Patent Application
20080164419
This invention relates generally to imaging methods and apparatus, and more particularly, to methods and apparatus that provide for reduction or elimination of keystone effect.
During an x-ray tomosynthesis exam, the relationship of the x-ray tube to the detector can vary causing tube angulation as described in U.S. Pat. Nos. 5,734,694 and 5,572,567. This tube angulation causes a keystone effect for the projected x-ray field. Typically, mathematical corrections are performed to compensate for the keystone effect. The x-ray field also exhibits a keystone effect whenever the collimator and tube is not perpendicular to the detector.
It would be desirable to, instead of using mathematical corrections to attempt to compensate for the keystone effect, but rather, to eliminate or reduce the keystone effect in the first place.
In one aspect, a method includes mechanically correcting for a keystone effect on an x-ray detector.
In another aspect, apparatus includes an x-ray source, an x-ray detector positioned to receive x-rays emitted from the source, and a collimator positioned between the x-ray source and the x-ray detector, the collimator configured to have movable parts that provide for a keystone correction.
In yet another aspect, a computer readable medium is embedded with a program configured to instruct the computer to operate at least one motor to reduce or eliminate a keystone effect.
In yet still another aspect, an imaging system includes an energy source, a detector positioned to receive energy emitted from the source, and a collimator positioned between the source and the detector. The collimator is configured to provide a rectangular FOV that utilizes all of the detector for single and dual energy exposures when the detector is not perpendicular to energy emitted from the source, such that all the collimated energy can be used for diagnosis.
In still yet another aspect, a computer is configured to receive image data from a first detector position acquisition, receive image data from a second detector position acquisition; wherein an x-ray source to detector angle is different between the acquisitions, and combine the received image data, without performing any keystone correction on the data, to generate a single image of an area greater than the size of the detector.
There are herein described methods and apparatus useful for imaging systems such as, for example, but not limited to an x-ray system. The apparatus and methods are illustrated with reference to the figures wherein similar numbers indicate the same elements in all figures. Such figures are intended to be illustrative rather than limiting and are included herewith to facilitate explanation of an exemplary embodiment of the apparatus and methods of the invention. Although, described in the setting of an x-ray system, it is contemplated that the benefits of the invention accrue to all diagnostic imaging systems and modalities such as PET, MRI, SPECT, Ultrasound, fused systems such as a CT/PET system, and/or any modality yet to be developed in which keystone effects occur.
The x-ray imaging system includes a processing circuit. The processing circuit (e.g., a microcontroller, microprocessor, custom ASIC, or the like) is coupled to a memory and a display device. The memory (e.g., including one or more of a floppy disk drive, CD-ROM drive, DVD drive, magnetic optical disk (MOD) device, or any other digital device including a network connecting device such as an Ethernet device for reading instructions and/or data from a computer-readable medium, such as a floppy disk, or an other digital source such as a network or the Internet, as well as yet to be developed digital means, and the like) stores imaging data.
The memory may also store a computer program including instructions executed by the processing circuit to implement the functions described herein. The processing circuit provides an image for display on a device. The detector may be a flat panel solid-state image detector, for example, although conventional film images stored in digital form in the memory may also be processed. In one embodiment, the processing circuit executes instructions stored in firmware (not shown). Oftentimes, a prescription will be for an area larger than the detector, and typically, the imaging is done with moving the detector linearly while pivoting the x-ray source. Therefore, some acquisitions are made at different tube angles. The different data sets from the different acquisitions can be collected in an image pasting system or computer that generates one image of the prescribed area. By using the below described keystone correction, the image data is more readily used by the image pasting processor to generate a single image.
Of course, the methods described herein are not limited to practice in system 10 and can be utilized in connection with many other types and variations of imaging systems. In one embodiment, the processing circuit is a computer that is programmed to perform functions described herein, and, as used herein, the term computer is not limited to just those integrated circuits referred to in the art as computers, but broadly refers to computers, processors, microcontrollers, microcomputers, programmable logic controllers, application specific integrated circuits, and other programmable circuits. Although the herein described methods are described in a human patient setting, it is contemplated that the benefits of the invention accrue to non-human imaging systems such as those systems typically employed in small animal research. Although the herein described methods are described in a medical setting, it is contemplated that the benefits of the invention accrue to non-medical imaging systems such as those systems typically employed in an industrial setting or a transportation setting, such as, for example, but not limited to, a baggage scanning CT system for an airport or other transportation center as shown in
Referring now to
As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.
Technical effects include an improved dose efficiency for non-perpendicular x-ray exams. By dose efficiency being improved, dose reduction will at least sometimes result. The herein described methods and apparatus provide for easy corrections to improve x-ray dose efficiency during tomosynthesis exams and elimination of image size/shape corrections during subsequent image reconstruction.
Exemplary embodiments are described above in detail. The assemblies and methods are not limited to the specific embodiments described herein, but rather, components of each assembly and/or method may be utilized independently and separately from other components described herein.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
