Siemens Aktiengesellschaft

Cheng Ni

Jin Chen

Ting Qiang Xue

Xiao Dong Zhou

Jing Gao

Zhong You Ren

Chao Wang

Hai Bo Yu

Marc Beckmann

Hong Yan Tao

Hui Cao

In a method and device for compensating the insufficient homogeneity of a magnetic field in a magnetic resonance system, the spatial position and size of a basic magnetic field region and at least one additional magnetic field region in a field to be homogenized and determined. An optimization calculation is implemented on the basic magnetic field region and the at least one additional magnetic field region. A homogenized magnetic field at the main magnetic field region and the at least one additional magnetic field region is output according to the result of the optimization calculation.

Method and apparatus for compensating insufficient homogeneity of the basic magnetic field in a magnetic resonance apparatus

A method for reducing magnetic resonance temperature measurement errors, which is used for the high-intensity focused ultrasound device for monitoring magnetic resonance imaging includes obtaining a magnetic resonance phase diagram as a reference image before the high-intensity focused ultrasound device heats the heating area; obtaining another magnetic resonance phase diagram as a heating image during or after the heating process of the high intensity focused ultrasound device; calculating the temperature changes in the heating area according to said heating image and reference image. The method further includes measuring the magnetic field changes caused by the position changes of the ultrasonic transducer of said high-intensity focused ultrasound device, and then compensating for the temperature changes according to said magnetic field changes. The present invention can significantly reduce the temperature errors caused by the position changes of the ultrasonic transducer.

Method for reducing magnetic resonance temperature measurement errors in a magnetic resonance monitored HIFU treatment

A method for magnetic resonance imaging, in which a magnetic resonance imaging device employs a multi-echo imaging sequence, includes the steps of: applying, to one of the multiple echoes, a first number of steps of phase encoding, applying a readout gradient, and collecting the data of this echo to reconstruct an anatomical image; and applying, to another one of the multiple echoes, a second number of steps of phase encoding, applying a readout gradient, and collecting the data of this echo to construct a temperature image. The method is capable of obtaining at the same time both a temperature image with high time resolution and an anatomical image with high spatial resolution.

Method for magnetic resonance imaging

A method for reducing errors in the measurement of temperature by magnetic resonance, for use in magnetic resonance imaging-guided HIFU equipment, includes acquiring an MR phase image, as a reference image, before heating an area to be heated with the HIFU equipment; acquiring another MR phase image, as a heated image, during or after the heating by the HIFU equipment; and calculating the temperature change in the heated area according to said heated image and said reference image; and making compensation to said temperature change according to the change in the magnetic field caused by the position change of an ultrasonic transducer in said HIFU equipment. The method can reduce significantly the temperature errors resulting from the position changes of the ultrasonic transducer.

Magnetic resonance thermometry method

A magnetic field adjusting device includes a pair of opposing pole plates mounted on respective magnetic field generating sources, forming a magnetic field space; a plurality of shimming plugs movably mounted at the periphery of the pole plates, with each shimming plug being mounted in a radially oriented retaining groove, so as to be moveable in the direction of the retaining groove. Additionally, or alternatively, the circumferences of the magnetic field generating sources are arranged with adjusting bars which can move perpendicular to the pole plates.

Magnetic field adjusting device

A method for reducing eddy currents caused by the gradient magnetic field in a magnetic resonance system employs an anti-eddy current device formed by a number of laminated metallic plates, and includes the steps of calculating the distribution of the main magnetic field of the magnetic resonance system in the anti-eddy current device, calculating the distribution of the main magnetic field and the gradient magnetic field in the anti-eddy current device, subtracting the calculated distribution of the main magnetic field in the anti-eddy current device from the calculated distribution of the main magnetic field and the gradient magnetic field in the anti-eddy current device, to obtain the distribution of the gradient magnetic field in the anti-eddy current device, and adjusting the setting of the metallic plates of the anti-eddy current device based on the distribution of the gradient magnetic field in the anti-eddy current device, so as to reduce the eddy current. The adjustment in the metallic plates of the anti-eddy current device should be such that the gradient magnetic field is parallel to or substantially parallel to the plane of the metallic plates. The metallic plates can be further divided into a number of areas, or the laminating direction of the metallic plates in different areas can be adjusted according to the specific distribution of the gradient magnetic field to obtain the optimum effect of eddy current reduction.

Method of reducing eddy currents caused by a gradient magnetic field in a magnetic resonance system

The present invention relates to a magnetic field adjusting device; such as may be used in MRI apparatus. The device can overcome the magnetic force to enable shimming plugs to move in a controlled continuous manner, thereby achieving continuous adjusting and accurate positioning. The magnetic field adjusting device comprises; a pair of opposing pole plates (), respectively mounted on magnetic field generating sources, forming a magnetic field space; a plurality of shimming plugs () movably mounted at the periphery of said pole plates (), each shimming plug () mounted in a radially oriented retaining groove (), so as to be movable in the direction of the retaining groove. Additionally, or alternatively, the circumferences of the magnetic field generating sources () are arranged with adjusting bars () which can move perpendicular to the pole plates. As an advantage of the present invention, the magnetic field can be shimmed conveniently quickly, and accurately to improve the imaging quality.

The invention proposes a method and an apparatus for testing a magnetic field of a coil. The method comprises applying an alternating current to the coil to generate an alternating magnetic field; measuring simultaneously the induced electromotive potential at a plurality of positions in the alternating magnetic field; and collecting and processing signals of the induced electromotive potential so as to obtain said coil's magnetic field distribution. The apparatus comprises probes positioned in said alternating magnetic field to generate the induced electromotive potential; a multi-channel data acquisition card for collecting the signals of the potential; and a processor for processing the collected signals to obtain said coil's magnetic field distribution. The method and the apparatus eliminate the interference by the magnetic field of the earth by testing the coil's alternating magnetic field to improve test accuracy and to improve the testing efficiency by multi-channel acquisition of the test signals.

Method for testing magnetic field distribution and apparatus therefor

In a magnetic resonance imaging apparatus and a method for shimming such an apparatus, at each of mirror-symmetrical assemblies respectively disposed at opposite faces of a static magnetic field generator, that each include a shimming ring, an additional shimming ring is provided that is adjustable in position relative to the other shimming ring to shim the static magnetic field. Additionally or alternatively, at each face of the static magnetic field generator, a permanently magnetic arrangement is provided that is divided into a number of permanently magnetic columns respectively having different energy levels. Additionally or alternatively, magnetic bolts, such as magnetically conducting bolts or permanently magnetic bolts can be symmetrically inserted into either of the mirror-symmetric assemblies, or the permanently magnetic columns, for additionally shimming adjustment.

Shimming structure and method for a magnetic resonance imaging apparatus

In a shimming method for an irregular object to be examined by magnetic resonant equipment magnetic field parameters are measured at measurement points located on the surface of an irregular object to be examined. Based on the measured magnetic field parameters, the positions and number of shims for adjusting magnetic field homogeneity are calculated when a passive shimming is to be performed, or the current value in a shimming coil are calculated when an active shimming is to be performed, or at the same time both the positions and number of shims and current value in the shimming coil are calculated when active shimming and passive shimming are to be performed at the same time. Shimming is then performed according to the calculated results. These above steps are repeated until achieving required magnetic field homogeneity. Since the homogeneous region is designed to have an irregular shape, it can provide a better coverage of the irregular object to be examined, and at the same time it reduces the shimming constraints to the unnecessary regions outside the irregular object to be examined, therefore avoiding shimming in those unnecessary regions.

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Shenzhen, China

Cheng Ni