【０００１】[0001]
【産業上の利用分野】この発明は、医療用磁気共鳴断層
撮影装置（以下ＭＲＩという）等に用いられる磁界発生
装置の改良に係り、特に継鉄として所謂Ｃ型継鉄を用い
ることによって被検者への圧迫感を低減するとともに、
磁界発生源としての永久磁石の配置構成や磁極片の構成
等を工夫することによって永久磁石の使用効率を大幅に
向上したＭＲＩ用磁界発生装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a magnetic field generator used for a magnetic resonance tomography apparatus (hereinafter referred to as MRI) for medical use, and more particularly, to a test using a so-called C-type yoke as a yoke. To reduce the feeling of pressure on the elderly,
The present invention relates to a magnetic field generator for MRI in which the use efficiency of a permanent magnet is greatly improved by devising the arrangement configuration of a permanent magnet as a magnetic field generation source, the configuration of a pole piece, and the like.
【０００２】[0002]
【従来の技術】従来のＭＲＩ用磁界発生装置において、
永久磁石を磁界発生源として使用する構成としては、図
５の（ａ），（ｂ）に示すような所謂４本柱型継鉄を採
用した構成が最も多用されている。なお、図５（ｂ）は
図５（ａ）のＢ−Ｂ断面図である。すなわち、図５の
（ａ），（ｂ）に示すＭＲＩ用磁界発生装置は、一対の
板状継鉄１１ａ，１１ｂを所定の空隙１２を形成して対
向配置するよう４本の円柱型継鉄１３ａ，１３ｂ，１３
ｃ，１３ｄにて接続支持する構成からなり、さらに一対
の板状継鉄１１ａ，１１ｂの各々空隙対向面に永久磁石
１４ａ，１４ｂとともに磁極片１６ａ，１６ｂを配置し
た構成からなっている（実公平２−４４４８３号公
報）。2. Description of the Related Art In a conventional magnetic field generator for MRI,
As a configuration using a permanent magnet as a magnetic field generation source, a configuration employing a so-called four-post type yoke as shown in FIGS. 5A and 5B is most frequently used. FIG. 5B is a cross-sectional view taken along line BB of FIG. 5A. In other words, the magnetic field generator for MRI shown in FIGS. 5A and 5B has four columnar yokes such that a pair of plate yokes 11a and 11b are opposed to each other while forming a predetermined gap 12. 13a, 13b, 13
(c) and (13d). Further, the pole pieces (16a, 16b) are arranged together with the permanent magnets (14a, 14b) on the facing surfaces of the pair of plate yokes (11a, 11b). 2-44483).
【０００３】また、上記の構成よりも永久磁石の使用効
率を高め、装置の小型化を可能とするＭＲＩ用磁界発生
装置として、図６に示すような所謂筒状（トンネル型）
継鉄を採用した構成が提案されている（特開平５−３２
６２５２号公報）。すなわち、図６に示すＭＲＩ用磁界
発生装置は、６角筒状継鉄２１の各々内周面に一対の主
永久磁石２４ａ，２４ｂと複数の補助永久磁石２５ａ，
２５ｂ，２５ｃ，２５ｄを環状に配置するとともに、一
対の主永久磁石２４ａ，２４ｂの空隙２２対向面に磁極
片２６ａ，２６ｂ（２６ａは図示せず）を配置した構成
からなっている。A so-called cylindrical (tunnel-type) magnetic field generator for MRI as shown in FIG.
A configuration employing a yoke has been proposed (Japanese Unexamined Patent Publication No. Hei 5-32).
No. 6252). That is, the magnetic field generator for MRI shown in FIG. 6 has a pair of main permanent magnets 24a, 24b and a plurality of auxiliary permanent magnets 25a,
25b, 25c, 25d are arranged annularly, and pole pieces 26a, 26b (26a is not shown) are arranged on the surfaces of the pair of main permanent magnets 24a, 24b facing the gap 22.
【０００４】さらに、診断時の被検者に与える圧迫感の
低減を可能とするＭＲＩ用磁界発生装置として、図７に
示すような所謂Ｃ型継鉄を採用した構成が提案されてい
る（意匠８４９８２５号公報）。すなわち、図７に示す
ＭＲＩ用磁界発生装置は、一対の板状継鉄３１ａ，３１
ｂを所定の空隙３２を形成して対向配置するよう該一対
の板状継鉄３１ａ，３１ｂの一方端を支持継鉄３３にて
接続支持する構成からなり、さらに一対の板状継鉄３１
ａ，３１ｂの各々空隙対向面に永久磁石３４ａ，３４ｂ
（３４ａは図示せず）とともに磁極片３６ａ，３６ｂを
配置した構成からなっている。Further, as an MRI magnetic field generator capable of reducing the feeling of pressure exerted on a subject at the time of diagnosis, a configuration employing a so-called C-type yoke as shown in FIG. 7 has been proposed (design). No. 498825). That is, the MRI magnetic field generator shown in FIG.
One end of the pair of plate yokes 31a and 31b is connected and supported by a support yoke 33 so that the pair of plate yokes 31a and 31b face each other so as to form a predetermined gap 32.
The permanent magnets 34a, 34b
(34a is not shown) and magnetic pole pieces 36a and 36b are arranged.
【０００５】[0005]
【発明が解決しようとする課題】上記の各種構成からな
るＭＲＩ用磁界発生装置のうち、図５の（ａ），（ｂ）
に示すＭＲＩ用磁界発生装置においては、被検者が挿入
される空隙１２の周囲には４本の円柱型継鉄１３ａ，１
３ｂ，１３ｃ，１３ｄが配置されるだけであることか
ら、被検者にとっては開放感があり、診断時の圧迫感が
比較的低減されるという長所を有している。しかし、磁
気回路の効率という観点からは、空隙１２外への磁束の
漏洩が多く、永久磁石の使用効率が悪いという欠点を有
している。Among the MRI magnetic field generators having the various configurations described above, FIGS. 5 (a) and 5 (b)
In the MRI magnetic field generator shown in FIG. 1, four cylindrical yokes 13a, 1 are provided around a gap 12 into which a subject is inserted.
Since only 3b, 13c, and 13d are arranged, the subject has an advantage that the subject has a feeling of openness and the feeling of pressure at the time of diagnosis is relatively reduced. However, from the viewpoint of the efficiency of the magnetic circuit, there is a large amount of leakage of the magnetic flux to the outside of the air gap 12, and the use efficiency of the permanent magnet is low.
【０００６】一方、図６に示すＭＲＩ用磁界発生装置に
おいては、空隙２２外への磁束の漏洩が少なく、永久磁
石の使用効率が高いという長所を有しているが、被検者
が挿入される空隙２２が複数の永久磁石２４ａ，２４ｂ
及び２５ａ，２５ｂ，２５ｃ，２５ｄにて取り囲まれて
形成されることから被検者に与える圧迫感が大きいとい
う欠点を有している。On the other hand, the magnetic field generator for MRI shown in FIG. 6 has the advantages that the leakage of magnetic flux to the outside of the gap 22 is small and the use efficiency of the permanent magnet is high, but the subject is inserted. Gap 22 is formed by a plurality of permanent magnets 24a, 24b.
And 25a, 25b, 25c, and 25d, so that the subject has a large sense of oppression.
【０００７】さらに、図７に示すＭＲＩ用磁界発生装置
は、図５の（ａ），（ｂ）に示すＭＲＩ用磁界発生装置
と同等以上の開放感を得ることができるが、永久磁石や
磁極片の配置構成は実質的に図５の（ａ），（ｂ）に示
す構成と同様であり、永久磁石の使用効率が悪く、装置
の小型軽量化を実現することができない。Further, the magnetic field generator for MRI shown in FIG. 7 can provide a feeling of openness equal to or greater than that of the magnetic field generator for MRI shown in FIGS. 5 (a) and 5 (b). The arrangement configuration of the pieces is substantially the same as the configuration shown in FIGS. 5A and 5B, the use efficiency of the permanent magnet is poor, and the reduction in size and weight of the device cannot be realized.
【０００８】この発明は、被検者への圧迫感を低減する
構成からなるＭＲＩ用磁界発生装置の提供を目的とし、
特に、磁界発生源としての永久磁石の配置構成や磁極片
の構成等を工夫することによって永久磁石の使用効率を
大幅に向上したＭＲＩ用磁界発生装置の提供を目的とす
るものであり、いままでに提案されている各種構成から
なるＭＲＩ用磁界発生装置が有する長所を積極的に活用
した構成からなるものである。An object of the present invention is to provide a magnetic field generator for MRI having a configuration for reducing a feeling of oppression to a subject,
In particular, the purpose of the present invention is to provide a magnetic field generator for MRI in which the use efficiency of the permanent magnet is greatly improved by devising the arrangement of the permanent magnet as a magnetic field source and the configuration of the pole pieces. The MRI magnetic field generator of the various configurations proposed in US Pat.
【０００９】[0009]
【課題を解決するための手段】この発明は、上記の目的
を達成するために種々の実験を繰り返した結果、図７に
示すＭＲＩ用磁界発生装置は、被検者に与える圧迫感を
低減する上では好ましい構成でありながら、装置全体の
小型軽量化の観点から永久磁石３４ａ，３４ｂと磁極片
３６ａ，３６ｂが一対の板状継鉄３１ａ，３１ｂを接続
支持する支持継鉄３３に近接して配置されることとな
り、特に、該支持継鉄３３への磁束の漏洩が多く、永久
磁石の使用効率を低下させていることを確認し、さら
に、支持継鉄３３に前記磁束の漏洩を防止する補助永久
磁石を配置することによって、結果として空隙３２内の
磁界強度及び磁界の均一度をともに向上させることが可
能であることを知見し、発明を完成したのである。According to the present invention, as a result of repeating various experiments in order to achieve the above object, the MRI magnetic field generator shown in FIG. 7 reduces the feeling of oppression given to a subject. Although the above configuration is preferable, the permanent magnets 34a, 34b and the pole pieces 36a, 36b are close to the support yoke 33 for connecting and supporting the pair of plate yoke 31a, 31b from the viewpoint of reducing the size and weight of the entire apparatus. In particular, it is confirmed that the leakage of the magnetic flux to the support yoke 33 is large, and the use efficiency of the permanent magnet is reduced, and further, the leakage of the magnetic flux to the support yoke 33 is prevented. By arranging the auxiliary permanent magnets, it was found that as a result, it is possible to improve both the magnetic field strength and the uniformity of the magnetic field in the air gap 32, and completed the invention.
【００１０】すなわち、この発明は、所定の空隙を形成
して対向配置する一対の板状継鉄と、該一対の板状継鉄
の一方端を接続支持する支持継鉄とを有し、前記一対の
板状継鉄の各々空隙対向面に主永久磁石を配置し、かつ
支持継鉄の空隙対向面に前記主永久磁石に隣接して一対
の補助永久磁石を配置するとともに、前記一対の主永久
磁石の空隙対向面に磁極片を配置したことを特徴とする
ＭＲＩ用磁界発生装置である。That is, the present invention comprises a pair of plate yoke which are opposed to each other by forming a predetermined gap, and a support yoke which connects and supports one end of the pair of plate yoke. A main permanent magnet is arranged on each of the pair of plate-shaped yokes on the gap-facing surface, and a pair of auxiliary permanent magnets is arranged on the gap-facing surface of the supporting yoke adjacent to the main permanent magnet. A magnetic field generator for MRI, wherein a pole piece is arranged on a surface of a permanent magnet facing a gap.
【００１１】また、上記の構成において、一対の磁極片
の各々空隙対向面における補助永久磁石配置側周縁部以
外の周縁部に突起部を形成したことを特徴とするＭＲＩ
用磁界発生装置を特に好ましい構成として提案する。さ
らに、上記の構成において、主永久磁石が断面略矩形状
からなるとともに、補助永久磁石が断面略三角形状から
なり、かつ主永久磁石及び補助永久磁石が希土類系永久
磁石またはフェライト系永久磁石からなることを特徴と
するＭＲＩ用磁界発生装置、さらにまた、主永久磁石が
断面略台形状の希土類系永久磁石からなり、補助永久磁
石が断面略三角形状のフェライト系永久磁石からなるこ
とを特徴とするＭＲＩ用磁界発生装置を併せて提案す
る。Further, in the above-mentioned structure, the MRI is characterized in that a projection is formed on a peripheral edge of each of the pair of magnetic pole pieces other than the peripheral edge on the side where the auxiliary permanent magnet is disposed on the gap facing surfaces.
The magnetic field generator for use is proposed as a particularly preferable configuration. Furthermore, in the above configuration, the main permanent magnet has a substantially rectangular cross section, the auxiliary permanent magnet has a substantially triangular cross section, and the main permanent magnet and the auxiliary permanent magnet are made of a rare earth permanent magnet or a ferrite permanent magnet. An MRI magnetic field generator, wherein the main permanent magnet is made of a rare earth permanent magnet having a substantially trapezoidal cross section, and the auxiliary permanent magnet is made of a ferrite permanent magnet having a substantially triangular cross section. We also propose a magnetic field generator for MRI.
【００１２】この発明において、使用する主永久磁石及
び補助永久磁石は、要求される磁界強度や装置の寸法、
経済性等に応じて材質を選定することが望ましく、特
に、希土類コバルト系永久磁石や希土類・鉄・ほう素系
永久磁石等の希土類系永久磁石、ストロンチュウムフェ
ライト永久磁石等のフェライト系永久磁石、さらにこれ
らを併用して使用することが有効であるが、これらの永
久磁石を使用する場合には上記の断面形状や配置構成を
採用することが望ましい。また、一対の板状継鉄や支持
継鉄の形状も上記の主永久磁石及び補助永久磁石の形
状、寸法等に応じて種々の構成を選定することが望まし
く、単に磁路形成の観点だけでなく機械的な強度や軽量
化等を考慮して選定することが望ましい。In the present invention, the main permanent magnet and the auxiliary permanent magnet used are required to have the required magnetic field strength, the dimensions of the device,
It is desirable to select a material in accordance with economy, etc., and in particular, rare earth permanent magnets such as rare earth cobalt-based permanent magnets and rare earth / iron / boron permanent magnets, and ferrite permanent magnets such as strontium ferrite permanent magnets It is effective to use these permanent magnets in combination, but when these permanent magnets are used, it is desirable to adopt the above-described cross-sectional shape and arrangement. Also, it is desirable to select various configurations for the shape of the pair of plate yoke and the support yoke according to the shapes, dimensions, etc. of the main permanent magnet and the auxiliary permanent magnet, and only from the viewpoint of magnetic path formation. Therefore, it is desirable to select in consideration of mechanical strength and weight reduction.
【００１３】[0013]
【作用】この発明の作用を以下に示す実施例に基づいて
詳細に説明する。ただし、この発明は実施例の構成に限
定されるものではない。図１はこの発明のＭＲＩ用磁界
発生装置の一実施例を示すもので、図１の（ａ）は縦断
面説明図であり、図１の（ｂ）は（ａ）のＡ−Ａ断面説
明図である。図中１ａ，１ｂは、所定の空隙２を形成し
て対向配置する一対の板状継鉄であり、各々の一方端
（図においては、左端）が支持継鉄３によって接続支持
され、他方端（図においては、右端）が開放する縦断面
が所謂Ｃ型の継鉄を構成する。図中４ａ，４ｂは、前記
一対の板状継鉄１ａ，１ｂの各々空隙２対向面に配置さ
れる主永久磁石であり、また５ａ，５ｂは前記支持継鉄
３の空隙対向面に各々主永久磁石４ａ，４ｂに隣接して
配置される補助永久磁石である。The operation of the present invention will be described in detail with reference to the following embodiments. However, the present invention is not limited to the configuration of the embodiment. FIG. 1 shows an embodiment of a magnetic field generator for MRI according to the present invention. FIG. 1 (a) is a longitudinal sectional view, and FIG. 1 (b) is an AA sectional view of (a). FIG. In the drawing, reference numerals 1a and 1b denote a pair of plate-like yokes which are opposed to each other while forming a predetermined gap 2. One end (the left end in the figure) is connected and supported by a supporting yoke 3, and the other end. The vertical cross section that opens (the right end in the figure) constitutes a so-called C-type yoke. In the figure, reference numerals 4a and 4b denote main permanent magnets disposed on the surfaces of the pair of plate yoke 1a and 1b, respectively, facing the gap 2, and reference numerals 5a and 5b denote main permanent magnets on the surfaces of the support yoke 3 facing the gap. It is an auxiliary permanent magnet arranged adjacent to the permanent magnets 4a and 4b.
【００１４】図に示す構成では、主永久磁石４ａ，４ｂ
は断面略矩形状の希土類系永久磁石から構成され、また
補助永久磁石５ａ，５ｂは断面略三角形状の希土類系永
久磁石から構成されている。一対の主永久磁石４ａ，４
ｂと一対の補助永久磁石５ａ，５ｂの磁化方向は図中に
矢印で示すように、いずれも板状継鉄１ａ，１ｂと支持
継鉄３との当接面に対して直角方向であり、また、図に
おいては主永久磁石４ａと補助永久磁石５ａの空隙対向
面がＳ極で、主永久磁石４ｂと補助永久磁石５ｂの空隙
対向面がＮ極に着磁されている場合を示している。In the configuration shown in the figure, the main permanent magnets 4a, 4b
Is composed of a rare earth permanent magnet having a substantially rectangular cross section, and the auxiliary permanent magnets 5a and 5b are composed of rare earth permanent magnets having a substantially triangular cross section. A pair of main permanent magnets 4a, 4
b, and the magnetization directions of the pair of auxiliary permanent magnets 5a and 5b are perpendicular to the contact surface between the plate yoke 1a and 1b and the support yoke 3, as shown by arrows in the figure. The figure shows a case where the gap facing surface of the main permanent magnet 4a and the auxiliary permanent magnet 5a is the S pole, and the gap facing surface of the main permanent magnet 4b and the auxiliary permanent magnet 5b is magnetized to the N pole. .
【００１５】これらの主永久磁石４ａ，４ｂ及び補助永
久磁石５ａ，５ｂをともにフェライト系永久磁石から構
成する場合も、実質的に上記と同様な断面形状、磁化方
向を採用することが好ましい。上記の主永久磁石４ａ，
４ｂ及び補助永久磁石５ａ，５ｂの形状、寸法等によっ
て、一対の板状継鉄１ａ，１ｂ及び支持継鉄３の好まし
い形状、寸法等を選定することが望ましい。例えば、図
示の構成では、主永久磁石４ａ，４ｂと板状継鉄１ａ，
１ｂの平面形状は実質的に同一となる。すなわち、空隙
２の略中央部に形成される高均一磁界からなる半径ｒの
球状空間２ａの中心点Ｏからの垂線と直交する主永久磁
石４ａ，４ｂ及び板状継鉄１ａ，１ｂの各々空隙対向面
上の点Ｏ’を中心とした半径Ｒの半円部と、支持継鉄３
配置側に展延する矩形部とを一体化した構成からなる。When the main permanent magnets 4a and 4b and the auxiliary permanent magnets 5a and 5b are both made of ferrite permanent magnets, it is preferable to adopt substantially the same cross-sectional shape and magnetization direction as described above. The main permanent magnets 4a,
It is desirable to select a preferable shape, size, and the like of the pair of plate yokes 1a, 1b and the support yoke 3 according to the shape, size, and the like of the 4b and the auxiliary permanent magnets 5a, 5b. For example, in the illustrated configuration, the main permanent magnets 4a, 4b and the plate-like yoke 1a,
The planar shape of 1b is substantially the same. That is, the gaps of the main permanent magnets 4a, 4b and the plate yokes 1a, 1b orthogonal to the perpendicular from the center point O of the spherical space 2a having a radius r and formed of a highly uniform magnetic field formed at substantially the center of the gap 2 A semicircular portion having a radius R centered on a point O ′ on the opposing surface;
It has a configuration in which a rectangular portion extending to the arrangement side is integrated.
【００１６】また、板状継鉄１ａ，１ｂの断面形状は、
主永久磁石４ａ，４ｂと同様な断面略矩形状としても良
いが、図示の如く板状継鉄１ａ，１ｂ内の磁束密度に応
じて前記半円部の厚さを開放端に向かって漸減する形状
とすることによって、磁路形成を阻害することなく軽量
化が達成できる。支持継鉄３は、補助永久磁石５ａ，５
ｂの形状に応じて選定することが必要である。本発明者
の実験によれば、補助永久磁石５ａ，５ｂは、主永久磁
石４ａ，４ｂによって形成される磁界の均一度を低下さ
せることなく、主永久磁石４ａ，４ｂ及び後述する磁極
片からの該支持継鉄３への磁束の漏洩を低減するために
は、図示の如き断面形状を略三角形状とすることが望ま
しく、それに伴い支持継鉄３の断面形状を図示の如き縦
断面く字型とすることが望ましい。従って、主永久磁石
４ａ，４ｂと補助永久磁石５ａ，５ｂ間にはそれぞれ隙
間２ｂ，２ｃが形成されている。The cross-sectional shape of the plate yoke 1a, 1b is
The cross section may be substantially rectangular, similar to the main permanent magnets 4a, 4b, but the thickness of the semicircular portion gradually decreases toward the open end according to the magnetic flux density in the plate-like yoke 1a, 1b as shown in the figure. By adopting the shape, weight reduction can be achieved without hindering magnetic path formation. The supporting yoke 3 includes auxiliary permanent magnets 5a, 5
It is necessary to select according to the shape of b. According to the experiment of the present inventor, the auxiliary permanent magnets 5a and 5b can be used to reduce the uniformity of the magnetic field formed by the main permanent magnets 4a and 4b without reducing the uniformity of the magnetic field formed by the main permanent magnets 4a and 4b. In order to reduce the leakage of the magnetic flux to the support yoke 3, it is desirable that the cross-sectional shape as shown in the drawing is substantially triangular. It is desirable that Therefore, gaps 2b and 2c are formed between the main permanent magnets 4a and 4b and the auxiliary permanent magnets 5a and 5b, respectively.
【００１７】すなわち、補助永久磁石５ａ，５ｂの組立
性（通常、複数のブロック状永久磁石を磁化方向に積層
固着して所定の断面形状となるように一体化する）等か
らその磁化方向を前記のように支持継鉄３の当接面と直
角方向とすると、該補助永久磁石５ａ，５ｂの空隙対向
面と前記球状空間２ａの中心点Ｏを含む水平面との最適
な角度θ1とともに、補助永久磁石５ａ，５ｂの支持継
鉄３との当接面と前記球状空間２ａの中心点Ｏを含む水
平面との最適な角度θ2が決定され、結果として支持継
鉄３の空隙対向面側の形状が決定され断面が略く字型と
なる。なお、本発明者の実験によれば、通常、θ1は３
０度〜６０度、θ2は４５度〜９０度の範囲で選定する
ことが望ましい。That is, the magnetizing direction is determined by the assemblability of the auxiliary permanent magnets 5a and 5b (normally, a plurality of block-shaped permanent magnets are stacked and fixed in the magnetizing direction and integrated so as to have a predetermined sectional shape). Assuming that the direction is perpendicular to the contact surface of the support yoke 3 as described above, the optimum angle θ1 between the air gap-facing surfaces of the auxiliary permanent magnets 5a and 5b and the horizontal plane including the center point O of the spherical space 2a, as well as the auxiliary angle The optimum angle θ2 between the contact surfaces of the permanent magnets 5a and 5b with the support yoke 3 and the horizontal plane including the center point O of the spherical space 2a is determined. The shape is determined, and the cross section becomes substantially rectangular. Incidentally, according to the experiment of the present inventors, θ1 is usually 3
It is desirable that 0 ° to 60 ° and θ2 be selected in the range of 45 ° to 90 °.
【００１８】また、支持継鉄３内の磁束密度に応じて、
厚さを板状継鉄１ａ，１ｂとの接続部に向かって漸減す
る形状とすることも可能であり、磁路形成を阻害するこ
となく軽量化が達成できる。機械的強度の観点から支持
継鉄３の下部（球状空間２ａの中心点Ｏを含む水平面よ
りも下方に位置する部分）を板状継鉄１ｂとの接続部に
向かって厚くする等の工夫を採用することも可能であ
る。すなわち、支持継鉄３は補助永久磁石５ａ，５ｂを
所定の位置に配置する機能とともに、磁気回路の上部に
配置される板状継鉄１ａと主永久磁石４ａ及び磁極片６
ａからなる重量物であるこれらの構成体を安全に支持す
る機能、さらに安定した磁路形成を確保する機能を有す
ることが要求されることから、先に説明したような、補
助永久磁石５ａ，５ｂの形状や寸法等に応じて最適条件
を選定することが望ましい。Further, according to the magnetic flux density in the supporting yoke 3,
It is also possible to make the thickness gradually decrease toward the connection portion with the plate-shaped yoke 1a, 1b, so that the weight can be reduced without hindering the formation of the magnetic path. From the viewpoint of mechanical strength, a device such as increasing the thickness of the lower portion of the supporting yoke 3 (the portion located below the horizontal plane including the center point O of the spherical space 2a) toward the connection portion with the plate-like yoke 1b. It is also possible to adopt. That is, the supporting yoke 3 has a function of arranging the auxiliary permanent magnets 5a and 5b at predetermined positions, and also has a plate-like yoke 1a, a main permanent magnet 4a, and a magnetic pole piece 6 which are arranged above the magnetic circuit.
It is required that the auxiliary permanent magnets 5a, 5a and 5a have a function of safely supporting these components, which are heavy objects made of a, and a function of ensuring stable magnetic path formation. It is desirable to select the optimal conditions according to the shape and dimensions of 5b.
【００１９】図において、６ａ，６ｂは、前記一対の主
永久磁石４ａ，４ｂの空隙対向面に配置した磁極片であ
り、図示の構成では、該磁極片６ａ，６ｂの各々空隙対
向面における補助永久磁石５ａ，５ｂの配置側周縁部以
外の周縁部に突起部７ａ，７ｂを形成している。すなわ
ち、この磁極片６ａ，６ｂの平面形状も前記主永久磁石
４ａ，４ｂと板状継鉄１ａ，１ｂと同様に半円部と矩形
部とが一体化した形状となり、また、突起部７ａ，７ｂ
の平面形状も補助永久磁石５ａ，５ｂの配置側周縁部以
外の周縁部に形成されることから所謂馬蹄型の形状とな
る。この突起部７ａ，７ｂの形成によって空隙２内の磁
界均一度の向上を達成することができる。さらに、図１
に示す構成からなるＭＲＩ用磁界発生装置において、例
えば、補助永久磁石５ａ，５ｂの空隙対向面側斜面部の
幅方向両端部に、図２に示すような所定幅からなる突起
部８，８を形成することによって、空隙２内の磁界均一
度を一層向上することが可能となる。In the drawing, reference numerals 6a and 6b denote magnetic pole pieces disposed on the gap-facing surfaces of the pair of main permanent magnets 4a and 4b. In the configuration shown in the drawing, auxiliary poles on the respective gap-facing surfaces of the magnetic pole pieces 6a and 6b are provided. Protrusions 7a and 7b are formed on the peripheral edge other than the peripheral edge on the arrangement side of the permanent magnets 5a and 5b. That is, the pole pieces 6a, 6b also have a planar shape in which a semicircular portion and a rectangular portion are integrated like the main permanent magnets 4a, 4b and the plate-shaped yokes 1a, 1b. 7b
Is also formed on the peripheral edge portion other than the peripheral edge portion on which the auxiliary permanent magnets 5a and 5b are arranged, so that the so-called horseshoe shape is obtained. By forming the projections 7a and 7b, the uniformity of the magnetic field in the gap 2 can be improved. Further, FIG.
In the MRI magnetic field generator having the configuration shown in FIG. 2, for example, protrusions 8 having a predetermined width as shown in FIG. 2 are provided at both ends in the width direction of the gap-facing surface side slopes of the auxiliary permanent magnets 5a and 5b. By forming, it is possible to further improve the magnetic field uniformity in the gap 2.
【００２０】また、前記磁極片６ａ，６ｂを図３に示す
如く、主永久磁石４ａ，４ｂとの当接部９及び突起部７
を純鉄、電磁軟鉄等の透磁率の高い磁性材料から構成す
るとともに、空隙対向面に電気抵抗が高くしかも透磁率
の高いソフトフェライトや無方向性けい素鋼板の積層体
からなる複数のブロック１０を敷設した構成とすること
によって、該磁極片６ａ，６ｂの近傍に配置される傾斜
磁界コイル（図示せず）に印加するパルス電流を要因と
する磁極片６ａ，６ｂ内での渦電流の発生や残磁現象を
低減することができる。As shown in FIG. 3, the pole pieces 6a and 6b are brought into contact with the main permanent magnets 4a and 4b and the projections 7 as shown in FIG.
Are made of a magnetic material having a high magnetic permeability such as pure iron or soft magnetic iron, and a plurality of blocks 10 made of a laminated body of soft ferrite or a non-oriented silicon steel sheet having a high electric resistance and a high magnetic permeability on the gap facing surface. , An eddy current is generated in the pole pieces 6a and 6b due to a pulse current applied to a gradient magnetic field coil (not shown) arranged near the pole pieces 6a and 6b. And the remanence phenomenon can be reduced.
【００２１】図４に示すＭＲＩ用磁界発生装置は、この
発明の他の実施例を示す断面説明図であり、特に、主永
久磁石に希土類系永久磁石を使用し、補助永久磁石にフ
ェライト系永久磁石を使用した構成を示している。図に
おいて、板状継鉄１ａと磁極片６ａは実質的に図１の構
成と同様である。しかし、希土類系永久磁石を使用した
主永久磁石４ａは断面が略台形状からなり、また、フェ
ライト系永久磁石を使用した補助永久磁石５ａは断面が
略三角形状からなる。The MRI magnetic field generator shown in FIG. 4 is a sectional view showing another embodiment of the present invention. In particular, a rare earth permanent magnet is used as a main permanent magnet, and a ferrite permanent magnet is used as an auxiliary permanent magnet. The configuration using a magnet is shown. In the figure, the plate yoke 1a and the pole piece 6a are substantially the same as those in FIG. However, the main permanent magnet 4a using a rare earth permanent magnet has a substantially trapezoidal cross section, and the auxiliary permanent magnet 5a using a ferrite permanent magnet has a substantially triangular cross section.
【００２２】主永久磁石４ａ，４ｂの磁化方向は図１の
構成と同様であるが、補助永久磁石５ａ，５ｂの磁化方
向は、該補助永久磁石５ａ，５ｂの空隙対向面に対して
それぞれ直角方向となっている。すなわち、図４の構成
においても補助永久磁石５ａ，５ｂの組立性（通常、複
数のブロック状永久磁石を磁化方向に積層固着して所定
の断面形状となるように一体化する）等を考慮すると、
その磁化方向が支持継鉄３の当接面と直角方向にする構
成か、該補助永久磁石５ａ，５ｂの空隙対向面に対して
直角方向とする構成かのいずれかが望ましいが、本発明
者によれば図４の構成の場合には、図示の如く補助永久
磁石５ａ，５ｂの空隙対向面に対して直角方向とする構
成の場合が組立性とともに、材質の異なる永久磁石の特
徴を最も効果的に活用でき、磁気的な効率に優れた構成
を提供できることを確認した。また、この補助永久磁石
５ａ，５ｂと主永久磁石４ａ，４ｂとの隣接部は互いの
対向面が実質的に当接している。補助永久磁石５ａ，５
ｂと磁極片６ａ，６ｂとの端部も図示の如く実質的に当
接している構成が望ましい。The magnetization directions of the main permanent magnets 4a, 4b are the same as those in FIG. 1, but the magnetization directions of the auxiliary permanent magnets 5a, 5b are respectively perpendicular to the gap-facing surfaces of the auxiliary permanent magnets 5a, 5b. Direction. That is, also in the configuration of FIG. 4, the assemblability of the auxiliary permanent magnets 5a and 5b (usually, a plurality of block-shaped permanent magnets are stacked and fixed in the direction of magnetization and integrated so as to have a predetermined sectional shape) is taken into consideration. ,
It is desirable that the magnetization direction be either perpendicular to the contact surface of the supporting yoke 3 or perpendicular to the gap-facing surfaces of the auxiliary permanent magnets 5a and 5b. According to the configuration shown in FIG. 4, the configuration in which the auxiliary permanent magnets 5a and 5b are in the direction perpendicular to the gap facing surfaces as shown in the drawing has the most advantageous effects of the permanent magnets made of different materials together with the assemblability. It has been confirmed that it can be utilized in an efficient manner and can provide a configuration excellent in magnetic efficiency. In addition, adjacent portions of the auxiliary permanent magnets 5a, 5b and the main permanent magnets 4a, 4b are substantially in contact with each other. Auxiliary permanent magnets 5a, 5
It is desirable that the ends of the pole pieces b and the pole pieces 6a and 6b also substantially abut as shown in the drawing.
【００２３】この希土類系永久磁石とフェライト系永久
磁石を併用した構成においても、板状継鉄１ａ，１ｂと
接続する支持継鉄３の形状はフェライト系永久磁石から
なる補助永久磁石５ａ，５ｂの形状によって好ましい形
状が決定される。すなわち、補助永久磁石５ａ，５ｂの
磁化方向を前記のように該補助永久磁石５ａ，５ｂの空
隙対向面に対して直角方向とすると、補助永久磁石５
ａ，５ｂの空隙対向面と前記球状空間２ａの中心点Ｏ
（図１参照）を含む水平面との最適な角度θ1ととも
に、補助永久磁石５ａ，５ｂの支持継鉄３との当接面と
前記球状空間２ａの中心点Ｏを含む水平面との最適な角
度θ2が決定され、結果として支持継鉄３の空隙対向面
側の形状が決定される。図示の場合は、図１の形状とは
異なり、実質的に平板状（断面矩形状）からなってい
る。なお、本発明者の実験によれば、通常、θ1は３０
度〜６０度、θ2は５５度〜１００度の範囲で選定する
ことが望ましい。この構成では、安価なフェライト系永
久磁石を使用することから、希土類系永久磁石のみを使
用する構成に比べ、あまり装置を大型化することなく、
安価なＭＲＩ用磁界発生装置を提供することが可能とな
る。In the configuration using both the rare-earth permanent magnet and the ferrite permanent magnet, the shape of the supporting yoke 3 connected to the plate-like yoke 1a, 1b is the same as that of the auxiliary permanent magnets 5a, 5b made of the ferrite-based permanent magnet. The preferred shape is determined by the shape. That is, if the magnetization direction of the auxiliary permanent magnets 5a and 5b is perpendicular to the gap facing surfaces of the auxiliary permanent magnets 5a and 5b as described above,
a, 5b and the center point O of the spherical space 2a.
With optimum angle theta1 between a horizontal plane containing the (see FIG. 1), the optimum angle between the abutment surface and the horizontal plane containing the center O of the spherical space 2a of the auxiliary permanent magnets 5a, 5b supporting yoke 3 θ2 is determined, and as a result, the shape of the support yoke 3 on the gap-facing surface side is determined. In the case of illustration, unlike the shape of FIG. 1, it has a substantially flat plate shape (rectangular cross section). Incidentally, according to the experiment of the present inventors, θ1 is usually 30
Degrees to 60 degrees, theta2 is preferably be selected in the range of 55 degrees to 100 degrees. In this configuration, since an inexpensive ferrite-based permanent magnet is used, compared to a configuration using only rare-earth-based permanent magnets, the apparatus is not greatly increased in size.
An inexpensive MRI magnetic field generator can be provided.
【００２４】以上の図１及び図４においては、いずれも
主永久磁石と板状継鉄の平面形状が半円部と矩形部とを
一体化した構成にて示したが、例えば、平面形状が矩形
となる構成等を採用することもできる。しかし、磁界の
均一度や磁気回路の磁気的な効率等を考慮すると図１及
び図４に示した構成が望ましいことを確認した。図１び
図４に示すＭＲＩ用磁界発生装置は、継鉄の構成が、一
対の板状継鉄１ａ，１ｂの一端のみを支持継鉄３にて接
続支持する構成であり、被検者が配置される空隙２中央
部は支持継鉄３側を除く三方が開放され、被検者の空隙
内への挿入方向の自由度が広がるとともに、診断時の被
検者への圧迫感が低減される効果を有する。In FIGS. 1 and 4 described above, the main permanent magnet and the plate-like yoke each have a plan shape in which a semicircular portion and a rectangular portion are integrated. A rectangular configuration or the like may be employed. However, it has been confirmed that the configurations shown in FIGS. 1 and 4 are desirable in consideration of the uniformity of the magnetic field, the magnetic efficiency of the magnetic circuit, and the like. The magnetic field generator for MRI shown in FIGS. 1 to 4 has a configuration in which the yoke is configured to connect and support only one end of a pair of plate-like yoke 1a, 1b with the support yoke 3, and the subject The central portion of the gap 2 to be arranged is opened on three sides except for the support yoke 3 side, so that the subject has a greater degree of freedom in the direction of insertion into the gap, and the feeling of pressure on the subject during diagnosis is reduced. Has the effect of
【００２５】また、支持継鉄３の空隙対向面に所定形状
からなる補助永久磁石５ａ，５ｂを配置することによっ
て主永久磁石４ａ，４ｂ及び磁極片６ａ，６ｂからの該
支持継鉄３への磁束の漏洩が低減でき、しかも空隙２内
の磁界強度及び磁界の均一度をともに向上させることが
可能となった。上記のことから磁石の使用効率を向上す
ることができ、また、主永久磁石４ａ，４ｂと支持継鉄
３との距離を必要以上に大きくすることがないため、一
対の板状継鉄１ａ，１ｂの各々の長さを短くすることも
でき、全体としてＭＲＩ用磁界発生装置の小型軽量化を
実現することが可能となる。Further, by arranging auxiliary permanent magnets 5a, 5b having a predetermined shape on the surface of the support yoke 3 facing the gap, the auxiliary yoke 3 is transferred from the main permanent magnets 4a, 4b and the pole pieces 6a, 6b to the support yoke 3. The leakage of the magnetic flux can be reduced, and the magnetic field strength in the gap 2 and the uniformity of the magnetic field can both be improved. From the above, the use efficiency of the magnet can be improved, and the distance between the main permanent magnets 4a, 4b and the support yoke 3 is not unnecessarily increased, so that a pair of plate-like yoke 1a, The length of each of the MRI magnetic field generators 1b can be shortened, and the overall size and weight of the MRI magnetic field generator can be reduced.
【００２６】[0026]
比較例１ 永久磁石として（ＢＨ）ｍａｘ＝４０ＭＧＯｅの希土類
・鉄・ほう素系永久磁石を使用した図７に示す従来のＭ
ＲＩ用磁界発生装置を作成した。そして、磁極間距離Ｌ
ｇを５００ｍｍとし、空隙中央部の半径ｒが２００ｍｍ
の球状空間における中心部の磁界強度を０．３Ｔ、磁界
均一度を５０ｐｐｍとした時の全磁石重量とＭＲＩ用磁
界発生装置の長さＬを測定した。Comparative Example 1 A conventional M shown in FIG. 7 using a rare-earth / iron / boron-based permanent magnet with (BH) max = 40 MGOe as the permanent magnet
A magnetic field generator for RI was created. And the distance L between the magnetic poles
g is 500 mm, and the radius r at the center of the gap is 200 mm.
The total magnet weight and the length L of the magnetic field generator for MRI were measured when the magnetic field strength at the center of the spherical space was 0.3 T and the magnetic field uniformity was 50 ppm.
【００２７】実施例１ 主永久磁石及び補助永久磁石として比較例１と同材質の
希土類・鉄・ほう素系永久磁石を使用した図１に示すこ
の発明によるＭＲＩ用磁界発生装置を作成した。そし
て、磁極間距離Ｌｇ、空隙中央部の球状空間における磁
界強度及び磁界均一度を比較例１と同一条件に設定した
場合の全磁石重量とＭＲＩ用磁界発生装置の長さＬを測
定し、それぞれ比較例１の全磁石重量Ｗと該装置の長さ
Ｌとの比率として表１に示した。ただし、補助永久磁石
の空隙対向面と前記球状空間の中心点Ｏを含む水平面と
の角度θ1は４５度であり、補助永久磁石の支持継鉄と
の当接面と前記球状空間の中心点Ｏを含む水平面との角
度θ2は５５度であった。Example 1 A magnetic field generator for MRI according to the present invention shown in FIG. 1 was manufactured using a rare earth / iron / boron permanent magnet of the same material as that of Comparative Example 1 as a main permanent magnet and an auxiliary permanent magnet. Then, when the distance Lg between the magnetic poles, the magnetic field strength and the magnetic field uniformity in the spherical space at the center of the gap were set to the same conditions as in Comparative Example 1, the total magnet weight and the length L of the MRI magnetic field generator were measured. Table 1 shows the ratio between the total magnet weight W of Comparative Example 1 and the length L of the apparatus. However, the angle θ1 between the gap facing surface of the auxiliary permanent magnet and the horizontal plane including the center point O of the spherical space is 45 degrees, and the contact surface of the auxiliary permanent magnet with the support yoke and the center point of the spherical space The angle θ2 with the horizontal plane containing O was 55 degrees.
【００２８】実施例２ 主永久磁石として（ＢＨ）ｍａｘ＝４０ＭＧＯｅの希土
類・鉄・ほう素系永久磁石を使用し、補助永久磁石とし
て（ＢＨ）ｍａｘ＝４ＭＧＯｅのフェライト系永久磁石
を使用した図４に示すこの発明の一実施例であるＭＲＩ
用磁界発生装置を作成した。そして、磁極間距離Ｌｇ、
空隙中央部の球状空間における磁界強度及び磁界均一度
を比較例１と同一条件に設定した場合の全磁石重量とＭ
ＲＩ用磁界発生装置の長さＬを測定し、それぞれ比較例
１の全磁石重量Ｗと該装置の長さＬとの比率として表１
に示した。ただし、補助永久磁石の空隙対向面と前記球
状空間の中心点Ｏを含む水平面との角度θ1が４５度で
あり、補助永久磁石の支持継鉄との当接面と前記球状空
間の中心点Ｏを含む水平面との角度θ2が９２度であっ
た。Embodiment 2 A rare earth / iron / boron permanent magnet of (BH) max = 40 MGOe is used as a main permanent magnet, and a ferrite permanent magnet of (BH) max = 4MGOe is used as an auxiliary permanent magnet. FIG. MRI which is an embodiment of the present invention shown in FIG.
A magnetic field generator was created. And the distance Lg between the magnetic poles,
The total magnet weight and M when the magnetic field strength and magnetic field uniformity in the spherical space at the center of the air gap were set to the same conditions as in Comparative Example 1.
The length L of the magnetic field generator for RI was measured, and the ratio of the total magnet weight W of Comparative Example 1 to the length L of the device was measured as shown in Table 1.
It was shown to. However, the angle θ1 between the gap facing surface of the auxiliary permanent magnet and the horizontal plane including the center point O of the spherical space is 45 degrees, and the contact surface of the auxiliary permanent magnet with the support yoke and the center point of the spherical space The angle θ2 with the horizontal plane containing O was 92 degrees.
【００２９】[0029]
【表１】[Table 1]
【００３０】比較例２ 永久磁石として（ＢＨ）ｍａｘ＝４ＭＧＯｅのフェライ
ト系永久磁石を使用した図７に示す従来のＭＲＩ用磁界
発生装置を作成した。そして、磁極間距離Ｌｇを５００
ｍｍとし、空隙中央部の半径ｒが２００ｍｍの球状空間
における中心部の磁界強度を０．１Ｔ、磁界均一度を５
０ｐｐｍとした時の全磁石重量とＭＲＩ用磁界発生装置
の長さＬを測定した。Comparative Example 2 A conventional magnetic field generator for MRI shown in FIG. 7 was manufactured using a ferrite-based permanent magnet of (BH) max = 4MGOe as the permanent magnet. Then, the distance Lg between the magnetic poles is set to 500
mm, the magnetic field strength at the center of the spherical space having a radius r of 200 mm in the center of 200 mm is 0.1 T, and the magnetic field uniformity is 5 mm.
At 0 ppm, the total magnet weight and the length L of the MRI magnetic field generator were measured.
【００３１】実施例３ 主永久磁石及び補助永久磁石として比較例２と同材質の
フェライト系永久磁石を使用した図１に示すこの発明に
よるのＭＲＩ用磁界発生装置を作成した。そして、磁極
間距離Ｌｇ、空隙中央部の球状空間における磁界強度及
び磁界均一度を比較例２と同一条件に設定した場合の全
磁石重量とＭＲＩ用磁界発生装置の長さＬを測定し、そ
れぞれ比較例２の全磁石重量Ｗと該装置の長さＬとの比
率として表１に示した。ただし、補助永久磁石の空隙対
向面と前記球状空間の中心点Ｏを含む水平面との角度θ
1は４５度であり、補助永久磁石の支持継鉄との当接面
と前記球状空間の中心点Ｏを含む水平面との角度θ2は
５６度であった。Example 3 A magnetic field generator for MRI according to the present invention shown in FIG. 1 was prepared using ferrite-based permanent magnets of the same material as Comparative Example 2 as a main permanent magnet and an auxiliary permanent magnet. Then, when the distance Lg between the magnetic poles, the magnetic field strength and the magnetic field uniformity in the spherical space at the center of the gap were set to the same conditions as those in Comparative Example 2, the total magnet weight and the length L of the MRI magnetic field generator were measured. Table 1 shows the ratio of the total magnet weight W of Comparative Example 2 to the length L of the device. However, the angle θ between the gap facing surface of the auxiliary permanent magnet and the horizontal plane including the center point O of the spherical space
1 is 45 degrees, the angle theta2 between the horizontal plane including the center point O of the contact surface and the spherical space of the support yoke of the auxiliary permanent magnet was 56 degrees.
【００３２】[0032]
【表２】[Table 2]
【００３３】以上の比較例１と実施例１並びに比較例２
と実施例３との対比から、この発明による構成は、被検
者が配置される空隙中央部が支持継鉄側を除く三方が開
放され、被検者の空隙内への挿入方向の自由度が大幅に
拡大しているにもかかわらず、使用する永久磁石の材質
が同一の場合でも、磁石効率を大幅に向上することがで
き、ＭＲＩ用磁界発生装置の小型軽量化が可能であるこ
とが分かる。また、比較例１と実施例２からこの発明に
よれば希土類系永久磁石とフェライト系永久磁石を効果
的に配置することにより、希土類系磁石の使用量を低減
し、ＭＲＩ用磁界発生装置の著しい大型化を招くことな
く経済性に優れた装置の提供が可能であることが分か
る。Comparative Example 1, Example 1 and Comparative Example 2
From the comparison between Example 3 and Example 3, the configuration according to the present invention is such that the center of the gap where the subject is arranged is open on all three sides except for the support yoke side, and the degree of freedom of the subject in the direction of insertion into the gap. However, even if the permanent magnets used are the same, the magnet efficiency can be greatly improved and the MRI magnetic field generator can be reduced in size and weight. I understand. Further, according to the present invention, from Comparative Example 1 and Example 2, the rare-earth permanent magnet and the ferrite-based permanent magnet are effectively arranged, so that the amount of the rare-earth magnet used is reduced. It can be seen that it is possible to provide a device that is economical without increasing the size.
【００３４】[0034]
【発明の効果】上述の実施例からも明らかなように、こ
の発明のＭＲＩ用磁界発生装置は、継鉄の構成や永久磁
石及び磁極片の配置構成によって、被検者の空隙内への
挿入方向の自由度を広げるとともに、診断時の被検者へ
の圧迫感を低減する効果を有するだけでなく、磁石効率
を大幅に向上することができ、ＭＲＩ用磁界発生装置の
小型軽量化を実現することができる。As is clear from the above embodiment, the magnetic field generator for MRI of the present invention can be inserted into the gap of the subject by the configuration of the yoke and the arrangement of the permanent magnets and the pole pieces. Not only has the effect of increasing the degree of freedom in the direction and the effect of reducing the feeling of pressure on the subject during diagnosis, but also the magnet efficiency has been greatly improved, and the MRI magnetic field generator has been reduced in size and weight. can do.
【図１】この発明のＭＲＩ用磁界発生装置の一実施例を
示すもので、（ａ）は縦断面説明図であり、（ｂ）は
（ａ）のＡ−Ａ断面説明図である。1A and 1B show an embodiment of an MRI magnetic field generator according to the present invention, in which FIG. 1A is a longitudinal sectional view, and FIG. 1B is an AA sectional view of FIG. 1A.
【図２】この発明のＭＲＩ用磁界発生装置の補助永久磁
石の一実施例を示す斜視説明図である。FIG. 2 is an explanatory perspective view showing one embodiment of an auxiliary permanent magnet of the magnetic field generator for MRI of the present invention.
【図３】この発明のＭＲＩ用磁界発生装置の磁極片の一
実施例を示す斜視説明図である。FIG. 3 is an explanatory perspective view showing one embodiment of a pole piece of the magnetic field generator for MRI of the present invention.
【図４】この発明のＭＲＩ用磁界発生装置の他の実施例
を示すも縦断面説明図である。FIG. 4 is an explanatory longitudinal sectional view showing another embodiment of the magnetic field generator for MRI of the present invention.
【図５】従来のＭＲＩ用磁界発生装置の一実施例を示す
もので、（ａ）は縦断面説明図であり、（ｂ）は（ａ）
のＡ−Ａ断面説明図である。5A and 5B show an embodiment of a conventional magnetic field generator for MRI, in which FIG. 5A is a longitudinal sectional view, and FIG.
FIG.
【図６】従来のＭＲＩ用磁界発生装置の他の実施例を示
す斜視説明図である。FIG. 6 is an explanatory perspective view showing another embodiment of the conventional magnetic field generator for MRI.
【図７】従来のＭＲＩ用磁界発生装置の他の実施例を示
す斜視説明図である。FIG. 7 is a perspective explanatory view showing another embodiment of the conventional MRI magnetic field generator.
１ａ，１ｂ 板状継鉄 ２ 空隙 ２ａ 球状空間 ２ｂ，２ｃ 隙間 ３ 支持継鉄 ４ａ，４ｂ 主永久磁石 ５，５ａ，５ｂ 補助永久磁石 ６ａ，６ｂ 磁極片 ７ａ，７ｂ 突起部 ８ 突起部 ９ 当接部 １０ ブロック １１ａ，１１ｂ 板状継鉄 １２，２２，３２ 空隙 １３ａ，１３ｂ，１３ｃ，１３ｄ 円柱型継鉄 １４ａ，１４ｂ 永久磁石 １６ａ，１６ｂ 磁極片 ２１ ６角筒状継鉄 ２４ａ，２４ｂ 主永久磁石 ２５ａ，２５ｂ，２５ｃ，２５ｄ 補助永久磁石 ２６ａ，２６ｂ 磁極片 ３１ａ，３１ｂ 板状継鉄 ３３ 支持継鉄 ３４ａ，３４ｂ 永久磁石 ３６ａ，３６ｂ 磁極片 1a, 1b Plate yoke 2 Air gap 2a Spherical space 2b, 2c Gap 3 Support yoke 4a, 4b Main permanent magnet 5, 5a, 5b Auxiliary permanent magnet 6a, 6b Magnetic pole piece 7a, 7b Projection 8 Projection 9 Contact Part 10 Block 11a, 11b Plate yoke 12, 22, 32 Void 13a, 13b, 13c, 13d Cylindrical yoke 14a, 14b Permanent magnet 16a, 16b Magnetic pole piece 21 Hexagonal cylindrical yoke 24a, 24b Main permanent magnet 25a, 25b, 25c, 25d Auxiliary permanent magnet 26a, 26b Magnetic pole piece 31a, 31b Plate yoke 33 Supporting yoke 34a, 34b Permanent magnet 36a, 36b Magnetic pole piece
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06197715AJP3113513B2 (en) | 1994-07-29 | 1994-07-29 | Magnetic field generator for MRI |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06197715AJP3113513B2 (en) | 1994-07-29 | 1994-07-29 | Magnetic field generator for MRI |
| Publication Number | Publication Date |
|---|---|
| JPH0845729A JPH0845729A (en) | 1996-02-16 |
| JP3113513B2true JP3113513B2 (en) | 2000-12-04 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP06197715AExpired - LifetimeJP3113513B2 (en) | 1994-07-29 | 1994-07-29 | Magnetic field generator for MRI |
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| JP (1) | JP3113513B2 (en) |
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