3012 results about "Magnetic field magnitude" patented technology

A combination MRI and radiotherapy system comprising: a) an MRI system for imaging a patient receiving radiotherapy, comprising a magnetic field source suitable for generating a magnetic field of strength and uniformity useable for imaging, capable of being ramped up to said magnetic field in less than 10 minutes, and ramped down from said magnetic field in less than 10 minutes; b) a radiation source configured for applying radiotherapy; and c) a controller which ramps the magnetic field source down to less than 20% of said magnetic field strength when the radiation source is to be used for radiotherapy, and ramps the magnetic field source up to said magnetic field strength when the MRI system is to be used for imaging.

An electromagnet comprises a pair of magnetic pole 1a and 1b, a return yoke 3, exciting coils 4 and 5, etc. In an interior portion of a magnetic pole, plural spacers 2a-2g are provided putting side by side in a horizontal direction. Each of the spaces 2a-2g is an air layer and a longitudinal cross-section is a substantially rectangular shape and the space has a lengthily extending slit shape in a vertical direction against a paper face in FIG. 1. The plural spaces are mainly arranged toward a right side from a beam orbit center O and an interval formed between adjacent spaces is narrower toward the right side. The electromagnet having a simple magnetic pole structure and a wide effective magnetic field area in a case where a maximum magnetic field strength is increased can be secured.

In one illustrative embodiment, the present subject matter is directed to a device adapted to determine the position of a target magnet, wherein the device includes a pair of orthogonal magnetic field sensors laterally disposed along an axis that is substantially transverse to an axis defined by one that is nominally parallel to the direction of the target magnet. In another illustrative embodiment, the subject matter is adapted for use on an automated guided vehicle (AGV), whereby detection of the target magnet's location facilitates correction of the vehicle's heading and position while traversing an AGV system. The present subject matter is also directed to a method whereby the position of a target magnet may be determined by triangulation, utilizing trigonometric calculations based upon the strength and direction of the magnet field to determine the magnet's position relative to the magnetic field sensors.

An implantable medical device that includes a magnetic sensor circuit that senses the presence of an external magnetic field and provides a signal that is proportionate to the strength of the magnetic field. The implantable medical device uses the variable signal to determine whether a magnetic field is being applied that is selected to activate a preselected function. In one implementation, the preselected function is a power up sequence.

A system for determining motion information including attitude and angular rate of a dynamic object. The system includes a magnetic-field sensing device to measure in the body coordinate frame of reference an intensity and/or direction of a magnetic field in three substantially orthogonal directions; an acceleration-sensing device adapted to measure total acceleration of the object in the body coordinate frame of reference; and a processor adapted to calculate attitude and angular rate by combining total acceleration measurement data and magnetic field measurement data with the kinematic model in a filter.

An implantable medical device includes a detector for detecting the presence of a magnetic field, where the presence of the magnetic field is detected in response to the strength of the magnetic field exceeding a first preselected magnetic field threshold. The device further includes a processor for adjusting a stimulation rate provided by the implantable medical device in response to determining that the strength of the detected magnetic field exceeds a second preselected magnetic field threshold. The second preselected magnetic field threshold is greater than the first preselected magnetic field threshold. In another embodiment, the implantable device includes a detector for detecting the presence of a high frequency (HF) radiation interference signal and a processor for adjusting a stimulation rate provided by the implantable medical device in response to determining that the strength of the detected HF radiation interference signal exceeds a preselected HF radiation threshold.

An integrated metal detector-portable medical device adapted to identify metals in a human body, where the metal detector is in connection with the portable medical device. The metal detector includes: at least one transmitting means adapted to generate a second magnetic field so as to induce a magnetic field generated by a metal; at least one sensor adapted to detect a magnetic field generated by the metals to be detected; and at least one signaling means adapted, upon detection of a magnetic field, to alert the identification of metals, if the intensity of a magnetic field is above a predetermined value.

Embodiments in accordance with the present invention provide a perpendicular recording magnetic head whose dimensional dependency on the nonuniformity of magnetic field strength and distribution during manufacture is minimized, with narrowed tracks and without attenuation or erasure of adjacent track data while maintaining high magnetic field strength. According to one embodiment, a magnetic material (trailing/side shield) for creating a steep gradient of magnetic field strength is provided at a trailing side of a pole tip of a main magnetic pole piece and in a direction of the track width. The magnetic head is formed so that a gap (side gap length “gl”) between a side shield and a throat height portion of the pole tip progressively decreases with an increasing distance from an air-bearing surface, in a direction of an element height. That is, side gap length “gl” (2) at an element height position P2 is made smaller than side gap length “gl” (1) at an air-bearing surface position P1 so as to satisfy a relationship of gl(1)>gl(2).

The instant invention is directed toward a method and an apparatus for mapping the magnetic field strength or flux density of a magnetic source. The invention provides a robotically controlled sensor which is moved in a controlled manner throughout an area of flux density and the variations in the flux density are recorded. The position and recorded magnetic field strength at numerous points throughout the test area are recorded and the data is assembled into a graphical representation the end result of which is a multi-dimensional mapping of the magnetic field strength as a function of distance from the source. The testing method and apparatus provide a convenient methodology for accurately determining dosimetry and tissue penetration of therapeutic magnetic devices.

A magnetic field sensing device for determining the strength of a magnetic field, includes four magnetic tunnel junction elements or element arrays (100) configured as a bridge (200). A current source is coupled to a current line (116) disposed near each of the four magnetic tunnel junction elements (100) for selectively supplying temporally spaced first and second currents. Sampling circuitry (412, 414) coupled to the current source samples the bridge output during the first and second currents and determines the value of the magnetic field from the difference of the first and second values. A method for sensing the magnetic field includes supplying a first current to the current line (116), supplying a second current the current line (116), sampling the value at the output for each of the first and second currents, determining the difference between the sampled values during each of the first and second currents, and determining a measured magnetic field based on the determined difference.

The present invention relates to a magnetic sensor with a sensitivity measuring function and a method thereof. Magnetic sensitivity surfaces detect flux density, and a switching unit extracts magnetic field intensity information of each axis, and inputs it to a sensitivity calculating unit. The sensitivity calculating unit calculates the sensitivity from the magnetic field intensity information about the individual axes from the magnetic sensitivity surfaces. The sensitivity calculating unit includes an axial component analyzing unit for analyzing the flux density from the magnetic sensitivity surfaces into magnetic components of the individual axes; a sensitivity decision unit for deciding the sensitivity by comparing the individual axial components of the magnetic field intensity from the axial component analyzing unit with a reference value; and a sensitivity correction unit for carrying out sensitivity correction in accordance with the sensitivity information from the sensitivity decision unit.

The use of magnetic field sensing to perform sophisticated command control and data input into a portable device is disclosed. A magnetic field sensor is embedded or fixedly attached to a portable device to measure changes in the magnetic field strength and/or direction accompanying movement, motion or tilt of the device in one-, two- or three-dimensions when the portable device is used to air-write or make gestures.

The position of a movable downhole component such as a sleeve in a choke valve is monitored and determined using an array of sensors, preferably Hall Effect sensors that measure the strength of a magnetic field from a magnet that travels with the sleeve. The sensors measure the field strength and output a voltage related to the strength of the field that is detected. A plurality of sensors, with readings, transmits signals to a microprocessor to compute the magnet position directly. The sensors are in the tool body and are not mechanically coupled to the sleeve. The longitudinal position of the sleeve is directly computed using less than all available sensors to facilitate the speed of transmission of data and computation of actual position using known mathematical techniques.

A method and apparatus for Magnetic Resonance Imaging with specialized imaging coils possessing high Signal-to-Noise-Ratio (SNR). Imaging and/or Radio Frequency receiving coils include a ballistic electrical conductor such as carbon nanotubes, the ballistic electrical conductor having a resistance that does not increase significantly with length. Due to their enhanced SNR properties, system designs with smaller static magnetic field strength can be constructed for the same quality of imaging, leading to substantial reductions in system size and cost, as well as to enhanced imaging with existing MRI systems.