US 4,375,068 A · Radiographic apparatus and method with logarithmic video compression

Abstract

A source of radiation irradiates an area of interest of a patient. An image intensifier receives the x-rays which have traversed the patient and provides an optical image of an x-ray shadowgraph through the examined area of the patient. A television camera converts the optical image into a video signal. A signal processor operates on the video signal by adding an offset signal to the gray scale signal and by logarithmically compressing the gray scale portion of the video signal. An automatic zero circuit is provided which readjusts the offset signal between each horizontal sweep of the television camera. The logarithmically compressed gray scale portion of the video signal and the synchronization portion are received by an image processor. The image processor digitally stores a mask image or shadowgraph of the patient before being injected with an x-ray opaque contrast agent. The image processor also stores in a post contrast image or shadowgraph of the same area of the patient after the patient has been injected with an x-ray opaque contrast agent. The image processor subtractively combines the mask image with the post contrast image to produce a difference image. A video monitor displays the difference image.

Claims13

Dependent claims

A radiographic apparatus comprising:

(a) a radiation source for irradiating an examined object with penetrating radiation, such as x-radiation;
(b) means for converting penetrating radiation into a video signal, said penetrating radiation to video signal converting means being disposed to receive from said radiation source penetrating radiation which has traversed the examined object, said video signal having a gray scale portion and a synchronization portion;
(c) logarithmic transfer means for logarithmically compressing the gray scale portion of the video signal, said logarithmic transfer means being operatively connected to said radiation to video signal converting means, the logarithmic transfer means producing an output signal that includes a logarithmically compressed video signal;
(d) base line restoring means for combining an offset signal with the gray scale portion of the video signal, said base line restoring means being operatively connected with said radiation to video signal converting means;
and
(e) an automatic zero circuit supplied with the output signal of the logarithmic transfer means and coupled to the base line restoring means, said automatic zero circuit generating the offset signal combined with the gray scale portion of the video signal.

3 more elements

In an apparatus for performing dynamic image enhancement of a portion of a subject into which a contrast agent is introduced during a diagnostic procedure, which apparatus comprises video signal generating means for successively generating a video signal of x-ray shadowgraph images of the subject, analog to digital conversion means for converting the video signal from the video signal generating means into a digitized video signal, a first memory for storing a first digitized image, said first memory means being operatively connected with said analog to digital converting means, a second memory for storing a second digitized image of the subject and introduced contrast agent, said second memory being operatively connected with said analog to digital conversion means, and means for subtractively combining said first digital image from said first memory with said second digital image from said second memory to produce a digitized differential image, the improvement comprising:

(a) a logarithmic transfer means operatively connected with said video signal generating means and said analog to digital converter for logarithmically compressing the video signal such that the differential image produced by the subtractive combination of the digitized images generally represents the difference in the density of the first and second images multiplied by a thickness related constant.

Dependencies are inferred from the claim text.

Radiographic apparatus and method with logarithmic video compression

Life of this patent

Radiographic apparatus and method with logarithmic video compression

Life of this patent

Abstract

Claims13