Scattered-ray grid, particularly for a medical X-ray device, and a method of determining the position of the absorption elements of a scattered-ray grid

• US 6,324,259 B1
• Filed: 05/03/2000
• Issued: 11/27/2001
• Est. Priority Date: 05/03/1999
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Lehmann, Volker, Keller, Wolfgang
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): Ho, Allen C.
• Application Number:
  US09/564,463
• Time in Patent Office: 573 Days
• Field of Search: 378/154, 378/155
• US Class Current: 378/154
• CPC Class Codes: A61B 6/027 characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
• CPC Class Codes: A61B 6/107 Protection against radiation, e.g. shielding
• CPC Class Codes: G03B 42/02 using X-rays
• CPC Class Codes: G21K 1/025 using multiple collimators, e.g. Bucky screens; other devices for eliminating undesired or dispersed radiation

Abstract

A scattered-ray grid has a carrier with absorption elements arranged thereon in spaced rows which proceed essentially spoke-like relative to a grid center. Except for one or more rows which originate at the grid center, the individual rows of the scattered-ray grid, or of substantially identical grid sectors of the scattered-ray grid each originate from respectively different radii. The origin of each row is situated in an angle section, which is determined on the basis of at least two points lying on a circle, or an arc of circle, with a predetermined radius and which is divided in a predefined ratio for determining the position of the origin. The predetermined radius is incremented in a stepwise manner to define respective origins for all of the rows.

Claims

1. In a scattered-ray grid having a carrier on which a plurality of radiation absorption elements are disposed in a plurality of rows, said grid having a grid center and each of said rows having an origin and radiating spoke-like away from said grid center, the improvement comprising:

at least one of said rows having an origin at said grid center; and

the respective origins of rows, other than said at least one row originating at said grid center, being disposed at intersections of respective radial lines with at least an arc of respective circles of predetermined radii relative to said grid center, each of said radial lines dividing an angle section between two adjacent rows by a predetermined ratio.

2. The improvement of claim 1 wherein only one of said rows originates at said grid center, and all other rows in said plurality of rows have respective origins at different radii relative to said grid center.

3. The improvement of claim 1 wherein each of said radial lines divides an angle section between two adjacent rows by a predetermined ratio p:

q, with p≠

q.

4. In a scattered-ray grid having a carrier on which a plurality of radiation absorption elements are disposed in a plurality of rows, said grid having a grid center and each of said rows having an origin and radiating spoke-like away from said grid center, the improvement comprising:

said grid being divided into a plurality of identical grid sectors;

in each of said grid sectors, at least one of said rows having an origin at said grid center; and

in each of said grid sectors, the respective origins of rows, other than said at least one row originating at said grid center, being disposed at intersections of respective radial lines with at least an arc of respective circles of predetermined radii relative to said grid center, each of said radial lines dividing an angle section between two adjacent rows by a predetermined ratio.

5. The improvement of claim 4 wherein, in each of said grid sectors, only one of said rows originates at said grid center, and all other rows in each of said sectors have respective origins at different radii relative to said grid center.

6. The improvement of claim 4 wherein each of said radial lines divides an angle section between two adjacent rows by a predetermined ratio p:

q, with p≠

q.

7. In a scattered-ray grid having a carrier on which a plurality of radiation absorption elements are disposed in a plurality of rows, said grid having a grid center and each of said rows having an origin and radiating spoke-like away from said grid center, a method for determining placement of the respective origins of said rows on said carrier comprising the steps of:

originating at least one of said rows at said grid center; and

placing the respective origins of rows, other than said at least one row originating at said grid center, at intersections of respective radial lines with at least an arc of respective circles of predetermined radii relative to said grid center, each of said radial lines dividing an angle section between two adjacent rows by a predetermined ratio.

8. A method as claimed in claim 7 comprising originating only one of said rows at said grid center, and placing the respective origins of all rows, other than said one row originating at said grid center, at different radii relative to said grid center.

9. A method as claimed in claim 8 comprising determining said different radii by starting with a predetermined origin radius and incrementing said predetermined origin radius in successive equal increments.

10. A method as claimed in claim 9 comprising:

(a) starting with a single row originating at said grid center and dividing an angle of 360°

defined by said single row originating at said grid center by a radial line at said predetermined ratio, and placing the origin of a next row at an intersection between said radial line and a circle having said predetermined origin radius;

(b) identifying a largest angle section between said next row and said radial line and dividing said largest angle section with a new radial line at said predetermined ratio and incrementing a radius of said circle having said predetermined origin radius by said increment to obtain a new circle and placing the origin of a next row at an intersection of said new line and said new circle; and

(c) repeating step (b) a selected number of times for successive new radial lines and with successive increments of said new circle by said equal increments.

11. A method as claimed in claim 7 comprising:

(a) starting with a circle of a predetermined origin radius and originating two of said rows at said grid center, said two rows intersecting said circle having said predetermined origin radius respectively at two points and defining an angle section therebetween;

(b) dividing said angle section with a line at said predetermined ratio and originating a next row at an intersection of said line and said circle having said predetermined origin radius, and thereby defining a largest remaining angle section between adjacent rows;

(c) incrementing said circle having said predetermined origin radius by an increment to obtain a new circle and dividing said largest angle section with a new line at said predetermined ratio and originating a next row at an intersection of said new line and said new circle, and thereby defining a new largest angle section between adjacent rows; and

(d) repeating step (c) for successive equal increments of said new circle by said increment.

12. A method as claimed in claim 11, comprising determining each new angle section by the steps of:

identifying said new angle section as an angle section having a largest sum of said angle section plus an additional angle value, and determining said additional angle value by weighting, with a predetermined weighting factor or, angular spacings from the adjacent rows of said angle section respectively to adjacent rows on opposite sides of said angle section.

13. A method as claimed in claim 12 comprising using a value for said weighting factor which is less than 1.

14. A method as claimed in claim 7 comprising using a ratio p:

q as said predetermined ratio, with p≠

q.

15. In a scattered-ray grid having a carrier on which a plurality of radiation absorption elements are disposed in a plurality of rows, said grid having a grid center and each of said rows having an origin and radiating spoke-like away from said grid center, a method for determining placement of the respective origins of said rows on said carrier comprising the steps of:

dividing said grid into a plurality of identical grid sectors

in each of said grid sectors, originating at least one of said rows at said grid center; and

in each of said grid sectors, placing the respective origins of rows, other than said at least one row originating at said grid center, intersections of respective radial lines with at least an arc of respective circles of predetermined radii relative to said grid center, each of said lines dividing an angle section between two adjacent rows by a predetermined ratio.

16. A method as claimed in claim 15 comprising in each of said grid sectors, originating only one of said rows at said grid center, and placing the respective origins of all rows in each of said grid sectors, other than said one row originating at said grid center, at different radii relative to said grid center.

17. A method as claimed in claim 16 comprising determining said different radii by starting with a predetermined origin radius and incrementing said predetermined origin radius in successive equal increments.

18. A method as claimed in claim 17 comprising:

(a) starting with a single row originating at said grid center and dividing an angle of 360°

defined by said single row originating at said grid center by a radial line at said predetermined ratio, and placing the origin of a next row at an intersection between said radial line and a circle having said predetermined origin radius;

(b) identifying a largest angle section between said next row and said radial line and dividing said largest angle section with a new radial line at said predetermined ratio and incrementing a radius of said circle having said predetermined origin radius by said increment to obtain a new circle and placing the origin of a next row at an intersection of said new line and said new circle; and

(c) repeating step (b) a selected number of times for successive new radial lines and with successive increments of said new circle by said equal increments.

19. A method as claimed in claim 15 comprising:

(a) starting with a circle of a predetermined origin radius and originating two of said rows at said grid center, said two rows intersecting said circle having said predetermined origin radius respectively at two points and defining an angle section therebetween;

(b) dividing said angle section with a line at said predetermined ratio and originating a next row at an intersection of said line and said circle having said predetermined origin radius, and thereby defining a largest remaining angle section between adjacent rows;

(c) incrementing said circle having said predetermined origin radius by an increment to obtain a new circle and dividing said largest angle section with a new line at said predetermined ratio and originating a next row at an intersection of said new line and said new circle, and thereby defining a new largest angle section between adjacent rows; and

(d) repeating step (c) for successive equal increments of said new circle by said increment.

20. A method as claimed in claim 19, comprising determining each new angle section by the steps of:

identifying said new angle section as an angle section having a largest sum of said angle section plus an additional angle value, and determining said additional angle value by weighting, with a predetermined weighting factor, angular spacings from the adjacent rows of said angle section respectively to adjacent rows on opposite sides of said angle section.

21. A method as claimed in claim 20 comprising using a value for said weighting factor which is less than 1.

22. A method as claimed in claim 15 comprising using a ratio p:

q as said predetermined ratio, with p≠

q.