Abstract:
An injector system for injection of a fluid medium into a patient within an electromagnetic isolation area. The injector system includes a powered injector, a system controller therefor, and a plurality of communication units. The powered injector is positioned within the isolation area. A first communication unit integral with the powered injector enables the first communication unit and the powered injector to be moved as a unit. The system controller is positioned outside the isolation area and has a second communication unit integral therewith. An intermediate communication unit ensures communication between the first and the second communication units and therethrough between the powered injector and the system controller using an authentication technique therewith. The first, second and intermediate communication units are adapted to communicate by transmission of radio frequency (RF) energy. The RF energy is chosen to avoid interfering with the operation of MRI scanners.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a division of application Ser. No. 09/586,140, filed on Jun. 2, 2000 now U.S. Pat. No. 6,704,592, the contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates generally to communication systems and methods of communication, and, especially, to communication systems and methods of communication for use in magnetic resonance imaging procedures. 
   In general, magnetic resonance imaging (MRI) systems require isolation from external sources of electromagnetic fields to optimize image quality. Conventional MRI systems, therefore, typically include some form of electromagnetic isolation shield or barrier. Most often, a room enclosed by copper sheeting or conductive mesh material isolates or shields the imaging system from undesirable sources of electromagnetic radiation, including the electromagnetic noise inherent in the atmosphere. 
   A number of powered injectors for use in MRI have been developed. These powered injectors are a potential source of electromagnetic radiation. To realize the full benefit of “shielded” rooms in MRI, injector systems typically employ a controller that is isolated from the powered injector. For example, the controller may be placed outside of a shielded room (e.g., in the MRI control room) in which the MRI scanner and the powered injector operate. Such isolation prevents undesirable electromagnetic radiation generated by the injector system controller from interfering with the signals used to create the magnetic resonance images. 
   The external, isolated location of the system controller creates various problems associated with the installation and operation of these systems. One such problem is the need to provide a communication link between the external controller and the injector (which is located within the shielded area), without introducing extraneous electromagnetic radiation. In other words, there is a need to provide injector control circuitry while maintaining the integrity of the electromagnetic shield. 
   Previous attempts to solve these problems included drilling holes in the wall of the electromagnetic shield for inserting the necessary lines or, alternatively, laying the lines under a shielded floor of the imaging room. These alternatives have proven to be less than optimum, since spurious radiation can arise from the presence of the various supply cables within the shielded imaging suite. Additionally, MRI systems, which employ these alternatives often, require substantial site dedication and are, therefore, not very portable. 
   U.S. Pat. No. 5,494,036, the disclosure of which is incorporated herein by reference, discloses, in one embodiment, an improved communication link that is made through a window in an isolation room barrier. These windows are typically in the form of a glass laminate containing a conductive wire mesh, or alternatively, a window that is coated with a thin sheet of conductive material such as gold to maintain the shielding characteristics of the isolation area or room. 
   The above-noted embodiment of the communications link of U.S. Pat. No. 5,494,036 includes electromagnetic transceivers that operate in a frequency range which permeates the window while maintaining the integrity of the isolation barrier. The internal transceiver is positioned on the window and is tethered or attached to the injector control in the MRI shielded room via a communication line. The external transceiver is positioned on the opposite side of the window (i.e., in the MRI control room) and is connected to the injector system controller. Infrared or electromagnetic energy in the visual range are noted to provide the best results. A fiber optic communication link is also disclosed. 
   Although improvements have been made in communication systems for use in magnetic resonance imaging, it remains desirable to develop improved communication systems. 
   SUMMARY OF THE INVENTION 
   In one aspect, the present invention provides a system for bi-directional communication during a magnetic resonance imaging procedure using an MRI scanner and an electromagnetic isolation barrier defining an isolation area within which the scanner is positioned. 
   The system includes generally at least a first source of RF signals outside the frequency range of the scanner and at least a first receiver for RF signals outside the frequency range of the scanner. The first source of RF signals and the first receiver of RF signals are in communication with a system controller positioned outside the isolation area. The system also includes at least a second source of RF signals outside the frequency range of the scanner and at least a second receiver for RF signals outside the frequency range of the scanner. The second source of RF signals and the second receiver for RF signals are positioned within the isolation area. 
   The system of the present invention allows bi-directional communication with and control of instrumentations within the isolation barrier from the system controller located outside of the isolation barrier. Preferably, the frequency of the RF signal is above approximately 1 Gigahertz. For example, the RF signal can be in the 2.4 GHz frequency range. 
   The system can, for example, include a powered injector to inject a fluid medium into a patient. In this embodiment, the second receiver and the second source are preferably in communicative connection with a control unit of the powered injector. The second receiver and the second source can, for example, be connected to the injector control unit so that the injector control unit, the second receiver and the second source can be moved as a unit. 
   In another aspect, the present invention provides an injector system for injection of a fluid medium into a patient within an electromagnetic isolation area. The injector system includes a powered injector positioned within the isolation area and a system controller positioned outside the isolation area. The system controller includes an operator interface. The powered injector includes a first communication unit, and the system controller includes a second communication unit. The first communication unit and the powered injector are connected so that the first communication unit and the powered injector can be moved as a unit. The first communication unit is also adapted to communicate with the second communication unit by transmission of energy through the air. The energy is chosen to not create substantial interference with a magnetic resonance imaging scanner positioned within the isolation area. 
   The energy can be electromagnetic energy outside the frequency range of the scanner (for example, RF energy above approximately 1 Gigahertz). The energy can also be vibrational energy, sonic energy or ultrasonic energy. Furthermore, the energy can be visible light or infrared light. 
   The injector system can further include at least one intermediate communication unit positioned within the isolation area through which the first communication unit can communicate with the second communication unit. The first communication unit communicates with the intermediate communication by transmission of energy through the air. A plurality of such intermediate communication units can be positioned within the isolation area to facilitate communication. 
   In another aspect, the present invention provides a system for use in an MRI procedure that includes an MRI scanner positioned on a first side of an electromagnetic isolation barrier and an injector control unit to control injection of a fluid medium into a patient. The injector control unit is also positioned on the first side of the isolation barrier. The system also includes a system controller positioned on a second side of the isolation barrier. The injector control unit includes a first communication unit, and the system controller includes a second communication unit. The first communication unit is adapted to communicate with the second communication unit in a bi-directional manner by transmission of energy through the air. As described above, the energy is chosen to not create substantial interference with a magnetic resonance imaging scanner. 
   The present invention also provides a communication system for use in an MRI procedure that includes a first communication unit positioned within a shielded housing on an interior side of the isolation barrier. The first communication unit includes a first receiver and a first transmitter. The communication system also includes a second communication unit positioned on an exterior side of the isolation barrier. The second communication unit includes a second receiver and a second transmitter. The first communication unit is in connection via optical cabling with a first light transmitting device positioned on an interior side of the isolation barrier adjacent a viewing window in the isolation barrier. The second communication unit is in connection via optical cabling with a second light transmitting device positioned on the exterior side of the isolation barrier adjacent a viewing window in the isolation barrier. The first communication unit and the second communication unit communicate via transmission of optical energy between the first light transmitting device and the second light transmitting device. 
   In one aspect, the first communication unit is positioned within a shielded housing of an injector control unit. The first light transmitting device can include a first lens assembly in communication with the first transmitter via optical cable and a second lens assembly in communication with the first receiver via optical cable. Likewise, the second light transmitting device can include a third lens assembly in communication with the second receiver via optical cable and a fourth lens assembly in communication with the second transmitter via optical cable. The first lens assembly and the third lens assembly are preferably in general alignment to enable communication between the first transmitter and the second receiver via transmission of light therebetween. Similarly, the second lens assembly and the fourth lens assembly are preferably in general alignment to enable communication between the first receiver and the second transmitter via transmission of light therebetween. 
   In another aspect, the present invention provides a method of controlling an injector within an isolation barrier of a magnetic resonance imaging area, including the steps of: transmitting RF signals outside the frequency range of the magnetic resonance imaging scanner from a system control unit positioned outside the isolation barrier to an injector control unit positioned inside the isolation barrier, the system control unit including an operator interface; and transmitting RF signals outside the frequency range of the magnetic resonance imaging scanner from the injector control unit to the system control unit. 
   The present invention also provides a method of transmitting data between the exterior of an isolation barrier of a magnetic resonance imaging area and the interior of the isolation barrier, including the steps of: positioning a first passive light transmitting assembly adjacent a translucent window in the isolation barrier on the outside of the isolation barrier; positioning a second passive light transmitting assembly adjacent the window on the interior of the isolation barrier in general alignment with the first light transmitting assembly such that light energy can be transmitted therebetween, and connecting the second light transmitting assembly via optical cable to a communication unit positioned within a shielded housing within the isolation barrier. 
   Numerous other objects and advantages of the present invention will be apparent from the following drawings and detailed description of the invention and its preferred embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  illustrates a perspective view of one embodiment of a injection/communication system of the present invention. 
       FIG. 1B  schematically illustrates the communication system of  FIG. 1A . 
       FIG. 1C  illustrates a perspective view of an embodiment of an injector and an injector control unit mounted in a single mobile base unit. 
       FIG. 1D  schematically illustrates an alternative embodiment of the communication system of  FIGS. 1A and 1B . 
       FIG. 2  illustrates another embodiment of a communication system of the present invention. 
       FIG. 3A  schematically illustrates an embodiment of an MRI communication system including passive optical communication through the viewing window of an MRI room to a communication unit positioned within a shielded housing of an injection control unit. 
       FIG. 3B  illustrates an expanded view of one embodiment of the communication system of  FIG. 3A . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1A and 1B  illustrate an embodiment of a magnetic resonance imaging system of the present invention. The MRI system preferably includes an external system controller  100  that preferably includes a processing unit  110  (for example, a digital microcomputer), a battery charger  120  and an operator interface  125  (including, for example a data entry unit  125 ′ and a display  125 ″). System controller  100  is located outside of a shielded area such as an imaging room  150  that is shielded from electromagnetic interference by, for example, a shield  160  (see  FIG. 1B ). Electromagnetic isolation can, for example, be achieved by completely enclosing the room with copper sheet material or some other suitable, conductive layer such as wire mesh. 
   Shielded imaging room  150  preferably includes a patient viewing window  170  in shield  160  to allow an observer and/or operator to view the room without breaching electromagnetic shield  160 . Window  170  can, for example, be formed by sandwiching a wire mesh material (not shown) between sheets of glass or by coating the window with a thin coating of conductive material such as gold (not shown) to maintain the continuity of electromagnetic shield  160 . 
   The magnetic resonance imaging system also preferably includes a contrast media injection control unit  200  located within shielded imaging room  150 . Injection control unit  200  is preferably powered by a rechargeable battery  210 . Injection control unit  200  preferably includes control circuitry which controls electric motors  220  and  220 ′, which are preferably located within injection control unit  200 . Injection control unit  200  is preferably contained within an electromagnetic shield  230  to reduce or eliminate any undesired electromagnetic radiation generated by electric motors  220  and  220 ′ from interfering with the magnetic field used to generate the magnetic resonance image. 
   Separation of the electric motors from the injection head  250 , as well as the additional electromagnetic shielding, results in improved system performance and improved overall image quality. Injection control unit  200  can be separated (for example, by ten to fifteen feet) from injection head unit  250 , which is typically placed near the patient. Although injection control unit  200  is preferably shielded to prevent RF interference, ferromagnetic material in injection control unit  200  can result in injection control unit  200  being drawn into magnet gantry  280 . This undesirable result can result in damage to magnetic gantry  280 , damage to injection control unit  200  and/or injury to personnel present in shielded room  150 . 
   Injection head unit  250  is preferably located in close proximity to the patient to decrease the distance that the contrast media fluid must travel from the contrast media from syringes  260  and  260 ′ connected to injection head unit  250 . Injection head unit  250  further includes drive members  262  and  262 ′ such as pistons that act to pressurize the contents of syringes  260  and  260 ′, respectively, for injection into the patient. Drive members  262  and  262 ′ are preferably connected to electric motors  220  and  220 ′, respectively, in injection control unit  200  by a non-rigid connection such as by flexible mechanical drive shafts  264  and  264 ′, respectively. Drive shafts  264  and  264 ′ are preferably made from a nonferrous metal such as hard brass. 
   As illustrated in  FIG. 1C , injection control unit  200  can also be part of or mounted on the same mobile base unit  270  as injection head unit  250 . In this embodiment, particular care is preferably take to limit the amount of ferromagnetic material used in injection control unit  200  to prevent mobile base  270  from being drawn into magnet gantry  280 . 
   For control of injection head unit  250  by system controller  100 , communication must be maintained between system controller  100  and injection control unit  200 . In one aspect of the present invention, injector control unit  200  is preferably in communication with a communication unit  320  that preferably includes a transmitter  322  and a receiver  324 . Likewise, control system  100  is preferably in communication with a communication unit  330 . Communication unit  330  preferably includes a transmitter  332  and a receiver  334 . Transmitters and receivers for use in the present invention can also be combined in transceivers as known in the art. 
   In one aspect of the present invention, transmitter  322  and receiver  324  of communication unit  320  are in wireless or cableless communication with communication unit  330 . For example, there is preferably no communication line (for example, fiber optic cabling or shielded electrical cabling) connecting injector control unit  250  to a generally stationary communication device positioned at window  170 . 
   Wireless communication (or communication through air) at any communication point between injection control unit  200  and system controller  100  within shielded room  170  can increase mobility of injection control unit  200 , injection head unit  250  and/or personnel within room  170  by decreasing the amount of wiring in room  170 . Communication unit  320  can, for example, be transportable/movable with mobile base  270 . Injector head unit  250  and injector control unit  200  are thus “untethered” and can be relatively freely moved to different positions within the shielded area. This increased mobility facilitates use thereof by, for example, facilitating positioning of injector head unit  250 . Moreover, eliminating communication lines on the floor of imaging room  150  may eliminate a potential source of tripping accidents in the shielded area. 
   In one embodiment, digital radio frequency (RF) energy that is outside the frequency range of the MRI scanner is used to transmit information to and/or from injector control unit  200 . The imaging frequency of a 0.2 Tesla to 1.5 Tesla MRI scanner is typically in the range of approximately 8 MHz (Megahertz) to 64 MHz. A two-Tesla system may operate at an imaging frequency of up to approximately 85 MHz. The communication system of the present invention, therefore, transmits and/or receives RF signals that are preferably above approximately 100 MHz. More preferably, the RF signals are above approximately 400 MHz. Most preferably, the RF signals are above approximately 1 GHz (Gigahertz). In that regard, RF signals outside of the imaging frequency of the MRI scanner can be transmitted through “leaks” or intentional RF gaps that act as leaks (for example, tuned ports of ventilation ports) in isolation shield  160  without creating substantial interference with the imaging procedure. The ability of current isolation barriers to block RF signals is typically substantially reduced at frequencies above approximately 1 GHz, making RF signals above that frequency particularly suited for transmission through such isolation barriers without substantial loss of signal or interference with scanner  300 . 
     FIG. 1D  illustrates an alternative embodiment of the present invention. In the embodiment of  FIGS. 1A and 1B , RF communication unit  330  (including, for example, transmitter  332  and receiver  334 ) is positioned outside of imaging room  150 . In the embodiment of  FIG. 1D , RF communication unit  330  is positioned within imaging room  150  and is connected to system controller  100  via non-RF-interfering cabling  340  (for example, fiber optic cabling or shielded cabling) through tuned port  350 . As used herein and commonly in the MR arts, the term “tuned port” prefers to an opening or aperture in shield  160  that is designed/dimensioned to prevent transmission of energy of certain frequencies therethrough. Communication unit  330  communicates with RF communication unit  320  as described above. 
   In one aspect, the radio frequency energy used in the communications system of the present invention is in the range of approximately 2.4 to 2.48 GHz, which is a band of energy set aside by the Federal Communication Commission and other national organizations for industry, scientific and medical (ISM) use. Operation in the 2.4 GHz ISM band allows license-free use and worldwide compliance. 
   Because many other communications systems may use RF signals in the range of frequencies used in the present invention, it may be desirable to modulate the signal between injector control unit  200  and system controller  100  to reduce or eliminate the potential for interference with or from such other communication systems. For example, frequency hopping spread spectrum modulation or direct sequencing spread spectrum modulation as known in the art may be used in the present invention. A detailed description of modulated transmissions is provided in WIT2410 2.4 GHZ Spread Spectrum Wireless Industrial Transceiver Integration Guide (Jun. 15, 1999) available from Digital Wireless Corporation of Norcross, Ga., the disclosure of which is incorporated herein by reference. Spread spectrum modulation is currently used at 900 MHz and 2.4 GHz. 
   However, even modulation techniques such as frequency hopping spread spectrum modulation or direct sequencing spread spectrum modulation are commonly use in RF communication devices, and the risk of interference with or from other devices may still be unacceptably high. Therefore, one or more unique data authentication techniques can be used for RF communication in the present invention. For example, at least a part of a communication sequence signal may be transmitted at two or more different RF frequencies (all of which are outside of the frequency range of the MRI scanner). For example, data can be transmitted at 2.4 GHz and 5.8 GHz simultaneously. 
   In general, any number of communication protocols or specifications can be used in digital RF transmission under the present invention. For example, the Bluetooth™ Technology of the Bluetooth Special Interest Group as set forth in the Bluetooth Specification Release 1.0 (the disclosure of which is incorporated herein by reference) is suitable for use in the present invention. The Bluetooth specification specifies a system solution comprising hardware, software and interoperability requirements and operates in the common 2.4 GHz ISM band. 
   Furthermore, any type(s) of energy that reduce or eliminate interference with the magnetic field used by the MRI scanner to generate an image are suitable for transmission of information in the present invention within the isolation barrier. For example, in addition to RF and other electromagnetic energy outside the frequency used by scanner  300  (for example, light energy (such as, visible light and/or infrared light), sonic energy, ultrasonic energy, and/or vibrational energy can be used. 
   In  FIG. 2 , injector control unit  200   a  includes a communication unit  320   a  that preferably includes a transmitter  322   a  and a receiver  324   a . Likewise, system controller  100   a  includes a communication unit  330   a . Communication unit  330   a  includes a transmitter  332   a  and a receiver  334   a . As described above, the transmitter/receiver pairings can be in the form of transceivers. 
   In one embodiment, optical and/or infrared light is used to transmit information between system controller  100   a  and injector control unit  200   a  through, for example, window  170 . In the case that optical/infrared light is used for a transmission signal, communication can be interrupted if there is not a direct “line of sight” between control communication unit  330   a  and injector communication unit  320   a . To assist in providing a substantially direct line of sight, an optical/infrared transceiver  126   a  in communication with control communication unit  330   a  can, for example, be positioned at the outside of window  170  to transmit/receive optical/infrared signals through window  170 . Signals to or from transceiver  126   a  can be transmitted directly from or to injector communication unit  320   a . To further assist in providing a substantially direct line of communication, an optical/infrared transceiver  226   a  may also be positioned on the interior of window  170  to transmit to and receive signals from injector communication unit  320   a . Furthermore, one or more intermediate/redirecting communication units  228   a  can be positioned at various locations about the shielded area. Intermediate communication units  228   a  may, for example, be adapted to redirect/relay signals between, for example, transceiver  226   a  and injector communication unit  320   a . In this manner, injector control unit  200   a  can be moved freely about the shielded area without losing a communication link with system controller  100   a.    
   Transceivers  226   a  and  126   a  and/or intermediate communication unit(s)  228   a  may also amplify or otherwise modify signals. For example, the signals between transceiver  126   a  and  226   a  may be in the form of light energy, ultrasonic energy, or vibrational energy. Transceiver  226   a  or intermediate communication unit(s)  228   a  may transform such signals into RF signals of an appropriate frequency (as described above) for communication with injector communication unit  320   a . Transceiver  226   a  and redirecting communication unit(s)  228   a  can be physically linked as represented by communication lines  270   a  in  FIG. 2 . Likewise, control communication unit  330   a  and transceiver  126   a  can be connected by communication line(s)  170   a . In this embodiment, like the embodiment of  FIGS. 1A through 1D , communication unit  320   a  preferably remains untethered by any communication line. 
   In other embodiments, sonic and/or ultrasonic energy may, for example, be used to transmit information to and/or from communication unit  320   a . Transceiver  226   a  and/or redirecting communications units  228   a  may, for example, transmit voice commands to communication unit  320   a  that may be interpreted by a processing unit  260   a  in communication connection with communication unit  320   a  for control of injector control unit  200   a.    
   In general, any type of energy that may be used to transmit information through the air to and/or from communication unit  320   a  and/or communication unit  330   a  and that does not substantially interfere with the MRI scanner (that is, create unacceptable artifacts on an image) is suitable for use in the present invention. 
   Another aspect of the present invention is illustrated in  FIGS. 3A and 3B . In this embodiment, electromagnetic interference in an MRI procedure is reduced or eliminated through the use of a passive optic communicative coupling (through window  170 ) of a system controller  100   b  on the exterior of an imaging room  150  and an injector system (including, for example, an injection control unit  200   b  and an injection head unit  250   b  as described above) in the interior of imaging room  150 . In that regard, system controller  100   b  includes a transmitter  332   b  and a receiver  334   b . Transmitter  332   b  and receiver  333   b  are preferably connected to a light transmitting or collimating device  600   a  (for example, one or more lenses) via fiber optic cabling  700  and/or  700 ′. Light collimating device  600   a  is aligned with a second light transmitting or collimating device  600   b  on the interior of imaging room  150  through window  170 . Light collimating device  600   b  is connected to a transmitter  322   b  and a receiver  324   b  positioned within injection control unit  200   b  via fiber optic cabling  710  and/or  710 ′. By locating transmitter  322   b  and a receiver  324   b  within the shielded housing  230   b  of injection control unit  200   b , electromagnetic interference therefrom can be greatly reduced or eliminated. 
     FIG. 3B  illustrates an expanded view of one embodiment of light collimating devices  600   a  and  600   b  for communication through window  170 . In general, light collimating devices  600   a  and  600   b  preferably act to transmit/focus one or more columns or beams of light (for example, visible light such as bright LCD light) for passage through window  170 . In the embodiment of  FIG. 3B , collimating device  600   a  includes a first lens assembly  720   a  and a second lens assembly  720   b . Lens assembly  720   a  is in communication with transmitter  332   b  via fiber optic cable  700 , while lens assembly  720   b  is in communication with receiver  334   b  via fiber optic cable  700 ′. Collimating device  600   b  includes a third lens assembly  730   a  and a fourth lens assembly  730   b . Lens assembly  730   a  is in communication with receiver  324   b  via fiber optic cable  710 , while lens assembly  730   b  is in communication with transmitter  322   b  via fiber optic cable  710 ′. In one embodiment, convex lens having a 25 mm diameter and a focal length of 9 mm were used in all lens assemblies  720   a ,  720   b ,  730   a  and  730   b . Lens assembly  720   a  is aligned with lens assembly  730   a  such that information in the form of a beam of light can be transmitted between transmitter  332   b  and receiver  324   b . Likewise, Lens assembly  720   b  is aligned with lens assembly  730   b  such that information in the form of a beam of light can be transmitted between transmitter  322   b  and receiver  334   b . Bi-directional transmission of data can also be achieved using a single lens assembly on each side of window  170  by, for example, multiplexing the transmission of data. 
   Information can be transmitted via light energy using a protocol such as the Ethernet 10baseT protocol. Examples of transceivers and receivers suitable for use in the present invention include the HFBR 1527 transmitter and the HFBR 2526 receiver available from Hewlett Packard. 
   Data transmission rates of, for example, 10 Mbps and higher are possible in the embodiment of  FIGS. 3A and 3B . Moreover, by positioning transmitter  322   b  and receiver  324   b  (or a transceiver) within shielded housing  230   b  of injection control unit  200   b  and passively transmitting light between collimating devices  600   a  and  600   b , potentially interfering electromagnetic fields are reduced as compared, for example, to the system of U.S. Pat. No. 5,494,036 in which a transceiver is positioned at the viewing window and connected to the injection control unit thereof via shielded cabling. 
   Although the present invention has been described in detail in connection with the above embodiments and/or examples, it is to be understood that such detail is solely for that purpose and that variations can be made by those skilled in the art without departing from the invention. The scope of the invention is indicated by the following claims rather than by the foregoing description. All changes and variations which come within the meaning and range of equivalency of the claims are to be embraced within their scope.