Apparatus for detecting ferromagnetic objects and screening people and equipment
Inventors
Goodyear, Simon Wray • Collinge, Simon Edward James • Keene, Mark Nicholas
Assignees
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Publication Number
US-9995713-B2
Publication Date
2018-06-12
Expiration Date
Abstract
Apparatus for detecting a ferromagnetic object located on or in a person being screened comprises a first magnetic sensor which in use measures an ambient magnetic field or gradient within a first volume of space and produces a corresponding measurement signal, a primary power supply which provides power to the magnetic sensor, a signal processing circuit arranged in communication with the magnetic sensors configured to identify temporal variations in the measurement signal and from the identified temporal variations provide an output signal indicative of the presence of a ferromagnetic object within the volume of space, and a warning device operable by the output from the signal processing circuit to provide within the vicinity the apparatus at least one of an audible and a visible warning in response to the output signal from the signal processing circuit. The apparatus include a user operable input means which enables the warning device to be disabled by a user without powering down the magnetic sensors.
Core Innovation
The invention is an MRI pre-screening apparatus for detecting a ferromagnetic object located on or in a person being screened. The apparatus includes at least a first magnetic sensor that measures an ambient magnetic field or gradient within a first volume of space and produces a corresponding measurement signal, and a signal processing circuit identifies temporal variations in the measurement signal and provides an output signal indicative of the presence of the ferromagnetic object within the volume of space.
The output signal is used to operate a warning device that provides within a vicinity the apparatus at least one of an audible and a visible warning in response to the output signal from the signal processing circuit. The apparatus includes a user operable input device that enables the warning device to be disabled by a user without powering down the at least first magnetic sensor, and the apparatus uses a primary power supply to provide power to the at least first magnetic sensor.
The described approach further supports gradiometer configurations by using additional magnetic sensors to measure ambient magnetic field or gradient within overlapping volumes and to configure the sensors as a gradiometer. The gradiometer arrangements increase near-field sensitivity and reduce distant interference by using a first-order gradiometer with two sensors and a second-order gradiometer with three sensors configured together with differential/summed outputs.
Claims Coverage
The document includes three independent claims unified by magnetic-sensor measurement of ambient magnetic field or gradient, identification of temporal variations, generation of an object-presence output signal, and audible/visible warning operation. Across the independent claims, the main inventive features are sensor-based temporal-variation detection, warning operation driven by a presence-indicative output, and the ability to disable the warning without powering down the magnetic sensor.
Temporal-variation detection from ambient magnetic field or gradient
At least a first magnetic sensor measures an ambient magnetic field or gradient within a first volume of space and produces a corresponding measurement signal; a signal processing circuit identifies temporal variations in the measurement signal and from the identified temporal variations provides an output signal indicative of the presence of a ferromagnetic object within the volume of space.
Audible/visible warning driven by presence-indicative output
A warning device is operable by the output from the signal processing circuit to provide within the vicinity the apparatus at least one of an audible and a visible warning in response to the output signal from the signal processing circuit.
Disable warning without powering down the magnetic sensor
The apparatus includes a user operable input device which enables the warning device to be disabled by a user without powering down the at least first magnetic sensor.
Screening by body positioning and rotation with observation of warnings
A method of screening a person or object positions an entire body within the first volume of space in a first orientation, rotates the entire body through 180 degrees to a second orientation, and includes observing any warning from the warning device.
The independent claims collectively require magnetic-sensor measurement of ambient magnetic field or gradient and identification of temporal variations to produce an output indicative of ferromagnetic-object presence, drive an audible/visible warning device, and provide a user input to disable the warning without powering down the magnetic sensor; the method claim further specifies screening by body positioning and rotating through 180 degrees followed by observing the warning.
Stated Advantages
Enables a user to disable the warning device without powering down the magnetic sensor.
Using gradiometer configurations increases near-field sensitivity and reduces distant interference.
Documented Applications
Pre-screening a person or object for ferromagnetic objects prior to MRI screening by positioning and rotating an entire body within a sensing volume and observing audible/visible warnings.
Screening implementations that use overlapping sensing volumes configured as a gradiometer (first-order with two sensors, second-order with three sensors) for near-field sensitivity and reduced distant interference.
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