MRI compatible pulse oximetry system

• US 5,323,776 A
• Filed: 10/15/1992
• Issued: 06/28/1994
• Est. Priority Date: 10/15/1992
• Status: Expired due to Term

• Current Assignee: Picker International, Inc. (Marconi Holdings Company Limited)
• Original Assignee: Picker International, Inc. (Marconi Holdings Company Limited)
• Inventors: Flugan, David C., Gauss, Robert C., Blakeley, Douglas M.
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US07/961,150
• Time in Patent Office: 621 Days
• Field of Search: 128/633, 128/653.2, 128/653.5, 128/666, 128/901, 128/687
• US Class Current: 600/324
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: G01R 33/465 applied to biological material, e.g. in vitro testing
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

Magnetic resonance imaging hardware (A) defines a patient receiving region (20) that is surrounded by a bore liner (22). A socket (50) is mounted in the bore liner with an appropriate receptacle for receiving a standard plug (52) of a conventional pulse oximetry system. Conventional pulse oximetry systems include a sensor unit (54) connected with a cable (56) having the plug (52) at one end thereof. A notch filter (62) attenuates currents near the resonance frequency of the imager. A preamplifier (60) amplifies signals from the sensor unit. Within the shielding (66) of the preamplifier, a low pass filter (68) is provided to remove induced radio frequency components from the preamplified sensor unit signal. A radio frequency filter (70) mounted at the shield of the shielded room (B) prevents radio frequency signals from reaching an exterior processing and display unit (E) and prevents radio frequency signals from a clock (72) of the processing and display unit from being conveyed into the shielded room (B). The processing and display unit processes the signal received from the preamplifier to generate a pulse rate display (78) and a blood oxygen concentration display (80).

Claims

1. A combined magnetic resonance imaging and pulse oximetry system comprising:

a bore liner for defining a patient receiving region;

a magnet assembly for generating a strong, substantially uniform magnetic field through the patient receiving region, the magnet assembly being mounted adjacent the bore liner;

a gradient coil assembly for inducing magnetic field gradients across the magnetic field, the gradient coil assembly being mounted between the magnet assembly and the bore liner;

an RF coil means for transmitting and receiving radio frequency signals into and from the patient receiving region, the RF coil means including a coil mounted between the gradient coil assembly and the bore liner;

a gradient control means for controlling the gradient coil assembly, the gradient control means being connected with the gradient coil assembly;

a radio frequency transmitter for controlling transmission of radio frequency signals by the RF coil means, the radio frequency transmitter being connected with the RF coil means;

a receiver means for receiving magnetic resonance signals from the patient receiving region, the receiver means being connected with the radio frequency coil means;

a reconstruction means for reconstructing magnetic resonance signals received by the radio frequency receiver into a digital image representation, the reconstruction means being connected with the receiver means;

a pulse oximetry sensor unit;

an electrical lead connected with the pulse oximetry sensor unit;

a socket mounted in the bore liner detachably receiving a plug on an end of the electrical lead connected with the pulse oximetry sensor unit;

a preamplifier connected with the socket for amplifying electrical signals from the sensor unit;

a processing and display means connected with the preamplifier for processing electrical signals therefrom to generate a display of at least patient blood oxygen concentration.

2. The apparatus as set forth in claim 1 further including a filter means disposed between the socket and the preamplifier for blocking the passage of resonance frequency signals.

3. The apparatus as set forth in claim 1 wherein the preamplifier is grounded to the magnet assembly and surrounded by a shield connected with the magnet assembly.

4. The apparatus as set forth in claim 3 including a low pass filter mounted inside the shield with the preamplifier for preventing radio frequency signals from being superimposed on the electrical signals from the sensor unit.

5. The apparatus as set forth in claim 1 wherein the bore liner, the socket, the magnet assembly, the gradient coils, the RF coil means, and the preamplifier are disposed within a shielded room which is surrounded by an electrically conductive shielding surface and further including:

a radio frequency filter means connected between the preamplifier and the processing and display means and connected with the shielding surface to (i) prevent the passage of radio frequency signals from the preamplifier to the processing and display means and (ii) prevent the passage of radio frequency signals from the processing and display means into the shielded room.

6. The apparatus as set forth in claim 5 wherein the processing and display means includes a clock generator which generates a radio frequency signal, the resonance frequency and the radio frequency signal being harmonics of each other.

7. The apparatus as set forth in claim 1 wherein:

the sensor unit includes means for sensing characteristics of a patient'"'"'s blood such that the electrical signals from the sensor unit are indicative of the sensed characteristics of the patient'"'"'s blood, an electrical power supply, the electrical lead connected with the electrical power supply to supply electrical power to the sensor unit, the preamplifier amplifies the electrical signals indicative of the blood characteristics, and the processing and display means processes electrical signals indicative of the blood characteristics from the preamplifier such that the generated display is a display of pulse and blood oxygen concentration, the processing and display means includes a radio frequency clock, and further including;

a filter means disposed between the sensor unit and the preamplifier for presenting a high impedance to radio frequency signals in a selected frequency range;

a radio frequency filter disposed between the preamplifier and the processing and display means for preventing radio frequency clock signals from the radio frequency clock from being conveyed to the preamplifier and for preventing radio frequency signals from being conveyed from the preamplifier to the processing and display means.

8. A pulse oximeter apparatus in conjunction with a magnetic resonance apparatus disposed in a shielded room, the magnetic resonance imaging apparatus including:

a bore liner which defines a patient receiving region;

a vacuum dewar connected with the bore liner;

a magnet assembly disposed in the vacuum dewar for generating magnetic fields through the patient receiving region;

an RF coil means disposed adjacent the bore liner for transmitting and receiving radio frequency signals into and from the patient receiving region;

the pulse oximeter apparatus comprising;

a pulse oximetry sensor unit with an electrical lead disposed in the bore liner;

a preamplifier grounded to the vacuum dewar and surrounded by a shield connected with the vacuum dewar, the preamplifier being connected with the sensor unit lead for amplifying electrical signals from the sensor unit;

a processing and display means disposed exterior to the shielded room and connected with the preamplifier for processing electrical signals therefrom to generate a display of at least patient pulse and blood oxygen concentration.

9. A pulse oximetry apparatus comprising:

a sensor unit means for sensing characteristics of a patient'"'"'s blood;

an electrical lead connected with the sensor unit means for supplying electrical power thereto and conveying electrical signals indicative of the blood characteristics;

an electrical plug connected with the lead;

an electrical socket releasably interconnected with the plug, the socket being adapted for mounting within a patient receiving bore of a magnetic resonance apparatus;

a preamplifier connected with the socket for amplifying the electrical signals indicative of the blood characteristics;

a filter means disposed between the sensor unit means and the preamplifier for presenting a high impedance to radio frequency signals in a selected range;

a processing and display means for processing the electrical signals indicative of the blood characteristics from the preamplifier to derive a display of pulse and blood oxygen concentration of a patient who is sensed by the sensing unit means, the processing and display means including a radio frequency clock;

a radio frequency filter disposed between the preamplifier and the processing and display means for preventing radio frequency signals from the clock from being conveyed to the preamplifier and for preventing radio frequency signals from being conveyed from the preamplifier to the processing and display means.

10. The apparatus as set forth in claim 9 wherein the preamplifier is housed in a grounded shield and further including a low pass filter within the shield.

11. The apparatus as set forth in claim 9 further including a notch filter constructed of a section of the lead wrapped in a coil arrangement, the notch filter being disposed between the socket and the preamplifier.

12. A magnetic resonance imaging apparatus comprising:

a bore liner which defines a patient receiving region therein;

a magnet assembly for generating a strong, substantially uniform magnetic field through the patient receiving region defined within the bore liner;

a gradient coil assembly disposed adjacent the patient receiving region for inducing magnetic field gradients across the magnetic field;

an RF coil means for transmitting radio frequency signals into and receiving radio frequency signals from the patient receiving region;

a pulse oximeter including;

a pulse oximetry sensor unit for sensing patient pulse and blood oxygen characteristics and generating electrical signals indicative thereof on a connected electrical lead disposed in the bore liner;

a preamplifier grounded to the magnet assembly and surrounded by a shield connected with the magnet assembly, the preamplifier being connected with the sensor unit electrical lead for amplifying the electrical signals from the sensor unit;

a processing and display means connected with the preamplifier for processing the amplified electrical signals therefrom to generate a display indicative of at least patient pulse and blood oxygen concentration.

13. The apparatus as set forth in claim 12 further including a filter means disposed between the sensor unit and the preamplifier for blocking the passage of resonance frequency signals.

14. The apparatus as set forth in claim 12 further including a low pass filter mounted inside the shield with the preamplifier for blocking the passage of radio frequency signals from the preamplifier to the processing and display means.

15. The apparatus as set forth in claim 14 wherein the processing and display means includes a clock generator which generates a radio frequency signal, the resonance frequency and the radio frequency signal being harmonics of each other.

16. The apparatus as set forth in claim 15 further including a radio frequency filter connected between the preamplifier with the processing and control means and connected with a shielded room which surrounds the magnet assembly and is disposed between the preamplifier and the processing and control means.

17. The apparatus as set forth in claim 12 further including a plug on the sensor unit lead and a socket mounted in the bore liner, the socket being connected with the preamplifier.

18. A combined magnetic resonance and pulse oximetry sensing apparatus comprising:

a bore liner for defining a patient receiving region;

a magnetic resonance means for inducing magnetic resonance in and receiving magnetic resonance signals from at least a selected region of a patient disposed within the bore liner;

a socket mounted in the bore liner detachably receiving a plug on the end of a lead connected with a pulse oximetry sensor unit;

a preamplifier connected with the socket for amplifying electrical signals from the sensor unit;

a processing and display means connected with the preamplifier for processing electrical signals therefrom to generate a display of at least patient blood oxygen concentration.

19. The apparatus as set forth in claim 18 further including a filter means disposed between the socket and the preamplifier for blocking the passage of resonance frequency signals.

20. The apparatus as set forth in claim 18 wherein the preamplifier is grounded to the magnet assembly and surrounded by a shield connected with the magnet assembly.