X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1997-11-26
2004-10-05
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S114000
Reexamination Certificate
active
06801594
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to computed tomography (CT) imaging and more particularly, to a CT fluoroscopic system.
BACKGROUND OF THE INVENTION
In at least one known CT system configuration, an x-ray source projects a fan-shaped beam which is collimated to lie within an X-Y plane of a Cartesian coordinate system and generally referred to as the “imaging plane”. The x-ray beam passes through the object being imaged, such as a patient. The beam, after being attenuated by the object, impinges upon an array: of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is dependent upon the attenuation of the x-ray beam by the object. Each detector element of the array produces a separate electrical signal that is a measurement of the beam attenuation at the detector location. The attenuation measurements from all the detectors are acquired separately to produce a transmission profile.
In known third generation CT systems, the x-ray source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged so that the angle at which the x-ray beam intersects the object constantly changes. A group of x-ray attenuation measurements, i.e., projection data, from the detector array at one gantry angle is referred to as a “view”. A “scan” of the object comprises a set of views made at different gantry angles, or view angles, during one revolution of the x-ray source and detector. In an axial scan, the projection data is processed to construct an image that corresponds to a two dimensional slice taken through the object. One method for reconstructing an image from a set of projection data is referred to in the art as the filtered back projection technique. This process converts the attenuation measurements from a scan into integers called “CT numbers” or “Hounsffield units”, which are used to control the brightness of a corresponding pixel on a cathode ray tube display.
To reduce the total scan time, a “helical” scan may be performed. To perform a “helical” scan, the patient is moved while the data for the prescribed number of slices is acquired. Such a system generates a single helix from a one fan beam helical scan. The helix mapped out by the fan beam yields projection data from which images in each prescribed slice may be reconstructed.
In CT fluoroscopic systems (“CT Fluoro”), data collected from a helical scan may be utilized to generate sequential frames of images to help, for example, in guiding a needle to a desired location within a patient. A frame, like a view, corresponds to a two dimensional slice taken through the imaged object. Particularly, projection data is processed at a frame rate to construct an image frame of the object.
With known CT Fluoro systems, the general objective is to increase the frame rate while minimizing image degradation. Increasing the frame rate provides many advantages including, for example, that an operator physician is provided with increased information regarding the location of a biopsy needle. Typically, however, increasing the frame rate is at odds with minimizing image degradation. In addition, it is desirable to provide an operator with control of the scanning process as well as the display of images for guiding the procedure.
SUMMARY OF THE INVENTION
These and other objects may be attained by a CT Fluoro system which, in one embodiment, includes an integrated controller, image reconstruction algorithms for increasing the speed of image display, and an enhanced image display. The integrated controller enables the radiologist to maintain control of the system throughout the fluoro scan. The image reconstruction algorithms are generally directed to increasing the image frame rate or reducing image artifacts, or both, in the CT fluoro scan. The image display generally provides enhanced images and control to the radiologist during a scan procedure.
REFERENCES:
patent: 4773086 (1988-09-01), Fujita et al.
patent: 4807273 (1989-02-01), Haendle
patent: 5220592 (1993-06-01), Blouir
patent: 5440606 (1995-08-01), Faul et al.
Ali Fazle
Davis Steven C.
Faessler Shawn P.
Hsieh Jiang
Senzig Robert F.
Armstrong Teasdale LLP
Church Craig E.
General Electric Company
Horton Esq. Carl B.
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