SELECTIVE MATERIAL X-RAY IMAGING SYSTEM

• US 3,848,130 A
• Filed: 06/25/1973
• Issued: 11/12/1974
• Est. Priority Date: 06/25/1973
• Status: Expired due to Term

• Current Assignee: Albert Macovski
• Original Assignee: Albert Macovski
• Inventors: Macovski, Albert
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Willis, Davis L.
• Application Number:
  US05/373,465
• Time in Patent Office: 505 Days
• Field of Search: 250/336,363,366,369,482,510
• US Class Current: 378/98.9
• CPC Class Codes: A61B 5/1075 for measuring dimensions by non-invasive methods, e.g. for determining thickness of tissue layer A61B8/0858 takes precedence
• CPC Class Codes: A61B 6/025 Tomosynthesis
• CPC Class Codes: A61B 6/4035 the source being combined with a filter or grating
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: G01N 23/043 using fluoroscopic examination, with visual observation or video transmission of fluoroscopic images
• CPC Class Codes: G21K 1/10 Scattering devices; Absorbing devices; Ionising radiation filters

Abstract

An array of x-ray images are obtained each representing a different spectral energy distribution. These images are scanned with the output signals applied to a computer. The computer is used to produce signals representing the absorption due to specific materials. These are displayed individually or in a composite color display.

Claims

1. Apparatus for providing a plurality of processed x-ray images represening specific materials in an object comprising:

a plurality of sources each having a different x-ray energy spectrum;

means for recording a plurality of images each representing the different x-ray energy spectrum transmitted through the object with the number of recorded images being at least as great as the number of processed images;

means for scanning each of the plurality of recorded images to generate a plurality of scanned signals;

a computer for processing the plurality of scanned signals to generate the plurality of processed signals represent specific materials in the object; and

mean for displaying the processed signals whereby processed xray images are formed representing specific materials in the object.

2. Apparatus as recited in claim 1 wherein the means for recording the plurality of images each representing the different x-ray spectrum transmitted through the object comprises:

a scintillating screen for converting the x-rays transmitted through the object into visible light image; and

means for recording the visible light image.

3. Apparatus as recited in claim 2 wherein the means for recording the visible light comprises a television camera whose target receives the light image from the scintillating screen and a video storage device for storing the electrical video signal generated by the television camera.

4. Apparatus as recited in claim 2 wherein the means for recording the visible light comprises photographic film.

5. Apparatus as recited in claim 4 wherein the means for scanning each of the plurality of recorded film images includes a flying spot scanner whose light output is imaged onto each of the recorded film images and a photocell for collecting the transmitted light and generating the scanned signal.

6. Apparatus as recited in claim 1 wherein the plurality of x-ray sources comprises an x-ray emitter and a plurality of filters positioned in the path of the emitted x-rays where each filter includes materials having a different x-ray transmission spectrum.

7. Apparatus as recited in claim 1 wherein the plurality of x-ray sources comprises an x-ray emitter and a plurality of secondary - emitters positioned in the path of the emitted x-rays each of which fluoresces and emits a monochromatic spectrum.

8. Apparatus as recited in claim 1 wherein the computer for processing thE plurality of scanned signals to generate a plurality of processed signals includes means for taking weighted sums of a pre-calculated constant term and the logarithms of each of the scanned signals.

9. Apparatus as recited in claim 1 wherein the computer for processing the plurality of scanned signals to generate a plurality of processed signals includes means for solving a plurality of simultaneous integral equations each representing the relationship between all of the processed signals and a different one of the scanned signals the relationship specifying each scanned signal being equal to the integral, over the energy spectrum used, of the products of the absorptions of each of the specific materials in the object.

10. Apparatus as recited in claim 9 wherein the means for solving the plurality of integral equations comprises:

an array of sub-computers for each of the plurality of integral equations with each sub-computer computing the output for a different subregion of the energy spectrum;

a plurality of oscillatory signals representing all possible values of the processed signals which are connected to each of the sub-computers;

a plurality of final adders for adding the outputs of each of the sub-computers to generate a plurality of trial signals;

a plurality of comparators for comparing each of the plurality of trial signals with the scanned signals and generating a comparator output signal when the trial signal equals the scanned signal;

a coincidence circuit for generating a coincidence signal when all of the comparator output signals are present; and

a sampling circuit for sampling all of the plurality of oscillatory signals with the coincidence signal to generate each of the plurality of processed signals.

11. Apparatus as recited in claim 10 wherein each of the array of subcomputers comprises:

a source of bias voltage representing the spectral amplitude of the filtered source in that region of the energy spectrum;

a plurality of amplifiers for each of the plurality of processed signals having a gain proportional to the absorption coefficient for the specific material in that region of the energy spectrum and having the oscillatory signal, representing all values of the processed signal, as an input;

a sub-adder for adding the source of bias voltage and the output voltages of each of the plurality of amplifiers; and

means for deriving the exponential of the output of the sub-adder to form the output of the sub-computer.

12. Apparatus as recited in claim 9 wherein the computer further comprises:

a memory in which are stored an array of pre-determined values of each of the plurality of processed signals for each value of each of the plurality of the scanned signals;

means for addressing the particular arrays of pre-determined values of each of the plurality of processed signals corresponding to the particular set of scanned signals being received by the computer;

means for comparing the particular arrays of pre-determined values of each of the plurality of processed signals with each other to determine a set of pre-determined values which provides the closest match of these signals amongest the arrays; and

means for utilizing the set of pre-determined values which provides the closest match to form the plurality of processed signals.

13. Apparatus as recited in claim 9 wherein the computer further comprises:

a memory in which are stored an array of pre-determined values of sets of the plurality of processed signals for each set of values of the plurality of scanned signals;

means for addressing a particular set in the array of pre-determined values of the plurality of processed signals corresponding to a particular set of the plurality of scanned signals; and

means for utilizing the particular set of the plurality of processed signals to form the plurality of processed signals.

14. Apparatus as recited in claim 1 wherein the means for displaying the processed signals iNcludes a monochrome display device which is connected to one of the plurality of processed signals whereby an image is displayed which represents the absorption due to one of the materials in the object.

15. Apparatus as recited in claim 1 wherein the means for displaying the processed signals includes a color display device where each color is modulated by one of the processed signals whereby an image is displayed which simultaneously represents the absorption due to the plurality of materials in the object.