Radiation sources and compact radiation scanning systems

• US 20040057554A1
• Filed: 07/19/2002
• Published: 03/25/2004
• Est. Priority Date: 07/19/2002
• Status: Active Grant

• Current Assignee: Varex Imaging Corporation
• Original Assignee: Varian Medical Systems Incorporated (Siemens AG)
• Inventors: Bjorkholm, Paul
• Granted Patent: US 7,162,005 B2
• Time in Patent Office: Days
• US Class Current: 378/143
• CPC Class Codes: G01V 5/0016 Active interrogation, i.e. using an external radiation source, e.g. using pulsed, continuous or cosmic rays
• CPC Class Codes: G01V 5/22 Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
• CPC Class Codes: H01J 35/116 Transmissive anodes acting as a window H01J35/186
• CPC Class Codes: H01J 35/16 Vessels; Containers; Shields associated therewith

Abstract

An X-ray source is disclosed comprising a source of high energy electrons that travel along a longitudinal path. Target material lies along the longitudinal path and X-ray radiation is generated due to impact of the high energy electrons with the target. Shielding material is provided around at least a portion of the target. The shielding material defines a slot extending from the target to an exterior surface of the shielding material, to allow passage of generated radiation. The slot has an axis transverse to the longitudinal path. The axis may be perpendicular longitudinal path. The shielding material may define a plurality of slots having transverse axes. The source of high energy electrons may be a linear accelerator, for example. Scanning systems incorporating such sources are also disclosed. The scanning system comprises a conveying system having a longitudinal axis and the radiation source may be positioned so that the longitudinal path forms an acute angle with respect to the longitudinal axis, to decrease the size of the scanning unit as compared to a unit where the longitudinal axis is perpendicular to the longitudinal path. The longitudinal axis may be parallel to the longitudinal path, to form a more compact scanning system. A plurality of slots may be defined in the shielding material and a corresponding number of conveying systems may be provided to examine a plurality of objects concurrently. Methods of generating radiation and methods of examining objects are also disclosed.

Claims

1. An X-ray source comprising:

a housing defining a chamber to accelerate electrons and an output of the chamber, the chamber having a first longitudinal axis, wherein the output is aligned with the first longitudinal axis to allow passage of accelerated electrons from the chamber;

a tube defining a passage having a second longitudinal axis, the tube having a proximal end coupled to the output of the housing such that the second longitudinal axis is aligned with the first longitudinal axis and accelerated electrons can enter the passage;

a target material within the tube, wherein impact of the target material by accelerated electrons causes generation of X-ray radiation; and

shielding material around at least a portion of the tube around the target, the shielding material defining a slot extending from the target to an exterior surface of the shielding material, the slot to allow passage of generated radiation;

wherein the slot has an axis transverse to the first and second longitudinal axes.

2. The X-ray source of claim 1, further comprising a source of electrons to emit electrons into the chamber, along the first longitudinal axis, the source being supported by the housing.

3. The X-ray source of claim 2, wherein;

the housing defines an input opening to the chamber; and

the source of electrons is coupled to the input opening.

4. The X-ray source of claim 1, wherein the target is at the distal end of the tube.

5. The X-ray source of claim 1, wherein the shielding material surrounds the entire tube and a portion of the housing proximate the tube.

6. The X-ray source of claim 1, wherein the axis of the slot is perpendicular to the first and second axes.

7. The X-ray source of claim 1, wherein the slot defines a fan beam or a cone beam.

8. The X-ray source of claim 1, wherein the shielding material defines a plurality of slots extending from the target to the exterior surface of the shielding material, the slots being transverse to the first and second axes.

9. The X-ray source of claim 8, wherein the slots each have a respective axis perpendicular to the first and second axes.

10. The X-ray source of claim 8, further comprising a respective shutter coupled to the housing adjacent to each slot to selectively open and close each slot.

11. The X-ray source of claim 1, further comprising:

a bend magnet;

a second tube coupling the bend magnet to the output of the housing, wherein the proximal end of the first tube is coupled to the output of the housing by the bend magnet and the second tube;

a third tube having a first end coupled to the bend magnet;

a second target material within the third tube; and

shielding material around at least a portion of the third tube surrounding the target material;

whereby electrons exiting the housing are selectively directed through the first or third tube, to the first or second target, respectively, by the bend magnet.

12. The X-ray source of claim 11, wherein the bend magnet is an electromagnet.

13. The X-ray source of claim 11, further comprising:

a second bend magnet; and

a fourth tube coupling the first bend magnet to the second bend magnet;

wherein;

the third tube is coupled to the first bend magnet through the fourth tube and the second bend magnet; and

the second tube, the bend magnet and the first target are aligned along the first and second longitudinal axes.

14. The X-ray source of claim 1, wherein the target is a refractory metal.

15. The X-ray source of claim 1, wherein the target is tungsten.

16. The X-ray source of claim 1, wherein the shielding material is chosen from the group consisting of tungsten, steel and lead.

17. The X-ray source of claim 1, wherein the housing defines a linear accelerator.

18. The X-ray source of claim 17, wherein the linear accelerator accelerates electrons to a selected one of a plurality of energies.

19. An X-ray source comprising:

a linear accelerator defining a chamber to accelerate electrons and an output of the chamber, the chamber having a first longitudinal axis, wherein the output is aligned with the first longitudinal axis to allow passage of accelerated electrons from the chamber;

a source of electrons associated with the chamber to emit electrons along the first longitudinal axis;

a tube defining a passage having a second longitudinal axis, the tube having a proximal end with an input coupled to the output of the housing such that the second longitudinal axis is aligned with the first longitudinal axis and accelerated electrons can enter the passage;

a target material of refractory metal at the distal end of the tube, wherein impact of the target material by electrons causes generation of X-ray radiation; and

shielding material around at least a portion of the tube around the target, the shielding material defining a slot extending from the target to an exterior surface of the shielding material, the slot allowing passage of radiation resulting from impact of the emitted electrons on the target, the slot being perpendicular to the first and second longitudinal axes.

20. The X-ray source of claim 19, wherein the shielding material defines a plurality of slots extending from the target to the exterior surface of the shielding material, each of the plurality of slots being perpendicular to the first and second axes.

21. An X-ray source, comprising:

a source of high energy electrons, wherein the high energy electrons travel along a longitudinal path;

a target material lying along the longitudinal path of the high energy electrons, the target material generating X-ray radiation due to impact of the high energy electrons with the target; and

shielding material around at least a portion of the target, the shielding material defining a slot extending from the target to an exterior surface of the shielding material, the slot allowing passage of radiation resulting from impact of the emitted electrons on the target;

wherein the slot has an axis transverse to the longitudinal path.

22. The X-ray source of claim 21, wherein the axis of the slot is perpendicular to the longitudinal path.

23. The X-ray source of claim 21, wherein the shielding material defines a plurality of slots extending from the target to an exterior surface of the shielding material.

24. The X-ray source of claim 23, wherein the axis of each of the plurality of slots is perpendicular to the longitudinal path.

25. The X-ray source of claim 21, wherein the source of high energy electrons comprises:

a source of electrons; and

an accelerating chamber to receive electrons from the source and to accelerate the electrons.

26. The X-ray source of claim 25, wherein the accelerating chamber is a linear accelerator.

27. The X-ray source of claim 21, wherein the shielding material is around a portion of the path to the target.

28. The X-ray source of claim 27, wherein the path extends, at least in part, through the source of high energy electrons.

29. The X-ray source of claim 28, wherein the shielding material is around at least a portion of the source of high energy electrons.

30. The X-ray source of claim 21, wherein the path is defined in part by a tube extending from the source of high energy electrons, wherein the shielding material is around at least a portion of the tube.

31. A system for examining an object, comprising:

a conveyor system to move the object through the system along a longitudinal axis; and

a source of radiation comprising;

a source of high energy electrons, wherein the high energy electrons travel along a longitudinal path;

a target material lying along the longitudinal path of the high energy electrons, the target material generating X-ray radiation due to impact of the high energy electrons with the target; and

shielding material around at least a portion of the target, the shielding material defining a slot extending from the target to an exterior surface of the shielding material, the slot allowing passage of generated radiation;

wherein;

the slot has an axis transverse to the longitudinal path; and

the radiation source is positioned with respect to the conveying system such that radiation emitted through the slot will irradiate an object for inspection on the conveying system.

32. The scanning system of claim 31, wherein the radiation source is on a first side of the conveying system, the system further comprising:

a detector on a second side of the conveying system, to detect radiation transmitted through the object.

33. The scanning system of claim 31, wherein the source of radiation is a source of X-ray radiation.

34. The scanning system of claim 31, wherein the radiation source has a longitudinal axis and the longitudinal path and the longitudinal axis form an acute angle.

35. The scanning system of claim 34, wherein the acute angle is less than or equal to 45 degrees.

36. The scanning system of claim 35, wherein the acute angle is less than or equal to 10 degrees.

37. The scanning system of claim 31, wherein the radiation source has a longitudinal axis and the longitudinal path and the longitudinal axis are parallel

38. The scanning system of claim 31, wherein the radiation source has a second slot having an axis transverse to the longitudinal path to emit generated radiation;

the scanning system further comprising;

a second conveying system to move an object through the system along a second longitudinal axis parallel to the first longitudinal axis, wherein the second slot is positioned to emit generated radiation to irradiate an object on the second conveying system.

39. The scanning system of claim 38, further comprising:

first and second shutters mechanically coupled to the system proximate the first and second slots, respectively, to selectively open and close the respective slot.

40. The scanning system of claim 38, wherein the radiation source has a third slot having an axis transverse to the longitudinal path to emit generated radiation;

the scanning system further comprising;

a third conveying system to move an object through the system along a third longitudinal axis parallel to the first longitudinal axis, wherein the third slot is positioned to emit generated radiation to irradiate an object on the third conveying system.

41. The scanning system of claim 31, wherein the radiation source has a fourth slot having an axis transverse to the longitudinal path to emit generated radiation;

the scanning system further comprising;

a fourth conveying system to move an object through the system along a fourth longitudinal axis parallel to the first longitudinal axis, wherein the fourth slot is positioned to to emit generated radiation to irradiate an object on the fourth conveying system.

42. The scanning system of claim 31, wherein the axis of the slot is perpendicular to the longitudinal path.

43. A scanning system to examine objects, comprising:

a conveyor system to move the object through the system along a longitudinal axis;

a source of high energy electrons to emit electrons along a path;

a bend magnet along the path;

a first target material, the target material generating X-ray radiation due to impact of the high energy electrons with the target; and

first shielding material around the first target material, the shielding material defining a first slot extending from the target material to an exterior surface of the first shielding material, the first slot having an axis transverse to the path;

a second target material, the target material generating X-ray radiation due to impact of the high energy electrons with the target; and

second shielding material around the second target material, the second shielding material defining a second slot extending from the second target material to an exterior surface of the shielding material, the second slot having an axis transverse to the path;

wherein;

the bend magnet is capable of selectively directing the high energy electrons to the first or the second target; and

the first slot and the second slot are positioned with respect to the first conveying system to irradiate different sides of the object on the conveying system.

44. The scanning system of claim 43, wherein the first target and the first bend magnet are aligned with the path, the system further comprising:

a second bend magnet, wherein the first bend magnet is capable of selectively directing the high energy electrons speed to the first target or the the second bend magnet, the second bend magnet capable of directing the high speed electrons to the second target.

45. An X-ray scanning system to examine an object, comprising:

a conveyor system to move the object through the system along a first longitudinal axis; and

an elongated X-ray source having a second longitudinal axis, the X-ray source capable of emitting X-ray radiation with an average energy of at least 1 MeV;

wherein the X-ray source is supported adjacent to the conveying system such that the first longitudinal axis is parallel to the second longitudinal axis.

46. The X-ray scanning system of claim 45, wherein the X-ray source is on a first side of the conveying system, the system further comprising:

a detector on a second side of the conveying system, to detect X-ray radiation transmitted through the object.

47. The X-ray scanning system of claim 45, wherein the X-ray source comprises:

a source of high energy electrons, wherein the high energy electrons travel along a longitudinal path;

a target material lying along the longitudinal path of the high energy electrons, the target material generating X-ray radiation due to impact of the high energy electrons with the target; and

shielding material around at least a portion of the target, the shielding material defining a slot extending from the target to an exterior surface of the shielding material to emit generated radiation;

wherein;

the slot has an axis transverse to the longitudinal path; and

the radiation source is positioned with respect to the conveying system such that radiation emitted through the slot will irradiate an object for inspection on the conveying system.

48. The X-ray scanning system of claim 46, wherein the shielding material defines a plurality of slots extending from the target to an exterior surface of the shielding material to emit generated radiation, wherein each slot has an axis transverse to the longitudinal path.

49. A method of generating X-ray radiation, comprising:

colliding high energy electrons traveling along a longitudinal path with a target surrounded by shielding material to generate radiation; and

collimating the generated radiation into a radiation beam transverse to the longitudinal path by a slot extending from the target through the shielding material.

50. The method of claim 49, wherein the high energy electrons are formed by accelerating electrons through a chamber.

51. The method of claim 50, wherein the chamber has an outlet lying along the longitudinal path, the method comprising:

colliding the accelerated electrons with a target displaced from the outlet of the chamber.

52. The method of claim 49, comprising collimating the radiation emitted from the target into a radiation beam perpendicular to the longitudinal axis.

53. The method of claim 49, comprising collimating the radiation emitted from the target into a plurality of radiation beams, each beam being transverse to the longitudinal path.

54. A method of examining contents of an object with a radiation source, the method comprising:

colliding high energy electrons traveling along a longitudinal path with a target surrounded by shielding material to generate radiation;

collimating the generated radiation into a radiation beam transverse to the longitudinal path by a slot extending from the target through the shielding material;

irradiating the object with the radiation; and

detecting radiation interacting with the object.

55. The method of claim 54, wherein the radiation source comprises a chamber having a longitudinal axis and an outlet along the longitudinal axis, the method comprising generating radiation to irradiate the object by:

accelerating electrons through the chamber; and

colliding the electrons with a target displaced from the outlet of the chamber.

56. The method of claim 54, comprising conveying the object along a second axis substantially parallel to the longitudinal path, through the radiation beam.

57. The method of claim 54, further comprising:

emitting a plurality of radiation beams from the source, each radiation beam being emitted in a direction transverse to the longitudinal axis;

irradiating a respective plurality of objects with the plurality of radiation beams; and

detecting radiation interacting with each of the objects.

58. The method of claim 54, comprising irradiating the object with X-ray radiation.

59. The method of claim 54, comprising irradiating a cargo container.