General Electric Company

Barry N Stone

Stephen J Riederer

Thomas W Lambert

Gary S Keyes

William D Love

Peter S Shelley

Apparatus and methods are provided for performing temporal and hybrid subtraction of X-ray images. In one mode, using three memories, a pair of low and high energy X-ray exposures are made before an X-ray contrast medium arrives in a blood vessel to provide mask images. After contrast arrival additional high and low energy exposures are made and the low energy mask is subtracted from the low energy post-contrast images and the high energy mask is subtracted from the high energy post-contrast images and the resulting sequence of low and high energy temporal difference images are stored. The low energy temporal difference images are displayed. If motion artifacts are perceived, hybrid subtraction of low and high energy temporal difference images is undertaken to produce an image data set in which motion artifacts are removed. In an alternate mode, which uses four memories, low and high energy pre-contrast mask images are stored in one pair of memories. Low and high energy live post-contrast images are subtracted from the stored images and the resulting low and high energy temporal difference images are stored in the other pair of memories. These are subtracted to produce hybrid images.

Method and apparatus for X-ray image subtraction

In a digital fluorography system a television (TV) camera converts X-ray images to analog video signals that are converted to digital pixel words in an analog-to-digital converter (ADC). The sync signals for the TV camera and the sample clock signals for the ADC are derived from a novel resettable crystal controlled sync generator. A phase-locked loop provides an ac reference signal at one-half power line frequency which is equivalent to TV frame rate. The sync generator is reset to start a new frame and an ensuing sequence of crystal controlled horizontal sync pulses only in response to occurrence of ac reference signals so every frame is in registration. A digital video processor (DVP) subtracts a mask image from each image in a sequence of images that are acquired while an X-ray contrast medium is appearing in and disappearing from a blood vessel. The resulting difference images are stored in analog video signal format in an analog video disk recorder. The DVP and, hence the horizontal and vertical sync signals recorded on disk for each frame are also locked to the ac reference signal and are independent of sync signals from the crystal controlled oscillator. A novel digital storage FIFO buffer system couples the digitized pixel data from the ADC to the DVP and compensates for the timing differences between them. During image reprocessing wherein recorded difference images are subtracted from a selected difference or substitute mask image, the sample clock for the ADC is derived from a phase-locked loop that is locked to the recorded horizontal sync signals so the sample clock is varied in correspondence with or modulated by the recorded sync signals.

Line-locked digital fluorography system

In a digital fluoroscopy system, analog video signals representative of successive x-ray image frames are converted to digital pixel values that are used as addresses, respectively. A digital memory stores at its respective locations a digital value corresponding to the logarithm of an address value so that when a digital pixel value represented by an address is fed from the analog-to-digital converter to the memory the memory will output the logarithm of the pixel value in digital form. Pixel values for successive x-ray images are subtracted in-phase on a pixel-by-pixel basis to produce digital difference pixel signals which are converted to analog video signals for driving a television monitor that displays an image representative of the difference between x-ray images.

X-Ray image digital subtraction system

In a convolver, analog video waveforms for each horizontal line to a raster scanned video monitor are sampled at regular intervals with a high speed shift register such as a charge coupled device to obtain trains of picture elements (pixels) which are transferred line-after-line to a series of registers to thereby delay the lines by the number of register stages used. As the trains are transferred the pixels are simultaneously supplied to delay elements to delay corresponding pixels in each line by a given amount in reference to the individual pixel which is to be convolved at the instant. The delayed pixel signals existing at the instant are variously processed in summing devices and the result is used to act on the individual pixel to convolve it in accordance with the filter function which is desired.

Analog video convolver for real time two-dimensional image processing

A detector for X-radiation or other ionizing radiation comprises a pair of curved metal bars lying in spaced apart parallel planes. Ceramic members are bonded to the respective bars in facing relationship. Each ceramic member has a plurality of radially extending circumferentially spaced grooves facing similar grooves in the other member. A plurality of electrode plates are held in juxtaposed and circumferentially spaced apart relationship by disposing their respective upper and lower edges in the grooves of opposed ceramic members. The faces of adjacent electrode plates define gas-filled gaps in which photoelectron-ion pairs are produced when radiation enters from the front edges of the plates. The above described assembly is disposed within a pressurized gas-filled chamber having an X-ray transmissive window adjacent the front edges of the plates. A cover encloses the chamber. It has insulator feed-throughs for connecting the electrode plates with external electric circuits. Photoelectrons and/or ions, created by the ionizing radiation, are collected on the electrode plates and thereby generate an electrical signal which corresponds to the incident ionizing radiation.

Growing community of inventors

Waukesha, WI, United States of America

Barry N Stone