Electronic calibration of focal spot position in an X-ray tube

Patent metadata

Field	Value
Publication number	US-10383203-B2
Application number	US-201615141240-A
Country	US
Kind code	B2
Filing date	Apr 28, 2016
Priority date	Apr 28, 2016
Publication date	Aug 13, 2019
Grant date	Aug 13, 2019

Abstract

Technology is described for calibrating a deflected position of a central ray of an x-ray tube to a radiation imager. An x-ray system includes an x-ray tube and a tube control unit (TCU). The x-ray tube includes a cathode that includes an electron emitter configured to emit an electron beam, an anode configured to receive the electron beam and generate x-rays with a central ray from electrons of the electron beam colliding on a focal spot of the anode, and a steering magnetic multipole between the cathode and the anode that is configured to produce a steering magnetic field from a steering signal. At least two poles of the steering magnetic multipole are on opposite sides of the electron beam. The TCU includes at least one steering driver configured to generate the steering signal. The TCU is configured to convert a position correction value to the steering signal.

First claim

What is claimed is:

1. A method of calibrating a deflected position of a central ray of an x-ray tube to a radiation imager using a tube control unit (TCU), the method comprising:
emitting a beam of electrons from an emitter in an x-ray tube;
deflecting the beam of electrons with a steering magnetic multipole between the emitter and an anode on the x-ray tube according to a specified deflection position;
generating x-rays with a central ray from the electrons colliding on a focal spot of an anode of the x-ray tube;
receiving, at the TCU, a position correction value representing a distance of a deflected central ray from the specified deflection position; and
generating a steering signal from at least one steering driver of the TCU based on the position correction value that is applied to the steering magnetic multipole; and
moving the focal spot on the anode with the steering magnetic multipole so the deflected central ray aligns with the specified deflection position, wherein at least two poles of the steering magnetic multipole are on opposite sides of a path of the electrons.

2. The method of claim 1 , wherein generating the steering signal further comprises:
summing steering position calibration data and the position correction value, wherein the steering position calibration data represent current values to generate at least one steering position using the steering magnetic multipole for a tube voltage and tube current combination, and each steering position has an associated position correction value for the tube voltage and tube current combination; and
combining the sum of the steering position calibration data and the position correction value with steering driver calibration data, wherein the steering driver calibration data represent current values of the at least one steering driver.

3. The method of claim 2 , wherein generating the steering signal further comprises:
summing steering position calibration data, the position correction value, and an offset value, wherein the offset value represents a distance of the central ray from a specified imager location for a tube voltage and tube current combination, and the at least one steering position is oriented from relative to the specified imager location; and
combining the sum of the steering position calibration data, the position correction value, and the offset value with steering driver calibration data.

4. The method of claim 1 , wherein generating the steering signal further comprises:
determining a position change of the central ray different from at least one steering position;
calculating an interpolated deflection value using the steering position calibration data for at least two steering positions;
calculating an interpolated position correction value using position correction values for the at least two steering positions; and
summing the interpolated deflection value representing a deflected position of the central ray and the interpolated position correction value representing the position correction value of the position change of the central ray.

5. The method of claim 1 , further comprising:
generating a focusing signal from at least one focus driver of the TCU that is applied to a focusing magnetic multipole between the emitter and the anode on the x-ray tube; and
narrowing an area of the focal spot on the anode with the focusing magnetic multipole.

6. The method of claim 5 , wherein generating the focusing signal further comprises:
receiving tube calibration data from the x-ray tube, wherein the tube calibration data represent current values to generate a specified focal spot size for the x-ray tube; and
combining the tube calibration data and focus driver calibration data, wherein the focus driver calibration data represents the current values of the at least one focus driver.

7. The method of claim 6 , further comprising before generating the focusing signal:
receiving, at the TCU, a size correction value representing an x-ray intensity difference between the deflected central ray and the central ray at a specified reference position.

8. The method of claim 7 , further comprising:
saving each size correction value for multiple specified reference positions in a size correction table.

9. The method of claim 6 , further comprising before combining the tube calibration data and the focus driver calibration data:
summing the tube calibration data and a size correction value, wherein the tube calibration data represent current values to generate a specified focal spot size using the focusing magnetic multipole for a tube voltage and tube current combination, and the size correction value represents current changes for the specified focal spot size associated with the specified deflection position for the tube voltage and tube current combination;
wherein combining the tube calibration data and the focus driver calibration data further comprises combining the sum of the tube calibration data and the size correction value with the focus driver calibration data.

10. The method of claim 1 , further comprising, prior to receiving the position correction value:
receiving, at a system control unit, image data from a radiation imager including a central ray position on the radiation imager;
calculating the position correction value based on the central ray position relative to the specified deflection position; and
sending the position correction value to the TCU.

11. The method of claim 10 , further comprising, prior to receiving the position correction value:
detecting x-rays;
converting detected x-rays into image data that includes the central ray position; and
sending the image data to the system control unit.

12. The method of claim 1 , further comprising:
saving each position correction value for multiple specified deflection positions in a position correction table.

13. An x-ray system, comprising:
an x-ray tube comprising:
a cathode including an electron emitter configured to emit an electron beam,
an anode configured to receive the electron beam and generate x-rays with a central ray from electrons of the electron beam colliding on a focal spot of the anode, and
a steering magnetic multipole between the cathode and the anode that is configured to produce a steering magnetic field from a steering signal and at least two poles of the steering magnetic multipole are on opposite sides of the electron beam, wherein the steering magnetic field moves the focal spot of the electron beam on the anode; and

a tube control unit (TCU) configured to receive a position correction value and convert the position correction value to the steering signal, wherein the position correction value represents a distance of a deflected central ray from a specified deflection position, and the TCU comprises:
at least one steering driver configured to generate the steering signal.

14. The x-ray system of claim 13 , wherein the steering magnetic multipole has a steering yoke with at least two evenly distributed pole projections extending from the steering yoke and oriented toward a central axis of the steering yoke and each of the at least two pole projections having a steering electromagnetic coil operably coupled to the at least one steering driver that provides a current to each steering electromagnetic coil to produce a steering magnetic field.

15. The x-ray system of claim 13 , wherein:
the steering magnetic multipole includes two sets of steering magnetic dipoles that provides two dimensional (2D) steering of the focal spot, and a first set of the steering magnetic dipoles include two poles on opposite sides o

Assignees

• Varex Imaging Corp

Inventors

• Meiler Michael
• Canfield Bradley D
• Woodman Colton B
• Yoon Inwoo

Classifications

• H05G1/52 Primary

  Target size or shape; Direction of electron beam, e.g. in tubes with one anode and more than one cathode · CPC title

• A61B6/583

  using calibration phantoms · CPC title

• A61B6/4435

  the source unit and the detector unit being coupled by a rigid structure · CPC title

• A61B6/032

  Transmission computed tomography [CT] · CPC title

• A61B6/40

  Arrangements for generating radiation specially adapted for radiation diagnosis · CPC title