Claims
- 1. A method for calibrating an, imaging system having an array of detector elements arranged with respect to a reference position and having an energy source moving in a pattern to irradiate the array of detector elements, said method comprising:
initiating estimated detector positions for the array of detector elements and an estimated motion pattern for the energy source, said estimated detector positions and motion pattern being defined with respect to a reference position in the imaging system; scanning a phantom having pins located at positions in the phantom; calculating estimated pin positions for the pins in the phantom, with respect to the reference position, based on at least one of said estimated detector positions and motion pattern; modifying at least one of said estimated detector positions and pin positions based on at least two of said estimated detector positions, motion pattern and pin positions; determining variation in the motion pattern based on at least one of said estimated detector positions and pin positions; and adjusting said motion pattern for the energy source based on said variation.
- 2. The method of claim 1, wherein said variation comprises variation in a radius of said motion pattern.
- 3. The method of claim 1, wherein said step of determining variation comprises determining a variation in a radius of said motion pattern using a coil current over time.
- 4. The method of claim 1, wherein said variation comprises variation in an angle of said motion pattern.
- 5. The method of claim 1, wherein said step of determining variation comprises determining a variation in an angle of said motion pattern using a coil current over time.
- 6. The method of claim 1, wherein said adjusting step comprises adjusting a radius of said motion pattern based on said variation.
- 7. The method of claim 1, wherein said adjusting step comprises adjusting an angle of said motion pattern based on said variation.
- 8. The method of claim 1, wherein said adjusting step further comprises adjusting a radius of said motion pattern based on variation of the radius from a desired radial value by at least one of increasing and decreasing a dipole current of the energy beam source in proportion to the variation.
- 9. The method of claim 1, wherein said adjusting step further comprises adjusting an angle of said motion pattern based on variation of the angle from a desired angular value by linearly combining quanta of deflection coil currents of the energy beam source to obtain a desired electron beam position at a desired time.
- 10. A system for calibration of an imaging system, said system comprising:
an array of detector elements arranged with respect to a reference point; an energy source moving in a pattern to irradiate said array of detector elements; a reconstruction system calculating estimated detector positions and estimated motion pattern of said energy source; a radial beam correction module for correcting a radius of said motion pattern of said energy source based on variation of said radius from a desired radius over time; and an angular beam adjustment module for adjusting an angle of said motion pattern based on variation of position of said motion pattern from a desired position over time.
- 11. The system of claim 10, further comprising a multipin phantom used in determining at least one of said radius, said position, and said angle of said motion pattern.
- 12. The system of claim 10, further comprising a deflection buffer for storing deflection values over time, said deflection values used to effect at least one of variation in radius, position, and angle of said motion pattern.
- 13. The system of claim 10, further comprising at least one of a focusing coil and a deflection coil for correcting said radius of said motion pattern.
- 14. The system of claim 10, further comprising at least one of a focusing coil and a deflection coil for adjusting said angle of said motion pattern.
- 15. The system of claim 10, further comprising a reconstruction system for obtaining said radius and angle data.
- 16. The system of claim 10, wherein said radial beam correction module increases or decreases a coil current to correct said radius of said motion pattern.
- 17. The system of claim 10, wherein angular beam adjustment module linearly combines quanta of coil currents at different times to adjust said angle of said motion pattern.
- 18. The system of claim 10, wherein said reconstruction system further modifies at least one of said estimated detector positions and estimated motion pattern based on at least two of said estimated detector positions, motion pattern, and positions of pins in a multipin phantom.
- 19. The system of claim 18, wherein said reconstruction system modifies at least one of said estimated detector positions and motion pattern by computing an error vector E=h*P, wherein E represents an error associated with at least one of said estimated detector positions, motion pattern and pin positions, h denotes adjustments to produce more accurate estimated detector positions, motion pattern and pin positions and P represents a matrix of derivatives for detector-phantom pin samples with respect to said detector positions, motion pattern and pin positions.
- 20. A method for tuning an electron beam in an x-ray system, said method comprising:
correcting radial fluctuations in an electron beam based on change in radius of a beam spot of the electron beam at a plurality of time intervals; and adjusting angular deviations in the electron beam based on change in position of the electron beam spot at a plurality of time intervals.
- 21. A method of tuning an electron beam in an x-ray imaging system, said method comprising: measuring x-ray system geometrical parameters using a multipin phantom to obtain measured parameter values;
correcting variations between said measured parameter values and a set of desired parameter values to produce corrected parameter values; and modifying coil currents of an electron beam based on said corrected parameter values.
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application relates to, and claims priority from, co-pending application (Attorney Docket Number 125690-2) filed on the same date as the present application and entitled “Method and Apparatus for Controlling Electron Beam Motion Based on Calibration Information.” The present application relates to, and claims priority from, U.S. Provisional Application No. 60/359,562, filed on Feb. 25, 2002, and entitled “High-Precision Measurement of Projection Geometry for CT Using a Low-Precision Multipin Phantom.” The provisional application names Erik Chell and John Couch as joint inventors, and the co-pending application names Erik Chell, John Couch, and Paul Magnuson as joint inventors. The co-pending and provisional applications are incorporated by reference herein in their entirety including the specifications, drawings, claims, abstracts and the like.
Provisional Applications (1)
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Number |
Date |
Country |
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60359562 |
Feb 2002 |
US |