Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-10-04
2003-02-18
Vo, Hieu T. (Department: 3754)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06522908
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a biomagnetic field measuring apparatus using SQUID (Superconducting Quantum Interference Device) sensors, which are superconducting devices for detecting a very weak magnetic field generated from a living body. Particularly, the invention is concerned with a biomagnetic field measuring apparatus and method capable of easily obtaining a combined image of functional information on the activity of the heart of a subject to be inspected and a morphological image of the heart, as well as a data processing method and a positioning method for the subject to be inspected using the biomagnetic field measuring apparatus.
In a conventional biomagnetic field measuring apparatus for measuring the function of the brain, as shown in
FIG. 16
, plural detecting coils
12
are arranged on a bottom
11
of Dewar whose external form is in conformity with the curvature of the head, magnetic field generating coils
13
, which are mounted at plural positions of the head, are energized and the resulting magnetic field is detected by the detecting coils
12
. Further, a relation between the magnetic field generated by the magnetic field generating coils
13
and the output of the detecting coils
12
is simulated. The positions of the magnetic field generating coils
13
, which minimize the difference between the measured data detected by the detecting coils
12
and the output of the detecting coils
12
after the simulation, are estimated to specify position coordinates at the head positions where the magnetic field generating coils
13
are arranged (see, for example, JP-A-No. Hei 4-303416).
As shown in
FIG. 17
, in measuring a morphological image of a head by an MRI (magnetic resonance imaging) device, MRI markers
21
are arranged at the same positions as the head positions where the magnetic generating coils
13
shown in
FIG. 16
are arranged, and a tomogram of the entire head, including the MRI markers
21
, is measured. Then, position coordinates of the MRI markers
21
are specified using an MRI image (see, for example, JP-A-No. Hei 4-303416).
In combining the results of measurement of the brain magnetic field with the MRI image of the head, which represents a form, there is determined a relation between the position coordinates of the magnetic field generating coils
13
and the position coordinates of the MRI markers
21
. For example, when the position of an active brain site obtained by measuring the brain magnetic field is to be displayed on the morphological image, a tomogram of the brain is reconstructed so as to include coordinates corresponding to the position of the active site with use of the head tomogram obtained by the MRI device, and then the active site of the brain and the MRI image are combined and displayed (see, for example, A. Uchida et al., AVS
th
based Brain Activity Analysis System with a Real Head Shape, Recent Advances in Biomagnetism, Edited by Y. Yoshimoto et al., Tohoku University Press, pp.177-180, 1999).
In connection with a biomagnetic field measuring apparatus, various methods have been reported for establishing a positional relation between a subject to be inspected on a bed and a Dewar (see, for example, JP-A-Nos. Hei 3-244433, Hei 2-180244. and Hei 4-109929).
SUMMARY OF THE INVENTION
In case of applying the above conventional technique in the measurement of a brain magnetic field to the measurement of a biomagnetic field generated from the chest of a living body, the conventional technique involves a problem in that a complicated simulation calculation is needed for specifying position coordinates of the magnetic field generating coils arranged to specify position coordinates of a head in the measurement of a brain magnetic field and a problem in that, in the case of an MRI image, it is necessary to read MRI markers.
Moreover, in combining the results of having measured a brain magnetic field with an MRI image, it is necessary to determine a relation between coordinates of the magnetic field generating coils and coordinates of MRI markers, and it is also necessary to perform a calculation for reconstructing a tomogram of the head so as to include coordinates corresponding to the position of an active site of the brain with use of a tomogram obtained by an MRI device.
It is an object of the present invention to provide a biomagnetic field measuring apparatus which is capable of solving the above-mentioned problems of the prior art. Particularly, the present invention aims at providing a biomagnetic field measuring apparatus and a method capable of realizing, in a short time and easily, an operation for aligning the position of the heart of a subject to be inspected with a sensor array and an operation for obtaining a large signal output from SQUID (Superconducting Quantum Interference Device) sensors.
It is another object of the present invention to provide a biomagnetic field measuring apparatus which is capable of easily forming and displaying a combined image of functional information on the activity of the heart obtained from the biomagnetic field measuring apparatus with a morphological image obtained by an image pick-up device other than the biomagnetic field measuring apparatus.
It is a further object of the present invention to provide a data processing method for displaying a combined image in the biomagnetic field measuring apparatus, as well as a positioning method which is suitable for establishing a position of a subject to be inspected using the biomagnetic field measuring apparatus at the time of displaying the combined image.
The following description is directed to typical constructions of biomagnetic field measuring apparatuses according to the present invention.
A biomagnetic field measuring apparatus according to the present invention is provided with a bed for supporting a subject to be inspected thereon, a bed support, a cryostat for cooling a plurality of SQUID sensors, and a gantry fixed to a floor surface for holding the cryostat at a known distance with respect to the floor surface. The bottom of the cryostat and an upper surface of the bed are positioned substantially in parallel with the floor surface.
The cryostat is provided at an outer peripheral surface of its bottom with an xz marking which represents an xz plane of a coordinate system (x, y, z) and a yz marking which represents a yz plane of the coordinate system. In the coordinate system (x, y, z), the xy plane is parallel to the bottom of the cryostat and z axis is perpendicular to the bottom of the cryostat.
A plurality of SQUID sensors are arranged, respectively, in x and y directions near an inner bottom of the cryostat to detect a component in the z direction of a magnetic field which is generated, for example, from the heart of the subject to be inspected. As such plural SQUID sensors, fluxmeters which detect components in both x and y directions of a magnetic field generated from the heart of the subject to be inspected may be used.
An optical system is used to adjust a positional relation between the bottom of the cryostat and the bed. The optical system comprises a first laser source for generating a first sectorial laser beam which spreads sectorially in the xz plane, a second laser source for generating a second sectorial laser beam which spreads sectorially in yz plane, and a third laser source for generating a dot-like laser beam which is radiated to the bed surface obliquely across the first and second sectorial laser beams. The first laser source is fixed to a frame which is secured to the gantry; the second laser source is fixed to a frame which is secured to the bed support; and the third laser source is fixed to a frame which is secured to any of the floor surface, ceiling, and wall surface.
As means for changing irradiating directions of the laser beams generated respectively from the three laser sources, there are first position changing means which changes the irradiating direction of the first sectorial laser beam so as to irradiate the xz marking, second position changing means which
Kandori Akihiko
Kondo Shoji
Miyashita Tsuyoshi
Sasabuchi Hitoshi
Tsukada Keiji
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Vo Hieu T.
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