Method and apparatus for digital control of scanning x-ray imaging systems

A method for producing radiographic image data by x-ray scanning of a subject which includes the steps of:

• scanning an electron beam in a first raster pattern on an anode plate to produce a moving x-ray origin point,
• generating said radiographic image data by detecting x-rays at a detection point situated at the opposite side of said subject from said anode plate and by producing a detector output signal that vary in accordance with variations of x-ray intensity at said detection point,
• selecting an area within said first raster pattern for magnification,
• encoding the location of the selected area of said first raster pattern in digital signals and initiating a zoom signal,
• reducing the size of said first raster pattern in response to said zoom signal to provide a smaller second raster pattern, and
• positioning the smaller second raster pattern at a location on said anode plate that corresponds to the location that is encoded in the digital signals.

A method of obtaining radiographic image data by x-ray scanning of a subject which includes the steps of:

• producing x-rays at an x-ray origin point on an anode plate of an x-ray tube by directing an electron beam to said anode plate,
• traveling said x-ray origin point in a raster scanning motion within a raster scan area on said anode plate by applying an x-axis sweep frequency signal and a y-axis sweep frequency signal to said x-ray tube,
• generating said radiographic image data by detecting x-rays at a detection point situated at the opposite side of said subject from said x-ray origin point and producing a detector signal that is indicative of variations of x-ray intensity at said detection point as said x-ray origin point moves to successive locations in said raster scan area,
• producing a first sequence of digital data bytes which encode successive values indicative of variations in the magnitude of said x-sweep frequency signal that are to occur during the course of said raster scanning motion at said raster scan area,
• producing a second sequence of digital data bytes which encode successive values indicative of variations in the magnitude of said y-sweep frequency signal that are to occur during the course of said raster scanning motion at said raster scan area,
• modulating the magnitudes of said x-sweep frequency signal and said y-sweep frequency signal during the course of said raster scanning at said first raster scan area by reference to the values encoded by successive data bytes of said first and second sequences thereof, and
• modifying at least one of said x-sweep frequency signal and said y-sweep frequency signal by modifying the values that are encoded by at least one of said first and second sequences of data bytes.