Quality of shadowgraphic x-ray images
First Claim
1. An x-ray machine comprising:
- a source of an x-ray beam;
a scanner means to move the beam relative to a patient;
an imaging device which has means to receive x-rays which have been attenuated by the patient during a succession of imaging intervals to form an x-ray image of the patient;
a feedback system for deriving pre-exposure measurements of x-rays attenuated by the patient during a succession of feedback intervals which alternate with said imaging intervals for a single image of the patient and for causing the radiation during the imaging intervals to be modulated as a function of respective pre-exposure measurements, said feedback system comprising an x-ray detector receiving x-rays attenuated by the patient during said feedback intervals and a circuit which modulates the intensity and hardness of the beam during said imaging intervals on the basis of the x-rays attenuated by the patient and received by the detector during respective feedback intervals previous to said imaging intervals.
1 Assignment
0 Petitions
Accused Products
Abstract
The quality of x-ray shadowgraphic images is improved by beam equalization controlled to ensure that just the right amount of radiation is used to accomplish the desired result, be it a desired image density and contrast or a desired signal-to-noise ratio or some other desired characteristic. The new techniques include: (1) maintaining a substantially constant signal-to-noise ratio throughout the image by measuring both scattered and primary radiation and using the results in a feedback loop to control the x-ray tube output, (2) raster scanning an x-ray beam along straight lines at constant velocity within a line by using a curved slit rotating aperture, (3) simultaneously controlling each of the intensity and hardness of a scanned x-ray beam as determined by post-patient x-ray measurements, and (4) using a segmented fan to scan the patient in a direction transverse to the plane of the fan and individually modulating each beam segment to achieve desired image characteristics.
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Citations
18 Claims
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1. An x-ray machine comprising:
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a source of an x-ray beam; a scanner means to move the beam relative to a patient; an imaging device which has means to receive x-rays which have been attenuated by the patient during a succession of imaging intervals to form an x-ray image of the patient; a feedback system for deriving pre-exposure measurements of x-rays attenuated by the patient during a succession of feedback intervals which alternate with said imaging intervals for a single image of the patient and for causing the radiation during the imaging intervals to be modulated as a function of respective pre-exposure measurements, said feedback system comprising an x-ray detector receiving x-rays attenuated by the patient during said feedback intervals and a circuit which modulates the intensity and hardness of the beam during said imaging intervals on the basis of the x-rays attenuated by the patient and received by the detector during respective feedback intervals previous to said imaging intervals. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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2. An x-ray machine comprising:
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a source of a fan-shaped beam of x-rays; a scanner means to move the beam relative to a patient in a direction transverse to the plane of the beam; means to divide said fan-shaped beam into a plurality of individual segments an imaging device which has means to receive x-rays which have been attenuated by the patient and forms an x-ray image therefrom; and a plurality of feedback loops, wherein each feedback loop includes a detector for x-rays attenuated by the patient and each feedback loop individually modulates a separate respective segment of the beam by selectively changing the velocity at which the respective beam segment moves relative to the patient. - View Dependent Claims (11)
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3. An x-ray machine comprising:
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a source of an x-ray beam; a scanner means to move the x-ray beam relative to a patient; an imaging device which--has means to receive x-rays which have been attenuated--by the patient and forms an x-ray image of the patient; a feedback loop which separately measures primary and scattered radiation components of the x-rays attenuated by the patient and modulates the beam on the basis of measurements of the primary and scattered components selected to maintain a constant signal-to-noise ratio in the x-ray image. - View Dependent Claims (12, 13, 14)
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4. An x-ray machine comprising:
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a source of an x-ray beam; a scanner which comprises means for moving the x-ray beam relative to a patient along straight raster lines, at constant velocity along a line, said means comprising a rotating pre-patient collimator having a curved slit aperture causing the beam to move relative to the patient along said straight raster lines and at constant velocity along each of said straight lines; and an imaging device which has means to receive the beam after attenuation thereof by the patient as a post-patient beam during a succession of imaging intervals to form an x-ray image of the patient; a feedback system having means for deriving pre-exposure measurements of the post-patient beam during a succession of feedback intervals which alternate with said imaging intervals for a single image of the patient and having means for causing the radiation during the imaging intervals to be modulated as a function of respective pre-exposure measurements. - View Dependent Claims (15)
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16. A method comprising:
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scanning an x-ray beam relative to a patient; forming an x-ray image of the patient on the basis of the beam after attenuation thereof by the patient; separately measuring primary and scattered post-patient radiation and modulating the beam on the basis of post-patient measurements of primary and scattered radiation to maintain a desired signal-to-noise ratio distribution in the x-ray image. - View Dependent Claims (17)
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18. An x-ray machine comprising:
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a source of a fan - shaped beam of x-rays; a scanner means to move the beam relative to a patient in a direction transverse to the plane of the beam; means to divide said fan-shaped beam into a plurality of individual segments; an imaging device which has means to receive x-rays which have been attenuated by the patient and forms an x-ray image therefrom; and a plurality of feedback loops, wherein each feedback loop includes a detector for x-rays attenuated by the patient and each feedback loop individually pulse width modulates a separate respective segment of the beam.
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Specification