X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
2001-03-06
2003-05-20
Dunn, Drew A. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C348S308000
Reexamination Certificate
active
06567495
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to detectors used in medical imaging systems, and more particularly, to detectors having programmable slice thickness and/or operational modes implemented via switching configurations stored in a memory device.
Typically in medical imaging systems, such as, for example, computed tomography (CT) systems, the system includes a detector comprising an array of photodiodes that detect radiation, such as, for example, x-rays, that are emitted from a radiation source. During detection of the radiation, it is desired that the radiation be collimated. When the radiation is collimated, the slice thickness of the radiation detected by the array of photodiodes of the detector can be controlled more easily. The collimated radiation is desired during various imaging techniques, during service of the detector and/or medical imaging system and during the performance of various experimental techniques.
In some medical imaging systems, the radiation is collimated using structural collimators that are placed on or near the detector. The structural collimators ensure that any radiation that is directed toward the array of photodiodes of the detector is parallel. These structural collimators are used not only to ensure that the radiation is parallel, but the structural collimators also control the slice thickness of the radiation detected by the array of photodiodes. However, structural collimators have some limitations. For example, a different structural collimator has to be fabricated for each slice thickness that is desired. In addition, to change the slice thickness, the structural collimator having the desired slice thickness must be installed in the medical imaging system. Installation of different structural collimators involves discontinuing operation of the medical imaging system for a prolonged period of time while a different structural collimator is installed.
In other medical imaging systems, the photodiode array of the detector is connected to a plurality of switches, such as, for example, transistors. The state of each of the plurality of switches is controlled such that specified photodiodes in the array of photodiodes are used to detect the radiation. The selection of the specified photodiodes also controls, among other things, the slice thickness of the radiation detected by the array of photodiodes of the detector. In the medical imaging systems that use switches connected to the photodiode array, a predetermined number of switching configurations is hardwired via a multiplexer to the switches, the switching configurations control the plurality of switches. Each of these switching configurations represents a different operational mode of the medical imaging system. However, these hardwire multiplexed-type medical imaging systems have some limitations. For example, the number of operational modes of these medical imaging systems is limited to the predetermined number of switching configurations that are hardwired to the multiplexer. For new operational modes or new switching configurations to be added to these medical imaging systems, the multiplexer must be re-wired to add the switching configuration and/or the operational mode to the medical imaging system. In addition, the re-wiring of the multiplexer to add switching configurations requires the medical imaging systems to be shut down for a prolonged period of time until the switching configurations are reconfigured.
Therefore, it is desired that a medical imaging system be produced having a programmable slice thickness that does not require fabrication or installation of structural elements and/or rewiring of the control electronics. Further, it is also desired that a medical imaging system be produced that can be re-programmed with new operational modes and/or new switching configurations without discontinuing operation of the medical imaging system for a prolonged period of time.
BRIEF SUMMARY OF THE INVENTION
In one exemplary embodiment, a detector device for use in an imaging system is provided. The detector device comprises a photodiode array positioned to detect radiation transmitted by the imaging system. A plurality of switch arrays is connected to the photodiode array. Each of the plurality of switch arrays has at least one output. In addition, each of the plurality of switch arrays comprises a plurality of switch banks wherein each of the plurality of switch banks includes a plurality of switches. A control logic circuit is connected to the plurality of switch arrays and controls the state of each of the plurality of switches in each of the plurality of switch banks based on a predefined switching configuration. The control logic circuit comprises a memory device that is programmed to store a plurality of predefined switching configurations. Each of the plurality of predefined switching configurations represents a respective operational mode of the imaging system. Additionally, each respective operational mode has a respective predetermined detector slice thickness.
In another exemplary embodiment, a method for selecting a slice thickness of a photodiode array of a detector in an imaging system is provided. The method comprises providing a plurality of switches connected to a detector. A plurality of switching configurations are defined wherein each of the plurality of switching configuration represents an operational mode of the imaging system. A memory device stores a plurality of switching configurations. Each of the plurality of switching configurations represents a respective operational mode of the imaging system. In addition, each respective operational mode has a respective predetermined detector slice thickness. One of the plurality of operational modes of the imaging system is selected. A corresponding switching configuration is retrieved, and the corresponding switching configuration relates to the selected one of the plurality of operational modes. The state of each of the plurality of switches is configured according to the corresponding switching configuration. The desired operational mode of the imaging system is performed with the switches configured in the retrieved switching configuration.
REFERENCES:
patent: 6198791 (2001-03-01), He et al.
Hoffman David Michael
McGrath Donald Thomas
Dunn Drew A.
Kiknadze Irakli
Patnode Patrick K.
Thompson John F.
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