Radiant energy – Invisible radiant energy responsive electric signalling – With or including a luminophor
Reexamination Certificate
1997-11-26
2002-02-05
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
With or including a luminophor
C250S368000
Reexamination Certificate
active
06344649
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to computed tomograph (CT) imaging and, more particularly, to detectors 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 adjacent the collimator, and photodiodes 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 three-dimensional (3-D) detectors. With such 3-D detectors, a plurality of detector cells form separate channels arranged in columns and rows.
A scintillator for a 3-D detector may have scintillator elements with dimensions of about 1×2×3 mm, with narrow gaps of about 100 micrometers, i.e., for example, about 0.004 inches, between adjacent elements. As a result of the small size and the close proximity of the elements, fabrication of such elements is difficult. Further, and in use, a signal impinged upon one scintillator element may be improperly reflected upward or to adjacent elements creating crosstalk and loss of resolution. Also, with such small scintillator elements, the magnitude of the generated optical signal may be small, and any losses that occur can significantly deteriorate signal quality.
It would be desirable to provide a scintillator element that increases the magnitude of the optical signal provided to the photodiode by minimizing the amount of light lost by the element. It would also be desirable to provide a scintillator element having increased spatial resolution. It would further be desirable to provide a scintillator element which includes a light absorber to minimize the amount of light transferred between adjacent elements.
SUMMARY OF THE INVENTION
These and other objects may be attained by a scintillator including a plurality of scintillator elements laid out as an array having gaps between the adjacent elements. The gaps are filled with a composition containing a reflective material, a light absorber, and a castable polymer. In one embodiment, the gaps are filled with a composition of a white, highly diffuse reflective material including titanium dioxide and a castable epoxy. The composition minimizes the amount light that is reflected out of the elements and increases the strength of a signal transmitted to a photodiode located adjacent the scintillator element.
In one embodiment, the scintillator is fabricated by temporally bonding together a stack of scintillator wafers and then cutting the wafers into first bar stacks. After separating the first bar stacks into individual bars, the bars are placed in a fixture with gaps between the bars. The gaps are then filled with the reflective material to form a 2 dimensional array. After the reflective material has cured, a plurality of arrays are stacked and cut into a plurality of second bar stacks. The second bar stacks are then separated into individual second bars and placed in a fixture with gaps between the second bars. The gaps are filled with the reflective material composition to form a 3-D scintillator array having, in one embodiment, 256 scintillator elements.
The above described scintillator provide a higher magnitude signal to the photodiode by minimizing the amount of light that is lost from the scintillator elements. Additionally, the described scintillator includes a light absorber to minimize the amount of light transferred between adjacent scintillator elements.
REFERENCES:
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patent: 5227633 (1993-07-01), Ryuo et al.
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patent: 5378894 (1995-01-01), Akai
patent: 5831269 (1998-11-01), Nakamura et al.
patent: 5866908 (1999-02-01), Novak
Applicants wish to call to Examiner's attention co-pending U.S. Application No. 08/977,441, filed Nov. 25, 1997 (sic) (PTO records may incorrectly indicate Nov. 25, 1997 but actual filing date is Nov. 26, 1997).
Englert August O.
Gurmen Erdogan O.
Hoffman David M.
Riedner Robert J.
Schedler Matthew R.
Armstrong Teasdale LLP
Carl B. Horton, Esq.
Gagliardi Albert
General Electric Company
Hannaher Constantine
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