Tomographic method of x-ray imaging
AssigneeAmerican Science and Engineering, Inc.
InventorsLee Grodzins, Charles G. Parsons
Life of this patent
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Abstract
A method is disclosed for obtaining the density distributions of three-dimensional elements that compose objects or groups of objects, by examining the objects with beams of x-rays or gamma radiation that are transmitted through the object in a plurality of approximately parallel paths and measuring the intensity of the radiation, scattered approximately perpendicular to the parallel paths, in arrays of detectors around the object. The energy of the x-rays or gamma rays is such that dominant interaction in the object is Compton scattering. The density of each element is determined from the totality of measurements by standard mathematical tomographic or relaxation techniques of data manipulation.
Claims36
A method for determining a three-dimensional density, distribution among volume elements in a volume containing at least one material, the method comprising:
- a. producing a beam of energetic photons for penetrating the volume;
- b. scanning the beam sequentially across incremental positions of the volume in a plurality, of paths having substantially parallel directions separated by incremental steps;
- c. detecting scattered photons of substantially all energies scattered by the material in said volume with a detector having a spatial resolution in a direction substantially parallel to the paths of the beam;
- d. measuring the intensity of scattered photons scattered approximately perpendicular to each substantially parallel direction of the beam at each incremental position of the beam to derive an independent measurement of intensity, of scattered photons scattered from the volume elements in the volume;
- e. identifying a volume element as the approximate origin of scattering along the path of the beam giving rise to the measurement of intensity of scattered photons;
- and
- f. calculating an independent density for each volume element of the material in the volume.
A device for determining densities in volume elements in a material present in an assembly of objects, the device comprising:
- a. a source for producing a beam of energetic photons having a direction for penetrating the material;
- b. an arrangement for scanning the beam of energetic photons in a sequence of sequential beams across the assembly in a manner such that successive directions of the sequential beams are substantially parallel to each other, the sequential beams passing through every volume of the assembly;
- c. a detector disposed substantially parallel to the direction of the beam of energetic photons for providing measurements of the intensity of scattered photons of substantially all energies scattered approximately perpendicular to the direction of the beam at each incremental position of the beam;
- and
- d. a computer for determining the densities in the volume elements of the material in the assembly from a totality of measurements of the intensity of scattered photons scattered approximately perpendicular to the direction of the beam at each incremental position of the beam by a mathematical reconstruction technique.
A tomography system for analyzing a material concealed within an enveloping surface, the system comprising:
- A. at least one source of penetrating radiation for emitting a beam along a beam axis having an orientation disposed with respect to the enveloping surface;
- B. a scanner for varying the orientation of the beam axis with respect to the material in incremental steps;
- and
- C. at least one array of segmented detectors disposed along a detector axis disposed substantially parallel to the beam axis for detecting scattered radiation of substantially all energies of scattered radiation and producing signals corresponding at least to the scattered radiation.
A method for analyzing material concealed within an enveloping surface, the method comprising:
- a. illuminating the enveloping surface with penetrating radiation propagating substantially along a beam axis, the penetrating radiation characterized by a first incident energy;
- b. measuring a profile of penetrating radiation characterized by a first incident energy that is scattered by the concealed material;
- c. illuminating the enveloping surface with penetrating radiation propagating substantially along the beam axis, the penetrating radiation characterized by a second incident energy;
- d. measuring a profile of penetrating radiation characterized by a first incident energy that is scattered by the concealed material;
- and
- e. determining at least one of the density and atomic number associated with each of a plurality of voxels based on the profiles of penetrating radiation characterized by the first and second incident energies and scattered by the concealed material.
A method for analyzing a material concealed within an enveloping surface, the method comprising:
- A. producing a beam of energetic photons for penetrating the volume;
- B. scanning the beam across the material incrementally in a plurality of beam directions;
- C. detecting scattered photons of substantially all energies scattered by the material with a detector array having a spatial resolution in a direction substantially parallel to the beam directions;
- D. measuring the intensity of scattered photons scattered approximately perpendicular to each direction of the beam;
- and
- E. characterizing the material based on the intensity of scattered photons scattered approximately perpendicular to each incremental direction of the beam.
An apparatus for generating sequential beams of penetrating electromagnetic radiation comprising:
- a. a source for producing a beam of charged particles;
- b. a target having a surface which receives the beam of charged particles and emits electromagnetic waves in response thereto;
- c. a beam director that directs the beam of charged particles to the plurality of specified locations on the target;
- and
- d. a collimator, the collimator having an array of transmitting regions and being disposed proximal to the target such that electromagnetic waves emitted from the target pass through the collimator and emerge from the array of transmitting regions in a series of parallel beams as the beam of charged particles is directed at a plurality of specified locations on the target.
A method for generating sequential beams of penetrating electromagnetic radiation comprising:
- a. providing a source for producing charged particles;
- b. directing the particles to a plurality of specified locations on a target having a surface to produce radiation;
- and
- c. collimating the radiation.
Dependencies are inferred from the claim text.