X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1997-11-26
2001-01-09
Church, Craig E. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C250S370090
Reexamination Certificate
active
06173031
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to computed tomograph (CT) imaging and, more particularly, to detector modules utilized in connection with CT systems.
BACKGROUND OF THE INVENTION
In at least some computed tomograph (CT) imaging system configurations, 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. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal spot. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector. A scintillator is located adjacent the collimator, and photodiodes are positioned adjacent the scintillator.
Multislice CT systems are used to obtain data for an increased number of slices during a scan. Known multislice systems typically include detectors generally known as 3-D detectors. With such 3-D detectors, a plurality of detector elements form separate channels arranged in columns and rows. Each row of detectors forms a separate slice. For example, a two slice detector has two rows of detector elements, and a four slice detector has four rows of detector elements. During a multislice scan, multiple rows of detector cells are simultaneously impinged by the x-ray beam, and therefore data for several slices is obtained.
Multislice detectors generate much more data than single slice detectors. This increased data generation capability is not, however, always required or desired. For example, a variety of tests performed by a CT system do not require high slice quantity or high slice resolution. Also, with such large amounts of data being collected, the time required to perform a scan may increase, resulting in higher costs and lower throughput.
Accordingly, it would be desirable to provide a detector module that allows data to transmitted from an alterable number of slices to accommodate the specific needs of a test. In addition, it is desirable to provide a detector module having an alterable slice resolution.
SUMMARY OF THE INVENTION
These and other objects may be attained by a detector module which, in one embodiment, enables modification of the quantity of slices and slice resolution, or slice thickness. The detector module includes a photodiode array optically coupled to a scintillator array. The photodiode array includes a plurality of photodiodes arranged in rows and columns. A collimator array is aligned and positioned adjacent to the scintillator array to collimate the x-ray beams.
The detector module further includes a switch apparatus and a decoder. The switch apparatus is electrically coupled between the photodiode output lines and a CT system data acquisition system (DAS). The switch apparatus, in one embodiment, is an array of FETs and alters the number of slices and the thickness of each slice by allowing each photodiode output line to be enabled, disabled, or combined with other photodiode output lines.
More specifically, after an operator has determined the desired number of slices and slice thickness, the appropriate switch apparatus configuration is electrically transmitted from the CT system computer to the decoder, e.g., via a flexible cable. The appropriate decoder output lines are then connected to the switch apparatus control lines so that data is transmitted from the photodiodes output lines in the selected configuration.
In one embodiment, the detector module is fabricated by depositing, or forming, the photodiode array, the switch apparatus, and the decoder on a substrate. Each photodiode output line is electrically connected to the switch apparatus inputs, and each switch apparatus output and each decoder control line are then electrically coupled to the first end of a flex cable. After installing the detector modules into the detector array, the second end of the flex cable is electrically connected to the CT system data acquisition system (DAS).
The above described detector module enables selection of the number of slices of data to be electrically transmitted for each rotation of the CT system. In addition, the detector module allows the slice thickness to be selected to produce various slice resolutions. As a result, the configuration of the detector module can be altered to accommodate the specific needs and requirements of the test.
REFERENCES:
patent: 4338521 (1982-07-01), Shaw et al.
patent: 4965726 (1990-10-01), Heuscher et al.
patent: 5592523 (1997-01-01), Tuy et al.
patent: 6-169912 (1994-06-01), None
He Hui David
Hoffman David M.
Johnston Brian D.
Kotian Francois
Cabou Christian G.
Church Craig E.
General Electric Company
Price Phyllis Y.
Teasdale Armstrong
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