Imaging

• US 4,768,214 A
• Filed: 04/15/1986
• Issued: 08/30/1988
• Est. Priority Date: 01/16/1985
• Status: Expired due to Term

• Current Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Original Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Inventors: Bjorkholm, Paul J.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Freeman, John C.
• Application Number:
  US06/853,368
• Time in Patent Office: 868 Days
• Field of Search: 378/5-7, 378/87, 378/146, 378/901, 364/414
• US Class Current: 378/87
• CPC Class Codes: G01N 23/20083 by using a combination of at least two measurements at least one being a transmission measurement and one a scatter measurement

Abstract

Method and apparatus for imaging using penetrating radiant energy provides a resulting image with elements of intensity related to atomic number. A penetrating radiant energy source is used for generating a flying spot. A first detector is located to be responsive to transmitted energy, e.g. the flying spot traverses the first detector. A second detector is located substantially coplanar with the first detector to be responsive to scattered energy, as the flying spot scans a target. The signals produced by the first and second detectors are combined to produce an image array having elements of intensity related to atomic number. A method and apparatus for non-invasively measuring density using the apparatus already recited, is also disclosed.

Claims

1. A projection radiographic apparatus useful in selectively imaging an object using penetrating radiant energy comprising:

source means for emitting penetrating radiant energy,

means for directing said penetrating radiant energy emitted by said source means towards a target area including scanning means for producing a flying spot of penetrating radiant energy for repeatedly sweeping a line in space at said target area,

first radiant energy detecting means located to be responsive to radiant energy from said source means passing directly through an object located in said target area for producing a first sequence of signals as said flying spot sweeps said target area, and

second radiant energy detecting means located substantially coplanar with said first radiant energy detecting means and further from said source means than said object, said second radiant energy detecting means responsive to radiant energy from said source scattered at an acute angle to a path of said radiant energy from said source means, by an object located in said target area, to produce a second sequence of signals as said flying spot sweeps said target area, said second sequence including only one single valued signal for each signal of said first sequence, and

combining means for combining said first and second sequences of signals to produce an image array as a nonlinear function of said signals from said first and second sequences.

2. Apparatus as recited in claim 1 in which said combining means includes means for producing an image array with elements of intensity related to atomic number.

3. A projection radiographic apparatus useful in selectively imaging an object using penetrating radiant energy comprising:

source means for emitting penetrating radiant energy,

means for directing said penetrating radiant energy emitted by said source means toward a target area including scanning means for producing a flying spot of penetrating radiant energy for repeatedly scanning said target area,

first radiant energy detecting means located to be responsive to said radiant energy passing directly through an object located in said target area for producing a first signal sequence as said flying spots scan said target,

5. Apparatus as recited in claim 3 in which said means for processing includes processing means for computing, for each element of said first and second arrays the quantity:

##EQU12## wherein S is an element from said second array, T is an element of said first array, I_o is a quantity related to illumination intensity of said source means;

and means for storing said quantity R as a corresponding element of said third array.

7. A method as recited in claim 5 in which said processing step includes sampling and A/D conversion and in which said producing step produces an image array with elements of intensity related to atomic number.

8. A method as recited in claim 5 or 6 in which said producing step produces the quantity:

##EQU13## where T and S are transmitted and scattered radiant energy signals, respectively, I_o is a constant related to intensity of said source and said image array consists of an ordered array of said quantity R.

9. A method as recited in claim 5 in which said producing step produces an image array of elements having intensity related to atomic number.

4. second radiant energy detecting means located substantially coplanar with said first radiant energy detecting means and responsive to radiant energy scattered by an object located in said target area for producing a second signal sequence as said flying spot scans said target area, said second sequence including only one single valued signal for each signal in said first sequence of signals,

combining means for combining said first and second sequences of signals to produce an image array in which said combining means includes:

means for sampling an output of said first and second radiant energy detecting means for developing first and second sequences of sampled signals;

means for A to D converting said sequences of sampled signals to produce first and second digital sequences;

means for storing said first digital sequence in a first ordered array T;

means for storing said second digital sequence in a second ordered array S; and

means for processing said first and second ordered arrays for producing a third ordered array R with a single element in said array R corresponding to each element of said first and second digital sequences.

6. A method of projection radiographic imaging producing an image array useful in isolating image components of particular tissues, compounds or elements from other image components comprising:

providing a radiant energy source and a scanning device for repeatedly sweeping a line in space at a target area;

providing relative movement, between an object located at said target area and said radiant energy, perpendicular to the sweep of said radiant energy;

detecting, in a given plane, radiant energy transmitted by said object as said radiant energy source sweeps said target area;

detecting, substantially in said given plane, radiant energy scattered at an acute angle to path of said radiant energy from said source, by said object as said radiant energy source sweeps said target area;

processing said detected radiant energy to produce transmitted and scattered radiant energy signals related respectively to transmitted and scattered radiant energy, wherein said processing step produces only a single scattered radiant energy signal for each transmitted radiant energy signal; and

producing result signals as a non-linear function of said radiant energy signals and producing an image array from said result signals.

10. A method of remote measurement of density of a component of a complex target in which said component is entirely submerged in another component of said complex target comprising the steps of:

measuring thickness of a selected section of said complex object and thickness of said component at said section;

illuminating said section of said complex object in at least two swaths with a sweeping beam of radiant energy directed approximately perpendicular to said selected section while slowly indexing said target relative to said sweeping beam so that said first swath has a line of sight excluding said component and said second swath has a line of sight including said component;

simultaneously detecting transmitted and scattered radiant energy from said target;

sampling and storing said detected transmitted and scattered radiant energy in a pair of ordered arrays T and S, respectively, and computing a representation of density as;

##EQU14## where the subscripts, i,b and i,a respectively identify said second and first swaths, t_B identifies said measured component thickness, t_T identifies said measured thickness of said complex object and σ

_KN is the Klein Nishina cross-section for a free electron.

11. Apparatus useful in selectively imaging an object using penetrating radiant energy comprising:

source means for emitting penetrating radiant energy,

means for directing said penetrating radiant energy emitted by said source means towards a target area,

first radiant energy detecting means located to be responsive to said radiant energy passing directly through an object located in said target area,

second radiant energy detecting means located to be responsive to said radiant energy scattered by an object located in said target area,

image developing means responsive to signals produced by said first and second radiant energy detecting means, said image developing means includes;

means responsive to said first and second radiant energy detecting means for deriving first and second sequences of signals therefrom,

means for storing said first sequence in a first ordered array T;

means for storing said second sequence in a second ordered array S; and

means for combining said first and second ordered arrays for producing and storing a third ordered array R, wherein

said means for combining includes means for computing, for each element of said first and second arrays the quantity;

##EQU15## wherein S is an element from said second array, T is an element of said first array, I_o is a quantity related to illumination intensity of said source means.

13. A method as recited in claim 11 in which said processing step includes sampling and A/D conversion.

15. A method as recited in claim 13 wherein said first ratio is multiplied by a quantity related to the ratio of the measured component thickness and measured thickness of said complex object.

16. The method of claim 13 or 14 in which said simultaneously detecting step is carried out with detectors located in substantially common planes.

12. A method of imaging producing an image array useful in isolating image components of particular tissues, compounds or elements from other image components comprising:

providing radiant energy source means for repeatedly sweeping a target with radiant energy;

providing relative movement between said target and said radiant energy perpendicular to the sweep of said radiant energy;

detecting radiant energy transmitted by said target;

detecting radiant energy scattered by said target;

processing said detected radiant energy to produce transmitted and scattered radiant energy signals related respectively to transmitted and scattered radiant energy; and

combining said radiant energy signals to produce the quantity;

##EQU16## where T and S are transmitted and scattered radiant energy signals, respectively, I_o is a constant related to intensity of said source and said image array consists of an ordered array of said quantity R.

14. A method useful in remote measurement of density of a component of a complex object in which said component is entirely submerged in said complex object comprising the steps of:

measuring thickness of a selected section of said complex object and thickness of said component at said selected section;

illuminating said selected section of said complex object in at least two swaths with a sweeping beam of radiant energy directed approximately perpendicular to said selected section while slowly indexing said target relative to said sweeping beam so that a first swath has a line of sight excluding said component and a second swath has a line of sight including said component;

simultaneously and separately detecting transmitted and scattered radiant energy from said target;

sampling and storing signals corresponding to said detected transmitted and scattered radiant energy in a pair of ordered arrays T and S, respectively,

computing for said first swath a first ratio of scattered and transmitted radiant energy,

computing for said second swath a second ratio of scattered to transmitted radiant energy, and

computing, with said first and second ratios, the density, of said component.

17. Projection radiographic apparatus useful in selectively imaging an object located in a target area using penetrating radiant energy comprising:

source means for emitting penetrating radiant energy,

means for directing said penetrating radiant energy emitted by said source means towards said target area including scanning means for producing a flying spot of penetrating radiant energy for repeatedly scanning said target area,

first radiant energy detecting means located to be responsive to said radiant energy passing directly through an object located in said target area for producing a first sequence of signals as said flying spots scan said target,

second radiant energy detecting means located substantially coplanar with said first radiant energy detecting means, further from said source means than said object and responsive to radiant energy scattered at an acute angle to a path of radiant energy from said source means, by an object located in said target area for producing a second sequence of signals as said flying spot scans said target area, said second sequence including only one valued signal for each signal in said first sequence, and

combining means responsive to said first and second signals for producing an image array with elements of intensity related to atomic number.

19. Apparatus as recited in claim 17 wherein said third ordered array R includes a plurality of elements, each of said elements being a function of a corresponding element in said first and second arrays T and S, respectively.

20. Apparatus as recited in claim 17 which includes means for producing from said array R an image with elements of intensity related to atomic number.

18. Apparatus useful for producing a projection radiograph for selectively imaging an object using penetrating radiant energy comprising:

source means for emitting penetrating radiant energy,

means for directing said penetrating radiant energy emitted by said source means toward a target area including scanning means for producing a flying spot of penetrating radiant energy for repeatedly scanning said target area,

first radiant energy detecting means for producing first signals and located to be responsive to said radiant energy passing directly through an object located in said target area as said flying spot scans said target area,

second radiant energy detecting means for producing second signals and located to be responsive to radiant energy scattered at an acute angle to a path of said penetrating radiant energy by an object located in said target area as said flying spot scans said target area,

combining means for combining said first and second signals to produce an image array in which said combining means includes;

means for sampling an output of said first and second radiant energy detecting means for simultaneously developing first and second sequences of sampled signals with a like number of signals in each sequence;

means for A to D converting said sequences of sampled signals to produce first and second digital sequences;

means for storing said first digital sequence in a first ordered array T to produce an array of a given number of elements;

means for storing said second digital sequence in a second ordered array S to produce an array of said given number of elements; and

means for processing said first and second ordered arrays for producing a third ordered array R of said given number of elements wherein R is a reflection of said object'"'"'s atomic number.