Susceptometers for foreign body detection
First Claim
1. A source-sensor unit for a magnetic susceptibility measuring instrument, comprising:
- at least one applied-field generating element; and
at least one magnetic sensor;
wherein said at least one applied-field generating element and said at least one magnetic sensor are arranged such that the signal due to the applied field is canceled out; and
wherein said entire source-sensor unit is constructed in such a way that said cancellation of the applied-field signal is preserved as the entire source-sensor unit expands and contracts uniformly.
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Accused Products
Abstract
Methods and apparatus for minimizing the effects of temperature drift in a magnetic susceptibility measurement instrument, such as an instrument used in pre-MRI screening for the presence of ferromagnetic foreign bodies. The magnetic field source and magnetic sensors can be combined into a single, rigid unit. The stability and sensitivity required in high quality magnetic susceptibility measurements can be achieved through symmetrical design of the source-sensor unit, minimization of thermal stresses, minimization of temperature variations, use of materials with low thermal expansion coefficients, or through appropriate combinations thereof. Use of patient eye movement where an eye is being screened, use of a water bag between the patient and the instrument, or use of telemedicine to facilitate performance of the necessary computations can also be incorporated.
71 Citations
38 Claims
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1. A source-sensor unit for a magnetic susceptibility measuring instrument, comprising:
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at least one applied-field generating element; and
at least one magnetic sensor;
wherein said at least one applied-field generating element and said at least one magnetic sensor are arranged such that the signal due to the applied field is canceled out; and
wherein said entire source-sensor unit is constructed in such a way that said cancellation of the applied-field signal is preserved as the entire source-sensor unit expands and contracts uniformly. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for performing pre-MRI screening, comprising:
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providing a magnetic susceptibility measuring instrument having at least one applied-field generating element, and at least one magnetic sensor;
constructing the structures which define the shapes, dimensions, and geometrical relationships of said instrument of materials with low thermal expansion coefficients;
canceling the signal due to the applied field by arrangement of said applied-field generating element and said sensor;
preserving said cancellation of the applied-field signal as the entire source-sensor unit expands and contracts uniformly;
generating an applied magnetic field in a region of interest of a patient, with said source-sensor unit; and
generating a magnetic susceptibility measurement relevant to the presence or absence of a ferromagnetic foreign body in said region of interest, with said source-sensor unit. - View Dependent Claims (22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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23. A method for performing pre-MRI screening for ferromagnetic foreign bodies, comprising:
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providing a source-sensor unit including at least one applied-field generating element and at least one magnetic sensor;
canceling the signal due to the applied magnetic field at the location of said at least one magnetic sensor by the relative arrangement of said at least one applied-field generating element and said at least one magnetic sensor in said source-sensor unit;
preserving said cancellation of the applied-field signal as said entire source-sensor unit expands and contracts;
generating an applied magnetic field in a region of interest of a patient, with said source-sensor unit; and
generating a magnetic susceptibility measurement relevant to the presence or absence of a ferromagnetic foreign body in said region of interest, with said source-sensor unit.
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Specification