WO2004017811A2 - Systeme et procede de magneto-encephalographie haute resolution - Google Patents

Systeme et procede de magneto-encephalographie haute resolution Download PDF

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Publication number
WO2004017811A2
WO2004017811A2 PCT/US2003/020523 US0320523W WO2004017811A2 WO 2004017811 A2 WO2004017811 A2 WO 2004017811A2 US 0320523 W US0320523 W US 0320523W WO 2004017811 A2 WO2004017811 A2 WO 2004017811A2
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WIPO (PCT)
Prior art keywords
millimeters
headrest
sensors
head
dewar
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
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PCT/US2003/020523
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English (en)
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WO2004017811A3 (fr
Inventor
Anthony P. Ewing
Sheldon J. Gott
Anthony D. Mascarenas
Yoshio Okada
Douglas N. Paulson
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TRISTAN TECHNOLOGIES Inc
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TRISTAN TECHNOLOGIES Inc
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Publication date
Priority claimed from US10/228,694 external-priority patent/US6784663B2/en
Priority claimed from US10/609,259 external-priority patent/US7197352B2/en
Priority claimed from US10/608,725 external-priority patent/US7130675B2/en
Application filed by TRISTAN TECHNOLOGIES Inc filed Critical TRISTAN TECHNOLOGIES Inc
Priority to AU2003263757A priority Critical patent/AU2003263757A1/en
Priority to EP03792953A priority patent/EP1538978A4/fr
Publication of WO2004017811A2 publication Critical patent/WO2004017811A2/fr
Anticipated expiration legal-status Critical
Publication of WO2004017811A3 publication Critical patent/WO2004017811A3/fr
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/035—Measuring direction or magnitude of magnetic fields or magnetic flux using superconductive devices
    • G01R33/0354—SQUIDS
    • 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
    • A61B5/242—Detecting biomagnetic fields, e.g. magnetic fields produced by bioelectric currents
    • A61B5/245—Detecting biomagnetic fields, e.g. magnetic fields produced by bioelectric currents specially adapted for magnetoencephalographic [MEG] signals

Definitions

  • the invention relates to medical diagnostic systems and methods.
  • the invention relates to medical diagnostic systems and methods.
  • the invention relates to a system and method for obtaining high-resolution
  • Dreyfus-Brisac, C The electroencephalogram of the premature infant and full- term newborn: normal and abnormal development of waking and sleeping patterns.
  • P. Kellaway and I. Petersen (eds.) Neurological and electroencephalo ⁇ raphic correlative
  • activities from a deep subcortical structure can be detected magnetically outside the brain
  • hypoxemic-ischemic encephalopathy in term or near-term infants is between about 3/1000 and 8/1000. Handicapped survivors may be as high as about 42% in such
  • the incidence of infants with neonatal seizures is between about 2/1000 and
  • the neonatal period is between about 1/1000 and 3/1000.
  • EEG electroencephalography
  • the staging is useful in detecting a delay or an arrest in brain
  • the waveforms and spatial topography such as hemispheric asymmetry of spontaneous EEG are also useful for detecting the presence of a tumor or a necrotic
  • magnatoencephalography MEG
  • electrophysiological monitoring technique complementing EEG, it may be desirable for
  • MEG instrument which may be different from the conventional whole-head MEG instruments.
  • a useful MEG instrument must be functional in any ordinary clinical
  • the spacing between the patient's head and the sensor should be precisely
  • spacing between the head and the sensors may be difficult to maintain in the presence
  • FIG. 1 A is a diagrammatic illustration of a high-resolution magneto-
  • MEG encephalography
  • Fig. 1B is a diagrammatic cross-sectional side view of the system illustrated in
  • Fig. 2A is a cross-sectional diagrammatic view of one embodiment of the headrest
  • Fig. 2B is a diagram illustrating the wall thickness of a portion of the headrest of
  • Fig. 3 is a diagrammatic view of the rear surface of the headrest of Fig. 2B and
  • Fig. 4 is a diagram illustrating a single 4-channel sensor module
  • Figs. 5A, 5B and 5C illustrate one embodiment of a 4-channel module according to the present invention
  • Figs. 6A, 6B and 6C illustrate a coil form for a pickup coil of the module illustrated
  • Fig. 6D and 6E illustrates a coil form for the cancellation coil of the module
  • Figs. 7 and 8 are charts illustrating noise spectra for a 4-channel module with
  • Figs. 9A and 9B are charts showing representative samples of the somatic
  • SEFs evoked magnet fields
  • Fig. 10 is a chart showing SEFs that are produced by a vibratory stimulation as a
  • Fig. 11 illustrates charts showing SEFs measured on a plane above the skull of
  • Fig. 12 illustrates charts showing an outline of the somatic evoked potential
  • Fig. 13A illustrates charts showing the distortions due to conductivity differences
  • Fig. 13B illustrates charts illustrating the Laplacian estimates of currents emerging
  • Fig. 14 are charts showing the somatic evoked potentials (SEPs) measured over
  • Figs. 15 illustrates charts showing the outputs from a 600 Hz signal for a piglet
  • Figs. 16 illustrates charts showing recordings of SEF outside the brain and intracortical SEP
  • Fig. 17 are charts showing that the Kyna-insensitive component was localized
  • Fig. 18 is a cross-sectional side view of a headrest according to one embodiment
  • Fig. 19 is a chart illustrating the cancellation of the ambient earth magnetic field
  • Fig. 20 is a chart showing the noise cancellation for the line frequency noise using
  • Fig. 21 is a pictorial view of another embodiment of an MEG system, which is
  • Fig. 22 is a side elevational view of the system of Fig. 21 , illustrating it with portions thereof partially broken away for illustration purposes;
  • Fig. 23 is an enlarged-scale sectional view of the system of Fig. 21 , illustrating the
  • Fig. 24 is an enlarged side elevational sectional view of the headrest assembly of
  • Fig. 25 is an enlarged sectional view of the headrest assembly of the system of
  • FIG. 21 similar to Fig. 24 except taken at a different sectional plane;
  • Fig. 26 is an enlarged-scale pictorial view of the array of sensors of the headrest assembly of the system of Fig. 21, illustrating the sensors in their relative positions;
  • Fig. 27 is an enlarged face view of the headrest assembly of the system of Fig. 21;
  • Fig. 28 is an enlarged face view of the rear surface of the headrest assembly of
  • Fig. 29 is an enlarged sectional side elevational view of the headrest assembly
  • magnetoencephalography system and method employing a portable cart having a
  • SQUID dewar mounted in an inverted manner thereon, and having a headrest assembly
  • the headrest assembly includes an array of magnetic sensors of the SQUID
  • dewar for responding to electrical activity of the brain of the head.
  • the dewar is inverted
  • a sensor array plate positions the sensors relative to the headset.
  • a plurality of second rods are fixed at one of their ends relative to the dewar and are
  • first and second rods is composed of material expandable and contractible with changes
  • a plurality of second rods are fixed at one of their ends relative to the dewar and are connected at their opposite Each one of the rods is composed of
  • the sensor array plate is supported from below by the first and second rods.
  • a movable is positioned below the sensor array plate and the second rods extend
  • the headrest is rigidly attached to the dewar.
  • disclosed embodiments of the present invention relates to a high-resolution magnetoencephalography (MEG) systemlO for evaluating neurological impairments of MEG
  • the system 10 is a portable, non-invasive MEG system that can be used next to a
  • crib 12 of any neonatal care unit without a cumbersome magnetically shielded room (not
  • the system 10 includes a cart 14 which may be the size and shape of an
  • Desirable spatial resolution and sensitivity may be provided by a closely- spaced evenly-distributed array (e.g., 19 x 4-channel modules) of superconducting MEG
  • the sensors may be housed between about 1 mm and about
  • the entire system is light enough to be portable, and the cart 14 includes
  • wheels such as wheels 23 and 25 for rollably supporting the cart on the ground.
  • a dewar 27 of a superconducting quantum interference device is
  • a patient bed or cushion 29 is mounted on the cart 14 adjacent to the headrest assembly 16 for supporting the body of the
  • the SQUID dewar 27 includes a liquid helium reservoir 32 and a fill port 34.
  • SQUID phase lock loop electronic circuits and routers unit 36 control the SQUID
  • the unit 36 is mounted on cart 14. A
  • computer and power supply unit 38 is mounted at the rear end of the cart 14.
  • a monitor and keyboard unit 41 are mounted above the unit 38 and communicate electrically
  • the system 10 may
  • MEG sensors e.g. Ahonen et al., 1992; Buchanan et al., 1994. Its sensitivity may be sufficiently high to measure not only spontaneous neuronal activity, but also evoked
  • spatial resolution system 10 will be greater by a factor of about four in comparison to the
  • the system 10 takes advantage of the fact that the infant's scalp and skull are
  • headrest 21 can have a thickness of about 1.0 mm or only slightly greater and is safe to
  • the sensitivity of the system 10 should be high enough to clearly detect evoked cortical
  • the MEG sensors are housed in a
  • the sensor array 18 of one embodiment of the system 10, includes of 19
  • each module having 4 channels of sensors. It will be understood hereinafter described in greater detail, the sensors can be arranged in clusters in accordance with
  • Such modules can be fabricated with a noise level
  • the sensitivity of the system 10 is sufficiently high to clearly detect evoked cortical
  • the system 10 is able to clearly detect such SEFs without signal averaging, since the system 10 requires between about 25 and about 36 times less averaging than the prior known similar MEG systems to obtain signals with comparable signal-to-noise ratios.
  • the system 10 is the size of an ordinary examination table in one embodiment of the invention.
  • the system 10 itself is provided the cart 14 with the mattress or bed 29
  • EEG EEG.
  • the measurements of MEG signals can start immediately after placing the baby on the bed 29 and the head in the headrest assembly 16.
  • EEG EEG.
  • the MEG system 10 is also able to function in clinical rooms without magnetic
  • the system 10 includes magnetic field, line frequency and radio frequency noises, for example.
  • SQUID control electronics may be equipped with SQUID control electronics with, for example, an effective dynamic range of about 32 bits that resolve magnetic fields between about 10 ⁇ T and ⁇ about 1
  • fT may also have a fast slew rate that can follow magnetic field changes as fast as about 10 ⁇ T/ms which is fast enough to follow changes in the line frequency noise
  • gradiometers and the reference channels enable the low frequency and 60 Hz noise to
  • the system 10 may operate in unshielded environments.
  • the above features make the system 10 useful in an ordinary clinical setting.
  • the MEG system 10 may have a sufficiently high level of
  • system 10 may satisfy this essential requirement by taking advantage of several unique
  • the skull and scalp of a newborn are quite thin.
  • the human skull at the age of 6 months after birth has an average thickness of about
  • the skull should be between about 1.7 and about 2.0 mm thick at birth.
  • scalp is also about 1 mm thick in the first several months of age.
  • coils can be placed as close as between about 5 and about 6 mm from the cortical
  • the system 10 may be thus configured
  • mm also increases spatial resolution.
  • the sensing coils are tightly packed in the system
  • the spatial resolution of the system 10 is about
  • abnormal cortical region such as the bilateral strip of cortical tissue along the anterior-
  • MEG signals are transparent to the scalp and skull, unlike EEG, even in the presence of
  • EEG signals may be significantly distorted by skull defects that are
  • the skull is not present within the fontanels; instead the brain is
  • the anterior fontanel may be
  • midpositions is 3-4 mm for infants between 0 and about 60 days after birth (Eramie and
  • sutures are 6 and 1 years, respectively. Thus, EEG signals may be profoundly affected
  • fontanels improves the sensitivity of the EEG.
  • skull defects may obscure
  • the conductivity of the skull is also expected to change with age and across individuals.
  • the skull thickness increases rapidly within the first three years of age from
  • the 10th-90th percentiles are 2.4-4.6 mm
  • the 10th-90th percentile range is 40-50% of the means for
  • EEG signals may be distorted not only by skull defects, but also by the brain-skull
  • a 6° cortical source may be as much as about 50 times greater for a 6° cortical source compared to a focal source at the center of the brain and as much as about 100 times greater for such a
  • focal cortical sources may be small relative to deeper sources and thus some of the cortical components may be difficult to be identified or distinguished, being
  • the MEG system 10 assesses neonatal brain functions and serves as a useful non-invasive clinical tool for monitoring physiological functions of the pre- term and full-term neonates born with possible neurological disorders.
  • Figs. 2 and 3 show one embodiment of the headrest assembly 16 of a system 10
  • honey-comb rear wall design enables the placement of the MEG detection sensor coils at a distance of about 1.5 mm or 2 mm (Fig. 2B) from the outer surface of the headrest
  • housed may be in vacuum to provide thermal insulation.
  • the sensor array of sensors 18 in one embodiment of the system 10 consists of
  • Such modules may be built with a noise level of less than 10 TV I Hz.
  • the preferred embodiment of the headrest uses a honey-comb rear-wall design with
  • each module (or cluster) including 4 channels of sensing coils.
  • the sensors 18 are positioned within the recesses in the rear wall where the headrest wall is the thinnest.
  • the headrest assembly 16 was tested to determine whether the individual
  • the deflection was less than about 100 ⁇ m for a 1.0 mm-thick window with a
  • the deflection was less than about 100 ⁇ m for a 1.0-mm thick window.
  • the vacuum was held by the window even for a 0.4-mm thick window.
  • honey comb rear wall design with a wall thickness of between about
  • chrome-alloy ball bearing was dropped from varying heights onto the center of selected
  • the window can withstand a significant impact even for a wall thickness of about 1 mm.
  • baby's head was modeled as an ellipsoidal volume with a radius of curvature of about 6
  • the headrest may be made from this positive
  • Each one of the sensors 18 is a first-order asymmetric, axial superconducting
  • the sensors 18 are arranged in clusters of 4 separated by the honeycomb
  • the expected noise level for the gradiometers with a pickup coil diameter of about 6 mm may be about 10 TV/ Hz or better.
  • Such a module has been fabricated and determined its noise level has been determined.
  • Fig. 5 shows the pickup coils, which are about 6 mm in diameter in one
  • Figs. 7 and 8 show the noise spectra for the two channels.
  • the noise spectra were quite clean with an elbow frequency (where the 1/f noise starts) of about 1 Hz. Based on these results, it appears that a 4-channel module can be constructed with a
  • Figure 9 is a graphical representation of the results of the study and show representative samples of the SEFs produced by piezoelectric vibratory stimulations
  • the latency delay of the initial component is approximately 35
  • the SEFs for airpuffs are averages of 36 epochs
  • the system 10 enables a study to be carried out by simply placing the baby's
  • the system 10 provides a sense of safety to the parents who would be present at such a
  • the 76-channel system 10 tends to speed up the study, since the measurement time is
  • the system 10 may well be very useful for neonatal brain assessment.
  • EEG is strongly affected by a hole in the skull mimicking the anterior fontanel in the
  • system 10 may well be capable of providing new information about the
  • skull of the piglet is virtually the same in waveform and spatial distribution with and
  • Figure 12 shows an outline (dashed square) of the SEP (somatic evoked potential)
  • conductivity of the sucrose-agar should be close to the conductivity of, in this case about
  • the scalp is about 1.5 mm in
  • Figure 14 shows the SEPs measured over a square
  • dashed curves are the scalp SEPs.
  • the results of this study indicate that it may be possible to measure SEF over the scalp as if the scalp and skull were absent, whereas the SEP on the dura may be distorted on the scalp.
  • electrocorticographic sensors were positioned on the cortex.
  • the SEF was first scanned over the SI and
  • Fig. 15B shows the wideband (1 Hz - 3,000 Hz) signal at locations SQ2 and SQ4 along with the narrowband (416-2,083Hz) SEF, the difference wave between the SEFs measured at SQ2 and SQ4 and the power of the difference
  • microSQUID and thus there is needed about 25 times less average or about 100 epochs
  • generator of this 600 Hz signal may be the thalamocortical axonal terminals (Gobbele et al., 1998), inhibitory interneurons in the cortex (Hashimoto et al, 1996a; Mackert et al.,
  • Fig. 17, left shows that the Kyna-insensitive component was localized within layer
  • the laminar profile at its peak (time point 4) is shown in Fig. 17. This is the first post ⁇
  • the MEG sensors are housed in a cryogenic container called a dewar that stores
  • the dewar consists of two cylindrical containers.
  • the inner container is
  • the dewar may be made from a special laminated G-10 fiberglass that is constructed to prevent leakage of helium gas into the vacuum space.
  • the dewar may be made from a special laminated G-10 fiberglass that is constructed to prevent leakage of helium gas into the vacuum space.
  • the dewar weight may
  • the total bed system may be about 300 lb, so that it should be portable on wheels.
  • the body of the inner container may be shielded against heat radiation leak using layers of low conductivity material such as aluminum.
  • the shielding may be installed in removable packs to enable ease of construction and rework.
  • the outside may be about 2 mm via independent mounts.
  • the top section of the dewar may be made separately from the bottom cylindrical
  • the plate may be a G-10 plate with a cylinder epoxied onto the plate.
  • the plate may be a G-10 plate with a cylinder epoxied onto the plate.
  • the exhaust hole may be sealed with a removal thermal shield to
  • the cylinder may be machined so that
  • the headrest can be epoxied onto the cut surface.
  • the headrest may have a curvature
  • the headrest may be ellipsoidal or semi-ovoid with the radii of curvature of about 6 and about 8 cm. This dimension should be sufficient to accommodate infants of up to about two years of age
  • the sensor pick up coils may be mounted at the top and the
  • an MEG system 44 may be mounted at the bottom of the inner container of the dewar 27. This sensor assembly may be maintained at the superconducting temperature, by a cold heat sink attached to the bottom of the inner container.
  • an MEG system 44 have a
  • headrest assembly 46 enables the sensor array 48 to be moved adjustably relative to
  • An actuating mechanism 53 may be installed that may enable an operator
  • the boil off rate for the system 44 is about 4 liters/day when it is not in use and 8
  • a sufficient size dewar such as a 25-liter dewar may
  • helium transfers may need to be made twice a week for some applications.
  • the actuating mechanism 53 may be made as illustrated in Fig. 18.
  • the shafts such as a shaft 50 supporting the sensor array may be spring loaded and moved up
  • the array consists of 19 modules of 4 channels each for the disclosed embodiment. Each module may be attached to an
  • ellipsoidal support as shown in Fig. 3.
  • the distance between the center of a module to the center of an adjacent module is approximately 24 mm for this embodiment.
  • Each module consists of 4 channels of first-order, asymmetric, axial gradiometers
  • the most suitable pick up coil configuration is a 12 turn, 6 mm-diameter pick up coil and a 6 turn (spaced by 1 mm), 8.49 mm-diameter cancellation coil. This is
  • the pickup coils within and across the clusters of 4 are densely packed to
  • the coil-to-coil diagonal distance within each module is
  • MEG systems made by the CTF Systems and 4D-Neuroimaging.
  • the leads from the pick up may be RF shielded.
  • coils may be shielded using superconducting lead tubes.
  • Each module may be RF shielded by
  • An electronic rack may be placed in the body of the portable cart 14 below the
  • This rack houses 84 channels of SQUID control units
  • the dc-SQUIDs may be connected via RF-
  • the SQUID electronics may be powered completely by a suitable dc power
  • the dc power reduces the line frequency noise that would be sensed by the MEG
  • the system 10 must operate in electromagnetically unshielded environments
  • the system 10 is portable and is
  • the second stage may be
  • Fig. 19 illustrates the
  • Figure 20 shows the noise cancellation for the line frequency noise using the 8
  • the eight channels of reference consisted of five gradiometer channels and three magnetometer channels comprising a complete field and field gradient measurement.
  • the test noise data was acquired at a 2 kHz sample rate for one
  • This noise cancellation scheme may be refined by finding the weights that may be time dependent. This refinement may provide a line
  • the data acquisition may be carried out by a PCI-based system that may be attached to the cart 14 as shown in Fig. 1.
  • control units may be fed to a set of data routers via fiber optic cables. This reduces the rf noise feeding back into the SQUID control unit and into the SQUIDs.
  • the control units are
  • the fiber optic outputs from four units (12 channels) may be
  • level 1 routers fed at a rate of 480 kByte/sec to a level 1 router.
  • Four of the level 1 routers are fed to the next router at a rate of 1.92 MB/sec. Since there are 84 channels, 7 level 1 routers
  • the level 2 routers may be fed into a PCI card with a transfer rate of 8 MB/s. This data
  • the acquisition system continuously acquires 4-byte data at 10 kHz from 84 channels.
  • a 1 GHz PCI-based PC may be is sufficient for some applications.
  • the STL system may
  • the data may be sampled at a rate of at least 8 kHz.
  • the data acquisition may be controlled by software. . It provides a complete control over all electronic features.
  • An optical technique may be used to determine the head shape of
  • This method uses one digital camera to take the pictures of a grid pattern
  • the distortions of the grid pattern seen by the camera are used to reconstruct the 3D shape of the head and face. This method may be selected since it is completely remote in operation, non-invasive, fast and economical.
  • the image can be obtained in less than 1 second and the reconstruction can be done offline, so that there is no need to worry about movement of the baby's head.
  • the conventional optical positioning system 28 from Eyetronics may be any optical positioning system 28 from Eyetronics.
  • the input parameters are the relative positions of the camera and the miniature slide projector that may project a single grid pattern onto the face and head,
  • overlapping pictures may be taken from different angles.
  • a software provided by Eyetronics, may be used to integrate the separate images. This process can be
  • the duration of sleep is typically between about 10 min and about 40 min. Monitoring the head position continuously during this period enables
  • the useful measurement period may also be extended due to the monitoring , to the period of wakefulness. Oftentimes
  • the baby keeps his/her head stationary for more than about 10 sec at a time during the
  • head position tracking there are optical, electromagnetic and laser tracking systems. It may be desirable for some applications to continuously monitor the head with an absolute positional accuracy of about 1 mm during measurements.
  • Optical tracking systems include two or more cameras of known locations. They track
  • the marks can be either passive (for example, reflective
  • Optical systems have 0.3 - 0.4 mm accuracy in a tracking volume of about 1 m 3 .
  • the update rate is in the 20 - 70 Hz range.
  • location can be synchronized with magnetic measurements.
  • Laser tracking Laser tracking system has the same advantage as optical systems in that it does not tend to interfere with magnetic measurements, and the object position can be synchronized with the MEG data.
  • These systems include a cost effective LaserBird
  • the accuracy is about 1 mm at about 1 m distance.
  • the tracking is done by scanning the work area with a laser beam.
  • Electromagnetic tracking systems are widely used with SQUID biomagnetic measurements (for example, EM tracking systems from Polhemus).
  • An electromagnetic transmitter is rigidly attached relative to the pick up coils, and three receivers are
  • MEG magnetoencephalography
  • the system 55 is generally similar to the system
  • system 55 employs clustered sensors instead of modular sensors
  • the system 55 is adapted to serve as a non-invasive neurodiagnostic tool in
  • System 55 includes a cart 59 having a headrest assembly 62 disposed
  • the headrest in an upwardly facing direction for receiving the head of the patient 57.
  • assembly 62 is generally similar to the headrest assembly 16, and includes a sensor
  • the cart 59 is designed to be portable and roll
  • a SQUID dewar 75 is mounted on the cart 57, and includes an optical positioning
  • the headrest 62 her head supported from below by the headrest 62.
  • a liquid helium reservoir 79 of the SQUID dewar 75 is a
  • the electronic components are connected to the SQUID via a group of
  • a portable trailer 93 is mounted rollably above the ground by means of a series of
  • a group of shielded cables generally indicated at 95
  • the trailer including a
  • DC power supply 97 and a transformer 99 can be moved along with the cart 57.
  • a pair of DC power supply 97 and a transformer 99 can be moved along with the cart 57.
  • the headrest assembly 62 has two curvatures for coronal and sagittal (axial)
  • the headrest assembly 62 is concave and is
  • a more preferred range of the sagittal radius is between about 90 mm and about 110
  • a more preferred range of the coronal radius is between about 70 mm and
  • coronal radius is about 75 mm.
  • the headrest 66 is composed of non-metallic head-insulating structurally strong
  • Each one of the sensors 64 is a superconducting gradiometer having a pick-up coil diameter of between about 4 mm and about 8 mm. More preferably, the pick-up coil diameter is between about 5 mm and about 7 mm. Currently, the most preferred pick-up diameter is about 6 mm.
  • the gradiometer sensors are uniformly distributed relatively to the head engageable surface of the headrest 66.
  • Each one of the sensor pick-up coils being
  • spacing distance is more preferably between about 8 mm and about 12 mm.
  • the sensors are arranged in groups of four, wherein the spacing
  • the distance between adjacent sensors of a group is about 8.5 mm and the spacing distance between diagonally disposed sensors of a group is about 12 mm.
  • the sensors 64 are arranged in groups, and
  • the headrest 66 has a corresponding series of windows or recesses such as a recess 108 in the rear surface of the headrest 66 positioned opposite to one of the groups of the
  • each one of the recesses is generally rectangular in shape and
  • the rear surface of the headrest is arranged in a honeycomb configuration to provide a thin wall
  • sensors 64 are arranged in clusters of four, it is to be understood that
  • each separate sensor may have its own recess or window and not be
  • the sensors are arranged in groups of four, and each one of the four sensors of a group provides a
  • the channel is usable individually, or in combination
  • the channels can be summed in various ways.
  • channels can be subtracted, or used individually.
  • the dewar 75 is radio frequency interference shielded by multiple techniques.
  • the external portions (those at room temperature) of the dewar is shielded by the external portions (those at room temperature) of the dewar.
  • coating conductivity and thicknesses is such to provide an eddy current shield with a roll-
  • the coating may be applied through various combinations
  • the interior portion of the dewar 75 is also shielded by the use of one
  • ultra-thin assemblies of conductive material such as aluminum.
  • the assemblies are such that they act as an eddy current shield with a
  • signals of interest typically less than 10 kHz.
  • magnetometer detection sensor coils in the dewar are magnetometer detection sensor coils in the dewar.
  • headrest 66 is maintained constant through various temperature changes of the dewar 75.
  • the system 10 either cools down or warms up, the differences in
  • the coefficient of thermal expansion of the various components may cause the small gap
  • a mounting ring 109 is fixed to the headrest assembly 62 and mounts it fixedly to
  • a coil array plate 110 supports the sensors 64 in close
  • a set of rods such as the rods
  • the longer rods such as the rod 111 is composed of
  • suitable material such as quartz so that when the system 10 cools down, the quartz rods
  • the shorter rods such as the rod 117 are also composed of
  • suitable material such as quartz so that when the system cools down, for example, the
  • quartz rods such as the rod 117 shrinks in length to pull the coil toward the headrest 66.
  • the coil array plate 110 is pre-adjusted to correct lift-off when the system is warm.

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  • Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)

Abstract

Dans certains modes de réalisation, l'invention concerne une magnéto-encéphalographie et un procédé mettant en application un chariot portable sur lequel est monté de façon inversée un récipient dewar SQUID, ainsi qu'un support de tête servant à supporter la tête du patient et faisant partie du récipient dewar. Ce support de tête comporte un ensemble de capteurs magnétiques du récipient dewar SQUID sensible à l'activité électrique du cerveau.
PCT/US2003/020523 2002-08-26 2003-06-27 Systeme et procede de magneto-encephalographie haute resolution Ceased WO2004017811A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2003263757A AU2003263757A1 (en) 2002-08-26 2003-06-27 High-resolution magnetoencephalography system and method
EP03792953A EP1538978A4 (fr) 2002-08-26 2003-06-27 Systeme et procede de magneto-encephalographie haute resolution

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US10/228,694 US6784663B2 (en) 2001-08-27 2002-08-26 Self-adjusting assembly and method for close tolerance spacing
US10/228,694 2002-08-26
US10/609,259 US7197352B2 (en) 2002-08-26 2003-06-26 High-resolution magnetoencephalography system, components and method
US10/608,725 2003-06-26
US10/609,259 2003-06-26
US10/608,725 US7130675B2 (en) 2002-06-28 2003-06-26 High-resolution magnetoencephalography system and method

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WO2004017811A2 true WO2004017811A2 (fr) 2004-03-04
WO2004017811A3 WO2004017811A3 (fr) 2005-04-14

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AU (1) AU2003263757A1 (fr)
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Citations (1)

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US6023633A (en) 1995-12-14 2000-02-08 Kanazawa Institute Of Technology Magnetomeasuring apparatus a having a coolant vessel with an access opening and sensor support for limiting heat transfer

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EP0361137A1 (fr) * 1988-09-16 1990-04-04 Siemens Aktiengesellschaft Dispositif magnétométrique avec un cryostat pour mesurer des champs magnétiques faibles
US4951674A (en) * 1989-03-20 1990-08-28 Zanakis Michael F Biomagnetic analytical system using fiber-optic magnetic sensors
JP2893714B2 (ja) * 1989-05-25 1999-05-24 株式会社日立製作所 薄膜型ｓｑｕｉｄ磁束計およびこれを用いた生体磁気計測装置
US5442289A (en) * 1989-07-31 1995-08-15 Biomagnetic Technologies, Inc. Biomagnetometer having flexible sensor
FI912656L (fi) * 1990-06-25 1991-12-26 Siemens Ag Kylanordning foer en squid-maetanordning.
DE4227878A1 (de) * 1992-08-22 1994-02-24 Philips Patentverwaltung Abschirmhülle für SQUID-Magnetometer gegen elektromagnetische Störfelder

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US6023633A (en) 1995-12-14 2000-02-08 Kanazawa Institute Of Technology Magnetomeasuring apparatus a having a coolant vessel with an access opening and sensor support for limiting heat transfer

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Title
See also references of EP1538978A4

Also Published As

Publication number Publication date
WO2004017811A3 (fr) 2005-04-14
EP1538978A4 (fr) 2005-11-23
EP1538978A2 (fr) 2005-06-15
AU2003263757A1 (en) 2004-03-11
AU2003263757A8 (en) 2004-03-11

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