Simplified water-bag technique for magnetic susceptibility measurements on the human body and other specimens
First Claim
1. A method for noninvasive determination of magnetic susceptibility variation in a patient by measuring magnetic susceptibilities of selected tissue of the patient, the method comprising:
- providing an instrument which includes at least one magnetic sensor, an applied field coil and a current source connected to the applied field coil and means for processing sensed signals from the at least one magnetic sensor;
positioning on the patient a flexible bag substantially filled with deformable material having a magnetic susceptibility substantially similar to that of body tissue, said bag being attached to a substantially rigid barrier, the barrier being spaced a predetermined distance from the patient by the material-filled bag, which predetermined distance remains substantially constant during a measuring sequence, the amount of deformable material in the flexible bag remaining constant during a measuring sequence, the instrument being moved with respect to the barrier during the measuring sequence;
positioning the instrument external to the patient in proximity to the tissue of interest and adjacent the barrier;
supplying the applied field coil with current thereby applying a magnetic field to the tissue of interest;
sensing a response from the tissue of interest wit the instrument; and
outputting data corresponding to the magnetic susceptibility variation in the tissue.
1 Assignment
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Accused Products
Abstract
A probe instrument using room-temperature sensor(s) that can measure variations in magnetic susceptibilities. The instrument has sufficient resolution to monitor paramagnetic materials in a human body, such as iron in a human liver, by noninvasively examining patients with iron-overload diseases. The instrument includes room temperature magnetic sensors, and detects the sample, that is, the tissue response to an alternating current field applied by an applied field coil. The applied field coil dimensions are chosen so that the applied field is optimized for maximum response from the liver while minimizing the effects due to the overlying abdominal tissue and at the same time not unduly increasing the sensitivity of the instrument to the lung. To overcome variations in the sensor output due to fluctuations in the applied field, change in the ambient temperature and mechanical relaxation of the instrument, the sensor-sample distance is modulated. The detector assembly is oscillated while the examined patient remains stationary. An improved water-bag technique is employed to eliminate background tissue response. The detector assembly forms part of a probe instrument for performing noninvasively the paramagnetic concentration of a patient.
92 Citations
105 Claims
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1. A method for noninvasive determination of magnetic susceptibility variation in a patient by measuring magnetic susceptibilities of selected tissue of the patient, the method comprising:
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providing an instrument which includes at least one magnetic sensor, an applied field coil and a current source connected to the applied field coil and means for processing sensed signals from the at least one magnetic sensor; positioning on the patient a flexible bag substantially filled with deformable material having a magnetic susceptibility substantially similar to that of body tissue, said bag being attached to a substantially rigid barrier, the barrier being spaced a predetermined distance from the patient by the material-filled bag, which predetermined distance remains substantially constant during a measuring sequence, the amount of deformable material in the flexible bag remaining constant during a measuring sequence, the instrument being moved with respect to the barrier during the measuring sequence; positioning the instrument external to the patient in proximity to the tissue of interest and adjacent the barrier; supplying the applied field coil with current thereby applying a magnetic field to the tissue of interest; sensing a response from the tissue of interest wit the instrument; and outputting data corresponding to the magnetic susceptibility variation in the tissue. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for noninvasively measuring magnetic susceptibility variations in the body tissue of a patient to determine a compositional state in the body, the apparatus comprising:
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a detector assembly that includes; at least one magnetic sensor and an applied field coil for generating a magnetic field; a current signal generating source which connects to said applied field coil; and means for processing signals from said at least one magnetic sensor of observed magnetic susceptibility variations in body tissue; a non-conductive, non-magnetic, substantially rigid barrier; a flexible membrane sealed to said barrier to form a container therewith, there being a deformable material within and occupying most of the volume within said container, said material having a magnetic susceptibility substantially equivalent to that of the body tissue, said container being shaped and configured to fill in substantially all gaps between said barrier and the patient'"'"'s body, said barrier being substantially stationary with respect to the patient and the amount of deformable material within said container being constant when magnetic susceptibility variations in the patient'"'"'s body tissue are measured, the patient remains stationary and said detector assembly moves with respect to said barrier when the measurements are being made; and means for outputting data from said detector assembly corresponding to a compositional state in the body tissue. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A magnetic susceptibility detector device comprising;
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an applied field coil configured to connect to a current source, said field coil being configured to create a first zone of a finite magnetic field within a selected region of an observed specimen, and a second zone of substantially zero magnetic field outside said selected region, said applied field coil having at least two concentric electric current carrying coils of conductor material; a sensing device comprising at least one magnetic sensor, said at least one sensor being positioned within said second zone of substantially zero magnetic field; a non-conductive, non-magnetic, substantially rigid barrier; and a flexible membrane sealed to said barrier to form a container therewith, there being a deformable material within and substantially filling said container, said material having a magnetic susceptibility substantially equivalent to that of the body tissue, said container being shaped and configured to fill in substantially all gaps between said barrier and the patient'"'"'s body, said barrier being substantially stationary with respect to the patient and the amount of deformable material within said container being constant when magnetic susceptibility variations in the patient'"'"'s body tissue are measured, the patient remains stationary and said detector assembly moves with respect to said barrier when the measurements are being made. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44)
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45. An apparatus for noninvasively determining magnetic susceptibility variations in body tissue, the apparatus comprising:
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a detector assembly comprising; at least one magnetic sensor and an applied field coil for generating a magnetic field wherein the applied field coil is designed to create a first zone of a finite magnetic field within a selected region of the body, and a second zone of substantially zero magnetic field outside the selected region; and said at least one magnetic sensor is positioned within said second zone of substantially zero magnetic field; means for oscillating said detector assembly; a current signal generating source which connects to the applied field coil; a non-conductive, non-magnetic, substantially rigid barrier; a flexible membrane sealed to said barrier to form a container therewith, there being a deformable material within and substantially filling said container, said material having a magnetic susceptibility substantially equivalent to that of the body tissue, said container being shaped and configured to fill in substantially all gaps between said barrier and the patient'"'"'s body, said barrier being substantially stationary with respect to the patient and the amount of deformable material within said container being constant when magnetic susceptibility variations in the patient'"'"'s body tissue are measured, the patient remains stationary and said detector assembly moves with respect to said barrier when the measurements are being made; and means for processing signals from said at least one magnetic sensor of observed magnetic susceptibility variation in the body. - View Dependent Claims (46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
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58. An apparatus to eliminate background tissue response in an instrument for non-invasively measuring magnetic susceptibility variations in the body tissue of a patient to determine a compositional state in the body, said apparatus comprising:
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a non-conductive, non-magnetic, substantially rigid barrier; and a flexible membrane sealed to said barrier to form a container therewith, there being a deformable material within and occupying mast of the volume within said container, said material having a magnetic susceptibility substantially equivalent to that of the body tissue, said container being shaped and configured to fill in substantially all gaps between said barrier and the patient'"'"'s body, said barrier and flexible membrane being configured to be substantially stationary with respect to the patient, and the amount of deformable material within said container remains constant when magnetic susceptibility variations in the patient'"'"'s body tissue are being measured. - View Dependent Claims (59, 60)
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61. An apparatus for noninvasively measuring magnetic susceptibility variations in the body tissue of a patient to determine a compositional state in the body, the apparatus comprising:
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a detector assembly that includes; at least one magnetic sensor and an applied field coil for generating a magnetic field, said applied field coil comprising at least two concentric circular spiral coils; and means for processing signals from said at least one magnetic sensor of observed magnetic susceptibility variations in body tissue; a non-conductive, non-magnetic, substantially rigid barrier; a flexible membrane sealed to said barrier to form a container therewith there being a deformable material within and occupying most of the volume within said container, said material having a magnetic susceptibility substantially equivalent to that of the body tissue, said container also being deformable to fill in substantially all gaps between said barrier and the patient'"'"'s body, said barrier being substantially stationary with respect to the patient and the amount of deformable material within said container being constant when magnetic susceptibility variations in the patient'"'"'s body tissue are measured, the patient remains stationary and said detector assembly moves with respect to said barrier when the measurements are being made; and means for outputting data from said detector assembly corresponding to a compositional state in the body tissue; wherein the at least two concentric spiral coils have diameters and numbers of turns chosen so tat the magnetic field due to an inner concentric spiral coil cancels the magnetic field due to an outer concentric spiral coil in a region near the common center of the at least two concentric coils, thereby producing a zone of substantially zero magnetic field, and wherein the at least one magnetic sensor is placed in said zone of substantially zero magnetic field. - View Dependent Claims (62, 63, 64, 65, 66, 67, 68, 69)
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70. An apparatus for noninvasively measuring magnetic susceptibility variations in the body tissue of a patient to determine a compositional state in the body, the apparatus comprising:
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a detector assembly that includes; at least one magnetic sensor and an applied field coil for generating a magnetic field; an alternating current signal generating source which connects to said applied field coil; means for processing signals from said at least one magnetic sensor of observed magnetic susceptibility variations in body tissues; and an electrostatic shield positioned between said at least one magnetic sensor and the sample to be measured; a non-conductive, nan-magnetic, substantially rigid barrier; a flexible membrane sealed to said barrier to form a container therewith, there being a deformable material within and occupying most of the volume within said container, said material having a magnetic susceptibility substantially equivalent to that of the body tissue, said container also being deformable to fill in substantially all gaps between said barrier and the patient'"'"'s body, said barrier being substantially stationary with respect to the patient and the amount of deformable material within said container being constant when magnetic susceptibility variations in the patient'"'"'s body tissue are measured, the patient remains stationary and said detector assembly moves with respect to said barrier when the measurements are being made; and means for outputting data from said detector assembly corresponding to a compositional state in the body. - View Dependent Claims (71, 72, 73, 74, 75, 76, 77, 78)
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79. An apparatus for noninvasively measuring magnetic susceptibility variations in the body tissue of a patient to determine a compositional state in the body, the apparatus comprising:
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a detector assembly that includes; at least one magnetic sensor and an applied field coil for generating a magnetic field; a current signal generating source, which connects to said applied field coil; and means for processing signals from said at least one magnetic sensor of observed magnetic susceptibility variations in body tissue; a non-conductive, non-magnetic, substantially rigid barrier; a flexible membrane sealed to said barrier to form a container therewith, there being a deformable material within and occupying most of the volume within said container, maid material having a magnetic susceptibility substantially equivalent to that of the body tissue, said container being shaped and configured to fill in substantially all gaps between said barrier and the patient'"'"'s body, said barrier being substantially stationary with respect to the patient and the amount of deformable material within said container being constant when magnetic susceptibility variations in the patient'"'"'s body tissue are measured, the patient remains stationary and said detector assembly moves with respect to said barrier when the measurements are being made; and means for outputting data from said detector assembly corresponding to a compositional state in the body; wherein the at least one magnetic sensor comprises a sensing coil and wherein the applied field coil and the sensing coil are mounted together in a rigid sensor unit, and wherein the instrument is provided with displacement means for displacing the at least one magnetic sensor and the applied field coil simultaneously, thereby compensating for noise introduced to the sensed signals. - View Dependent Claims (80, 81, 82, 83, 84, 85, 86, 87)
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88. An apparatus for noninvasively measuring magnetic susceptibility variations in the body tissue of a patient to determine a compositional state in the body, the apparatus comprising:
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a detector assembly that includes; at least one magnetic sensor and an applied field coil for generating a magnetic field; a current signal generating source, which connects to said applied field coil; and means for processing signals from said at least one magnetic sensor of observed magnetic susceptibility variations in body tissue; a non-conductive non-magnetic, substantially rigid barrier; a flexible membrane sealed to said barrier to form a container therewith, there being a deformable material within and occupying most of the volume within said container, said material having a magnetic susceptibility substantially equivalent to that of the body tissue, said container being shed and configured to fill in substantially all gaps between said barrier and the patient'"'"'s body, said barrier being substantially stationary with respect to the patient and the amount of deformable material within said container being constant when magnetic susceptibility variations in the patient'"'"'s body tissue are measured, the patient remains stationary and said detector assembly moves with respect to said barrier when the measurements are being made; and means for outputting data from said detector assembly corresponding to a compositional state in the body; wherein the at least one magnetic sensor comprises a sensor unit, said sensor unit comprising two sensing coils connected in series, equal in area, but oppositely wound, and oppositely spaced from the applied field coil on a cylindrical coilform in a first-order gradiometer configuration; wherein the sensing coils and applied field coil have areas and geometric locations chosen so as to cancel out the detected signal due to the applied magnetic field; wherein the applied field coil and the sensing coils are mounted together in said sensor unit, and wherein the instrument is provided with means for displacing the sensor unit, thereby compensating for the effects of temperature drift; and wherein the instrument further comprises an electrostatic shield between the sensing coils and the body tissue to be measured. - View Dependent Claims (89, 90, 91, 92, 93)
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94. A method for noninvasive determination of magnetic susceptibility variations in a patient by measuring magnetic susceptibilities of selected body tissue of the patient, the method comprising:
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providing an instrument which includes at leant one magnetic sensor and an applied field coil; positioning on the patient a flexible bag substantially filled with deformable material having a magnetic susceptibility substantially similar to that of the body tissue, said bag being attached to a substantially rigid barrier, the barrier being spaced a predetermined distance from the patient by the deformable material filled bag, which predetermined distance remains substantially constant during a measuring sequence, the amount of deformable material in the flexible bag remaining constant during a measuring sequence, the instrument being moved with respect to the barrier during the measuring sequence; positioning the instrument external to the patient in proximity to the tissue of interest and adjacent the barrier; supplying the applied field coil with current thereby applying a magnetic field to the tissue of interest; scanning the at least one magnetic sensor along the rigid barrier to generate a map of susceptibility variations of the underlying body tissues; and outputting data corresponding to the magnetic susceptibility variations in the tissue.
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95. A method for noninvasive determination of magnetic susceptibility variation in a patient by measuring magnetic susceptibilities of selected body tissue of the patient, the method comprising:
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providing an instrument which includes at least one magnetic sensor and an applied field coil; positioning on the patient a flexible bag substantially filled with a first amount of deformable material having a magnetic susceptibility substantially similar to that of the body tissue, said bag being attached to a substantially rigid barrier to form a container having a first volume, the barrier being spaced a first predetermined distance from the patient by the deformable material filled bag; positioning the instrument external to the patient in proximity to the tissue of interest and adjacent the barrier; supplying the applied field coil with current thereby applying a magnetic field to the tissue of interest; periodically displacing the instrument with respect to the barrier, sensing a response from the tissue of interest with the instrument; outputting data corresponding to the magnetic susceptibility variation in the tissue;
tenmoving the instrument and the substantially rigid barrier simultaneously with respect to the patient, the barrier being thereby spaced from the patient by a second predetermined distance and changing the container to have a second volume, the second volume being filled with a second amount of deformable material; repeating the supplying step, the periodically displacing step, the sensing step and outputting step; and subtracting the susceptibility measurement observed after the moving step from the susceptibility measurement observed before the moving step. - View Dependent Claims (96, 97, 98, 99)
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100. An apparatus for noninvasively measuring magnetic susceptibility variations in the body tissue of a patient to determine a compositional state in the body, the apparatus comprising:
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a detector assembly that includes; at least one magnetic sensor and an applied field coil for generating a magnetic field; a signal refinement means adjustably positioned with respect to the sensor; a current signal generating source which connects to said applied field coil; and means for processing signals from said at least one magnetic sensor of observed magnetic susceptibility variations in body tissue; a non-conductive, non-magnetic, substantially rigid barrier; a flexible membrane sealed to said barrier to form a container therewith, there being a deformable material within and occupying moat of the volume within said container, said material having a magnetic susceptibility substantially equivalent to that of the body tissue, said container being shaped and configured to fill in substantially all gaps between said barrier and the patient'"'"'s body, said barrier being substantially stationary with respect to the patient and the amount of deformable material within said container being constant when magnetic susceptibility variations in the patient'"'"'s body tissue are measured, the patient remains stationary and said detector assembly moves with respect to said barrier when the measurements are being made; and means for outputting data from said detector assembly corresponding to a compositional state in the body tissue; wherein said applied field coil is designed to produce a region of nearly zero magnetic field and said sensor is positioned in said region of nearly zero magnetic field and wherein adjustment of said signal refinement means improves cancellation of the applied field at the sensor location. - View Dependent Claims (101, 102, 103, 104, 105)
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Specification