Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
  • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
  • A61B5/6813—Specially adapted to be attached to a specific body part
  • A61B5/6825—Hand
  • A61B5/6826—Finger
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
  • A61B5/024—Detecting, measuring or recording pulse rate or heart rate
  • A61B5/02416—Detecting, measuring or recording pulse rate or heart rate using photoplethysmograph signals, e.g. generated by infrared radiation
  • A61B5/02427—Details of sensor
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
  • A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
  • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
  • A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
  • A61B5/14552—Details of sensors specially adapted therefor
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/25—Bioelectric electrodes therefor
  • A61B5/276—Protection against electrode failure
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
  • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
  • A61B5/683—Means for maintaining contact with the body
  • A61B5/6838—Clamps or clips
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64

Definitions

• Magnetic Resonance Imaging MRI
• the patient is placed supine on a moveable, horizontal table which moves through a field wherein the patient is subjected to rapidly changing, intense R.F. (Radio Frequency) electric and magnetic fields.
• R.F. Radio Frequency
• the nuclear resonance produced by the rapidly changing fields is detected and by computer analysis detailed information of the interior of the human body can be obtained which, in many instances, is more detailed than that available from X-ray and simultaneously at less patient detriment than is occasioned by the use of X-ray. Since, obviously, most patients undergoing MRI may be ill for one reason or another and since subjecting a patient to the environment to which MRI
• Oximeters provide information as to the patient's blood flow characteristics, such as the blood oxygen saturation and pulse rate. Oximeters are currently available on the
• the typical oximeter includes a probe attached to a patient's body portion, such as to the patient's finger, with conductors extending from the probe to instrumentation.
• a light source such as light emitting diodes and a photodetector
• the light source and detector being placed on opposite sides of the patient's body portion, such as the patient's finger.
• Signals generated by the photodetector are carried by conductors to circuitry wherein the blood flow characteristics are determined and indicated.
• This system works very successfully in normal environments. However, in an MRI environment electrical voltage signals are induced in the conductors extending from the probe to the oximeter. These voltages can induce currents which interfere with the oximeter, as well as produce risk of R.F. burn to the patient. Also, the electronic logic within the oximeter can place distorting
• An object of this disclosure is to provide an oximeter that can be used on a patient undergoing MRI or otherwise used in an area of large R.F. and/or magnetic fields and wherein the debilitating effects of the large fields do not deteriorate the effectiveness and reliability of the oximetry measurements while providing distortion free
• the present disclosure is for an apparatus for indicating characteristics of a patient undergoing MRI in which the patient is exposed to high intensity changing R.F. and magnetic fields.
• the characteristics of the patient are determined by one or more beams of light through a body portion of the patient.
• the characteristics determined are blood oxygen saturation and pulse rate.
• a probe having a first portion and a second portion is adapted for fitting against opposed surfaces of a body portion of a patient, such as a finger.
• the two portions may be located adjacent one another for operation in a reflective or scattered light oximeter mode.
• the means for generating light preferably includes light emitting diodes within one of the probe portions or conducted thereto via optical fibers.
• An elongated fiberoptic cable has a first and a second end. The first end is juxtaposed to the patient's body portion for receiving light from the light generating source passing through the patient's body portion. This first end of the fiberoptic cable
• a photodetector such as a photodetector
• the photodetector has output leads.
• a circuit having an indicator, is connected to the photodetector output leads for determining the patient's characteristics, such as blood oxygen saturation, pulse rate or the like.
• An indicator discloses these measured characteristics of the patient to medical personnel.
• the fiberoptic cable transmits light that is passed through the patient's body portion in a highly efficient manner to the photodiode and other circuitry components located in an area remote from the patient
• the light generating source required may be transmitted from the remote location to the patient via optical fibers. Transmission of the light source via the optical fibers may be avoided where the source illumination itself can be chosen or designed to be free of the deleterious effects of R.F. and magnetic fields, and where such source placement can be made so as to have little risk of coupling burning R.F. currents onto the subject patient and where the source drive can be properly filtered so that MRI imagine degrading noise is removed.
• an embodiment wherein all of the communication between the probe and the remotely located instrumentation is carried out using fiberoptic cables. That is, in the alternate system no electric current carrying conductor is required to extend between the probe and the controlling circuitry.
• the alternate embodiment there is a first and a second fiberoptic cable.
• the second cable functions as has been described, that is, one end of the second cable is contoured to fit against a person's body part and the other end is in engagement with a photodetector remotely located from the patient.
• a first fiberoptic cable most of the length of which can be
• the first fiberoptic cable has opposed ends, one end being contoured to engage the body portion of a patient
• the other end of the first fiberoptic cable is attached to a photodiode or other similar light emitting source, and is preferably placed in the same instrumentation with the photodetector. In this manner, light is generated and ultimately received in instrumentation which is remotely located from the patient and in an area of substantially reduced R.F. and magnetic fields.
• the probe employed is essentially the same as that heretofore described except that the probe first portion receives the first end of the first fiberoptic cable which is bent in an arcuate curve adjacent the first end thereof so as to position the first end
• the bundle of fiberoptic cables consists of three portions, that is, part A and part B of the first portion which transmits two different light frequencies from remotely located instrumentation; and the second fiberoptic cable which transmits light from the patient back to the remotely located instrumentation, the light having passed through a body portion of a patient.
• the light is converted into electric signals by a photodetector.
• Figure 1 is a diagrammatic representation of the use of an apparatus for indicating characteristics of a patient undergoing magnetic resonance imaging (MRI) and specifically, wherein the characteristic to be determined is blood oxygen
• the right portion of Figure 1 shows a finger probe as used to attach to the patient, whereas the left-hand portion of Figure 1 shows oximetry equipment for use in determining the patient's blood oxygen saturation and pulse rate and for displaying such information.
• the right-hand portion of Figure 1 is separated from the left-hand portion by an elongated fiberoptic cable so that the right-hand
• Figure 1 is in an area of rapidly changing, intense R.F. and magnetic fields and the left-hand portion is in an area remote from the patient and in an area of reduced MRI produced changing R.F. and magnetic fields.
• Figure 2 is an enlarged cross-sectional view of the finger probe as in Figure 1 positioned on the finger of a patient, such as a patient undergoing MRI.
• Figure 3 is a cross-sectional view of a finger probe, as in Figure 2, positioned on the finger of a patient, such as a patient undergoing MRI, illustrating the alternate
• Figure 4 is a diagrammatic view of the arrangement of Figure 3 showing a
• the fiberoptic cable package having a first and second fiberoptic cable.
• the first cable transmits light from a remote location, such as generated by a light emitting diode, to the probe.
• the first fiberoptic cable is bent and contoured to engage the patient's body portion.
• One end of the second fiberoptic cable is received within the probe and is bent and contoured to engage the opposite side of the patient's body portion to receive light having passed therethrough.
• the opposite end of the second fiberoptic cable has attached to it a photodetector that converts the light into an electric signal that is analyzed for indicating the patient's body characteristics.
• Figure 5 is a fragmentary view of one end of the cable package system as shown in Figure 4 illustrating the use of three fiberoptic cables, two for transmitting light of different frequencies and one for transmitting light having passed through the patient's body portion back to remotely located instrumentation.
• This invention relates broadly to an apparatus for indicating characteristics of a patient undergoing Magnetic Resonance Imaging (MRI) in which the patient is exposed to changing high intensity R.F. and magnetic fields produced by the MRI and in which the characteristics of the patient are determined by passage of one or more beams of
• MRI Magnetic Resonance Imaging
• a non- invasive blood oximeter of the type having a finger probe and an indicating instrument.
• An oximeter determines a patient's arterial blood oxygen saturation (SaC by measuring the absorption of two selected wavelengths of light.
• SaC arterial blood oxygen saturation
• the light generated in the sensor (probe) passes through the blood and tissue and is converted into electronic signals by a photodetector.
• Hb0 2 oxygenated, with 0 2 molecules loosely bound
• Hb reduced, with no molecules bound
• Arterial blood oxygen saturation is the ratio of oxygenated hemoglobin to total hemoglobin, and can be expressed by the formula:
• the electronic signals vary in relation to both the amount of blood present in the tissue (the pulse waveform) and the amount of
• the signals are amplified and filtered so that artifacts from motion and ambient room light are discarded.
• the signals that remain are those from the arterial blood. Processing of the signal then provides information that can be used such as for numeric display of Sa0 2 and pulse rate as well as other uses, such as display of pulse strength on a light bar and storage of data in memory for trend
• the figure is divided into a right-hand portion 10 and a left- hand portion 12 by a dividing line 14.
• the right-hand portion 10 is in an area of R.F. and intense magnetic fields, exemplified by an electromagnetic coil 16 indicative of a MRI installation. Due to the high intense fields in area 10, electrical instruments that include electrical conductors experience difficulty since the rapidly changing magnetic and R.F. fields can induce electrical voltages within the conductors. The present device reduces this problem as it pertains, by way of example, to an oximeter.
• the left portion 12 is in an area remote from that of area 10 and has reduced R.F. and magnetic field intensities and represents those circuits of portion 12 which may not be within the MRI scanner bore.
• FIG. 10 of Figure 1 Within right portion 10 of Figure 1 is an oximeter finger probe, generally indicated by the numeral 18 and which is illustrated in Figure 2 in cross-sectional view.
• the probe 18 includes a first portion 22 and a second portion 24, the portions being pivoted together about a pin 26.
• a spring 28 normally holds the portions closed.
• the portions are in the old-fashioned "clothespin" arrangement so that the rearward portion may be manually squeezed to pivot the forward portion open to receive finger 20 of a patient.
• a light emission source such as light emitting diodes, and particularly and preferably a pair of light emitting diodes 30 and 32.
• the diodes 30 and 32 emit light of different frequencies and in pulsed arrangement.
• a R.F. squelching capacitor 34 is positioned in parallel
• a conductor 36 supplies electrical energy to sequentially pulse
• the diodes to generate light of two different frequencies.
• the fiberoptic cable 38 is indicated by the numeral 38 and is typically surrounded with a rubber jacket 38A so that the numeral 38A indicates the rubber jacketed fiberoptic cable.
• the fiberoptic cable 38 has a first end 40 received within finger probe 18 and
• the fiberoptic cable is bent at 44 and the end surface 40 is contoured to engage finger 20 of the patient.
• a pillow type arrangement identified by the numeral 46, that may be filled with silicon rubber, is used to support light emitting diodes 30 and 32, and in the finger probe second portion 24 a similar pillow 48 supports end 40 of fiberoptic cable 38.
• Pillow 48 has a recess 50 therein and the end portion of the fiberoptic cable adjacent the end 40 is retained within recess 50 in the pillow, such by means of potting
• the light emitting diodes 30 and 32 are preferably supported in an insulating light transmitting potting compound 54 within a pocket in pillow 46, and the light transmitting potting compound having diodes 30 and 32 is in contact with the patient's fingernail 56.
• the potting compound is chosen to both inhibit RF coupling and promote light transmission to the subject.
• the fiberoptic cable first end 40 is in contact with the patient's finger opposite fingernail 56 so that light emitted by diodes 30 and 32 passes through the patient's finger and enters the fiberoptic cable at first end 40.
• the rubber mounted fiberoptic cable 38A extends to a sensor filter chassis 58.
• a photodetector 60 Mounted within the chassis in juxtaposed, that is contiguous, contact with the fiberoptic cable second end 42 is a photodetector 60 that may be in the form of a photodiode.
• the photodetector has output leads 62.
• conductor 36 that is used to activate the light emitting diodes 30 and 32 is mounted within rubber covering 38A surrounding
• Fiberoptic cable 38 fiberoptic cable 38.
• Conductor 36 emerges from within cable rubber jacket 38A adjacent sensor filter chassis 58, as shown in Figure 1.
• the leads of cable 38 pass through a tuned ferrite shielding bead 64 and then enter and transverse the sensor filter chassis 58 via a series of feed through filter capacitors and R.F. chokes which remove oximeter logic and electronic interference as well as MRI induced R.F. signals.
• a cable 66 extends from the sensor filter chassis 58 to an oximeter logic and electronics housing 68 whereon indications of the measured body characteristics are displayed. For instance, in housing 68 blood oxygen saturation may be shown in window 70, such as by a liquid crystal display or the like. The patient's pulse rate may be shown in the window 72.
• a pulse track light bar 74 may also be of the liquid crystal display type that varies in height with pulse and signal strength.
• Other features may be employed in blood oximeter housing 68, such as a system status display 76.
• the oximeter also typically includes other features such as an "on” and “off” switch 78, at least one alarm system control 80, and so forth, that are exemplary of a typical state
• the essence of this invention is a system that employs a fiberoptic cable for coupling light to a remote area wherein the light is used as a means of measuring the characteristics of a patient, such as blood oxygen saturation, pulse rate or the like.
• the high intensity R.F. and magnetic fields in the area wherein the patient is positioned (MRI bore) and where the body characteristics must be measured do not deleteriously effect light as transmitted by the fiberoptic cable. That is, the fiberoptic cable is essentially non-electrically conductive and therefore is not significantly effected by the MRI magnetic and R.F. fields.
• the high intensity fields will effect conductor 36, however, this conductor is used only for pulsing light emitting diodes 30, 32, and conductor 36 is not involved with the sensitive received signal used
• FIG. 1 a diagrammatic illustration, there is shown, in addition to fiberoptic cable 38, a first fiberoptic cable 82.
• the first fiberoptic cable 82 has a first end 84 and a second end 86. Secured at the second end 86 is a light emitting diode assembly 88 controlled by conductors 90.
• first fiberoptic cable 82 Light to be passed through the body portion of a patient is generated by the light emitting diode assembly 88 and flows through first fiberoptic cable 82 to the first end 84.
• the first fiberoptic cable 82 has an arcuate curve 92 therein so that the first end 84 is positioned to engage the body portion of the patient.
• Fiberoptic cables 38 and 82 are preferably bundled together in a sheath 38B to extend the fiberoptic cable from the probe to the instrumentation that is positioned within remote area 12.
• Figure 3 shows the way the first fiberoptic cable 82 is positioned within first probe portion 22.
• the first fiberoptic cable is bent in an arcuate curve 92 to pass through the pillow portion 46 and is supported in position by potting material 54, as described with reference to Figure 2.
• first end 84 of the first fiberoptic cable is held into intimate contact with the patient's body portion, such as a patient's fingernail.
• the second end 42 of fiberoptic cable 38 engages a photodetector 60 that converts light from fiberoptic cable 38 into electrical signals that appear on conductors 62. These signals are carried to instrumentation as previously
• fiberoptic cable 38 has, by example, a diameter of .125 inches, whereas first fiberoptic cable 82 has a diameter of only .05 inches.
• Each of the fiberoptic cables is made up of a bundle of very small diameter light transmitting strands.
• First fiberoptic cable 82 can be of relatively small diameter since it carries light from light emitting diode 88 with a high degree of efficiency, that is, very little light is lost in transmittal and therefore a relatively small cable is required to transmit sufficient light for passage through a patient's body portion.
• Cable 38 must be of larger diameter since relatively weak, low intensity light is transmitted through the patient's body portion and therefore larger light gathering and transmitting characteristics are required for cable 38.
• Figure 5 shows a fragmentary view of a slightly altered embodiment.
• light of two different frequencies be transmitted through the patient's body portion.
• this is accomplished by two separate photodiodes positioned within the probe first portion. The photodiodes are energized by current carried to the probe by the electrical conductor. The advantages of two light frequencies can be obtained
• each portion of the first cable has a light emitting diode in the instrumentation section as shown in Figure 5, the first light emitting diode being indicated by the numeral 88 and the second light emitting diode being indicated by the numeral 94. Since, as has been discussed before, the bundle
• fiberoptic strands required to transmit light are relatively small and need only be about .05 inches in diameter, two of such bundles can easily be carried along with cable 38 and encompassed in sheath 38C.
• Light of two different frequencies, preferably alternately energized, can be employed for passing through the body portion of the patient to more effectively determined the patient's characteristics, such as blood oxygen saturation.

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• 1992
  • 1992-05-21 EP EP92912524A patent/EP0587718A1/de not_active Withdrawn
  • 1992-05-21 WO PCT/US1992/004297 patent/WO1992021281A1/en not_active Application Discontinuation

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