X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1999-07-13
2001-06-26
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S004000
Reexamination Certificate
active
06252925
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to computed tomography and more particularly to performing high speed x-ray computed tomography with fiber waveguides.
In computed tomography, an x-ray source projects a fan-shaped beam at an object being imaged, such as a medical patient or an engineered part. The intensity of the transmitted radiation is dependent upon the attenuation of the x-ray beam by the object. The x-ray beam passes through the object and impinges upon an array of radiation detectors. Each detector in the array produces a separate electrical signal that is a measurement of the beam attenuation. The attenuation measurements from all of the detectors are acquired separately to produce a transmission profile.
In a conventional x-ray computed tomography (CT) system, the x-ray source and detector array are rotated on a gantry within the imaging plane and around the object, so that the angle at which the x-ray beam intersects the object constantly changes. A group of x-ray attenuation measurements from the detector array at a given angle is referred to as a “view”. A “scan” of the object represents a set of views made at different angular orientations during one revolution of the x-ray source and the detector. The data for a given scan is stored in memory as a two-dimensional array with storage locations along one axis of the array representing the data from each radiation detector and the storage locations along the other axis containing data for the different views. The scan data is then processed to construct an image that corresponds to a two-dimensional slice taken through the object. A series of two-dimensional slices are used to form a three-dimensional scan.
A problem with the conventional CT system is that its use in medical and industrial applications is limited by the speed of the x-ray source and the gantry that is used to rotate the source around the object being imaged. In particular, for medical applications, the gantry rotates the x-ray source around the object at a scan cycle ranging from about 0.5 seconds to about 1.0 seconds. The x-ray source uses x-ray tube inserts that have rotating target velocities ranging between 2000RPM and 9000 RPM. The dynamic forces resulting from moving a rotating target within a tube limit the gantry rotational speed. In addition to constraining scanning speed, the dynamic forces decrease the life of the x-ray tube and increase the amount of service needed to maintain the CT system. Typically, these x-ray tubes are limited to about 100,000 to about 200,000 scans. As a result of the decreased x-ray tube life and increased service, the overall reliability of the CT system for medical applications is jeopardized over time. In industrial applications, the conventional CT system has its limitations in viewing certain rotating components under load and for nondestructive testing of new designs. Viewing a component's internal mechanical integrity while under load is useful for design verification and optimization, quality assurance, and preventative maintenance. With the conventional CT system, incipient flaws and structural integrity are difficult to identify. Accordingly, there is a need for a faster, mechanically simpler, and more reliable CT system that can be used for medical and industrial applications.
SUMMARY OF THE INVENTION
In accordance with this invention, there is provided a system and method for performing CT that is faster, mechanically simple, and more reliable for medical and industrial applications. Instead of using a complicated mechanical device for moving the delicate x-ray vacuum tube, this invention uses flexible waveguides such as optical fibers to concentrate and direct the x-ray beams generated from the x-ray tube. The waveguides direct the x-ray beam to the object to be scanned at predetermined orientations and distances.
Thus, in accordance with one embodiment of this invention, there is provided a system and method for performing x-ray computed tomography of an object. In this embodiment, an x-ray energy source emits x-ray energy towards the object. A waveguide directs the x-ray energy from the x-ray energy source to the object at a plurality of predetermined orientations. A detector acquires x-ray energy passing through the object, wherein the x-ray energy acquired on the detector is x-ray projection data.
In accordance with a second embodiment of this invention, there is provided a system and method for performing x-ray computed tomography of an object. In this invention, an x-ray energy source emits x-ray energy towards the object. A waveguide directs the x-ray energy from the x-ray energy source to the object at a plurality of predetermined orientations. A multiplexing unit optically coupled to the x-ray energy source and the waveguide, steers the x-ray energy from the x-ray energy source to the waveguide.
REFERENCES:
H. Goldberg, et al, “Evaluation of Ultrafast CT Scanning of the Adult Abdomen”, Investigative Radiology, vol. 24, 1989, pp. 537-543.
T. Iinuma, et al, “Proposed System for Ultrafast Computed Tomography”, Journal of Computer Assisted Tomography, vol. 1, No. 4, 1977, pp. 494-499.
C. MacDonald, et al, “Medical Applications of Polycapillary X-ray Optics”, SPIE vol. 2519, 1995, pp. 1-11.
M. Kumakhov, “Channeling of Photons and New X-ray Optics”, Nuclear Instruments and Methods in Physics Research, B48, 1990, pp. 283-286.
L. Wang, et al, “Measurement of Capillary Optic Performance for Hard X-rays”, SPIE, vol. 2519, pp. 218-223.
Johnson Christopher Donald
Wang Weiping
Breedlove Jill M.
Church Craig E.
General Electric Company
Goldman David C.
LandOfFree
System and method for performing computed tomography with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System and method for performing computed tomography with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System and method for performing computed tomography with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2514051