Dynamic collimators

• US 6,353,227 B1
• Filed: 08/11/1999
• Issued: 03/05/2002
• Est. Priority Date: 12/18/1998
• Status: Expired due to Fees

• Current Assignee: Izzie Boxen
• Original Assignee: Izzie Boxen
• Inventors: Boxen, Izzie
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): HANIG, RICHARD E
• Application Number:
  US09/372,071
• Time in Patent Office: 937 Days
• Field of Search: 250/363.1, 250/363.06, 250/363.07, 250/505.1, 378/147, 378/149, 378/154, 378/155
• US Class Current: 250/363.1
• CPC Class Codes: G21K 1/025 using multiple collimators, e.g. Bucky screens; other devices for eliminating undesired or dispersed radiation
• CPC Class Codes: G21K 1/04 using variable diaphragms, shutters, choppers

Abstract

Apparatus for collimating particle emanations, whether photons or material particles, comprises a collimator plate and a motion means. The collimator plate is made of an attenuating material capable of attenuating the particle emanations. The collimator has a plurality of apertures of defined cross-sectional diameter, cross-sectional shape and three-dimensional distribution which restricts the emanations to pass through the plate in a plurality of defined collimated beams. The motion means moves the collimator to enable the plurality of collimated beams to form a defined combined beam having a preselected cross-sectional distribution of flux, when averaged over a specified time. The resolution of the collimator is essentially the cross-sectional diameter of the apertures, which is limited only by technical manufacturing capabilities. This allows the final imaging or detecting resolution to be essentially the intrinsic resolution of the imaging or detecting device, such as a gamma camera, independent of the energy of the emanations. The collimator may also be used to produce beams of particles with predefined cross-sectional size, cross-sectional shape and cross-sectional relative flux, averaged over time, for physics experiments or other uses.

Claims

1. Apparatus for collimating particle emanations, comprising:

(a) a collimator plate made of an attenuating material capable of attenuating particle emanations, the collimator plate having a plurality of apertures of pre-selected cross-sectional shape and three-dimensional distribution for restricting the emanations to pass through in a plurality of defined collimated beams; and

(b) motion means operatively coupled to the collimator plate for moving the collimator plate as a whole relative to an emanation detector during a detection time, in a manner which enables the plurality of collimated beams to form a defined combined beam during the detection time yielding a pre-selected detector cross-sectional sampling of the emanations within an image space;

(c) wherein the collimator face is described by coordinates x and y, and the apertures are of such cross-sectional shape and distribution that the ratio of distance occupied by the apertures in the x-coordinate direction of motion to the distance traveled by the collimator as a whole in the x-coordinate direction during the detection time is essentially a constant, independent of y, for y orthogonal to x.

2. The apparatus defined in claim 1, wherein the collimator plate is planar and has:

(a) a beam exit face within a specified x-y plane having an x-axis defining distance in an x-direction and a y-axis perpendicular to the x-axis defining distance in a y-direction; and

(b) wherein the apertures in cross-section in the x-y plane are;

(i) arranged in rows and columns;

(ii) aligned in a specified direction with respect to the x-axis and the y-axis; and

(iii) arranged in a pattern of repeating cells of apertures extending a linear distance in the x-direction and y-direction, wherein the linear distance in the x-direction occupied by apertures in each of the cells is a constant, independent of the distance in the y-direction.

3. The apparatus defined in claim 2, wherein the apertures are arranged with central long axes:

(i) parallel to each other; and

(ii) at a specified three-dimensional angle to the x-y plane.

4. The apparatus defined in claim 2, wherein the apertures are arranged:

(i) in rows, specified by position y, with central long axes parallel to each other; and

(ii) in columns, specified by position x, with the central long axes convergent on a specified line coplanar with the x-axis and parallel to the x-y plane, and with the apertures tapered in the plane specified by each column, proportionally to the separation of their central long axes.

5. The apparatus defined in claim 2, wherein the apertures are arranged:

(i) in rows, specified by position y, with central long axes convergent on a specified line coplanar with the y-axis and parallel to the x-y plane, and with apertures tapered in the plane specified by each such row in proportion to the separation of their central long axes; and

(ii) in columns, specified by position x, with central long axes parallel to each other.

6. The apparatus defined in claim 1, wherein the collimator plate is a shell section of a rectangular cylinder, having a central axis, straight sides and length parallel to the central axis, and a curved beam exit face lying in a curvilinear plane defined by x and y curvilinear orthogonal coordinates embedded in the beam exit face such that one of x, y is specified as parallel to the central axis and with the apertures:

(a) in cross-section on the beam exit face being;

(i) arranged in rows and columns specified by the x and y coordinates, respectively;

(ii) aligned in a specified direction with respect to the x and y coordinates; and

(iii) arranged in a pattern of repeating cells of apertures extending in curvilinear distance along the x and y curvilinear coordinates, wherein the distance along the x coordinate occupied by apertures in each of the cells is a constant, independent of y.

7. The apparatus defined in claim 6, wherein the apertures are arranged with long axes:

(i) parallel to each other; and

(ii) at a specified three-dimensional angle to the curvilinear x-y plane.

8. The apparatus defined in claim 6, wherein the apertures are arranged:

(i) in rows, specified by position y, with central long axis parallel to each other; and

(ii) in columns, specified by position x, with central long axes convergent on a specified line parallel to the central axis, and with apertures tapered in the plane specified by each column, proportionally to the separation of their central axes.

9. The apparatus defined in claim 2, wherein the apertures have cross-sections in the beam exit face which are;

(a) of diameter d in the x-coordinate;

(b) separated by collimator septa of at least specified thickness T; and

(c) arranged in patterns of repeating cells with specified separation t≧

T of apertures in the x-coordinate and, thereby, with specified minimal cell x-coordinate dimension t+d.

10. The apparatus defined in claim 9, wherein the apertures have crosssections in the beam exit face which are:

(a) square, with sides parallel to the x and y-coordinates; and

(b) positioned such that, except for the edges of the collimators where cells are incomplete;

(i) there is zero separation along the y-coordinate of adjacent rows of apertures; and

(ii) for any chosen aperture, the next nearest aperture in the adjacent row in negative y-coordinate direction is separated in the positive x-coordinate direction from the chosen aperture by distance T=nd, where n is a positive integer, with the result that apertures in any row are separated by distance t=[(n+1)²−

1]d along the x-coordinate.

11. The apparatus defined in claim 10, wherein n=1.

12. The apparatus defined in claim 9, wherein the motion means moves the collimator plate in specified x-coordinate direction at specified constant speed through a distance that is a specified multiple of t+d.

13. The apparatus defined in claim 9, wherein the motion means moves the collimator plate in specified x-coordinate direction in steps:

(a) of specified size md, where 0<

m<

2;

(b) with time allotted for detection at each step a specified constant; and

(c) with total distance covered a specified multiple of t+d, with the result that the sampling of emanations within the image space is uniform for m=1 and substantially uniform otherwise.

14. The apparatus defined in claim 13, wherein the motion is repeated in specified combination of positive and negative x-coordinate directions, the last repeat not necessarily complete.

15. The apparatus defined in claim 1, wherein the collimator plate is planar and has:

(a) a beam exit face in a specified x-y plane; and

(b) the apertures in cross-section in the x-y plane are;

(i) arranged in concentric rings and radial columns, thereby defining a central axis;

(ii) arranged with septum thickness at least specified value T; and

(iii) arranged in a pattern of repeating cells of apertures around any ring, such that, the fraction of distance along any circular arc occupied by apertures in each of the cells is a constant, independent of radial distance from the center, except for a central portion in which there are no apertures.

16. The apparatus defined in claim 15, wherein the apertures are arranged with their central long axes parallel to the central axis of the collimator aperture pattern.

17. The apparatus defined in claim 15, wherein the apertures are arranged with their central long axes convergent on a specified point, and with the apertures tapered in proportion to the separation of their central long axes.

18. The apparatus defined in claim 15, wherein the motion means rotates the collimator plate about the central axis at a constant speed.

19. The apparatus defined in claim 1, wherein the apertures have a maximum diameter less than half the linear resolution capability of apparatus used to detect the collimated beams.

20. The apparatus defined in claim 1, wherein the collimator plate is planar and has:

(a) a beam exit face within a specified x-y plane; and

(b) the apertures in cross-section in the x-y plane;

(i) are square, with sides of specified linear size d, and oriented with sides parallel to the x and y-axes;

(ii) arranged in rows and columns separated in each row and each column by distance T=nd, n a positive integer; and

(c) the apertures have central long axes parallel to each other and at a specified three-dimensional angle to the x-y plane.

21. The apparatus defined in claim 20, wherein the motion is linear, of constant speed, in positive x-direction, through distance (n+1)d, followed by a step in the negative y-direction and repeat of the motion in negative x-direction, followed by another step in the negative y-direction and repeat of the motion in the positive x-direction, and so on until n+1 rows have been passed over, with repeat of this whole process a specified multiple number of times, the last of which need not necessarily be complete.

22. The apparatus defined in claim 1,

wherein the collimator plate comprises at least two stacked plate members, the stacked plate members comprising at least a first plate member having first apertures arranged in a pre-selected plate aperture pattern and a second plate member adjacent the first plate member having second apertures arranged in the preselected plate aperture pattern,

wherein the plate members are displaced relative to each other such that the first apertures are offset diagonally from the second apertures in a specified direction and by a specified amount, resulting in obscuring part of the apertures and forming an aperture pattern for the collimator plate similar to the pre-selected plate aperture pattern, but with smaller apertures.

23. The apparatus defined in claim 1, wherein the apertures are arranged in a two-dimensional pattern extending in a first direction along a first axis and a second direction along a second axis not perpendicular to the first axis, the pattern comprising a repeating unit cell of apertures, wherein within the unit cell of the pattern, the ratio of the distance along the first axis taken up by the apertures to the total distance in the first direction taken up by the pattern is a constant independent of second direction.

24. The apparatus defined in claim 1, wherein the motion means comprises a motor operatively coupled to the collimator plate, and an electronic controller for controlling the operation of the motor.

25. Apparatus for collimating particle emanations, comprising:

(a) a collimator plate having a plurality of apertures of pre-selected cross-sectional shape and three dimensional distribution, wherein the apertures are separated by septa made of a material capable of attenuating the particle emanations;

(b) a motor operatively coupled to the collimator plate for moving the collimator plate relative to an emanation detector during a detection time in a pre-determined manner of motion; and

(c) wherein the cross-sectional shape and the three-dimensional distribution are selected relative to the pre-determined manner of motion so as to achieve a substantially uniform sampling of the emanations within a pre-determined image space, as the motor moves the collimator plate during the detection time.

26. The apparatus defined in claim 25, wherein the manner of motion comprises movement in a direction of travel, and the shape and the distribution of the apertures are selected such that the ratio of the distance occupied by the apertures along an axis aligned with the direction of travel to the distance traveled by the collimator plate during the detection time is a constant throughout the collimator plate.

27. The apparatus defined in claim 25, wherein the collimator plate is planar and has:

(a) a beam exit face within a specified x-y plane having an x-axis defining distance in an x-direction and a y-axis perpendicular to the x-axis defining distance in a y-direction; and

(b) wherein the apertures in cross-section in the x-y plane are;

(i) arranged in rows and columns;

(ii) aligned in a specified direction with respect to the x-axis and the y-axis; and

(iii) arranged in a pattern of repeating cells of apertures extending a linear distance in the x-direction and y-direction, wherein the linear distance in the x-direction occupied by apertures in each of the cells is a constant, independent of the distance in the y-direction.

28. The apparatus defined in claim 25, wherein the collimator plate is planar and has:

(a) a beam exit face in a specified x-y plane; and

(b) the apertures in cross-section in the x-y plane are;

(i) arranged in concentric rings and radial columns, thereby defining a central axis;

(ii) arranged with septum thickness at least specified value T; and

(iii) arranged in a pattern of repeating cells of apertures around any ring, such that, the fraction of distance along any circular arc occupied by apertures in each of the cells is a constant, independent of radial distance from the center, except for a central portion in which there are no apertures.

29. The apparatus defined in claim 25, wherein the collimator plate comprises at least two stacked plate members, the stacked plate members comprising at least a first plate member having first apertures arranged in a preselected plate aperture pattern and a second plate member adjacent the first plate member having second apertures arranged in the preselected plate aperture pattern, wherein the plate members are displaced relative to each other such that the first apertures are offset diagonally from the second apertures in a specified direction and by a specified amount, resulting in obscuring part of the apertures and forming an aperture pattern for the collimator plate similar to the pre-selected plate aperture pattern, but with smaller apertures.

30. The apparatus defined in claim 25, wherein the apertures are arranged in a two-dimensional pattern extending in a first direction along a first axis and a second direction along a second axis not perpendicular to the first axis, the pattern comprising a repeating unit cell of apertures, wherein within the unit cell of the pattern, the ratio of the distance along the first axis taken up by the apertures to the total distance in the first direction taken up by the pattern is a constant independent of second direction.

31. The apparatus defined in claim 25, wherein the motor comprises an electric motor operatively coupled to the collimator plate, and an electronic controller for controlling the operation of the electric motor during the detection time.