Image analysis – Applications – Biomedical applications
Reexamination Certificate
1998-07-17
2001-07-24
Boudreau, Leo (Department: 2621)
Image analysis
Applications
Biomedical applications
C382S128000
Reexamination Certificate
active
06266434
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to computed tomograph (CT) imaging and, more particularly, to reducing spectral artifacts in a multislice CT system.
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 2-D detectors. With such 2-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 are typically segmented into a series of individual scintillator cells in the X and Z axes. These scintillator cells can be separated by narrow gaps of only a few micrometers between adjacent cells. The gaps are filled with a light reflecting material. The detector elements could accept off-axis, or scattered, x-ray beams which decrease contrast resolution and increase image artifacts.
Accordingly, it would be desirable to provide a detector array that collimates and separates the x-ray beams toward individual detector elements to reduce scatter and spectral artifacts. In addition, it is desirable to provide a detector array collimator that protects the gaps between the elements from x-ray beams so that radiation damage, beam hardening, punch through noise and spectral effects of the light reflecting material is minimized.
SUMMARY OF THE INVENTION
These and other objects may be attained by a detector array, which in one embodiment, includes a collimator for reducing scatter, spectral artifacts and x-ray damage. The detector array includes a detector housing, a plurality of detector modules and a collimator having a plurality of collimator plates. Each detector module is mounted to the detector housing and includes a photodiode array optically coupled to a scintillator array. The collimator plates are configured so that x-ray beam signals directed at the scintillator array are allowed to pass and those signals directed toward the gaps in the scintillator array are blocked.
In one embodiment, the detector array is fabricated by spacing and securing each collimator plate to the detector housing so that a x-ray beam shadow is centered over the scintillator gap. More specifically, each collimator plate is positioned so that the centerline of the collimator plate is displaced from, or not collinear with, the centerline of the scintillator array gap. In one embodiment, one wire is then extended the length of the collimator perpendicular to the longitudinal axis of the plates forming a plurality of sections. The number of sections corresponds to the size of the photodiode array so that the X-ray beams are separated to correspond to the number of detector elements.
The above described detector array enables X-ray beams to be separated so that the X-ray beams impinge only on the scintillator array resulting in reduced scatter and spectral artifacts. Additionally, the collimator prevents the x-ray beams from impinging upon the scintillator array gaps. As a result, radiation damage to the scintillator gaps is reduced.
REFERENCES:
patent: 4392057 (1983-07-01), Mathieson et al.
patent: 5093850 (1992-03-01), Dinwiddie et al.
patent: 5168532 (1992-12-01), Seppi et al.
patent: 5335255 (1994-08-01), Seppi et al.
patent: 5684855 (1997-11-01), Aradate et al.
patent: 5692507 (1997-12-01), Seppi et al.
patent: 5812629 (1998-09-01), Clauser
patent: 5903008 (1999-05-01), Li
patent: 5961457 (1999-10-01), Raylman et al.
patent: 5970113 (1999-10-01), Crawford et al.
patent: 6115448 (2000-09-01), Hoffman
Gurmen O. Erdogan
Shen Bing
Toth Thomas L.
Armstrong Teasdale LLP
Boudreau Leo
Cabou Christian G.
Choobin M. B.
General Electric Company
LandOfFree
Methods and apparatus for reducing spectral artifacts in a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods and apparatus for reducing spectral artifacts in a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods and apparatus for reducing spectral artifacts in a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2557693