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Magnetic field adjustment method for MRI device

A technology of magnetic field adjustment and tomography, applied in measurement devices, diagnosis, applications, etc., can solve problems such as time-consuming recovery, inability to correctly output distribution, and difficulty in determining wrong parts.

Inactive Publication Date: 2012-09-12
HITACHI LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0010] (3) In the case of wrong compensation work, it is difficult to identify the wrong part, and it takes time to recover
For example, a uniform magnetic field distribution is the distribution with the lowest order of the spherical tuning function. However, in practice, this distribution cannot be output correctly unless there is a magnetic field adjustment mechanism that completely surrounds the magnetic field adjustment area. There is no such magnetic field adjustment mechanism in MRI

Method used

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  • Magnetic field adjustment method for MRI device
  • Magnetic field adjustment method for MRI device
  • Magnetic field adjustment method for MRI device

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0123] Examples will be described. Application of magnetic field adjustment (compensation) to an open MRI apparatus having a vertical magnetic field will be described as a first embodiment. Figure 5 It is a system that compensates (magnetic field adjustment) the magnetic field generated by the magnet of the MRI apparatus. This figure assumes an open type where the direction of the magnetic field (lines of force) is oriented vertically. exist Figure 5 The conceptual shape of the open MRI magnet is also shown in . The connecting posts are connected between the magnet device 62 divided up and down. Among them are a vacuum container 62c for securing a vacuum for heat insulation, a radiation shield 62d, a cryogenic container 62e, and a coil group 62a including a magnetic shield coil 62b. The examinee is lying on the upper part of the examinee probe 61, and nuclear magnetic resonance tomography is performed.

[0124] In the space with the imaging area (magnetic field measurem...

Embodiment 2

[0146] A second embodiment will be described. It has already been explained that it has been used for the inspection of manufactured goods, but this method can also be used in the design of magnets by the same judgment. Figure 10 Indicates the flow at this time. In this embodiment, the magnetic field adjustment is carried out computationally, and it is confirmed that the target magnetic field accuracy can be achieved, thereby applying it to the design of the magnetic force arrangement. After starting 51S of the magnetic force configuration study, step 52S of assuming the magnetic force configuration is performed. According to the magnetizing force configuration, the magnetic field calculation step 53S is performed. In addition, according to the configuration of the magnetic force, a singular value decomposition is performed based on the configuration of the compensation disk, and its results are saved. Same as the first embodiment. The part 1B executes the preparatory cal...

Embodiment 3

[0154] The above calculation method and compensation steps are performed in the same way in the vertical magnetic field type magnet device 62 and the horizontal magnetic field type magnet device 62. Therefore, in the horizontal magnetic field type MRI magnet device 62, the magnetic field adjustment ( Compensation), quality management and magnetic configuration design can be applied. However, since the shape of the magnet device 62 is different, there are also points in which the calculation procedure, the arrangement position of the iron piece 4, and the like are also different. Therefore, the following description will be made as Example 3. FIG. In Example 3, Figure 11 The magnet device 62 for the horizontal magnetic field type MRI shown is applied. In this case, through Figure 11 In the hole 62f (cylindrical hollow) at the center of the magnet device, the region (shim disk 5 ) used for compensation is arranged in a cylindrical shape. Such as Figure 12 The surface of ...

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Abstract

Measured magnetic field distribution aberrations are decomposed into eigenmode components by means of singular value decomposition, and iron piece arrangements which correspond to each mode are combined and arranged on a shim tray. The eigenmode to be corrected is selected according to the attainable magnetic field precision (homogeneity) and the suitability of the iron piece arrangement. Adjustment can be made whilst being aware of the attainable magnetic field precision (homogeneity), thus incorrect adjustments can also be ascertained and can be automatically corrected during repeated adjustments. If magnetic field adjustment is carried out with the aid of the disclosed method or a device incorporating the disclosed method, the adjustment can be reliably completed during repeated operations. Thus, the device has good magnetic field precision. Furthermore, defective magnets can be detected early by investigating the attainable homogeneity, and the method or device can be adapted to vertical field magnetic devices (open MRIs) and horizontal field MRI magnet devices.

Description

technical field [0001] The present invention relates to a superconducting magnet device and a nuclear magnetic resonance tomography device (Magnetic Resonance Imaging). Background technique [0002] In the diagnosis using nuclear magnetic resonance, the magnetic field strength corresponds to the diagnosis site, so the accuracy required for the magnetic field strength generated by the magnetic system is such that if there is a fluctuation of one millionth of the magnetic field strength, it will become a problem. There are roughly three types of magnetic fields in an MRI apparatus. They are: [0003] (1) In a magnetic field that is constant in time and space, it is usually about a few ppm in the space where the image is taken (usually a spherical or ellipsoid space with a diameter of 30-40 cm) with a strength from 0.1 to several Tesla or more Range of change. [0004] (2) A spatially inclined magnetic field that changes with a time constant of about 1 second or less. [00...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): A61B5/055
CPCG01R33/3873G01R33/3875
Inventor 阿部充志安藤龙弥
Owner HITACHI LTD
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