Digital radiographic imaging system and method therefor

• US 4,873,708 A
• Filed: 05/11/1987
• Issued: 10/10/1989
• Est. Priority Date: 05/11/1987
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Possin, George E., Cusano, Dominic A.
• Primary Examiner(s): Fields, Carolyn E.
• Assistant Examiner(s): Porta, David P.
• Application Number:
  US07/048,236
• Time in Patent Office: 883 Days
• Field of Search: 378/62, 378/19, 378/10, 378/11, 250/369, 250/361 R, 250/370.09, 250/370.11, 250/327.2
• US Class Current: 378/19
• CPC Class Codes: G01T 1/2006 using a combination of a scintillator and photodetector which measures the means radiation intensity
• CPC Class Codes: G01T 1/202 the detector being a crystal

Abstract

A digital radiographic imaging system which employs co-operative means for converting the x-rays to an optical image having enhanced quality and detecting said optical image. The x-ray conversion medium employed in the improved radiographic system is positioned physically contiguous to a bi-directional array of electrical charge transfer devices which convert the optical image to an electronic analog representation thereof. Digital information processing means are further included in the improved radiographic system to convert the electronic analog representation of the optical image to a recorded digital representation thereof. The x-ray conversion medium being employed in the improved radiographic system is a high efficiency scintillator body which moves co-operatively with the photo detection means being employed in a further synchronious relationship with a moving fan beam of X radiation being employed to generate the desired optical image after passage through a stationary object.

Claims

1. A digital radiographic image recording system which comprises:

(a) a movable scintillator body having a dense, self-supporting and substantially void-free single flat layer configuration which is substantially transparent to the optical radiation emitted by said medium, said scintillator body comprising a polycrystalline scintillator ceramic with a high X-ray absorption value and a material density of at least 99% so that substantially all X radiation impinging thereon will be converted therein to optical radiation without excessive scattering and loss of the converted optical radiation,

(b) a stationary X-ray source to expose said scintillator body to an X-ray fan beam moving in a linear non-arcuate travel direction after passage through an object,

(c) a photodetection member positioned physically contiguous with said moving scintillator body and movable therewith so that both scintillator body and photodetection member move synchronously together with the moving x-ray fan beam in the same linear non-arcuate travel direction for conversion of said moving fan beam to an optical image for simultaneous detection of said optical image in a point-by-point and line-by-line manner,

(d) said movable photodetection member having a plurality of charge transfer devices arranged in electrically connected columns and rows, said columns being aligned in the same linear non-arcuate travel direction as the moving X-ray fan beam while said rows being aligned substantially transverse thereto in order to also synchronously shift the signals being generated by optical radiation impinging on the individual charge transfer device located in the same column in the opposite travel direction to the travel direction of said moving photodetection member and with said synchronous signal shifting being carried out by a time delay and integration mode of operation to form an electrical analog representation of said optical image without experiencing substantial optical attenuation, the pixel arrangement in said photo-detection member also being unbroken so that all impinging optical radiation will be collected, the synchronous signal shifting further being carried between adjoining charge transfer devices such that signals are shifted from a device having received optical radiation to the next adjoining device at the same velocity rate as the physical movement, and

(e) digital processing means for immediately converting said electrical analog representation of said optical image to a recorded digital representation thereof with higher quantum detection efficiency, resolution and contrast.

2. A digital radiographic image recording system as in claim 1 wherein said time delay and integration mode of operation for said moving photodetector member is achieved with a spatial orientation of the individual charge transfer devices such that the individual charge transfer devices forming a row are aligned in an offset but overlapping positional relations with respect to the next adjoining row of individual charge transfer devices.

3. A digital radiographic image recording system as in claim 2 wherein a like spatial relationship is maintained between all alternate rows of individual charge transfer devices in said photodetection member to form a parallel alignment for the column orientation of said charge transfer devices in said photodetection member.

4. A digital radiographic image recording system as in claim 1 wherein the charge transfer devices are charge coupled devices.

5. A digital radiographic image recording system as in claim 1 wherein the synchronized signal shifting between adjoining charge transfer devices proceeds serially throughout each column of charge transfer devices in said photodetector member and with the output signals from each column being further stored in the digital processing means of said radiographic image recording system.

6. A digital radiographic image recording system as in claim 1 which further includes visual display of the digitized information.

7. A digital radiographic image recording system as in claim 6 wherein said visual display is operatively associated with said means for digital recording of the optical image.

8. A digital radiographic image recording system as in claim 1 wherein said scintillator body comprises a sintered polycrystalline rare earth doped rare earth oxide ceramic exhibiting high density, optical clarity, and a cubic crystalline structure.

9. A digital radiographic image recording system as in claim 8 wherein said rare earth oxide is selected from the group consisting of Gd₂ O₃, Y₂ O₃, La₂ O₃ and Lu₂ O₃.

10. A digital radiographic image recording system as in claim 9 wherein said rare earth dopant ion is selected from europium, neodymium, ytterbium and dysprosium.

11. A digital radiographic image recording system as in claim 8 wherein said ceramic comprises between about 5 and 50 mole percent Gd₂ O₃, between about 0.02 to about 12 mole percent of at least one rare earth activator oxide selected from the group consisting of Eu₂ O₃, Nd₂ O₃, Yb₂ O₃, Dy₂ O₃, Tb₂ O₃, and Pr₂ O₃, the remainder being Y₂ O₃.

12. A digital radiographic image recording system as in claim 1 wherein said scintillator body comprises a composite of x-ray stimulable phosphor crystals suspended in a matrix of a solid synthetic organic polymer having an optical refractive index closely matching the optical refractive index of said phosphor crystals while also being substantially transparent to the optical radiation being emitted by said phosphor crystals.

13. A digital radiographic image recording system as in claim 12 wherein said phosphor is barium fluorochloride activated with europium ion and said synthetic organic polymer is a polysulfone.

14. A digital radiographic image recording system as in claim 12 wherein the phosphor crystals occupy a minimum weight fraction in said member of at least 50%.

15. A digital radiographic image recording system as in claim 12 wherein the polysulfone polymer is a homopolymer.

16. A digital radiographic image recording system as in claim 12 wherein said phosphor crystals comprise a europium activated barium fluorohalide further containing a sufficient level of an impurity ion selected from Group 1A and 3A elements in the periodic table of elements to reduce the optical refractive index of said phosphor.

17. A digital radiographic image recording system as in claim 16 wherein said impurity ion is incorporated as a halide compound of the impurity element.

18. A digital radiographic image recording system as in claim 16 wherein the europium activator level is in the approximate range from 0.1-2.0 weight percent based on the weight of said phosphor.

19. A digital radiographic image recording system as in claim 16 wherein the level of impurity ion is in the approximate range from 0.3-3.0 weight percent based on the weight of said phosphor.

20. A digital radiographic image recording system as in claim 16 wherein the phosphor is europium activated barium fluorochloride.

21. A method to record a digital radiographic image which comprises:

(a) forming an optical image by scanning an object exposed to a stationary X-ray source with a moving scintillator body in a linear non-arcuate travel direction during exposure of said object to a moving X-ray fan beam to form said optical image as a point-by-point and line-by-line composite of the subject being scanned,

(b) said scintillator body having a dense, self-supporting and substantially void-free single flat layer configuration which is substantially transparent to the optical radiation emitted from said medium, said scintillator body comprising a polycrystalline scintillator ceramic with a high X-ray absorption value and a material density of at least 99% so that substantially all X radiation impinging thereon will be converted therein to optical radiation without excessive scattering and loss of the converted optical radiation,

(c) simultaneously transmitting said optical image when formed to a moving photodetection member aligned with said moving x-ray fan beam and moving synchronously in the same linear non-arcuate travel direction as said moving x-ray fan beam,

(d) said moving photodetection member being positioned physically contiguous with said moving scintillator body and movable therewith so that both scintillator body and photodetection member move synchronously with the moving x-ray fan beam in the same linear non-arcuate travel direction for conversion of said moving X-ray fan beam to an optical image for simultaneous detection of said optical image as an electrical analog representation thereof and without experiencing substantial optical attenuation,

(e) said moving photodetection member also having a plurality of charge transfer devices arranged in electrically connected columns and rows, said columns being aligned in the same linear non-arcuate travel direction as the moving x-ray fan beam while said rows being aligned substantially transverse thereto in order to also synchronously shift the signals being generated by optical radiation impinging on an individual charge transfer device located in the same column in the opposite direction to the travel direction of said moving photodetection member and with said synchronous signal shifting being carried out by a time delay and integration mode of operation, the pixel arrangement in said photodetection member also being unbroken so that all impinging optical radiation will be collected, the synchronous signal shifting further being carried out between adjoining charge transfer devices such that signals are shifted from a device having received optical radiation to the next adjoining device at the same velocity as the physical movement, and

(f) immediately converting said electrical analog representation of said optical image to a recorded digital representation thereof with digital processing means at higher medium detection efficiency, resolution and contrast.

22. A method as in claim 21 wherein said time delay and integration mode of operation for said moving photodetection member is achieved with a spatial orientation of the individual charge transfer devices such that the individual charge transfer devices forming a row are aligned in an offset but overlapping positional relationship with respect to the next adjoining row of individual charge transfer devices.

23. A method as in claim 21 wherein a like spatial relationship is maintained between all alternate rows of individual charge transfer devices in said photodetection member to form a parallel alignment for the column orientation of said charge transfer devices in said member.

24. A method as in claim 21 wherein the synchronized signal shifting between adjoining charge transfer devices proceeds such that signals are shifted from a device having received optical radiation to the next adjoining device after the latter device has received optical radiation.

25. A method as in claim 21 wherein the synchronized signal shifting between adjoining charge transfer devices, proceeds serially through each column of charge transfer devices in said composite member and with the output signals from each column being further stored by the digital processing means.

26. A method as in claim 21 wherein the signal shifting is carried out with charge coupled devices.

27. A method as in claim 21 which further includes digital imaging of the optical image.

28. A digital radiographic image recording system which comprises:

(a) a movable scintillator body having a dense, self-supporting and substantially void-free single flat layer configuration which is substantially transparent to the optical radiation emitted by said medium, said scintillator body comprising a polycrystalline scintillator ceramic with a high x-ray absorption value and a material density of at least 99% so that substantially all X radiation impinging thereon will be converted therein to optical radiation without excessive scattering and loss of the converted optical radiation,

(b) a stationary X-ray source to expose said scintillator body to an X-ray fan beam moving in a linear non-arcuate travel direction and after passage through an object,

(c) a photodetection member positioned in direct physical contact with said movable scintillator body and moving therewith so that both scintillator body and photodetection member move synchronously with the moving x-ray fan beam in the same linear non-arcuate travel direction for conversion of said moving X-ray fan beam to an optical image for simultaneous detection of said optical image in a point-by-point and line-by-line manner without experiencing substantial optical attenuation,

(d) said movable photodetection member having a plurality of charge transfer devices arranged in electrically connected columns and rows, said columns being aligned in the same linear non-arcuate travel direction as the moving x-ray fan beam while said rows being aligned substantially transverse thereto in order to synchronously shift the signals being generated by optical radiation impinging on the individual charge transfer devices located in the same column in the opposite direction to the travel direction of said movable photodetection member and with said synchronous signal shifting being carried out by a time delay and integration mode of operation to form an electrical analog representation of said optical image, the pixel arrangement in said photodetection member also being unbroken so that all impinging optical radiation will be collected, the synchronous signal shifting further being carried out between adjoining charge transfer devices such that signals are shifted from a device having received optical radiation to the next adjoining device at the same velocity rate as the physical movement, and

(e) digital processing means for immediately converting said electrical analog representation of said optical image to a recorded digital representation thereof with higher quantum detection efficiency, resolution and contrast.

29. A method to record a digital radiographic image which comprises:

(a) forming an optical image by scanning an object exposed to a stationary X-ray source with a moving scintillator body in a linear non-arcuate travel direction during exposure of said object to a moving X-ray fan beam to form said optical image as a point-by-point and line-by-line conversion of the subject being scanned,

(b) said scintillator body having a dense, self-supporting and substantially void-free single flat layer configuration which is substantially transparent to the optical radiation being emitted from said medium, such scintillator body comprising a polycrystalline scintillator ceramic with a high x-ray absorption value and a material density of at least 99% so that substantially all X radiation impinging thereon will be converted therein to optical scintillator without excessive scattering and loss of the converted optical radiation,

(c) simultaneously transmitting said optical image when formed to a moving photodetection member aligned with said moving x-ray fan beam and moving in the same linear non-arcuate travel direction as said moving x-ray fan beam,

(d) said moving photodetection member being positioned in direct physical contact with said moving scintillator body and movable therewith so that both scintillator body and photodetection member move synchronously with the moving x-ray fan beam in the same linear non-arcuate travel direction for conversion of said moving x-ray fan bean to an optical image for simultaneous detection of said optical image as an electrical analog representation thereof and without experiencing substantial optical attenuation,

(e) said moving photodetection member also having a plurality of charge transfer devices arranged in electrically connected columns and rows, said columns being aligned in the same linear non-arcuate travel direction as the moving x-ray fan beam while said rows being aligned substantially transverse thereto in order to also synchronously shift the signals being generated by the optical radiation impinging on an individual charge transfer device located in the same column in the opposite direction to the travel direction of said moving photodetection member and with said synchronous signal shifting being carried out in a time delay and integration mode of operation, the pixel arrangement in said photodetection member also being unbroken so that all impinging optical radiation will be collected, the synchronous signal shifting further being carried out between adjoining charge transfer devices such that signals are shifted from a device having received optical radiation to the next adjoining device at the same velocity rate as the physical movement, and

(f) immediately converting said electrical analog representation of said optical image to a recorded digital representation thereof with digital processing means at higher quantum detection efficiency, resolution and contrast.