Abstract:
A base unit operable with a wireless patient monitoring unit used to acquire physiological data during an MRI examination is constructed to have a detachable display unit. The detachable display unit wirelessly communicates with the base unit when in a roving mode. The detachable display unit may also have a magnetically-hardened power supply that does not saturate during an MRI examination. Such a magnetically-hardened power supply allows the display unit to operate when proximate or in the magnetic field generated by an MRI machine during an MRI examination.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application 60/799,884, filed May 12, 2006, the disclosure of which is incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Background of the Invention 
       [0002]    The present invention relates generally to electronic patient monitors and, in particular, to a detachable display unit suitable for use in the severe electromagnetic environment of a magnetic resonance imaging (MRI) machine. 
         [0003]    Magnetic resonance imaging allows images to be created of soft tissue from faint electrical resonance (NMR) signals emitted by nuclei of the tissue. The resonance signals are generated when the tissue is subjected to a strong magnetic field and excited by a radiofrequency pulse. 
         [0004]    A patient undergoing an MRI scan may be received into a relatively narrow bore, or cavity, in the MRI magnet. During this time, the patient may be remotely monitored to determine, for example, heartbeat, respiration, temperature and blood oxygen. A typical remote monitoring system provides an “in-bore” patient sensor near the patient connected by electrical or optical cables or by RF data link to a base unit outside of the bore of the MRI magnet. 
         [0005]    The base unit customarily includes a display unit that may be consulted before the MRI scan to ensure that the monitoring sensors, for example, ECG leads or blood pressure cuffs are properly positioned and functioning. During the scan, when it is critical that the patient be continuously monitored, one operator may be stationed near the base unit in the MRI room and another will attend to the control of the MRI machine in the control room. The control room is normally separated from the MRI room holding the MRI magnet, and provides consoles and terminals for the MRI machine that allow control of the machine and the display of images from the MRI scan. 
         [0006]    Conventional base units are cabled to the patient sensor in the bore of the magnet using optical or electrical cables. Such cable runs can be cumbersome and interfere with access to the patient and free movement of personnel about the magnet itself. This problem is addressed in pending U.S. patent application Ser. Nos. 11/080,958, filed Mar. 15, 2005, and 11/080,743, filed Mar. 15, 2005, assigned to the assignee of the present invention and hereby incorporated by reference, which describe a wireless patient monitor that may be positioned near the patient to provide real-time monitoring of patient physiological signals without cumbersome cables that extend outside of the bore of the magnet. 
         [0007]    The inventions described in these applications overcome problems of the electrically noisy environment of the MRI, such as would normally be expected to interfere with radio communications, by using combined diversity techniques including: frequency diversity, antenna location diversity, antenna polarization diversity, and time diversity in the transmitted signals. The quality of the signals is monitored to select among diverse pathways, dynamically allowing low error rates and high bandwidth at practical transmission powers. 
         [0008]    Despite these diversity techniques, it may not be practical to transmit wirelessly from within the bore of the magnet into the control room, such as would allow the base unit to be repositioned in the control room itself to be monitored by the operator of the MRI machine. Accordingly, there is a need for a base unit operable in or near the MRI machine during an MRI examination. It would also be desirable to have a display unit detachable from the base unit that would enable an operator to roam with the display unit detached from the base unit, thereby allowing an operator to monitor the display unit remote from the base unit. It would also be desirable to control operation of a wireless patient monitoring system through inputs to the display unit that are wirelessly communicated to the base unit. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is generally directed to a base unit having a display that may be detached and used remotely allowing continuous, yet flexible, monitoring of the patient, both near the bore and at other locations without the need for separate displays. The base unit may operate as a repeater to transmit information received from the wireless units in the bore to a remote location where the display is located. The display unit may also operate to transmit information wirelessly to the wireless units in the bore. A magnet-hardened display allows the repositioning of the display at points closer to the magnet bore than would normally be possible with the base unit. In one embodiment, the display unit may be docked to the base unit or other docking stations, such as a wall dock. 
         [0010]    Therefore, in accordance with one aspect, the invention includes a base station for an MRI machine having a magnet defining a patient bore. The base station is positionable outside the bore of the magnet during an MRI examination and has a monitor unit that receives wireless transmissions of data from a patient sensor that acquires physiological signals of a patient. The base station further has a display unit that may be positioned remotely from the monitor unit and is capable of wireless communication with the monitor unit to display information associated with the data received from the patient sensor by the monitor unit. 
         [0011]    According to another aspect of the present disclosure, a base station for an MRI machine is presented. The base station may be positioned outside or near the magnetic field generated by the MRI machine during an MRI examination. In one embodiment, the base station has a dock, a monitor unit connected to the dock and receives physiological information from a patient during an MRI examination. The base station also has a display unit that may be connected to the dock when desired and configured to wirelessly receive data from the monitor unit during the MRI examination when remote from the dock. 
         [0012]    In accordance with another aspect, the present disclosure is directed to a display unit operable to display information acquired from a patient during an MRI examination. The display unit includes a display unit housing enclosing electronic components and having a quick-connect connector for repeated connection to and disconnection from a dock. The display unit also has a screen that displays data associated with information received from the patient during the MRI examination. A battery supplies power to the electronic components and is managed by a magnetically-hardened power supply. The magnetically-hardened power supply is operative in the presence of a high-flux magnetic field, without saturation, during an MRI examination. 
         [0013]    Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The drawings illustrate one preferred embodiment presently contemplated for carrying out the invention. 
           [0015]    In the drawings: 
           [0016]      FIG. 1  is a perspective view of an MRI suite showing the MRI magnet with a patient positioned for scanning and connected to a patient sensor, the latter communicating with a base unit positioned within the MRI room away from the bore of the magnet, and further showing a control room outside of the MRI suite shielded from the MRI suite against radiofrequency interference; 
           [0017]      FIG. 2  is a detailed view of a “hot shoe” attached to a pole supporting the display unit, the hot shoe removably holding a display associated with the base unit and providing power to that display; 
           [0018]      FIG. 3  is a block diagram of the base unit showing electrical connections through the hot shoe between a power supply of the base unit and the display; 
           [0019]      FIG. 4  is a block diagram of the display of  FIG. 3 , incorporating a magnet-hardened power supply offering several power supply options during local or remote connection; 
           [0020]      FIG. 5  is a figure similar to that of  FIG. 4  showing the principal components of the base unit, including a computer and a port for the attachment of local displays and keyboard devices; 
           [0021]      FIG. 6  is a block diagram of a second embodiment of the hot shoe transmitting, not only electrical power, but also data communication; and 
           [0022]      FIG. 7  is a flow chart of a program executed by the computer of  FIG. 5  of the base unit in coordinating the communications between one or more of the patient sensor, base unit and the remote display. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    The present invention will be described with the wireless acquisition and transmission of physiological data to a remote display unit that is operative in the magnetic field generated by an MRI magnet. However, it is understood that the present invention may also be useful in other applications involving high-flux magnetic fields. 
         [0024]    Referring now to  FIG. 1 , a magnet room  10  provides radiofrequency, and possibly magnetic shielding, enclosing an MRI magnet  12 . The magnet  12  may be part of an MRI machine controlled from a control room  16  providing a console  18  outside of the magnet room  10  and normally providing a shielded window  20  allowing viewing of the magnet  12  from the control room  16 . 
         [0025]    A patient  14  may be positioned to be received into a bore  22  of the magnet  12  on a movable table  24  for an MRI scan. Before the scan, a wireless patient sensor or monitor  26  may be connected to the patient  14  to monitor patient physiological signals, including ECG, blood oxygen, blood pressure, and the like. 
         [0026]    The patient sensor  26  may communicate via radio waves  28  to a base station  30  positioned outside the bore  22  of the magnet  12  using diversity techniques described in the above referenced co-pending patents hereby incorporated by reference. The base station  30  includes a monitor unit  32  and a display unit  34 , both mounted on a stanchion  38 , the latter extending upward from an optional wheeled base unit for easy movement. Generally, the monitor unit  32  receives wireless transmissions of data from the patient sensor  26 , processes the same, and displays the data (or information associated therewith) on a graphic screen of the display unit  34 . The display unit  34  may also include additional processing and user input controls, such as pressure-sensitive switches or a touch screen to provide commands to the monitor unit  32 . 
         [0027]    In communicating with the display unit, the monitor unit  32  may transmit the data on radio waves  36  implementing a different channel than the radio waves  28  received from the patient sensor(s)  26 . In this case, a channel may refer to any combination of logical and physical channel parameters including, for example, frequency, frequency hop patterns, packet identifiers, and the like. Wireless transmission of data to the display unit  34  allows the display unit  34  to be located either on a dock, such as stanchion  38 , or remotely located, per display unit  34 ′, for example, on a stanchion or other dock in the control room  16 . Alternately, the display unit may be docked on a wall or desk dock in the magnet room  10  or in the control room  16 . The control room  16  is normally shielded from the magnet room  10  but may provide a passive or active repeater penetrating the shield and passing radio waves  36  used by the monitor unit  32 . The display unit  34  may not only receive physiological data from the base station  30  but may also transmit commands to the base station  30  and, via the base station  30 , to the patient sensors  26 , for example, as input by an operator. Wireless communication eliminates the problem of cable management and allows the display unit  34  easy, and repeated detachability from the base station  30 . 
         [0028]    Referring now to  FIGS. 2 and 3 , freedom to relocate the display unit  34  is provided by a hot shoe  40 , held by the stanchion  38 , which may connect mechanically and electrically with a hot shoe socket  42  mounted on the rear surface of the display unit  34 . The hot shoe  40  and the hot shoe socket  42  present a quick-connect connection for attaching or detaching the display unit from stanchion  38 . Connecting the hot shoe  40  with the hot shoe socket  42  attaches the display unit  34  to the stanchion  38  or to another remotely located hot shoe (e.g., in the control room  16 ). 
         [0029]    The hot shoe  40  presents a plurality of direct current power contacts  44  that may connect with corresponding contacts  46  in the hot shoe socket  42 . When the hot shoe socket  42  is engaged with the hot shoe  40 , electrical contact may be had between individual pairs of contacts in  44  and  46 . A switch operator  48  may protrude from the hot shoe  40  to be depressed by a surface of the hot shoe socket  42  when the hot shoe socket  42  is engaged with the hot shoe  40 . The switch operator  48  closes a switch  50  to connect electrical power and/or ground to the contacts  44  so that power may be provided to the display unit  34  when it is attached to the stanchion  38 , but so that power is not exposed on the contacts  44  when the display unit  34  has been removed. 
         [0030]    In a preferred embodiment of the invention, the terminal of the switch  50  not connected to one of the contacts  44  is connected to a radiofrequency filter  52  that, in turn, connects to the power side of a storage battery  54  held in the base of the stanchion  38 . The filter  52  prevents electromagnetic interference picked up by the wiring of the stanchion  38  from being introduced into the display unit  34  and vice versa. 
         [0031]    The monitor unit  32  is also attached to the stanchion  38  and also internally connected to the battery  54 . A charge jack  56  is on the base of the stanchion  38  accepting a charger “brick” (not shown) to provide charging current to the battery  54  and operating power to the display unit  34  and monitor unit  32 . The display unit  34  also includes an internal battery (as will be described), which may be charged by the charger brick. 
         [0032]    The monitor unit  32  includes an antenna  58 , which, as described above, allows it to communicate wirelessly with the patient sensor  26  on a first channel formed by radio waves  28  and with the display unit  34  through antenna  62  on a second channel formed by radio waves  36 . 
         [0033]    Referring now to  FIG. 4 , the display unit  34  receives power through the hot shoe socket  42  at a special magnetically “hardened” power supply  66  in which a standard switching power supply circuit is modified by removal of “soft” ferrite or steel core transformers and replacing them with air core or “hard ferrite” core transformers that may operate without saturation in the environment of the high flux field of the MRI up to approximately 15,000 Gauss. In this way the display unit may operate in magnetic fields of up to 15,000 Gauss in strength. 
         [0034]    The power supply  66  may alternatively receive power directly through a charger jack  68  exposed at one side of the display unit  34  that may receive power from a charger brick  70 , in turn having a standard line cord  72  for connecting to line power. In addition, charger brick  70  may also supply electrical power to the base station  30  directly through the interconnection of contacts  44  and  46 . 
         [0035]    When the power supply  66  is receiving power, it, in turn, provides power to a transmitter/receiver  76  connected to the antenna  62  and to control circuitry  78 , which may include, for example, a processor, a digital signal processor implemented through discrete circuits or with a field programmable gate array (“FPGA”). The control circuitry  78  may provide signals to a liquid crystal display (LCD) touch screen  80  (or an LCD and switch panel) allowing both the display of data and the acceptance of user commands. 
         [0036]    Power supply  66  may also provide power to a string of LEDs  82  allowing for back-lighting of the LCD screen  80  without the need for cold cathode fluorescent tubes and their associated power supplies, which could produce unnecessary interference in the MRI environment and be inoperative in high field environments. 
         [0037]    Finally, the switching power supply  66  provides charging power to an internal battery  74  that may be used when the display unit  34  is in a roving mode not connected to the stanchion  38 , but communicating with the base unit via the antenna  62 . Alternately, or in addition thereof, the display unit may have one or more supercapacitors to provide power to the internal electronic components of the display unit and charged in a known manner using an appropriate charger, when necessary. 
         [0038]    Referring now to  FIG. 5 , the monitor unit  32  may receive power through a direct connection  84  with the stanchion  38  at a power supply  86 . Because the stanchion  38  is normally positioned away from the magnet  12  during an MRI examination, the monitor unit  32  may use standard switching power supply components to provide power to processing electronics  88  and transmitter/receiver  90 , communicating with antenna  58  to receive information from the patient sensor  26  and to communicate with the display unit  34 . The monitor unit  32  may also include a port system  92  providing for communication ports similar to those in a standard personal computer, allowing for the connection of a keyboard  94 , a standard display, such as an LCD display  96  and a cursor control device, such as a mouse,  98 . This allows the monitor unit  32  to be used independently of connection to the display unit  34 . 
         [0039]    Referring now to  FIG. 6 , in an alternative embodiment, the hot shoe  40  may also provide for a data connector  100 , in addition to the power contacts  44 . Data connector  100  is operationally connected to output data from or input data to the monitor unit  32 . Similarly, the hot shoe socket  42  may provide for a corresponding data connector  102  connecting with data connector  100 . The data connectors  100  and  102  may, for example, provide for a parallel or serial digital connection of conductors or optical cable or the like, and provide for a path between the monitor unit  32  and the display unit  34  when the display unit  34  is docked on the stanchion  38 . When the connectors  100  and  102  are connected, internal software may optionally disconnect the transmitter/receiver  76  in the display unit  34 , thereby preventing the generation of unnecessary radiofrequency signals. Similarly, the monitor unit  32  may suppress transmissions from the transmitter/receiver  90  to the display unit  34 . 
         [0040]    Connectors  100  and  102  allow for the introduction of a jumper cable  104  of arbitrary length allowing a direct cable connection between the monitor unit  32  and display unit  34  for situations where a remote display is required on a semi or permanent basis. By using the jumper cable  104 , a remote semi-permanent display may be used in addition to the roving wirelessly-connected display unit  34 . 
         [0041]    Referring now to  FIG. 7  and  FIG. 5 , the processing electronics  88  may execute a stored program  106  coordinating the wireless communications between the monitor unit  32  and the display unit  34  by properly assigning channels to the communications permitting, for example, the use of multiple display units  34  with one monitor unit  32  or multiple monitor units  32  communicating with one display unit  34  without interference. In order to provide for this unique connection between devices, a channel selection process is employed to logically connect a given monitor unit  32  with a given display unit  34 . 
         [0042]    As indicated by process block  108 , this commissioning process begins with the identification of a particular display unit  34  and monitor unit  32  by the entry of a display identifier or the like, and possibly the entry of a unique serial number or MAC address. 
         [0043]    At process block  110 , a logical channel or network address is selected for the communication, such as will be provided to both the display unit  34  and monitor unit  32 , either manually or by a default communication channel. As before, a channel may refer to any combination of logical and physical channel parameters including, for example, frequency hop patterns, packet identifiers, and the like. 
         [0044]    The user may lock the channel selected, preventing inadvertent channel changes, such as may confuse the unique path between a particular patient  14  and a particular display unit  34 , such as might permit a user to be misled about the source of particular signals. If the channel is not locked, then, at process block  114 , the channel may be changed. 
         [0045]    If the channel is locked, then, at decision block  112 , the program jumps to decision block  116 , which allows the lock state to change per process block  118 , possibly requiring a password or the like. 
         [0046]    It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.