X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1999-09-27
2001-12-04
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S004000, C378S194000
Reexamination Certificate
active
06327327
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the radiography arts. It finds particular application in conjunction with computerized tomography (CT) scanners and will be described with particular reference thereto. However, it is to be appreciated that the present invention is also amenable to other like applications requiring electrical signal transfer between a moving part and a stationary part.
Heretofore, CT scanners have commonly included a floor mounted frame assembly or gantry which remains stationary during an imaging procedure. A radiation generator, such as an x-ray tube, is mounted to a rotatable frame assembly or section which rotates around a patient being imaged. In third generation scanners, a radiation detector array is located within the rotating frame along with the x-ray tube. It is therefore necessary to provide a mechanism to transfer electrical signals to and from the rotating frame. That is, electrical power and control signals are transferred from the stationary frame to the rotating frame to power and control electronics, hardware, and the x-ray tube.
Additionally, a communications path is provided to transfer imaging data from the radiation detector array in the rotating frame to the stationary frame for image processing. The rotating gantry rotates rapidly, preferably one (1) revolution per second or less. The detector array includes numerous individual detectors, e.g. hundreds or even thousands. The detectors are sampled rapidly, typically in a fraction of a degree of rotation, to a high resolution, e.g. 32 bits or more. The amount of data to be transferred is so massive, that the data transfer rate is becoming a limiting factor in scanner speed and resolution.
Various devices are known for providing the communication path between the rotating frame and the stationary frame. Older CT scanners employed an umbilical cable. Typically, one or more flexible, shielded cables were hardwired to electronics such as the detector array, in the rotating frame. The cables were connected at the other end to stationary side electronics including image processing computers. Unfortunately the umbilical cable is typically capable of +/−360° of rotation. Accordingly, the rotating frame on such umbilical devices is limited to a total of 720° of rotation in one direction before the frame is stopped and rewound in the opposite direction.
Such “cycling” type scanners were good for imaging small number of slices. For larger volumes, continuous rotating scanners are preferred. The subject moves axially to create a spiral scanning pattern. In continuous rotate third generation systems, slip rings are commonly used to transfer power, data, and control signals. However, continuing improvements keep increasing rates of data transfer. On slip ring data links, the time required to propagate data signals around the circular rings effectively limits the maximum data transfer rate. Signals propagating around the ring in opposite directions may arrive at a reception point at offset times causing interference or garbled reception. Similar limitations are observed in slip ring data links employing capacitance-type data transfer.
Demands for higher data rates are increasingly being met, not through electrical slip ring configurations, but by optical data transmission links. Such data links typically employ a series of pulsating lights distributed around either the stationary frame or the rotating frame. On the opposing frame, an optical receiver is used to detect the synchronously strobing lights. The received light signals are then translated back into electronic image data for follow-on processing. Unfortunately, optical systems are more costly per channel of image data supplied, and greatly depend on the alignment of the optical transmitters and receivers. Moreover, optical systems are unusually sensitive to dirt and/or dust obscuring the optics.
Accordingly, a need exists for yet higher data transfer rates in CT type scanners which provide continuous rotation and reliable high-speed communications.
The present invention contemplates a new and improved method and apparatus for transferring electrical signals which overcomes the above-referenced problems and others.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a computerized tomography system includes a stationary section defining a central opening and a concentric annular section positioned within the opening. At least one interconnecting data link provides communication between the stationary section and the rotating section. The interconnecting data link includes a plurality of receiving elements spaced angularly around the stationary, section. On the rotating section, a plurality of transmitting elements are also angularly spaced. The transmitting elements are equal in number to, and in selective electrical communication with, the plurality of receiving elements.
In accordance with another aspect of the present invention, the plurality of receiving elements includes a ring configured as a plurality of electrically conductive segments separated by non-conductive interruptions.
In accordance with another aspect of the present invention, the transmitters include a number of brushes in selective physical contact with the conductive segments.
In accordance with another aspect of the present invention, the transmitters include capacitive couplers in selective electrical communication with the conductive segments.
In accordance with another aspect of the present invention, the tomography system includes an angular encoder which generates an angular displacement signal corresponding to a relative position of the rotating section within the stationary section. A de-multiplexer is also included which uses data including the angular displacement signal to arrange image data from the plurality of receiving elements into a desired format.
In accordance with another aspect of the present invention, the interconnecting data link further includes a second plurality of receiving elements axially spaced from the first set of receiving elements. On the rotating section, a second plurality of transmitting elements is likewise axially spaced from the first plurality of transmitting elements.
In accordance with another aspect of the present invention, the second plurality of receiving elements are angularly offset from the first plurality of receiving elements such that electrical communication between the stationary section and the rotating section is continuously provided.
In accordance with another embodiment of the present invention, a diagnostic imaging machine includes a rotating frame housing at least one array of radiation detectors selectively outputting imaging signals. A stationary frame is provided to support the rotating frame, and a plurality of simultaneous communication paths are provided for electrically transferring the imaging signals from the rotating frame to the stationary frame.
In accordance with another aspect of the present invention, the plurality of communication paths includes a ring configured as a plurality of electrically conductive segments separated by non-conductive interruptions. Further, a plurality of transmitting elements are in electrical communication with at least a portion of the radiation detectors, and in electrical communication with exactly one of the conductive segments when the rotating frame is at selected rotational angles.
In accordance with another aspect of the present invention, a rotational position sensor provides an angular displacement signal corresponding to the rotational angle of the rotating frame. A multi-channel decoder reorders data from each receiver into data channels based on the angular displacement signal provided.
In accordance with another aspect of the present invention, the imaging machine further includes at least a second slip ring parallel to the first slip ring also having a plurality of electrically conductive segments separated by non-conductive interruptions.
In accordance with another aspect of the present in
Herold Mark D.
Resnick Theodore A.
Fay Sharpe Fagan Minnich & McKee LLP
Kim Robert H.
Picker International Inc.
Song Hoon K.
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