X-ray or gamma ray systems or devices – Specific application – Mammography
Reexamination Certificate
1999-03-03
2001-09-18
Church, Craig E. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Mammography
C378S022000
Reexamination Certificate
active
06292531
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to an imaging system, and more particularly, to generating three dimensional mammography images.
In at least one known mammography imaging system, 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's breast. 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.
At least one present mammography imaging system radiates x-rays from a single projection angle to generate two dimensional images of each breast. As a result of using a single projection angle, the images, like known x-ray systems, provide no depth information. Consequently, the exact location of the pathology cannot be localized. In addition, overlapping structures reduce the contrast of the object of interest to its background and, therefore, reduce the accuracy of diagnosis.
To improve diagnosis and pathology accuracy, it is desirable to provide an imaging system which generates three dimensional images of the object of interest. It would also be desirable to provide such a system without significantly increasing the costs of such a system.
BRIEF SUMMARY OF THE INVENTION
These and other objects may be attained in a digital x-ray imaging system which, in one embodiment, collects projection data from at least two projection angles so that three dimensional mammography images are generated. The three dimensional images are then used for diagnosis and exact location of a breast pathology. More specifically, and in accordance with one embodiment of the present invention, the imaging system includes an x-ray source and at least one digital detector array for altering the projection angle and collection of high spatial resolution projection data.
In one embodiment, the imaging system collects projection data from a plurality of projection angles by altering the x-axis position of the x-ray source and each x-ray detector. More specifically, the x-ray source and the x-ray detector are translatable along a patient x-axis to alter the projection angle of each scan so that the entire object of interest, the breast, remains within a field of view of the imaging system. The resulting projection data for each projection angle includes a set of cone beam projections with, in one embodiment, a large cone angle. By performing a cone beam reconstruction of the collected cone beam data set, cross sectional images of the breast are generated. The three dimensional images are then utilized to diagnosis the breast. In one embodiment, the translation distance of at least one of the x-ray source and the detector array may be configured so that projection data is collected from large oblique projection angles.
In another embodiment, the projection angle is altered by radiating an x-ray beam from a stationary x-ray source having a plurality of focal spots. More specifically, the x-ray source includes a plurality of focal spots displaced along the patient x-axis. The projection angle is altered by emitting the x-ray source from at least two different focal spots and altering the x-axis position of the detector so that the entire object of interest remains within the field of view.
In another embodiment using an x-ray source having a plurality of focal spots, the source is arc shaped so that the object of interest remains entirely within the field of view without moving the detector. In another embodiment, the x-ray source rotates about a patient z-axis so that the projection angle is altered by rotating the x-ray source.
In another embodiment, the imaging system includes two detector arrays so that three dimensional images are simultaneously generated for each breast. More specifically, using a collimator, the x-ray beam is collimated so that projection data of the first breast is collected using the first detector array and projection data of the second breast is collected using the second detector array for each projection angle. The collected data is then processed as described above so that three dimensional images are generated for each breast.
By collecting the projection data sets as described above, three dimensional images of the object of interest are generated. As a result, diagnosis and pathology accuracy is improved. In addition, such images are generated without significantly increasing the costs of such a system.
REFERENCES:
patent: 4340816 (1982-07-01), Schott
patent: 5872828 (1999-02-01), Niklason et al.
Armstrong Teasdale LLP
Cabou Christian G.
Church Craig E.
General Electric Company
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