METHOD FOR REDUCING X-RAY TUBE POWER DE-RATING DURING DYNAMIC FOCAL SPOT DEFLECTION

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the components inside a typical X-ray tube that utilizes focal spot deflection;

FIG. 2 is a graph illustrating a heating and cooling cycle for a particular point in the focal spot on the anode without focal spot deflection;

FIG. 3 is a graph illustrating a heating and cooling cycle for a particular point on a rotating anode X-tube with dynamic focal spot deflection where the transition time, anode rotation frequency, deflection distance and target radius are selected such that the relative speed between the target surface and the electron beam impact area is zero;

FIG. 4 is a flowchart of a method to reduce X-ray tube power de-rating during dynamic focal spot deflection according to an embodiment;

FIG. 5 is a graph illustrating a heating and cooling cycle for a particular point on a rotating anode X-ray tube with dynamic focal spot deflection where beam manipulation is used to reduce anode heating where the transition time, anode rotation frequency, deflection distance and target radius are selected such that the relative speed between the target surface and the electron beam impact area is zero;

FIG. 6 is a flowchart of a method to reduce X-ray tube power de-rating during dynamic focal spot deflection according to an embodiment;

FIG. 7 is a flowchart of a method to reduce X-ray tube power de-rating during dynamic focal spot deflection according to an embodiment; and

FIG. 8 is a block diagram of the hardware and operating environment in which different embodiments can be practiced.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense.

Method Embodiments

FIG. 4 is a flowchart of a method to reduce X-ray tube power de-rating during dynamic focal spot deflection according to an embodiment. Method 400 solves the need in the art to reduce X-ray tube power below manufacturer's limits to prevent overheating during oversampling.

In one embodiment, Method 400 includes generating an electron beam in a rotating anode X-ray tube 402, focusing the electron beam to a first position on an anode 404, defocusing the electron beam on the anode 406 and refocusing the electron beam at a second position on anode 408.

In reference to FIG. 5, when the electron beam 108 is focused to the first position 120, the impact area begins to heat up rapidly as shown. Prior to deflecting the electron beam 108 in the +x-direction to a second location 122, the electron beam 108 is defocused. The flux density of the defocused beam is reduced as the beam is spread out over a larger area. The impact temperature decreases as the flux density decreases. The electron beam is then refocused at the second position 122 on the anode 110 and the impact temperature begins to increase and peak a second time but total heating will be minimized because of the additional cooling obtained by defocusing the electron beam 108 during the transition.

In one embodiment, the electron beam 108 is focused to a first focal spot position 120 on anode 110 by applying a bias voltage 114 to a first electrode 112 and by applying a second bias voltage 118 to a second electrode 116 where the second bias voltage 118 is less than the first bias voltage 114. In another embodiment, magnets are placed in close proximity to the electron beam 108 in place of or in conjunction with biasing the electrodes 112, 116 to focus the electron beam 108 to first position 120 on the anode 110.

In another embodiment, the electron beam 108 is defocused prior to transitioning to a second position 122 on an anode 110 using electrostatic means by increasing the second bias voltage 118 on the second electrode 116. Increasing the second bias voltage 118 such that it approximates the first bias voltage 114 causes electron beam 108 to spread out across the transition area thereby reducing the flux density and the peak temperature of any particular spot in the transition area on the anode 110.

In another embodiment, the electron beam 108 is defocused by applying a magnetic field near the electron beam 108 where the magnetic poles spread the electron beam causing a reduction in flux density for any particular spot in the impact area on the anode 110.

In another embodiment, the electron beam 108 is refocused to a second position 122 on an anode 110 by decreasing a first bias voltage 114 on a first electrode 112 to a voltage less than a second bias voltage 118 on a second electrode 116. The differential in voltages will cause the electron beam 108 to move in the +x direction and focus on the second position 122 on the anode where the second position is located on a nominal focal spot radius 124 on the anode 110. In another embodiment, magnetic fields are used to move the electron beam 108 in the +x direction and to focus it on the second position 122.

In another embodiment, the electron beam is inhibited by applying a reverse bias to at least one electrode 112, 116, 126, 128 that is sufficiently strong to deflect the electron beam 108 and prevent it from impacting the surface of the anode 110 during the transition from a first position 120 and a second position 122 on the anode 110. The temperature of the anode decreases because the electron beam is prevented from impacting the anode.

In another embodiment, the electron beam is inhibited by applying a reverse bias to a dedicated beam suppression electrode (not shown) which is sufficiently strong to suppress the electron beam 108 and prevent it at least partially from impacting the surface of the anode 110 during the transition from a first position 120 and a second position 122 on the anode 110. The temperature of the anode decreases because some or all of the electron beam is prevented from impacting the anode.

In another embodiment, a method for reducing X-ray tube power de-rating during dynamic focal spot deflecting comprising generating an electron beam in a rotating anode X-ray tube 402, then focusing the electron beam to a first position on the anode 404, then steering the electron beam away from a nominal focal spot radius on the anode 702 and then refocusing the electron beam at a second position on the anode 408. The steering can be accomplished using electrostatic or magnetostatic means. Typically the electron beam would be steered to a larger focal spot radius where the impact temperature is reduced inversely proportional to the focal spot radius. The beam would then be advanced in +x direction to the new x-location. Finally the focal spot would be refocused at the second position by moving the electron beam radially to the nominal focal spot radius.

In yet another embodiment, the electron beam 108 is steered away from the nominal focal spot area 124 during the transition from a first position 120 on an anode 110 and a second position 122 on an anode 110 by biasing one or more electrodes 112, 116, 126, 128 to deflect and/or defocus the electron beam 108 out of the first position 120 on the anode 110. The electron beam can be steered in the +x or −x direction using electrodes 112, 116 such that the beam impact area is outside the nominal focal spot radius 124 on the anode or the beam may be steered to a different radius on the anode using electrodes 126, 128. The electron beam can be steering to practically any area on the anode 108 using different electrodes and biases to attract and deflect the electron beam 108.

After the electron beam 108 is moved outside the nominal focal spot radius 124 on the anode 110, the temperature on the impact area at the first position 120 decreases rapidly. As the beam deflected in the +x direction to its second position 122 and refocused on the second position 122 for oversampling, the anode 110 begins to heat up again but the maximum temperature of any spot in the nominal focal spot has been decreased.

In yet another embodiment, the electron beam is steered using magnetic fields.

FIG. 8 is a block diagram of the hardware and operating environment 800 in which different embodiments can be practiced. Through beam steering, inhibiting or defocusing the beam during the transition, the additional heating cycle is minimized as the electron beam 108 is refocused on the second position 112 on the anode 110. The reduction in anode temperature achieved through the precise manipulation of the electron beam during the transition from the first position 120 to the second position 122 allows the use of higher tube power without requiring the X-ray tube power de-rating to stay within the manufacturers maximum ratings.

In some embodiments, methods 400, 600-700 are implemented as a computer data signal embodied in a carrier wave, that represents a sequence of instructions which, when executed by a processor, such as processor 404 in FIG. 8, cause the processor to perform the respective method. In other embodiments, methods 400, 600-700 are implemented as a computer-accessible medium having executable instructions capable of directing a processor, such as processor 804 in FIG. 8, to perform the respective method. In varying embodiments, the medium is a magnetic medium, an electronic medium, or an optical medium.

Hardware and Operating Environment

FIG. 8 is a block diagram of the hardware and operating environment 800 in which different embodiments can be practiced. The description of FIG. 8 provides an overview of computer hardware and a suitable computing environment in conjunction with which some embodiments can be implemented. Embodiments are described in terms of a computer executing computer-executable instructions. However, some embodiments can be implemented entirely in computer hardware in which the computer-executable instructions are implemented in read-only memory. Some embodiments can also be implemented in client/server computing environments where remote devices that perform tasks are linked through a communications network. Program modules can be located in both local and remote memory storage devices in a distributed computing environment.

Computer 802 includes a processor 804, commercially available from Intel, Motorola, Cyrix and others. Computer 802 also includes random-access memory (RAM) 806, read-only memory (ROM) 808, and one or more mass storage devices 810, and a system bus 812, that operatively couples various system components to the processing unit 804. The memory 806, 808, and mass storage devices, 810, are types of computer-accessible media. Mass storage devices 810 are more specifically types of nonvolatile computer-accessible media and can include one or more hard disk drives, floppy disk drives, optical disk drives, and tape cartridge drives. The processor 804 executes computer programs stored on the computer-accessible media.

Computer 802 can be communicatively connected to the Internet 814 via a communication device 816. Internet 814 connectivity is well known within the art. In one embodiment, a communication device 816 is a modem that responds to communication drivers to connect to the Internet via what is known in the art as a “dial-up connection.” In another embodiment, a communication device 816 is an Ethernet® or similar hardware network card connected to a local-area network (LAN) that itself is connected to the Internet via what is known in the art as a “direct connection” (e.g., T1 line, etc.).

A user enters commands and information into the computer 802 through input devices such as a keyboard 818 or a pointing device 820. The keyboard 818 permits entry of textual information into computer 802, as known within the art, and embodiments are not limited to any particular type of keyboard. Pointing device 820 permits the control of the screen pointer provided by a graphical user interface (GUI) of operating systems such as versions of Microsoft Windows®. Embodiments are not limited to any particular pointing device 820. Such pointing devices include mice, touch pads, trackballs, remote controls and point sticks. Other input devices (not shown) can include a microphone, joystick, game pad, satellite dish, scanner, or the like.

In some embodiments, computer 802 is operatively coupled to a display device 822. Display device 822 is connected to the system bus 812. Display device 822 permits the display of information, including computer, video and other information, for viewing by a user of the computer. Embodiments are not limited to any particular display device 822. Such display devices include cathode ray tube (CRT) displays (monitors), as well as flat panel displays such as liquid crystal displays (LCD's). In addition to a monitor, computers typically include other peripheral input/output devices such as printers (not shown). Speakers 824 and 826 provide audio output of signals. Speakers 824 and 826 are also connected to the system bus 812.

Computer 802 also includes an operating system (not shown) that is stored on the computer-accessible media RAM 806, ROM 808, and mass storage device 810, and is and executed by the processor 804. Examples of operating systems include Microsoft Windows®, Apple MacOS®, Linux®, UNIX®. Examples are not limited to any particular operating system, however, and the construction and use of such operating systems are well known within the art.

Embodiments of computer 802 are not limited to any type of computer 802. In varying embodiments, computer 802 comprises a PC-compatible computer, a MacOS®-compatible computer, a Linux®-compatible computer, or a UNIX®-compatible computer. The construction and operation of such computers are well known within the art.

Computer 802 can be operated using at least one operating system to provide a graphical user interface (GUI) including a user-controllable pointer. Computer 802 can have at least one web browser application program executing within at least one operating system, to permit users of computer 802 to access intranet or Internet world-wide-web pages as addressed by Universal Resource Locator (URL) addresses. Examples of browser application programs include Netscape Navigator® and Microsoft Internet Explorer®.

The computer 802 can operate in a networked environment using logical connections to one or more remote computers, such as remote computer 828. These logical connections are achieved by a communication device coupled to, or a part of, the computer 802. Embodiments are not limited to a particular type of communications device. The remote computer 828 can be another computer, a server, a router, a network PC, a client, a peer device or other common network node. The logical connections depicted in FIG. 8 include a local-area network (LAN) 830 and a wide-area network (WAN) 832. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet.

When used in a LAN-networking environment, the computer 802 and remote computer 828 are connected to the local network 830 through network interfaces or adapters 834, which is one type of communications device 816. Remote computer 828 also includes a network device 836. When used in a conventional WAN-networking environment, the computer 802 and remote computer 828 communicate with a WAN 832 through modems (not shown). The modem, which can be internal or external, is connected to the system bus 812. In a networked environment, program modules depicted relative to the computer 802, or portions thereof, can be stored in the remote computer 828.

Computer 802 also includes power supply 838. Each power supply can be a battery.

CONCLUSION

A method for reducing X-ray tube power de-rating during dynamic focal spot deflection is described. Although specific embodiments are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations. For example, although described as pertaining to X-ray tubes used in CT systems, one of ordinary skill in the art will appreciate that implementations can be made in any usage where X-ray generation is desired or any other X-ray system that provides the required function.

In particular, one of skill in the art will readily appreciate that the names of the methods and apparatus are not intended to limit embodiments. Furthermore, additional methods and apparatus can be added to the components, functions can be rearranged among the components, and new components to correspond to future enhancements and physical devices used in embodiments can be introduced without departing from the scope of embodiments. One of skill in the art will readily recognize that embodiments are applicable to different manners of producing an electron beam. Also, although the generation of the electron beam is described as boiling electrons off a heated filament, any form of electron gun may be substituted and still provide the required function. Also, although an X-ray tube with four electrodes is described, the method may be practiced with at least two electrodes.

Claims

1. A method for reducing X-ray tube power de-rating during dynamic focal spot deflection comprising: generating an electron beam in a rotating anode X-ray tube;focusing the electron beam to a first position on an anode;defocusing the electron beam on the anode; andrefocusing the electron beam at a second position on the anode.
2. The method of claim 1 wherein focusing the electron beam to a first position further comprises: biasing a first electrode with a first bias voltage; andbiasing a second electrode with a second bias voltage where the second bias voltage is less than the first bias voltage to direct the electron beam to a first position located on a nominal focal spot radius on the anode.
3. The method of claim 1 wherein defocusing the electron beam further comprises: increasing a bias voltage on a second electrode to defocus the electron beam.
4. The method of claim 1 wherein refocusing the electron beam at a second position on the anode further comprises: decreasing a first bias voltage on a first electrode to a voltage less than a second bias voltage on a second electrode to direct and focus the electron beam to a second position located on a nominal focal spot radius on the anode.
5. The method of claim 1 wherein focusing the electron beam to a first position further comprises: applying one or more magnetic field to direct the electron beam to a first position.
6. The method of claim 1 wherein defocusing the electron beam further comprises: applying one or more magnetic field to defocus the electron beam.
7. The method of claim 1 wherein refocusing the electron beam at a second position on the anode further comprises: applying one or more magnetic fields to refocus the electron beam at the second position on the anode.
8. A method for reducing X-ray tube power de-rating during dynamic focal spot deflection comprising: generating an electron beam in a rotating anode X-ray tube;biasing a first electrode with a first bias voltage;biasing a second electrode with a second bias voltage where the second bias voltage is less than the first bias voltage to direct the electron beam to a first position located on a nominal focal spot radius on the anode;increasing the bias voltage on the second electrode to defocus the electron beam; anddecreasing the bias voltage on the first electrode where the first bias voltage is less than the second bias voltage to direct the electron beam to a second position located on the nominal focal spot radius on the anode.
9. A method for reducing X-ray tube power de-rating during dynamic focal spot deflection comprising: generating an electron beam in a rotating anode X-ray tube;focusing the electron beam to a first position on an anode;inhibiting part or all of the electron beam; andrefocusing the electron beam at a second position on the anode.
10. The method of claim 9 wherein focusing the electron beam to a first position further comprises: biasing a first electrode with a first bias voltage; andbiasing a second electrode with a second bias voltage where the second bias voltage is less than the first bias voltage to direct an electron beam to a first position located on a nominal focal spot radius on the anode.
11. The method of claim 9, wherein inhibiting the electron beam further comprises: applying a reverse bias to at least one electrode to prevent part or all of the electron beam from impacting the anode.
12. The method of claim 9 wherein refocusing the electron beam at a second position on the anode further comprises: removing reverse bias from suppression electrode;biasing a first electrode with a first bias voltage; andbiasing a second electrode with a second bias voltage where the second bias voltage is greater than the first bias voltage to direct the electron beam to a second position located on a nominal focal spot radius on the anode.
13. A method for reducing X-ray tube power de-rating during dynamic focal spot deflection comprising: generating an electron beam in a rotating anode X-ray tube;biasing a first electrode with a first bias voltage;biasing a second electrode with a second bias voltage where the second bias voltage is less than the first bias voltage to direct an electron beam to a first position located on a nominal focal spot radius on the anode;applying a reverse bias to the first and second electrodes to prevent part or all of the electron beam from impacting the anode; andbiasing a first electrode with a first bias voltage while simultaneously biasing a second electrode with a second bias voltage where the second bias voltage is greater than the first bias voltage to direct the electron beam to a second position located on the nominal focal spot radius on the anode.
14. A method for reducing X-ray tube power de-rating during dynamic focal spot deflection comprising: generating an electron beam in a rotating anode X-ray tube;focusing the electron beam to a first position on the anode;steering the electron beam away from a nominal focal spot radius on the anode; andrefocusing the electron beam at a second position on the anode.
15. The method of claim 14 wherein focusing the electron beam to a first position further comprises: biasing a first electrode with a first bias voltage; andbiasing a second electrode with a second bias voltage where the second bias voltage is less than the first bias voltage to direct the electron beam to a first position located on a nominal focal spot radius on the anode.
16. The method of claim 14 wherein steering the electron beam away from the nominal focal spot area further comprises: biasing one or more electrodes to deflect the electron beam out of a nominal focal spot radius on the anode.
17. The method of claim 14 wherein refocusing the electron beam at a second position on the anode further comprises: biasing a first electrode with a first bias voltage; andbiasing a second electrode with a second bias voltage where the second bias voltage is greater than the first bias voltage to direct the electron beam to a second position located on a nominal focal spot radius on the anode.
18. The method of claim 14 wherein focusing the electron beam to a first position further comprises: applying one or more magnetic fields to direct the electron beam to a first position.
19. The method of claim 14 wherein steering the electron beam away from the nominal focal spot area further comprises: applying one or more magnetic field to deflect the electron beam out of the nominal focal spot radius on the anode.
20. The method of claim 14 wherein refocusing the electron beam at a second position on the anode further comprises: applying one or more magnetic fields to refocus the electron beam at the second position on the anode.
21. A method for reducing X-ray tube power de-rating during dynamic focal spot deflection comprising: generating an electron beam in a rotating anode X-ray tube;biasing a first electrode with a first bias voltage;biasing a second electrode with a second bias voltage where the second bias voltage is less than the first bias voltage to direct the electron beam to a first position located on a nominal focal spot radius of the anode;biasing one or more electrodes to deflect the electron beam out of the nominal focal spot radius on the anode;biasing the first electrode with a third bias voltage; andbiasing a second electrode with a fourth bias voltage where the fourth bias voltage is greater than the third bias voltage to direct the electron beam to a second position located on the nominal focal spot radius of the anode.

METHOD FOR REDUCING X-RAY TUBE POWER DE-RATING DURING DYNAMIC FOCAL SPOT DEFLECTION

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