Hitachi, Ltd.

Hitachi Medical Corporation

Hitachi Engineering Co., Ltd.

Hitachi Engineering Services Co., Ltd.

Mitsushi Abe

Yukinobu Imamura

Takeshi Nakayama

Hiroyuki Watanabe

Ryuya Ando

Kenji Sakakibara

Akira Kurome

Hikaru Hanada

Masanao Terada

Takuya Fujikawa

Hiroyuki Takeuchi

Masanori Takahashi

Hirotaka Takeshima

Tsutomu Yamamoto

Takeshi Yatsuo

Tomoo Chiba

Takeshi Kawamura

Jun Kawamura

Takuro Honda

Manabu Aoki

Yoshio Hamadate

Shigeki Tounosu

Akihisa Miyazoe

Yoshiya Higuchi

Kunihiro Takayama

Keiichiro Shibata

In order to provide a static magnetic field homogeneity adjustment method capable of reducing an arrangement amount of magnetic pieces and achieving desired magnetic field homogeneity with high accuracy in magnetic field homogeneity adjustment, there is provided a static magnetic field homogeneity adjustment method in an imaging space of computing positions of a plurality of magnetic pieces separated from the imaging space through shimming computation with respect to a static magnetic field in the imaging space generated by a magnetic field generation device, and disposing the plurality of magnetic pieces at the positions obtained through the shimming computation, the method including an adjustment step of imposing restriction that a polarity of a magnetic field distribution generated in the imaging space by the magnetic pieces disposed at the positions is either positive or negative during the shimming computation, and adjusting the static magnetic field homogeneity.

Magnetic resonance imaging apparatus, static magnetic field homogeneity adjustment method, program, and computer

The objective of the present invention is to provide a conduction-cooling-type super-conducting magnet, wherein a surface pressure is applied between a super-conducting coiled wire portion and a cooling member, the non-uniformity of the surface pressure in the diameter direction of the coiled wire portion has been improved, whereby the uniformity of contact heat resistance has been improved, moreover, warping due to a thermal contraction difference between the cooling member and the coiled wire portion arising at cooling time has been decreased sufficiently, and a surface pressure application mechanism can be installed solely in the low-temperature portion where the super-conducting coiled wire portion is installed. Provided is a conduction-cooling-type super-conducting magnet characterized by: an adequate heat conductor, which is connected to a cooler, in contact with the super-conducting coiled wire portion; the inclusion of an elastic body, which is capable of imparting, in the form of a displacement, an amount of contraction that is sufficiently greater than the amount of contraction of the adequate heat conductor and the wound wire portion at cooling time; and at least one elastic body disposed on each of the inner peripheral side and the outer peripheral side of the coiled wire portion in the same radial direction of the coiled wire portion.

Superconducting magnet

In the present invention, a current plane which is virtually disposed and surrounds a measurement position is assumed from magnetic field measurement values, and a current distribution (or magnetic moment distribution) which mimics a measured magnetic field is reproduced with current potentials. This is used to perform shimming calculation by a truncated singular value decomposition method with discrete shim trays that are actually used and ideal virtual continuous shim trays to carry out shimming under conditions for shimming having a uniformity that is close to ideal shimming.

Magnetic field adjusting method

To provide an operator with operability similar to that of conventional devices with an electromagnetic device that accurately maintains a magnetic field distribution by adjusting the magnetic field for each eigenmode obtained by singular value decomposition. The strength of a unique mode is found from a measurement magnetic field, a current for each unique mode of a negative feedback control according to the magnetic field is calculated and the current is added to each mode to obtain a current for each shim coil, and a coil current is controlled so as to reach the obtained current value. In an interface for an operator, a target for a corrected magnetic field and a magnetic field generated by a shim coil are displayed using a spherical surface harmonic function strength. Due to this configuration, a device which enables accurate magnetic field adjustment while offering operability similar to conventional devices can be provided.

Magnetic field adjustment device and magnetic resonance imaging device

The present invention provides a shimming method in which an electric current surface that is virtually placed so as to surround a measurement position is assumed from a magnetic field measurement value, in which an electric current distribution that reproduces a measurement magnetic field is reproduced through an electric current potential, and in which the reproduced magnetic field distribution is used. A magnetic moment or an electric current distribution that reproduces a magnetic field distribution obtained by a magnetic field measurement device is estimated on a predetermined closed surface, and, from the estimated magnetic moment or electric current distribution, a magnetic field distribution of an arbitrary point that exists in the closed surface is estimated. Then, on the basis of the estimated magnetic field distribution, a shim magnetic body distribution that produces a correction magnetic field for correcting the magnetic field distribution at the arbitrary point is output.

Shimming system and shimming method including a sensor unit having a pluraly of magnetic field sensors

A magnetic moment arrangement calculation method for magnetic field adjustment by combining correction of a component of a low-order mode with correction of a component of a high-order mode among the eigenmodes so as to calculate arrangement of the magnetic moment for approximately correcting the error magnetic field distribution, in which the low-order mode is an eigenmode group from the first of eigenmode numbers assigned to respective eigenmodes in the magnitude order of singular values to an eigenmode number specified by a first threshold value, in which the high-order mode is an eigenmode group with an eigenmode number more than the first threshold value, and in which a correction amount of the component of the high-order mode is smaller than a correction amount of the component of the low-order mode.

Magnetic moment arrangement calculation method for magnetic field adjustment, magnetic field adjustment device and program

Even if there is a restriction in an amount of magnetic pieces which can be disposed at each position in a shim tray, a distribution of a static magnetic field is measured so that an error magnetic field between the distribution of the static magnetic field and a target magnetic field is calculated, and respective reachable magnetic field homogeneities in a case where the magnetic pieces are disposed at one or more of the plurality of positions in the shim tray are calculated while changing the target magnetic field. The target magnetic field is selected in which an amount of magnetic pieces at each of the positions in the shim tray is equal to or less than a predetermined upper limit value, and the reachable magnetic field homogeneity is equal to or less than a predetermined value.

Magnetic field homogeneity adjustment method, magnetic field homogeneity adjustment program and magnetic field homogeneity adjustment device

The shimming work assistance unit performs singular value decomposition of a response matrix, which represents the relationship between an error magnetic field distribution and an adjusted magnetic moment placement distribution. From the multiple eigenmodes obtained, the eigenmodes are selected and added one by one in order from the eigenmode with the highest singular value, and the residual magnetic field error, which represents the fluctuation range of the difference between the magnetic field distribution, generated by the placement of the shimming magnetic moments corresponding to said eigenmode, and the error magnetic field distribution, is displayed on a display unit as a function graph of eigenmode order (line graph ()).

Shimming assistance unit, shimming assistance method, MRI apparatus and magnet apparatus

A gradient magnetic field coil device is provided in which an eddy current magnetic field of an even-ordered component can be reduced. The gradient magnetic field coil device includes a forward coil and a reverse coil which faces the forward coil so as to sandwich a middle surface and through which flows an electric current directed opposite to the forward coil. The forward coil and the reverse coil have a middle region approaching the middle surface and an outside-the-middle region where the distance from the middle surface is greater than the middle region. A line width of coil lines in the middle region is narrower than a line width of coil lines in the outside-the-middle region.

Gradient magnetic field coil device and magnetic resonance imaging device

An open-type magnetic resonance imaging device provides uniformity of a magnetic field without the necessity of lowering the degree of openness, and without increasing the superconducting wire material. The device includes at least one pair of main coils; at least one pair of shield coils; a pair of annular first magnetic substances disposed on an inner radial side of the main coils so that the first magnetic substances are plane symmetrical to each other; and second magnetic substances as protrusion portions disposed on an outer circumferential side of an end surface of the first magnetic substances on an opposite side of the first magnetic substances.

Magnetic resonance imaging device

In a gradient magnetic field coil device including: a plurality of main coils generating in an imaging region of a magnetic field resonance imaging device a magnetic field distribution in which an intensity linearly inclines; and a plurality of shield coils, arranged on an opposite side of the imaging region across the main coils, suppressing residual magnetic field generated by the main coils on the opposite side. The plurality of main coils and the plurality of shield coils are connected in series. The device further includes a plurality of current adjusting devices, connected to the shield coils in parallel, independently adjusting currents flowing through the shield coils, respectively, to enhance symmetry of the residual magnetic field. The gradient magnetic field coil device is provided which can suppress generation of eddy current magnetic field even if there is a relative position deviation between the main coils and shield coils.

Gradient magnetic field coil device, adjustment method therefor, and magnetic resonance imaging apparatus

A device includes: a static magnetic field generating device including static magnetic field generating sources generating a homogeneous magnetic field in a space; gradient magnetic field generating sources superimposing a gradient magnetic field on the homogeneous magnetic field, and conductor rings arranged between the static magnetic field generating sources and the gradient magnetic field generating sources in a pair of arranging regions on both sides in a direction of the homogeneous magnetic field in a region where the homogeneous magnetic field is generated (imaging region), respectively, the conductor rings being separated from each other and making a pair. The conductor rings are mechanically connected to the gradient magnetic field generating device or the static magnetic field generating device. This provides an MRI device 1 capable of reduction in vibration with suppression of the image quality deterioration of the tomographic images.

Magnetic resonance imaging device with vibration suppression

A gradient coil device includes a major axis gradient coil, having an ellipse in a cross section generating a gradient magnetic field inclined in a major axis direction of the ellipse at a magnetic field space; and a minor axis gradient coil, having an ellipse in a cross section generating a gradient magnetic field inclined in a minor axis direction of the ellipse at the magnetic field space. A length of the minor axis field coil in the center axis direction is shorter than a length of the major axis gradient coil in the center axis direction. A maximum value of a residual magnetic field generated by the minor axis gradient coil at a space outside the magnetic field space is equal to or smaller than a maximum value of a residual magnetic field generated by the major axis gradient coil at a space outside the magnetic field space.

Gradient coil device and magnetic resonance imaging device

A method for designing a coil pattern, whereby the production of an error magnetic field and further an eddy current can be suppressed to improve the quality of a cross-sectional image irrespective of cylindrical cross-sectional shape of the main coil and the shield coil. The difference between the initial values of the target magnetic field and the magnetic field vector is set as a difference target magnetic field. An approximate value of the current potential vector that produces the difference target magnetic field is represented by a polynomial of an eigenvector group of the current potential. The coefficient of each of the terms of the polynomial is determined on the basis of the singular value and the eigenvector group of the magnetic field distribution.

Gradient coil, magnetic resonance imaging device, and method for designing coil pattern

In the magnetic resonance imaging device, the distance between the first and second coils is different in the circumferential direction and has a first region (A) (&#x3b8;=0, &#x3c0;) and a second region (A) (&#x3b8;=&#x3c0;/2) narrower than the first region (A). In the first coil, wiring patterns () on the side of a zero-plane (F) passing through the center of the first coil and perpendicular to the axis direction (z-axis direction) meander in the circumferential direction such that the wiring patterns () depart from the zero-plane (F) in the first region (A) and approach the zero-plane (F) in the second region (A). This provides a gradient magnetic field coil capable of configuring wiring patterns without using a loop coil that does not pass through the z-axis.

Growing community of inventors

Hitachinaka, Japan

Mitsushi Abe