Quality of shadowgraphic x-ray images

An x-ray machine comprising:

• 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.

An x-ray machine comprising:

• 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.

An x-ray machine comprising:

• 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.

An x-ray machine comprising:

• 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.