Magnetically shielded x-ray tube

• US 20070030958A1
• Filed: 07/11/2006
• Published: 02/08/2007
• Est. Priority Date: 07/15/2005
• Status: Active Grant

• Current Assignee: Stereotaxis, Inc.
• Original Assignee: Stereotaxis, Inc.
• Inventors: Munger, Gareth T.
• Granted Patent: US 7,416,335 B2
• Time in Patent Office: Days
• US Class Current: 378/203
• CPC Class Codes: H01J 2235/166 against electromagnetic radiation
• CPC Class Codes: H01J 35/16 Vessels; Containers; Shields associated therewith

Abstract

Methods of designing an x-ray tube shielded for operation in static and dynamic externally applied magnetic fields are described. The methods include passive shielding of the insert frame, housing, design of an external shield envelope, tube port, tube collimator, and combinations thereof. The resulting x-ray tube devices are appropriate for use in a variety of applications ranging from magnetic navigation with x-ray monitoring and guidance for interventional procedures to multi-modality imaging and interventional procedures using an x-ray system in the vicinity of an MRI system.

Claims

1. A method for the design of an x-ray tube passively shielded from an externally applied magnetic field, comprising:

(a) selecting magnetically permeable materials suitable for the design of at least two of the group of x-ray tube components consisting of an x-ray tube insert frame, an x-ray tube housing, an x-ray tube external shield envelope, an x-ray tube port, and an x-ray tube scatter cone; and

(b) combining the x-ray tube components of step (a) with x-ray tube components made of non-permeable materials to obtain an x-ray tube that shields the space between the insert cathode and the insert anode from an externally applied magnetic field.

2. The method of claim 1 further comprising:

(a) determining the maximum acceptable magnetic field within the x-ray tube insert;

(b) determining the maximum externally applied magnetic field magnitude; and

(c) determining the maximum shielded tube weight;

whereby the x-ray tube design meets the weight constraints of step (c) and the reduced field within the insert frame is less than the maximum of step (a) when the x-ray tube is subjected to an externally applied field of magnitude less than that of the maximum of step (b).

3. The method of claim 1, wherein the step (a) of selecting magnetically permeable materials suitable for the design further comprises selecting at least two materials with different permeability and magnetic saturation properties.

4. The method of claim 3, wherein the materials are selected to form a layered magnetic shield.

5. The method of claim 4, wherein the material selected for the outer shield layer has higher magnetic saturation than the material selected for the inner shield layer.

6. A method for the design of an x-ray tube shielded from an externally applied magnetic field, comprising:

(a) selecting magnetically permeable materials suitable for the design of at least two of the group of x-ray tube components consisting of an x-ray tube insert frame, an x-ray tube housing, an x-ray tube external shield envelope, an x-ray tube port, and an x-ray tube scatter cone;

(b) combining the x-ray tube components of step (a) with x-ray tube components made of non-permeable materials to obtain an x-ray tube that shields the space between the insert cathode and the insert anode from an externally applied magnetic field; and

(c) selecting an active shielding method from the group comprised of active electromagnetic shielding, active electrostatic shielding, and permanent magnetic desensitization.

7. An x-ray tube for operation in an externally applied magnetic field, comprising means for passive shielding of at least two of the group consisting of an x-ray tube insert frame, an x-ray tube housing, an external tube shield, an x-ray tube port, and an x-ray tube scatter cone.

8. The x-ray tube of claim 7, further comprising means for active shielding of the anode-cathode space.

9. The x-ray tube of claim 7, wherein the means for active shielding is selected from the group consisting of active electromagnetic shielding and active electrostatic shielding.

10. The x-ray tube of claim 9, wherein the electrostatic voltages are determined by magnetic field measurements and estimations and calculating the necessary compensations.

11. The x-ray tube of claim 7, further comprising means for the generation of a magnetic field parallel to the anode-cathode axis.

12. The x-ray tube of claim 11, further comprising means for the detection of a residual field within the x-ray tube and means to generate the magnetic field parallel to the anode-cathode axis in function of the detected residual field.

13. The x-ray tube of claim 7, wherein the insert frame is made of a nickel-iron alloy approximately 3 mm thick and wherein the housing is made of a nickel-iron-cobalt alloy approximately 6 mm thick.

14. The x-ray tube of claim 7, wherein an external tube shield is made of a cast iron material approximately 6 mm thick and the housing is made of a nickel-iron-cobalt alloy approximately 6 mm thick.

15. The x-ray tube of claim 7, wherein an external tube shield is made of a cast iron material approximately 6 mm thick and the insert frame is made of a nickel-iron alloy approximately 3 mm thick.