X-ray apparatus

• US 5,949,811 A
• Filed: 10/08/1997
• Issued: 09/07/1999
• Est. Priority Date: 10/08/1996
• Status: Expired due to Term

• Current Assignee: Hitachi Medical Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi Medical Corporation (Hitachi, Ltd.)
• Inventors: Ishiguro, Takashi, Ueki, Hironori, Baba, Rika, Ueda, Ken, Kuba, Akira, Ishikawa, Ken
• Primary Examiner(s): Porta, David P.
• Application Number:
  US08/947,156
• Time in Patent Office: 699 Days
• Field of Search: 378/97, 378/106, 378/108, 378/109, 378/110, 378/111, 378/112, 378/114, 378/115, 378/116
• US Class Current: 378/108
• 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 6/542 involving control of exposure
• CPC Class Codes: A61B 6/548 Remote control of the apparatus or devices
• CPC Class Codes: H05G 1/42 using arrangements for switching when a predetermined dose of radiation has been applied, e.g. in which the switching instant is determined by measuring the electrical energy supplied to the tube

Abstract

An X-ray apparatus acquires an X-ray image of an object by radiating X-rays to the object and includes an X-ray radiator for radiating X-rays to an object. An imager acquires an X-ray image of the object and radiation dose controller controls the radiation dose so as to acquire an X-ray image having a predetermined X-ray relative noise level on the basis of an image level of a predetermined area in the X-ray image.

Claims

1. An x-ray apparatus comprising:

an X-ray tube for radiating X-rays;

an X-ray collimator for regulating an X-ray exposing area of an object;

an X-ray filter for changing energy spectrum of X-ray exposing the object and/or an X-ray grid for eliminating X-ray scattered when the X-ray transmits the object;

X-ray detection means for acquiring an X-ray image of the object;

display means for displaying the X-ray image;

storage means for storing a first function showing a relation among an averaged output value of the X-ray detection means and a tube voltage of the X-ray tube and a thickness of the object, wherein the relation is preliminarily measured in a state where predetermined values are, respectively, set to mAs value of the X-ray tube, the X-ray exposing area of the object, a distance between the object and an input face of the X-ray detection means, and a gain of the X-ray detection means, with respect to combinations of the plurality of X-ray filters and/or the plurality of X-ray grids, and for storing a second function showing a ratio of change in the averaged output values of the X-ray detection means preliminarily measured by setting change amounts of the X-ray exposing area of the object and the distance from the object to the input face of the X-ray detection means for predetermined values to variables, with respect to combinations of the plurality of X-ray filters and/or the plurality of X-ray grids;

radiographic conditions calculation means for calculating imaging conditions for radiography on the basis of imaging conditions for fluoroscopy and the first and second functions stored in the storage means; and

control means for controlling the mAs value and the tube voltage of the x-ray tube and the gain of the X-ray detection means on the basis of the calculation result of the radiographic conditions calculation means.

2. The X-ray apparatus according to claim 1, wherein the radiographic conditions calculation means approximates the averaged output value of the X-ray detection means by a product of a ratio of the mAs value of the X-ray tube to the predetermined value for the mAs value of the X-ray tube, a ratio of the gain of the X-ray detection means to predetermined value for the X-ray detection means, the first function and the second function, and calculates the X-ray radiographic conditions from the product, the averaged output value of the X-ray detection means at the time of a fluoroscopic exposure, and the imaging conditions for fluoroscopy.

3. The X-ray apparatus according to claim 1, wherein the second function is a product of a third function and a fourth function, the third function shows a ratio of change in the averaged output values of the X-ray detection means when the change amount of the x-ray exposing area for the predetermined value is set to a variable, and the fourth function shows a ratio of change in the averaged output values of the X-ray detection means when the change amount of the distance from the object to the input face of the X-ray detection means for the predetermined value is set to a variable.

4. The X-ray apparatus according to claim 3, wherein the third function is a predetermined value.

5. The X-ray apparatus according to claim 3, wherein the fourth function is a predetermined value.

6. The X-ray apparatus according to claim 1, wherein when the tube voltage of the X-ray tube and/or the thickness of the object are set to variables of the second function, if a ratio of the change amount of the second function is equal to or larger than a predetermined value, the second function is corrected for the tube voltage of the X-ray tube and/or the thickness of the object.

7. The X-ray apparatus according to claim 1, wherein the radiographic conditions calculation means comprises:

average object thickness calculation means for approximating the averaged output value of the X-ray detection means by a product of a ratio of the mAs value of the X-ray tube to the predetermined value for the mAs value of the X-ray tube, a ratio of the gain of the X-ray detection means to predetermined value for the X-ray detection means, the first function and the second function, and for calculating a average thickness of the object from the product, the averaged output value of the X-ray detection means at the time of fluoroscopic exposure, and the fluoroscopic conditions; and

means for calculating the radiographic conditions on the basis of the product and the average object thickness.

8. The X-ray apparatus according to claim 7, wherein the average object thickness calculation means comprises means for approximating the averaged output value of the X-ray detection means by a product of ratio of the mAs value of the X-ray tube to the predetermined value for the mAs value of the X-ray tube, a ratio of the gain of the X-ray detection means to the predetermined values for the gain of the X-ray detection means, the first function and second function, and for approximately calculating the average thickness of the object from the product and the fluoroscopic conditions.

9. The X-ray apparatus according to claim 1, wherein the radiographic conditions calculation means comprises:

tube saturation monitor means for monitoring whether the tube voltage and the mAs value of the X-ray tube and the gain of the X-ray detection means at the time of fluoroscopic exposure are within a preset permissible range or not; and

output level corrector means for increasing the mAs value of the X-ray tube and/or the gain of the X-ray detection means at the time of radiographic exposure by predetermined times when the tube saturation monitor means determines that the tube voltage and the mAs value of the X-ray tube and the gain of the X-ray detection means are not included in the preset permissible range.

10. The X-ray apparatus according to claim 2, further comprising:

signal control means for setting an X-ray relative noise value on the basis of a maximum image level of a predetermined area in the X-ray image.

11. The X-ray apparatus according to claim 1, further comprising:

radiation dose control means for setting an X-ray relative noise value on the basis of a minimum image level of a predetermined area in the X-ray image.

12. The X-ray apparatus according to claim 1, wherein an X-ray relative noise value is set on the basis of a preliminary acquired X-ray image of the object.

13. The X-ray apparatus according to claim 1, wherein an X-ray relative noise value is set on the basis of information of the object acquired by measurement except for radiographic exposure and radiation dose of radiographic exposure executed in the past.

14. The X-ray apparatus according to claim 1, further comprising:

radiation dose control means for controlling an X-ray pulse width.

15. The X-ray apparatus according to claim 1, further comprising:

radiation dose control means for controlling the tube voltage of the X-ray tube.

16. The X-ray apparatus according to claims 1, further comprising:

rotation means for rotating the X-ray and the X-ray detection means around the object; and

reconstruction means for reconstructing slice images of the object from the X-ray images.

17. The X-ray apparatus according to claim 2, further comprising:

signal control means for controlling an optical iris or an amplification gain of the X-ray detection means.

18. An X-ray apparatus comprising:

X-ray radiation means for radiating X-rays to an object;

imaging means for acquiring an X-ray image of the object;

X-ray image prediction means for forming a predicted X-ray image to be acquired next by using linear lines or two-or larger-dimensional curves on the basis of at least one X-ray image acquired just before forming the predicted X-ray image;

radiation dose control means for controlling a radiation dose so that the X-ray image having a predetermined X-ray relative noise value can be acquired on the basis of an image level of a predetermined area in the X-ray image; and

signal control means for controlling an optical iris and/or an amplification gain of the imaging means so that an analog signal before being digitized in the imaging means is equal to or less than a predetermined value on the basis of the image level of the predetermined area in the X-ray image,

wherein the radiation dose control means calculates a ratio of a first transformed level to a second transformed level, and calculates the radiation dose from a product of the ratio and an X-ray dose in a preset standard condition, the first transformed level is obtained by transforming a minimum image level of a predetermined area in the predicted X-ray image into the preset standard condition, and the second transformed level is obtained by transforming a minimum image level of the predetermined area in the X-ray image acquired already into the preset standard condition.

19. The X-ray apparatus according to claim 18, wherein the signal control means sets the X-ray relative noise value on the basis of a maximum image level of the predetermined area in the X-ray image.

20. The apparatus according to claim 18, further comprising:

rotation means for rotating the X-ray radiation means and the imaging means around the object; and

reconstruction means for reconstructing a slice image of the object from the X-ray images.

21. An X-ray apparatus comprising:

X-ray radiation means for radiating X-rays to an object;

imaging means for acquiring an X-ray image of the object;

X-ray image prediction means for forming a predicted X-ray image to be acquired next by using linear lines or two-or larger-dimensional curves on the basis of at least one X-ray image acquired just before forming the predicted X-ray image; and

radiation dose control means for controlling a radiation dose so that the X-ray image having a predetermined X-ray relative noise value can be acquired on the basis of an image level of a predetermined area in the predicted X-ray image,

wherein the radiation dose control means controls an X-ray pulse width on the basis of a minimum image level of the predetermined area in the predicted X-ray image.

22. An X-ray apparatus comprising:

X-ray radiation means for radiating X-rays to an object;

imaging means for acquiring an X-ray image of the object;

X-ray image prediction means for forming a predicted X-ray image to be acquired next on the basis of at least one X-ray image acquired just before forming the predicted X-ray image; and

radiation dose control means for controlling a radiation dose by controlling an X-ray pulse width on the basis of a minimum image level of the predetermined area in the predicted X-ray image.

23. An X-ray apparatus comprising:

X-ray radiation means for radiating X-rays to an object;

imaging means for acquiring an X-ray image of the object;

X-ray image prediction means for forming a predicted X-ray image to be acquired next by using linear lines or two-or larger-dimensional curves on the basis of at least one X-ray image acquired just before forming the predicted X-ray image; and

signal control means for controlling an optical iris and/or an amplification gain of the imaging means so that an analog signal before being digitized in the imaging means is equal to or less than a predetermined value on the basis of an image level of a predetermined area in the predicted X-ray image,

wherein signal control means controls the optical iris on the basis of a maximum image level of the predetermined area in the predicted X-ray image.

24. An X-ray apparatus comprising:

X-ray radiation means for radiating X-rays to an object;

imaging means for acquiring an X-ray image of the object;

X-ray image prediction means for forming a predicted X-ray image to be acquired next on the basis of at least one X-ray image acquired just before forming the predicted X-ray image; and

signal control means for controlling an optical iris of the imaging means on the basis of a maximum image level of a predetermined area in the predicted X-ray image.

25. An X-ray apparatus comprising:

X-ray radiation means for radiating X-rays to an object;

imaging means for acquiring an X-ray image of the object;

X-ray image prediction means for forming a predicted X-ray image to be acquired next on the basis of at least one X-ray image acquired just before forming the predicted X-ray image;

radiation dose control means for controlling a radiation dose by controlling an X-ray pulse width on the basis of a minimum image level of a predetermined area in the predicted X-ray image; and

signal control means for controlling an optical iris of the imaging means on the basis of a maximum image level of the predetermined area in the predicted X-ray image.

26. An X-ray apparatus comprising:

X-ray radiation means for radiating X-rays to an object;

imaging means for acquiring an X-ray image of the object;

X-ray image prediction means for forming a predicted X-ray image to be acquired next by using linear lines or two-or larger-dimensional curves on the basis of at least one X-ray image acquired just before forming the predicted X-ray image; and

radiation dose control means for controlling a radiation dose so that the X-ray image having a predetermined X-ray relative noise value can be acquired on the basis of an image level of a predetermined area in the X-ray image,

wherein the radiation dose control means calculates a ratio of a first transformed level to a second transformed level, and calculates the radiation dose from a product of the ratio and an X-ray dose in a preset standard condition, the first transformed level is obtained by transforming a minimum image level of a predetermined area in the predicted X-ray image into the preset standard condition, and the second transformed level is obtained by transforming a minimum image level of the predetermined area in the X-ray image acquired already into the preset standard condition.

27. The X-ray apparatus according to claim 26, further comprising permissible range storage means for storing a radiation dose which is within a permissible range in the X-ray apparatus, and storing a radiation dose which exceeds the permissible range, wherein when the calculated radiation dose value exceeds the permissible range, the radiation dose value stored in the permissible range storage means is used as the calculated radiation dose value.

28. The X-ray apparatus according to claim 26, wherein the radiation dose control means sets the X-ray relative noise value on the basis of the minimum image level of the predetermined area in the X-ray image.

29. The X-ray apparatus according to claim 26, wherein the X-ray relative noise value is set on the basis of a preliminary acquired X-ray image of the object.

30. The X-ray apparatus according to claim 26, wherein the X-ray relative noise value is set on the basis of information of the object acquired by measurement except for radiographic exposure and radiation dose of radiographic exposure executed in the past.

31. The X-ray apparatus according to claim 26, wherein the radiation dose control means controls an X-ray pulse width in the X-ray radiation means.

32. The X-ray apparatus according to claim 26, wherein the radiation dose control means controls an X-ray tube voltage in the X-ray radiation means.

33. The X-ray apparatus according to claim 26, further comprising:

rotation means for rotating the X-ray radiation means and the imaging means around the object; and

reconstruction means for reconstructing a slice image of the object from the X-ray images.

34. An X-ray apparatus comprising:

X-ray radiation means for radiating X-rays to an object;

imaging means for acquiring an X-ray image of the object; and

radiation dose control means for controlling a radiation dose so that the X-ray image having a predetermined X-ray relative noise value can be acquired on the basis of an image level of a predetermined area in the X-ray image,

wherein the radiation dose control means calculates a ratio of a transformed level obtained by transforming a minimum image level of the predetermined area in the X-ray image into a preset standard condition to a standard minimum level in the X-ray image obtained in the preset standard condition, and calculates the radiation dose from a product of the ratio and an X-ray dose in the preset standard condition.

35. The X-ray apparatus according to claim 34, further comprising permissible range storage means for storing a radiation dose which is within a permissible range in the X-ray apparatus, and storing a radiation dose which exceeds the permissible range, wherein when the calculated radiation dose value is exceeds the permissible range, the radiation dose value stored in the permissible range storage means is used as the calculated radiation dose value.

36. The X-ray apparatus according to claim 34, further comprising:

rotation means for rotating the X-ray radiation means and the imaging means around the object; and

reconstruction means for reconstructing a slice image of the object from the X-ray images.