X-ray or gamma ray systems or devices – Specific application – Stereoscopy
Reexamination Certificate
1999-03-16
2001-07-03
Porta, David P. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Stereoscopy
C378S042000
Reexamination Certificate
active
06256372
ABSTRACT:
FIELD OF THE INVENTION
This disclosure concerns an invention relating generally to radiographic imaging, and more specifically to apparata and methods for generating stereoscopic (three-dimensional) radiographic images.
BACKGROUND OF THE INVENTION
The classic radiographic or “X-ray” image is obtained by situating an object to be imaged between an X-ray emitter (i.e., an X-ray tube) and an X-ray detector. Emitted X-rays pass through the object to strike the detector, with the response of the detector varying over its area as a function of the intensity of the incident X-rays. Since the intensity of the X-rays incident on the detector is largely a function of the density of the object along the path of the X-rays, the detector receives a shadow image of the object which may then be viewed and analyzed by X-ray technicians, e.g., radiologists. In the case of analog radiographic systems, the detector is formed of X-ray film, whereas digital radiographic systems have solid-state detector components (e.g., scintillator/photodiode arrays) whereby the image is provided in electronic form.
One difficulty which is commonly encountered with the analysis of radiographic images is the proper identification of objects contained within the image. As an example, the identification of organs and other body structures is particularly important in radiographic thoracic imaging (the taking of chest X-rays). In the most common type of chest X-ray, a patient will place his/her chest against a detector and the emitter will be activated to send X-rays through the patient from the posterior-to-anterior direction and into the detector. When the image is captured, a radiologist must then systematically evaluate the image to identify the chest wall, diaphragm, lungs, pleura, mediastinum, etc. To properly identify and analyze matters of medical importance, it is desirable to be able to identify extremely small objects on the image, e.g., details as small as 0.7-2.0 mm near the center of the lungs and 0.3-2.0 mm near their periphery. However, it is difficult for a radiologist to identify objects this small on a two-dimensional image, particularly since some objects may be overlapping and their boundaries may be difficult to accurately discern.
SUMMARY OF THE INVENTION
The invention, which is defined by the claims set out at the end of this disclosure, is directed to apparata and methods of stereo radiographic imaging which allow a three-dimensional view of the interior of an X-rayed target, thereby making it easier to see and accurately identify small objects therein. The invention is preferably implemented using a standard digital radiographic imaging system, wherein an X-ray emitter may be activated to emit an X-ray beam through a target and towards a digital X-ray detector. An image of a target resting between the X-ray emitter and the X-ray detector is thereby generated on the X-ray detector. When the invention is in use, the X-ray emitter is initially activated to emit the X-ray beam from a first imaging position relative to the X-ray detector to thereby obtain a first image of the target. The X-ray emitter is then moved by an actuator along a path in an imaging plane oriented at least substantially parallel to the X-ray detector until the X-ray emitter is situated in a second imaging position relative to the X-ray detector. The X-ray emitter is then activated to emit the X-ray beam from the second imaging position to thereby obtain a second image of the target. Because of the different locations of the X-ray emitter when obtaining the first and second images, the first and second images will display parallax, that is, an apparent displacement of objects contained within the images due to the displacement of the X-ray emitter. The first and second images can then be stereoscopically combined so as to be perceived by a viewer as a single three-dimensional image, for example, by alternately displaying the first and second images in rapid succession and masking each of a viewer's right and left eyes in synchronization with the display so that each eye sees only one of the images. If the displays of the first and second images are alternated rapidly enough (e.g., several times per second), the separate images will be perceived as a single image owing to the persistence of vision and the parallax within the images will be perceived as depth.
In this method, it is also possible to provide the X-ray detector with an actuator so that it may be moved instead of (or in addition to) the X-ray emitter, to thereby locate the X-ray emitter in the different first and second imaging positions relative to the X-ray detector. It is notable that if both of the X-ray emitter and the X-ray detector are moved—for example, in opposite directions along parallel paths—each need only be moved by half of the distance that the X-ray emitter or X-ray detector alone would need to be moved in order to generate the same parallax. This can be advantageous insofar as smaller and less expensive actuators can be used to effect the motion. Additionally, since the emitter and detector are simultaneously moved by lesser distances, lesser time is necessary to obtain the overall motion. This can be helpful insofar as it is often desirable to obtain both of the first and second images within the time that a patient can comfortably hold his/her breath.
It is also desirable to orient the X-ray emitter differently when it is resting in the first and second imaging positions so that the axes of the X-ray beams emitted at the first and second imaging positions intersect, preferably at or close to the X-ray detector. In other words, when the X-ray emitter and/or X-ray detector are translated to situate the X-ray emitter in the first and second imaging positions relative to the X-ray detector, it is also preferable to rotate the X-ray emitter and/or X-ray detector so that the axes of the emitted X-ray beams are always centered on the same area on the X-ray detector. This will have the effect of centering the first and second images about approximately the same area on the detector (and target). Since both images will then feature substantially the same imaged objects, this allows a greater effective field of view when the first and second images are stereoscopically combined.
Advantageously, the invention also allows for the measurement of the depths of objects located within the first and second images. Since the relative locations of the X-ray emitter and X-ray detector are known when the X-ray emitter is at the first and second imaging positions, and since the source-to-image distance (SID) between the X-ray emitter and X-ray detector is generally known, this data can be related to the distances between objects contained within the first and second images to allow calculation of the depths of these objects within the target.
It is noted that the invention can also obtain and stereoscopically combine more than two images of the target. As an example, three images of the target may be successively obtained, each from a different imaging position. All of the images, or selected pairs of the images, may then be stereoscopically combined. It should be apparent that a stereoscopic combination of any one pair of images will provide a different view of the target than a different pair of the images. Further, some known methods of stereoscopic combination allow combination of numerous images to provide a three-dimensional image, for example, where the several images are interleaved and then viewed through a lens array which generates a three-dimensional view from the images.
Further advantages, features, and objects of the invention will be apparent from the following detailed description of the invention in conjunction with the associated drawing.
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Aufrichtig Richard
Kautzer Jeffrey Alan
Cabou, Esq. Christian G.
DeWitt Ross & Stevens S.C.
Fieschko, Esq. Craig A.
General Electric Company
Ho Allen C
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