Contactless data communication in CT systems

A CT imaging system for imaging an object is provided. The CT imaging system includes a stationary component, a rotating component configured to rotate with respect to the stationary component, a first conductive line coupled to the stationary component, and a second conductive line coupled to the rotating component, wherein the first and second conductive lines are positioned proximate one another such that inductive crosstalk between the first and second conductive lines provides a contactless communication channel for communicating data between the stationary component and the rotating component.

BACKGROUND

The embodiments described herein relate generally to CT imaging systems, and more particularly, to contactless data communication for CT imaging systems.

In some computed tomography (CT) imaging systems, an x-ray source projects a fan-shaped beam that is collimated to lie within an X-Y plane of a Cartesian coordinate system and generally referred to as an “imaging plane”. The x-ray beam passes through an object being imaged. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated radiation beam 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 intensity at each detector location. The intensity measurements from all the detectors are acquired separately to produce a transmission profile and reconstruct an image of the object.

At least some known CT systems include a gantry that rotates within a stationary housing. To control operation of the CT system, data is communicated between the rotating gantry and stationary housing. For example, imaging data acquired by detectors on the gantry may be communicated to a computing device for processing (e.g., image reconstruction). To communicate between the gantry and housing, at least some known CT systems use an optical communication system (e.g., a laser transmitter and an optical receiver). Further, at least some known CT systems use capacitive coupling between a transmitter on one of the gantry and the housing and a receiver on the other of the gantry and the housing. However, these known communication systems may be unidirectional, and may also require relatively high tolerances for proper operation.

BRIEF SUMMARY

In one aspect, a CT imaging system for imaging an object is provided. The CT imaging system includes a stationary component, a rotating component configured to rotate with respect to the stationary component, a first conductive line coupled to the stationary component, and a second conductive line coupled to the rotating component, wherein the first and second conductive lines are positioned proximate one another such that inductive crosstalk between the first and second conductive lines provides a contactless communication channel for communicating data between the stationary component and the rotating component.

In another aspect, a method for contactless data communication in a CT imaging system is provided. The method includes coupling a first conductive line to a stationary component of the CT imaging system, coupling second conductive line to a rotating component of the CT imaging system, wherein the second conductive line is positioned proximate the first conductive line, and wherein the rotating component is configured to rotate with respect to the stationary component, and communicating data between the stationary component and the rotating component using a contactless communication channel, wherein inductive crosstalk between the first and second conductive lines provides the contactless communication channel.

In yet another aspect, a contactless communication system is provided. The contactless communication system includes a first conductive line, and a second conductive line located proximate the first conductive line, wherein inductive crosstalk between the first and second conductive lines provides a contactless communication channel for communicating data between the first and second conductive lines, and wherein orthogonal frequency-division multiplexing (OFDM) is used as the physical layer to communicate data over the contactless communication channel.

DETAILED DESCRIPTION

The systems and methods described herein provide a contactless communication system for a CT imaging system. At least one first conductive line is coupled to a stationary component of the CT imaging system. At least one second conductive line is coupled to a rotating component of the CT imaging system. Inductive crosstalk between the first and second conductive lines provides a contactless communication channel that may be used to communicate data bi-directionally between the stationary component and the rotating component.

Referring now toFIGS. 1 and 2, a computed tomography (CT) imaging system10is shown. CT imaging system10is shown having a gantry12, which is representative of a CT scanner, a control system14, and a motorized conveyor belt16for positioning an object18, such as a piece of luggage, in a gantry opening20defined through gantry12. Gantry12includes an x-ray source22that projects a fan beam of x-rays24toward a detector array26on the opposite side of gantry12. Detector array26is formed by detector elements28, which are radiation detectors that each produce a signal having a magnitude that represents and is dependent on the intensity of the attenuated x-ray beam after it has passed through object18being imaged. During a helical scan that acquires x-ray projection data, gantry12along with the x-ray source22and detector array26rotate within an x-y plane and around object18about a center of rotation, while object18is moved through gantry12in a z-direction32perpendicular to the x-y plane of rotation. In the exemplary embodiment, detector array26includes a plurality of detector rings each having a plurality of detector elements28, the detector rings having an angular configuration corresponding to x-ray source22.

Gantry12and x-ray source22are controlled by control system14, which includes a gantry controller36, an x-ray controller38, a data acquisition system (DAS)40, an image reconstructor42, a conveyor controller44, a computer46, a mass storage system48, an operator console50, and a display device52. Gantry controller36controls the rotational speed and position of gantry12, while x-ray controller38provides power and timing signals to x-ray source22, and data acquisition system40acquires analog data from detector elements28and converts the data to digital form for subsequent processing. Image reconstructor42receives the digitized x-ray data from data acquisition system40and performs an image reconstruction process that involves filtering the projection data using a helical reconstruction algorithm.

Computer46is in communication with the gantry controller36, x-ray controller38, and conveyor controller44whereby control signals are sent from computer46to controllers36,38,44and information is received from controllers36,38,44by computer46. Computer46also provides commands and operational parameters to data acquisition system40and receives reconstructed image data from image reconstructor42. The reconstructed image data is stored by computer46in mass storage system48for subsequent retrieval. An operator interfaces with computer46through operator console50, which may include, for example, a keyboard and a graphical pointing device, and receives output, such as, for example, a reconstructed image, control settings, and other information, on display device52.

Communication between the various system elements ofFIG. 2is depicted by arrowhead lines, which illustrate a means for either signal communication or mechanical operation, depending on the system element involved. Communication amongst and between the various system elements may be obtained through a hardwired or a wireless arrangement. For example, inductive crosstalk between two conductive lines may be used as a communication channel, as described herein. Computer46may be a standalone computer or a network computer and may include instructions in a variety of computer languages for use on a variety of computer platforms and under a variety of operating systems. Other examples of computer46include a system having a microprocessor, microcontroller, or other equivalent processing device capable of executing commands of computer-readable data or program for executing a control algorithm. In order to perform the prescribed functions and desired processing, as well as the computations therefor (e.g., the execution of filtered back projection, Fourier analysis algorithm(s), the control processes prescribed herein, and the like), computer46may include, but not be limited to, a processor(s), memory, storage, register(s), timing, interrupt(s), communication interfaces, and input/output signal interfaces, as well as combinations including at least one of the foregoing. For example, computer46may include input signal filtering to enable accurate sampling and conversion or acquisitions of such signals from communications interfaces. As described above, exemplary embodiments can be implemented through computer-implemented processes and apparatuses for practicing those processes.

FIG. 3is a block diagram of a computing device300that may be used to reconstruct an image of object18, as described herein. Computing device300may be implemented as part of control system14or may be a separate computing device in communication with CT imaging system10or another imaging system. Computing device300includes at least one memory device310and a processor315that is coupled to memory device310for executing instructions. In some embodiments, executable instructions are stored in memory device310. In the exemplary embodiment, computing device300performs one or more operations described herein by programming processor315. For example, processor315may be programmed by encoding an operation as one or more executable instructions and by providing the executable instructions in memory device310.

Processor315may include one or more processing units (e.g., in a multi-core configuration). Further, processor315may be implemented using one or more heterogeneous processor systems in which a main processor is present with secondary processors on a single chip. In another illustrative example, processor315may be a symmetric multi-processor system containing multiple processors of the same type. Further, processor315may be implemented using any suitable programmable circuit including one or more systems and microcontrollers, microprocessors, reduced instruction set circuits (RISC), application specific integrated circuits (ASIC), programmable logic circuits, field programmable gate arrays (FPGA), graphics processing units (GPU), and any other circuit capable of executing the functions described herein.

In the exemplary embodiment, memory device310is one or more devices that enable information such as executable instructions and/or other data to be stored and retrieved. Memory device310may include one or more computer-readable media, such as, without limitation, dynamic random access memory (DRAM), static random access memory (SRAM), a solid state disk, and/or a hard disk. Memory device310may be configured to store, without limitation, application source code, application object code, source code portions of interest, object code portions of interest, configuration data, execution events and/or any other type of data. Further, reference templates may be stored on memory device310.

In the exemplary embodiment, computing device300includes a presentation interface320that is coupled to processor315. Presentation interface320presents information to a user325. For example, presentation interface320may include a display adapter (not shown) that may be coupled to a display device, such as a cathode ray tube (CRT), a liquid crystal display (LCD), an organic LED (OLED) display, and/or an “electronic ink” display. In some embodiments, presentation interface320includes one or more display devices.

In the exemplary embodiment, computing device300includes a user input interface335. User input interface335is coupled to processor315and receives input from user325. User input interface335may include, for example, a keyboard, a pointing device, a mouse, a stylus, a touch sensitive panel (e.g., a touch pad or a touch screen), a gyroscope, an accelerometer, a position detector, and/or an audio user input interface. A single component, such as a touch screen, may function as both a display device of presentation interface320and user input interface335.

Computing device300, in the exemplary embodiment, includes a communication interface340coupled to processor315. Communication interface340communicates with one or more remote devices (e.g., in some embodiments, CT imaging system10). To communicate with remote devices, communication interface340may include, for example, a wired network adapter, a wireless network adapter, and/or a mobile telecommunications adapter.

To control operation of CT imaging system10, data is communicated between one or more static components (e.g., a stationary housing for gantry12) and one or more rotating components (e.g., gantry12itself). As used herein, a ‘rotating component’ refers to a component that rotates relative to a ‘static component’. In the systems and methods described herein, inductive crosstalk is utilized to communicate data between static components and rotating components. This enables contactless communications between rotating and static components, as described herein.

In the exemplary embodiment, communication utilizing inductive crosstalk is accomplished using at least two conductors, or lines. At least one first line is located on a static component of CT imaging system10, and at least one second line is located on a rotating component of CT imaging system10. Notably, first and second lines do not physically contact one another, but data is communicated between first and second lines using inductive crosstalk.

FIG. 4is a schematic diagram illustrating electromagnetic interactions between a first conductive line402and a second conductive line404. For example, as a first current travels along first conductive line402, a first magnetic field406is generated around first conductive line402. First magnetic field406in turn induces a second magnetic field408around second conductive line404. As shown inFIG. 4, first magnetic field406is in a direction opposite second magnetic field408(e.g., if first magnetic field406is clockwise, second magnetic field408is counterclockwise). Second magnetic field408causes a second current to flow through second conductive line404.

In this example, because the first current in first conductive line402causes generation of the second current in second conductive line404, first conductive line402may be referred to as the ‘aggressor’ line, and second conductive line404may be referred to as the ‘victim’ line. Of course, those of skill in the art will appreciate that an initial current in second conductive line404will generate a subsequent current in first conductive line402, in which case second conductive line404is the aggressor line and first conductive line402is the victim line.

Because first and second conductive lines402and404do not physically contact one other (either directly or through other conductive components), first and second conductive lines402and404do not have a common ground. As such, there is no capacitive crosstalk between first and second conductive lines402and404. Rather, there is only inductive crosstalk between first and second conductive lines402and404.

There are two components of inductive crosstalk between first and second conductive lines402and404: near end crosstalk and far end crosstalk. The near end crosstalk between first and second conductive lines402and404can be represented as:

NEXT=14⁢(CMCL+LMLL)(Equation⁢⁢1)
where CMis the mutual capacitance between first and second conductive lines402and404, CLis the capacitance per unit length of first and second conductive lines402and404, LMis the mutual inductance between first and second conductive lines402and404, and LLis the inductance per unit length of first and second conductive lines402and404.

The far end crosstalk between first and second conductive lines402and404can be represented as:

FEXT=12⁢(lengthvel*trise)⁢(CMCL-LMLL)(Equation⁢⁢2)
where ‘length’ is the coupling length of first and second conductive lines402and404, triseis the risetime of the signal on the aggressor conductive line (i.e., first conductive line402), CMis the mutual capacitance between first and second conductive lines402and404, CLis the capacitance per unit length of first and second conductive lines402and404, LMis the mutual inductance between first and second conductive lines402and404, and LLis the inductance per unit length of first and second conductive lines402and404.

As can be seen from Equation 1, the near end crosstalk does not depend on trise. Further, the near end crosstalk is always a positive value. In contrast, as can be seen from Equation 2, the far end crosstalk does depend on trise. Further, if the ratios of capacitances and inductances are equal, the far end crosstalk cancels out. This occurs if all of the magnetic field lines are contained within a homogenous dielectric material.

The total crosstalk is the superposition of the near end cross talk and the far end crosstalk. Further, the near end crosstalk results in a flat magnitude variation on the communication channel, and the far end crosstalk contributes to distortion in the flatness of the communication channel.

Turning now toFIGS. 5-7, one example embodiment of CT imaging system10for implementing inductive crosstalk is illustrated. More particularly,FIG. 5is a front view of a portion of CT imaging system10,FIG. 6is a perspective view of a portion of CT imaging system10, andFIG. 7is another perspective view of a portion of CT imaging system10. As shown inFIG. 5, CT imaging system10includes a stationary component502and a rotating component504. In the illustrated embodiment, stationary component502is embodied as one or more brackets510,512. In other embodiments, stationary component502may include, for example, a housing or stationary frame of CT imaging system10. In the illustrated embodiment, rotating component504includes, for example, gantry12of CT imaging system10or a slip ring of CT imaging system10.

As shown inFIG. 6, a first conductive line506is coupled to rotating component504. First conductive line506, embodied as two parallel wires520,522, extends circumferentially about gantry12. Moreover, each of wires520,522includes a respective seam524, at which a first end and a second end of each wire520,522meet come together to close the loop of the wire520,522. Seam524represents a discontinuity in first conductive line506, and, accordingly, seam524is preferably as small as possible. The size of seam524may be limited by the need to ensure completion of the loop of each wire520,522. It should be understood that the size of seam524is exaggerated inFIG. 6for clarity.

As shown inFIG. 7, a cut-away view of bracket510, a second conductive line508is coupled to stationary component502, specifically to bracket510. Second conductive line508is embodied as a wire524substantially the same as wire520,522of first conductive line506, except that wire524forms a much smaller loop (i.e., a loop positioned on a bottom surface514of bracket510) and wire524is stationary.

First and second conductive lines506and508are positioned proximate one another, such that inductive crosstalk occurs between first and second conductive lines506and508, as described above. Communication between first and second conductive lines506and508is bidirectional. Specifically, to communicate data from stationary component502to rotating component504, first conductive line506functions as the aggressor and second conductive line508functions as the victim. To communicate data from rotating component504to stationary component502, second conductive line508functions as the aggressor and first conductive line506functions as the victim.

In the exemplary embodiment, orthogonal frequency-division multiplexing (OFDM) is used as the physical layer to communicate over the communication channel between first and second conductive lines506and508provided by inductive crosstalk. Further, in the exemplary embodiment, communication is accomplished by shifting the WiFi frequency standard (which typically operates in a 5 to 6 Gigahertz (GHz) frequency band) to below the 5 to 6 GHz band. Specifically, OFDM is used to modulate the frequency into the RF band, which results in relatively lower tolerances and allows for bidirectional communication. The error vector magnitude (EVM) of such a configuration may be kept relatively low (e.g., below 1.5%).

As explained above, the inductive crosstalk between first and second conductive lines506and508has a near end component and a far end component. The far end component of the crosstalk may be reduced by tuning the system and adjusting the mechanical design of the system. Moreover, the discontinuity at seam524may be reduced as rotating component504is rotated at high speeds. In addition, CT imaging system10includes two brackets510,512. Each bracket510,512is configured to act as an antenna for CT imaging system10to facilitate inductive crosstalk as described herein. In the example embodiment, brackets510,512are positioned opposite one another across CT imaging system10, or about 180° from one another about the circumference of a frame or housing of CT imaging system10. Brackets510,512may be otherwise spaced from one another about the circumference the housing of CT imaging system10.

When the discontinuity at seam524is near and/or directly under one bracket510, acting as the antenna, bracket510begins to experience two discontinuous waveforms, causing signal interference. Accordingly, CT imaging system10is configured to switch to bracket512as the antenna substantially immediately before bracket510encounters seam524, to avoid the discontinuity of the seam524disrupting communications. Specifically, in one embodiment, each bracket510,512includes an optical sensor526at a leading end thereof (i.e., the end of bracket510,512that will first encounter seam524). When optical sensor526detects seam524, optical sensor526transmits a signal (e.g., to computer46, shown inFIG. 1) that causes a switch, such that the opposite bracket510,512acts as the antenna (until that opposite bracket encounters seam524, which triggers another switch).

The embodiments described herein provide a contactless communication system for a CT imaging system. A first conductive line is coupled to a stationary component of the CT imaging system. A second conductive line is coupled to a rotating component of the CT imaging system. Inductive crosstalk between the first and second conductive lines provides a contactless communication channel that may be used to communicate data bi-directionally between the stationary component and the rotating component. Notably, the embodiments described herein are not limited to use with CT imaging systems, but may be used for contactless bi-directional data communication in other implementations.

The systems and methods described herein may be used to detect contraband. As used herein, the term “contraband” refers to illegal substances, explosives, narcotics, weapons, special nuclear materials, dirty bombs, nuclear threat materials, a threat object, and/or any other material that a person is not allowed to possess in a restricted area, such as an airport. Contraband may be hidden within a subject (e.g., in a body cavity of a subject) and/or on a subject (e.g., under the clothing of a subject). Contraband may also include objects that can be carried in exempt or licensed quantities intended to be used outside of safe operational practices, such as the construction of dispersive radiation devices.

A computer, such as those described herein, includes at least one processor or processing unit and a system memory. The computer typically has at least some form of computer readable media. By way of example and not limitation, computer readable media include computer storage media and communication media. Computer storage media include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules, or other data. Communication media typically embody computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism and include any information delivery media. Those skilled in the art are familiar with the modulated data signal, which has one or more of its characteristics set or changed in such a manner as to encode information in the signal. Combinations of any of the above are also included within the scope of computer readable media.

Exemplary embodiments of methods and systems are described above in detail. The methods and systems are not limited to the specific embodiments described herein, but rather, components of systems and/or steps of the methods may be used independently and separately from other components and/or steps described herein. Accordingly, the exemplary embodiment can be implemented and used in connection with many other applications not specifically described herein.