to opposing peripheral edges of the second impact area.

34. The system as recited in claim 28, wherein the radiation source comprises an x-ray source.