Computerized tomography calibrator

• US 5,056,130 A
• Filed: 10/06/1989
• Issued: 10/08/1991
• Est. Priority Date: 10/06/1989
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Engel, Herbert P.
• Primary Examiner(s): Howell, Janice A.
• Assistant Examiner(s): WONG, DON KITSUN
• Application Number:
  US07/418,364
• Time in Patent Office: 732 Days
• Field of Search: 378/207, 378/2, 378/18, 378/165, 378/5, 378/50, 378/54, 378/24, 378/45, 378/53, 378/56, 378/163, 378/33, 250/252.1 R
• US Class Current: 378/207
• CPC Class Codes: A61B 6/035 Mechanical aspects of CT
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: G01D 18/00 Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00

Abstract

A set of interchangeable pieces comprising a computerized tomography calibrator, and a method of use thereof, permits focusing of a computerized tomographic (CT) system. The interchangeable pieces include a plurality of nestable, generally planar mother rings, adapted for the receipt of planar inserts of predetermined sizes, and of predetermined material densities. The inserts further define openings therein for receipt of plural sub-inserts. All pieces are of known sizes and densities, permitting the assembling of different configurations of materials of known sizes and combinations of densities, for calibration (i.e., focusing) of a computerized tomographic system through variation of operating variables thereof. Rather than serving as a phanton, which is intended to be representative of a particular workpiece to be tested, the set of interchangeable pieces permits simple and easy standardized calibration of a CT system. The calibrator and its related method of use further includes use of air or of particular fluids for filling various openings, as part of a selected configuration of the set of pieces.

Claims

1. An industrial computerized tomography calibrator, comprising:

a plurality of nestable, planar rings, removably received relative one another, and each respectively defining at least one opening of predetermined size situated therein, between their respective inside and outside diameters; and

a plurality of planar inserts for being fit and removably received in said predetermined-size openings;

wherein said rings and inserts are comprised of selected materials having known densities and dimensions;

so that differing combinations of said rings and inserts are provided to establish predetermined density and dimensional material relationships in a given plane, for use in calibrating an industrial computer tomography system; and

further wherein

said inserts each respectively define a plurality of sub-openings of predetermined size therein, and said calibrator further includes a plurality of planar sub-inserts for being fit and removably received in said sub-openings;

a central ring of said plurality of rings defines a disc with a generally square opening therein, and the remainder of said plurality of rings each respectively define a generally square opening and a separate circular opening therein; and

said sub-openings and sub-inserts are generally rectangular in shape.

2. A calibrator as in claim 1, further including non-corrosive fluid of a predetermined, known density removably entrapped within a given sub-opening.

3. An industrial computerized tomography calibrator, comprising:

a plurality of nestable, planar rings, removably received relative one another, an each respectively defining at least one opening of predetermined size situated therein, between their respective inside and outside diameters; and

a plurality of planar inserts for being fit and removably received in said predetermined-size openings;

wherein said rings and inserts are comprised of selected materials having known densities and dimensions;

so that differing combinations of said rings and inserts are provided to establish predetermined density and dimensional material relationships in a given plane, for use in calibrating an industrial computer tomography system; and

further

wherein said inserts each respectively define a plurality of sub-openings of predetermined size therein, and said calibrator further includes a plurality of planar sub-inserts for being fit and removably received in said sub-openings; and

wherein said plurality of sub-openings comprise nine sub-openings defined in each insert, said nine sub-openings being situated in a predetermined, fixed spatial pattern and having different dimensional characteristics in grouped sets of three.

4. An industrial computerized tomography calibrator, comprising:

a plurality of nestable, planar rings, removably received relative one another, and each respectively defining at least one opening of predetermined size situated therein, between their respective inside and outside diameters; and

a plurality of planar inserts for being fit and removably received in said predetermined-size openings;

wherein said rings and inserts are comprised of selected materials having known densities and dimensions;

so that differing combinations of said rings and inserts are provided to establish predetermined density and dimensional material relationships in a given plane, for use in calibrating an industrial computer tomography system; and

further

wherein said inserts each respectively define a plurality of sub-openings of predetermined size therein, and said calibrator further includes a plurality of planar sub-inserts for being fit and removably received in said sub-openings; and

wherein the thickness of said planar rings, said planar inserts, and said planar sub-inserts is 10 mm, and all of such planar members comprise material having a known, fixed density in a range of from near 0 to 10 gm/cc.

5. A calibrator as in claim 4, wherein said planar members comprise one of aluminum, copper, and stainless steel.

6. A device to aid in the image focusing of a computer tomography system having computer means with adjustable variables for generating an image from exposure detection data gathered with such system, said device including:

a plurality of generally planar mother block means, of predetermined size, thickness, and density, for being removably associated with one another, and having primary openings therein, for establishing a dimensionally known planar pattern of such primary openings;

a plurality of generally planar insert means, of predetermined size, thickness, and density, and for being removably received in said mother block means primary openings, for filling same; and

wherein said mother block means includes a plurality of nestable concentric members and one central disc, each having at least one primary opening therein;

so that selected planar configurations of varying combinations of known sizes and densities are provided, to permit adjustment of the system computer means variables for optimum image detection and image contrast and spatial resolution.

7. A device as in claim 6, wherein said concentric members are annular, and said primary openings thereof are respectively situated between the inside and outside diameters of each such annular member.

8. A device as in claim 6, wherein said primary openings are rectangular, and said insert means are correspondingly rectangular for selectively fitting therein.

9. A device as in claim 6, wherein said primary openings are circular, and said insert means are correspondingly circular for selectively fitting therein.

10. A device as in claim 6, wherein said densities are in a range of from near 0 to 10 gm/cc.

11. A device as in claim 6, wherein said predetermined thickness of said mother block means and said insert means is 10 mm.

12. A device as in claim 6, wherein said insert means comprise non-corrosive fluids received within a given mother block means primary opening.

13. A device to aid in the image focusing of a computer tomography system having computer means with adjustable variables for generating an image from exposure detection data gathered with such system, said device including:

a plurality of generally planar mother block means, of predetermined size, thickness, and density, for being removably associated with one another, and having primary openings therein, for establishing a dimensionally known planar pattern of such primary openings; and

a plurality of generally planar insert means, of predetermined size, thickness, and density, and for being removably received in said mother block means primary openings, for filling same;

so that selected planar configurations of varying combinations of known sizes and densities are provided, to permit adjustment of the system computer means variables for optimum image detection and image contrast and spatial resolution; and

wherein said insert means further define secondary openings therein, and said device further includes secondary inserts of predetermined size, thickness, and density, for being removably received in said secondary openings; and

wherein said mother block means includes four two-inch wide nested rings varying from a maximum diameter of fourteen inches to a central ring of two inches in diameter, and further wherein said insert means comprise either circular members having 25 mm in diameter or square members having 25 mm on each side, with said secondary openings thereof comprising squares of varying sizes with sides in a range of from 2 mm to 0.5 mm.

14. A device as in claim 13, wherein said secondary inserts comprise non-corrosive fluids received within a given insert means secondary opening.

15. A set of interchangeable pieces for use in focusing the level of detectability and the contrast and spatial resolution of a computer tomography system having settable variables for adjusting effective image detectability and resolution of the system, said pieces including a plurality of nestable, generally planar mother rings, each ring having at least one predetermined opening within its respective circumference for the receipt of planar inserts of predetermined sizes in such openings, and said pieces further including a plurality of removable planar inserts for being received in said mother ring openings, wherein said mother rings and inserts are comprised of materials having known densities, so that different configurations of materials of known sizes and combinations of densities are provided generally in a given plane to be scanned with the computer tomography system for focusing of such system through adjustment of the settable variables thereof;

and

wherein said planar inserts each define plural openings therein of predetermined, fixed sizes and relative spacing, and said set of pieces further includes a plurality of sub-inserts for being received in said planar insert openings, so that various configurations of said interchangeable pieces are resolved into selected, progressively smaller orders of magnitude through use of said plurality of sub-inserts;

said planar mother rings have an outside diameter preferably in a range of from two to fourteen inches, and said predetermined openings therein are either circular with a radius of about 25 mm, or square with side lengths of about 25 mm;

said planar inserts are either generally circular with a radius of 25 mm, or square with side lengths of 25 mm, and said insert openings are generally square with side lengths in a range of from 2 mm to 0.5 mm; and

said mother rings, planar inserts, and sub-inserts have about the same predetermined thickness.

16. A set of interchangeable pieces as in claim 15, wherein said predetermined thickness is 10 mm.

17. A set of interchangeable pieces as in claim 15, wherein said pieces are respectively comprised of one of aluminum, copper, stainless steel, carbon, carbon composite, a non-corrosive fluid, and air.

18. A set of interchangeable pieces for use in focusing the level of detectability and the contrast and spatial resolution of a computer tomography system having settable variables for adjusting effective image detectability and resolution of the system, said pieces including a plurality of nestable, generally planar mother rings, each ring having at least one predetermined opening within its respective circumference for the receipt of planar inserts of predetermined sizes in such openings, and said pieces further including a plurality of removable planar inserts for being received in said mother ring openings, wherein said mother rings and inserts are comprised of materials having known densities, so that different configurations of materials of known sizes and combinations of densities are provided generally in a given plane to be scanned with the computer tomography system for focusing of such system through adjustment of the settable variables thereof;

and

wherein said planar inserts each define plural openings therein of predetermined, fixed sizes and relative spacing, and said set of pieces further includes a plurality of sub-inserts for being received in said planar insert openings, so that various configurations of said interchangeable pieces are resolved into selected, progressively smaller orders of magnitude through use of said plurality of sub-inserts;

wherein the predetermined density of said mother rings, planar inserts, and sub-inserts is in a range of from 2 to 10 gm/cc.

19. A set of interchangeable pieces for use in focusing the level of detectability and the contrast and spatial resolution of a computer tomography system having settable variables for adjusting effective image detectability and resolution of the system, said pieces including a plurality of nestable, generally planar mother rings, each ring having at least one predetermined opening within its respective circumference for the receipt of planar inserts of predetermined sizes in such openings, and said pieces further including a plurality of removable planar inserts for being received in said mother ring openings, wherein said mother rings and inserts are comprised of materials having known densities, so that different configurations of materials of known sizes and combinations of densities are provided generally in a given plane to be scanned with the computer tomography system for focusing of such system through adjustment of the settable variables thereof;

and

wherein said planar inserts each define plural openings therein of predetermined, fixed sizes and relative spacing, and said set of pieces further includes a plurality of sub-inserts for being received in said planar insert openings, so that various configurations of said interchangeable pieces are resolved into selected, progressively smaller orders of magnitude through use of said plurality of sub-inserts;

wherein there are a total of four mother rings, seven planar inserts, and sixty-three sub-inserts, for a total of seventy-four pieces comprising a complete set of said interchangeable pieces.

20. A method of focusing a computer tomography system of the type having a radiation source for exposing an object to be scanned, an exposure support surface for supporting an object to be scanned, detector means for detecting scan information, and computer means with operating variables for processing scan information into images, said method including:

providing a set of interchangeable pieces, each piece comprising a given material of generally known density and dimensions, said set of pieces including a plurality of nestable mother rings, and inserts for removable selected association with each of said mother rings;

assembling at least certain of said pieces into a given configuration thereof, with such configuration being received on the computer tomography system exposure support surface;

operating the computer tomography system for exposing the assembled configuration of pieces; and

processing detected scan information into images, including adjusting the computer means operating variables so as to obtain optimum image quality based on the known configuration of certain densities and dimensions provided with the assembled pieces.

21. A method as in claim 20, wherein:

said mother rings include primary openings for receipt of said inserts, and further wherein said inserts include secondary openings therein for receipt of sub-inserts; and

said assembling step includes selected inclusion of sub-inserts of known density and dimensions in the insert secondary openings.

22. A method as in claim 21, wherein said assembling step includes the step of selecting use of given mother rings and sub-inserts based on the relative dimensions thereof in relation to the size of an intended object to be scanned with the system and the anticipated size of defects in such intended object, generally such that the dimensions of the largest mother ring selected are at least as large as the intended object to be scanned, and the dimensions of the smallest sub-insert selected are no larger than the smallest anticipated defect in such intended object.

23. A method as in claim 21, wherein said assembling step further includes selectively entrapping air or non-corrosive fluids of known density in predetermined areas of the assembled configuration, for further variety in the known density and location of material to be scanned.

24. A method as in claim 21, wherein said primary and secondary openings and said inserts and sub-inserts comprise corresponding selected geometric shapes, including circular shapes to selectively avoid artifact stimulation, and rectangular shapes to selectively stimulate artifact generation, whereby selective use of rectangular shapes permits simultaneous testing of geometry and density resolution with a single opening/insert pair.

25. A method as in claim 20, wherein:

the interchangeable pieces are generally planar and have respective thicknesses which are greater than the usual thickness of a given plane to be scanned with the computer tomography system; and

the assembling step includes the stacking of at least two thicknesses of some of the interchangeable pieces of the same or of differing densities to permit testing of the level of system rejection of scan information from adjacent planar locations, outside the intended given plane to be scanned.

26. A method as in claim 20, further including the step of placing a test piece of known size and density on the computer tomography system exposure support surface, outside the assembled configuration of said interchangeable pieces, to permit monitoring of drift in relative density indications from one processed image to another, by not changing such test piece between formation of such images.