Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Patent
1986-01-17
1988-05-31
Tokar, Michael J.
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
324319, 335296, G01R 3320
Patent
active
047484144
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention proceeds from a nuclear spin tomograph comprising a magnet system with a, preferably, elongated holder for a test object arranged in its one axis to slide in a longitudinal direction, the test object being further surrounded by coil systems. for generating gradient fields and for irradiating a radio-frequency field.
BACKGROUND ART
A nuclear spin tomograph in which a human body is positioned within an electromagnetic system which may comprise ferromagnetic parts, has been known already from German Disclosure Document No. 28 54 774. According to this arrangement, however, the patient is surrounded on all sides, at least during the measurement, by magnetic coils and electromagnetic bodies of an unspecified type, so that it is not apparent how the patient is to be introduced into the test space and how exactly the coils for generating the magnetic field are to be arranged. This makes the magnetic system of the known arrangement absolutely unsuited for practical use because there is no opening through which the test object can be introduced and because in addition it requires magnet dimensions which, for reasons of weight, rule out their realization as iron magnets.
The term nuclear spin tomography or NMR tomography is understood to describe a method in which a test object, in particular a live human body or animal body is subjected simultaneously to a strong homogenous magnetic field and an r.f. field directed perpendicularly thereto. At the same time, one generates in the area of the test object a gradient field acting in the same direction as the homogenous magnetic field and decreasing in strength in the axis of the test object. Now, when the r.f. field is applied, nuclear magnetic resonance occurs only in the area of one plane of the test object because, due to the active gradient field, the magnetic field has a strength which, given the gyromagnetic ratio of protons, corresponds to the frequency of the irradiated r.f. field only in the area of this same plane. This makes it possible to produce sectional images of the test object.
In order to obtain sufficient measuring signals, it is necessary to work at relatively high magnetic field strengths. Known nuclear spin tomographs operate, for example, at a magnetic field having a strength of 0.23 Tesla.
On the other hand, relatively large sample spaces are required to permit, for example, measurement on human bodies. This is the reason why one has used to this day mainly magnetic systems using air-cored coils which were operated either in the normally conductive or in the superconductive operating mode. However, such air-cored coils have quite a number of drawbacks.
Firstly, the extreme homogeneity of the magnetic field required in the sample space is impaired already by minor disturbing factors occurring outside the magnetic system. Such disturbing factors may be either of a stationary nature, as for example reinforcing steel in the walls of the room in which the nuclear spin tomograph is installed, or else of a moving type, such as instrument trolleys moved in the neighborhood of the tomograph or even cars passing outside the examination building.
Secondly, air-cored coils give rise to a considerable leakage field since the homogenous magnetic field extending along the axis of the air-cored coil closes via the external space of the air-cored coil. This leakage field of the air-cored coil may influence equipment placed near the magnet system, such as electronic equipment, data processing systems or radiological equipment in a hospital. In addition, the leakage field may also disturb the operation of pacemakers so that it may be connected with certain risks for pacemaker patients to stay near the magnet system.
In an effort to overcome these disadvantages, a known system described in German Disclosure Document No. 31 23 493 has been provided with a shielding of a soft-magnetic material which absorbs the largest part of the leakage field. But due to the solenoid design of the air-cored coil, in which the direction of th
REFERENCES:
patent: 3345523 (1967-10-01), Grunwald
patent: 3513422 (1970-05-01), Watson et al.
patent: 3789832 (1974-05-01), Damadian
patent: 4038622 (1977-07-01), Purcell
patent: 4318043 (1982-03-01), Crooks et al.
patent: 4354499 (1982-10-01), Damadian
patent: 4411270 (1983-10-01), Damadian
patent: 4442404 (1984-04-01), Bergmann
patent: 4456881 (1984-06-01), Compton
patent: 4490675 (1984-12-01), Knuettet et al.
patent: 4613820 (1986-09-01), Edelstein et al.
P. Hanley, Superconducting . . . NMR Scanning, Proceedings on NMR Imaging at Bowman Gray School of Medicine, Oct. 1-3, 1981.
G. Parzen, "Magnetic Fields for Transporting Charged Beams," Brookhaven National Laboratory BNL-50536 (Jan. 1976).
C.-M. Lai et al., Electro/78 Boston, Mass. pp. 30/2:1-15 (May 23-25, 1978).
Knuttel Bertold
Laukien Gunther R.
Bruker Medizintechnik GmbH
Tokar Michael J.
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