C-frame X-ray diagnostic device for producing tomographic recordings

• US 5,764,719 A
• Filed: 03/13/1996
• Issued: 06/09/1998
• Est. Priority Date: 03/13/1995
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Noettling, Alois
• Primary Examiner(s): Porta, David P.
• Assistant Examiner(s): Bruce, David Vernon
• Application Number:
  US08/614,625
• Time in Patent Office: 818 Days
• Field of Search: 378/4, 378/15, 378/17, 378/901
• US Class Current: 378/4
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4225 using image intensifiers
• CPC Class Codes: A61B 6/4291 the detector being combined with a grid or grating
• CPC Class Codes: A61B 6/4441 the rigid structure being a C-arm or U-arm
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: A61B 6/585 Calibration of detector units
• CPC Class Codes: G06T 2207/10116 X-ray image
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: H04N 25/61 the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4"
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30
• CPC Class Codes: H05G 1/60 Circuit arrangements for obtaining a series of X-ray photographs or for X-ray cinematography
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

A device and a process for producing tomograms by means of an X-ray diagnostic device which has a C-frame-like mount (7) on which a radiation transmitter (5) and a planar detector as radiation receiver (6) are arranged at opposite ends facing each other. Various signals stored in memory (17, 18, 19, 27) are used by a signal processing device (4) in the calculation of processed image signals. These signals include signals (I_P) relating to the central point of rotation (31) for the scanning operation, and signals (ΔS, ΔU) for correction geometric distortions and/or vignetting effects and/or the film-focus distance.

Claims

1. A process for producing tomograms by means of an X-ray diagnostic device comprising:

a recording unit comprising a radiation transmitter, supported at one end of a C-frame-like mount, for transmitting a fan-shaped beam of radiation, and a planar detector, arranged as a radiation receiver, opposite the radiation transmitter, at another end of the C-frame-like mount, for receiving the beam of radiation and for producing electric signals;

a supporting device for an object to be examined;

means for producing a relative displacement between the recording unit and the supporting device during a radiation scanning procedure of the object in a cross section;

a signal transmitter for producing radiation direction signals as a function of the relative displacement; and

a computing unit and at least one associated memory;

said process comprising;

inputting the electric signals of at least one row of the planar detector, obtained through the radiation scanning procedure, into the computing unit; and

in the computing unit, calculating image signals for at least one sectional plane from the electric signals, obtained through the radiation scanning procedure, in conjunction with the radiation direction signals, the image signals being capable of being displayed as an image of the sectional plane on a display device;

wherein, in a first process step of said calculating step, signals relating to a central point of rotation of the radiation scanning procedure and stored in the memory are used in the calculation of the image signals.

2. The process as claimed in claim 1, further comprising:

inputting the signals relating to the central point of rotation to the memory via an input device during the first process step.

3. The process as claimed in claim 1, further comprising:

in the computing unit, evaluating signals obtained during a radiation scan of a test object, to determine a maximum spacing value for the radiation scan;

calculating a mean spacing value from the maximum spacing value; and

storing the calculated mean spacing value in the memory as the signals relating to the central point of rotation, during the first process step.

4. The process as claimed in claim 3, further comprising:

in the computing unit, evaluating, based on the radiation direction signals, whether electric signals associated with the maximum spacing value are produced at respective radiation directions offset from one another by 180°

.

5. The process as claimed in claim 3, wherein an object region of the object to be examined is used as the test object.

6. The process as claimed in claim 1, wherein, in a second process step of said calculating step, correction signals stored in memory for correcting vignetting effects are retrieved for use in the calculation of the image signals.

7. The process as claimed in claim 6, further comprising:

inputting the correction signals into memory via an input device during the second process step.

8. The process as claimed in claim 6, wherein, in a third process step of said calculating step, correcting signals which are stored in memory for correcting geometric distortions are retrieved for use in the calculation of the image signals.

9. The process as claimed in claim 8, further comprising:

inputting the correcting signals into memory via an input device during the third process step.

10. The process as claimed in claim 8, wherein, in a fourth process step of the calculating step, focus signals which are stored in memory and represent a film-focus spacing calculation parameter are retrieved for use in the calculation of the image signals.

11. The process as claimed in claim 10, further comprising:

inputting the focus signals into memory via an input device during the third process step.

12. The process as claimed in claim 1, wherein, in a second process step of said calculating step, correcting signals which are stored in memory for correcting geometric distortions are retrieved for use in the calculation of the image signals.

13. The process as claimed in claim 12, further comprising:

inputting the correcting signals into memory via an input device during the second process step.

14. The process as claimed in claim 12, wherein, in a third process step of the calculating step, focus signals which are stored in memory and represent a film-focus spacing calculation parameter are retrieved for use in the calculation of the image signals.

15. The process as claimed in claim 14, further comprising:

inputting the focus signals into memory via an input device during the third process step.

16. The process as claimed in claim 1, wherein, in a second process step of the calculating step, focus signals which are stored in memory and represent a film-focus spacing calculation parameter are retrieved for use in the calculation of the image signals.

17. The process as claimed in claim 16, further comprising:

inputting the focus signals into memory via an input device during the second process step.

18. The process as claimed in claim 1, further comprising:

inputting arbitrarily selectable parameters of the cross section which has been scanned with radiation via an input device into the computing unit; and

in the computing unit, calculating, on the basis of the input parameters, image signals of at least one sectional plane defined by the input parameters.

19. An X-ray device for producing tomograms, comprising:

a recording unit comprising a radiation transmitter, supported at one end of a C-frame-like mount, for transmitting a fan-shaped beam of radiation, and a planar detector, arranged as a radiation receiver, opposite said radiation transmitter, at another end of said C-frame-like mount, for receiving the beam of radiation and for producing electric signals;

a supporting device for an object to be examined;

means for producing a relative displacement between said recording unit and said supporting device during a radiation scanning procedure of the object in a cross section;

a signal transmitter for producing radiation direction signals as a function of the relative displacement;

a computing unit, and at least one memory for storing image processing signals;

wherein, as a result of the radiation scanning procedure, said computing unit receives the electric signals of at least one row of said planar detector;

wherein said computing unit calculates image signals for at least one sectional plane from the electric signals received in conjunction with the radiation direction signals, the image signals being capable of being displayed as an image of the sectional plane on a display device; and

wherein the image processing signals stored in said memory are retrieved for use in the calculation of the image signals.

20. The device as claimed in claim 19, wherein the electric signals of at least the one row of said planar detector are stored in said memory.

21. The device as claimed in claim 19, wherein the image processing signals stored in said memory include signals relating to a central point of rotation.

22. The device as claimed in claim 19, wherein the image processing signals stored in said memory include signals for correcting vignetting effects.

23. The device as claimed in claim 19, wherein the image processing signals stored in said memory include signals for correcting geometric distortions.

24. The device as claimed in claim 19, wherein the image processing signals stored in said memory include signals which represent film-focus spacing information.

25. The device as claimed in claim 19, wherein the image processing signals stored in said memory include:

signals relating to a central point of rotation,

signals for correcting vignetting effects,

signals for correcting geometric distortions, and

signals which represent film-focus spacing information.

26. The device as claimed in claim 19, further comprising:

an input unit for inputting the image processing signals into said memory.

27. The device as claimed in claim 19, further comprising:

an adjustable anti-scattering grid positioned over a radiation-receiving surface of said planar detector.

28. The device as claimed in claim 19, further comprising:

a multi-line anti-scattering grid positioned over a radiation-receiving surface of said planar detector.

29. A process for producing tomograms by means of an X-ray diagnostic device comprising:

a recording unit comprising a radiation transmitter, supported at one end of a C-frame-like mount, for transmitting a fan-shaped beam of radiation, and a planar detector, arranged as radiation receiver, opposite the radiation transmitter, at another end of the C-frame-like mount, for receiving the beam of radiation and for producing electric signals;

a supporting device for an object to be examined;

means for producing a relative displacement between the recording unit and the supporting device during a radiation scanning procedure of the object in a cross section;

a signal transmitter for producing radiation direction signals as a function of the relative displacement; and

a computing unit;

said process comprising;

inputting the electric signals of at least two rows of the planar detector as pixel signals into the computing unit;

in a first process step of the computing unit, producing averaged pixel signals from respective ones of the pixel signals that are assigned to a column of the planar detector that is common to the respective ones of the pixel signals; and

in a subsequent process step of the computing unit, calculating from the averaged pixel signals image signals for at least one sectional plane, the image signals being capable of being displayed as an image of the sectional plane on a display device.

30. The process as claimed in claim 29, further comprising:

inputting arbitrarily selectable parameters of the cross section which has been scanned with radiation via an input device into the computing unit; and

in the computing unit, calculating, on the basis of the input parameters, image signals of at least one sectional plane defined by the input parameters.

31. An X-ray device for producing tomograms, comprising:

a recording unit comprising a radiation transmitter, supported at one end of a C-frame-like mount, for transmitting a fan-shaped beam of radiation, and a planar detector, arranged as a radiation receiver, opposite said radiation transmitter, at another end of said C-frame-like mount, for receiving the beam of radiation and for producing electric signals at pixel locations arranged in rows and columns;

a supporting device for an object to be examined;

means for producing a relative displacement between said recording unit and said supporting device during a radiation scanning procedure of the object in a cross section;

a signal transmitter for producing radiation direction signals as a function of the relative displacement; and

a computing unit;

wherein, as a result of the radiation scanning procedure, said computing unit receives the electric signals of at least two rows of said planar detector as pixel signals;

wherein said computing unit produces averaged pixel signals from respective ones of the pixel signals that are assigned to a column of said planar detector that is common to the respective ones of the pixel signals; and

wherein said computing unit calculates, from the averaged pixel signals, image signals for at least one sectional plane, the image signals being capable of being displayed as an image of the sectional plane on a display device.

32. The device as claimed in claim 31, further comprising:

an input device for inputting arbitrarily selectable parameters of the cross section which has been scanned with radiation into said computing unit; and

wherein said computing unit calculates, on the basis of the input parameters, image signals of at least one sectional plane defined by the input parameters.

33. A process for producing tomograms by means of an X-ray diagnostic device comprising a recording unit, a supporting device, and a processing unit,

the recording unit comprising a C-frame-shaped mount, a radiation transmitter, supported at a first end of the C-frame-shaped mount, and a planar detector, provided as a radiation receiver and supported opposite the radiation transmitter at a second end of the C-frame-shaped mount, and

the supporting device being configured to support an object to be examined,

said process comprising:

transmitting divergent beams of radiation from the radiation transmitter, receiving the beams of radiation at the planar detector, and converting the received beams into electrical signals, for at least one row of the planar detector;

during said transmitting, receiving and converting step, displacing the recording unit relative to the supporting device for the purpose of producing a cross-sectional radiation scan of the object to be examined, the radiation scan being characterized by a central point of rotation;

producing radiation direction signals indicative of the relative displacement;

inputting the electrical signals of the planar detector for at least the one row of the planar detector to the processing unit;

inputting signals defining the central point of rotation of the radiation scan to the processing unit;

in the processing unit, calculating image signals for at least one sectional plane on the basis of the electrical signals, the radiation direction signals and the signals defining the central point of rotation of the radiation scan, whereby the calculated image signals can be used for producing an image of the sectional plane on a display device connected to the processing unit.

34. The process according to claim 33, further comprising:

in the processing unit, correcting the image signals in accordance with correction signals input to the processing unit, wherein the correction signals are;

signals for correcting geometrical distortions in the image of the sectional plane,

signals for correcting signal-level distortions in the image of the sectional plane, or

signals for averaging at least some of the electrical signals over at least a predetermined portion of the planar detector.

35. The process according to claim 34, further comprising:

prior to producing the radiation scan of the object to be examined, generating the signals for correcting geometrical distortions by comparing reference spacing signals with actual spacing signals, wherein the actual spacing signals are generated by transmitting at least one test beam of radiation through a test object, receiving the test beam, and converting the test beam into the actual spacing signals.

36. The process according to claim 34, further comprising:

prior to producing the radiation scan of the object to be examined, generating the signals for correcting geometrical distortions by transmitting at least one test beam of radiation through a test object having regions of contrasting radiation absorption arranged in a regular pattern, receiving the test beam, converting the test beam into actual spacing signals, calculating an average spacing signal from the actual spacing signals, and comparing the average spacing signal with the actual spacing signals.

37. The process according to claim 34, further comprising:

prior to producing the radiation scan of the object to be examined, generating the signals for correcting signal-level distortions by comparing a reference signal-level signal with actual signal-level signals, wherein the actual signal-level signals are generated by transmitting at least one test beam of radiation, receiving the test beam, and converting the test beam into the actual signal-level signals.

38. The process according to claim 34, further comprising:

prior to producing the radiation scan of the object to be examined, generating the signals for correcting signal-level distortions by transmitting at least one test beam of radiation, receiving the test beam, converting the test beam into actual signal-level signals, calculating an average signal-level signal from the actual signal-level signals, and comparing the average signal-level signal with the actual signal-level signals.

39. The process according to claim 33, wherein the radiation scan is further characterized by a major axis and by a plurality of displacement locations, said process further comprising:

determining at least one subset of the electrical signals corresponding to any of the displacement locations that intersect the major axis;

calculating a mid-point signal representing a mid-point on the major axis of the radiation scan; and

storing the mid-point signal in memory as the signals defining the central point of rotation.

40. The process according to claim 39, further comprising:

performing a self-diagnostic routine by using the radiation direction signals in order to determine whether the one subset of the electrical signals correspond to radiation directions offset by 180°

.

41. An X-ray diagnostic system for producing tomograms, comprising:

a C-frame-shaped mount;

a radiation transmitter, supported at a first end of said C-frame-shaped mount, for transmitting divergent beams of X-ray radiation;

a planar detector, provided as a radiation receiver having a matrix surface defined by rows and columns and supported opposite said radiation transmitter at a second end of said C-frame-shaped mount, for converting the received beams of X-ray radiation into electrical signals;

a supporting device configured to support an object to be examined;

means for displacing said radiation transmitter relative to said supporting device for the purpose of producing a cross-sectional radiation scan of the object to be examined, the radiation scan being characterized by a central point of rotation;

a detector for producing radiation direction signals indicative of the relative displacement; and

a computing unit, and at least one memory for storing image processing signals, said computing unit being configured to;

receive the electrical signals from said planar detector for at least the one row of said planar detector, receive the radiation direction signals, and receive signals defining the central point of rotation of the radiation scan; and

calculate image signals for at least one sectional plane on the basis of the electrical signals, the radiation direction signals and the signals defining the central point of rotation of the radiation scan, whereby the calculated image signals can be used for producing an image of the sectional plane on a display device connected to the processing unit.

42. The system according to claim 41, wherein, during the radiation scan, said C-frame-shaped mount stepwise traverses an arcuate path extending through an angle of substantially 180°

about an isocenter of said C-frame-shaped mount.

43. The system according to claim 41, wherein the angle of substantially 180°

consists essentially of 180°

plus an angle of divergence of the divergent beams of X-ray radiation.