JPS61204551A - Magnetic field generator of nuclear magnetic resonance diagnosis device - Google Patents

Abstract

PURPOSE:To obtain a stable magnetic field with a simple refrigerant device by detecting the temp. of an electromagnet from the change of a magnetic field and feeding back the deviation between the detected temp. and reference temp. to a reference value which is so generated as to apply prescribed electric current to the electromagnet. CONSTITUTION:The temp. deviation signal DELTAEt between the voltage signal Ec proportional to a coil temp. and the reference temp. signal Er equiv. to the temp. of the coil 2a of the electromagnet 2 is obtd. at an addition point P3. The signal DELTAEt is converted to a temp. deviation signal Et' normalized by a buffer amplifier 7. The reference voltage Eref and the deviation signal DELTAEt' of the coil temp. are added at an addition point P4. As a result, the next reference signal Eref' is Eref'=Eref+DELTAEt' and is corrected by the coil temp. of the electromagnet 2. Excitation current I0 is thus outputted in accordance with the signal Eref'. The extremely stable magnetic field is thus obtd. even the temp. of the cooling water for cooling the coil of the electromagnet 2, the flow rate of said water or the temp. of the secondary coil 2a fluctuates.

Description

【発明の詳細な説明】 〔発明の利用分野〕 本発明は核磁気共鳴診断装置の磁界発生装置に関する。[Detailed description of the invention] [Field of application of the invention] The present invention relates to a magnetic field generating device for a nuclear magnetic resonance diagnostic apparatus.

〔発明の背景〕[Background of the invention]

核磁気共鳴診断装置の計測手法及び構成等は特開昭５１
−５３８８８　、特開昭５２−１２７３８９．　　ｒＮ
ＭＲ医学」　（核磁気共鳴医学全編、昭和５９年−１月
）等に記載されているので、説明を省略するが、本装置
で得られる生体の断層像の精細度は核磁気共鳴の場を与
える磁場発生装置の磁場安定度により大きな影響を受け
るので、その磁場の高安定度が要求される。実用化され
ている電磁石形の磁場発生装置においては、磁場安定後
は１〜１０ｐｐｍの範囲である。また電磁画形磁場発生
装置では、実用的限界から磁場強度は０．１〜０．２テ
スラであり、人体の画像診断を目的としていることから
電磁石のコイル径は０．７〜１．０ｍである。従つて電
磁石の消費電力は３０〜５０ｋｗにも達する。The measurement method and configuration of nuclear magnetic resonance diagnostic equipment are disclosed in Japanese Patent Application Laid-Open No. 1983
-53888, JP-A-52-127389. rN
MR Medicine (Complete Edition of Nuclear Magnetic Resonance Medicine, January 1980), etc., so I will omit the explanation, but the definition of the tomographic image of a living body obtained with this device is similar to that of the nuclear magnetic resonance field. Since it is greatly affected by the stability of the magnetic field of the magnetic field generator, high stability of the magnetic field is required. In electromagnet-type magnetic field generators that have been put into practical use, the magnetic field is in the range of 1 to 10 ppm after the magnetic field is stabilized. In addition, in electromagnetic image magnetic field generators, the magnetic field strength is 0.1 to 0.2 Tesla due to practical limits, and the electromagnet coil diameter is 0.7 to 1.0 m because the purpose is image diagnosis of the human body. be. Therefore, the power consumption of the electromagnet reaches as much as 30 to 50 kW.

電磁石を常温（２０，３０℃）で使用するためには冷却
を必らず必要とする。その冷却は効率を考慮し、一般的
に水冷却を採用している。In order to use an electromagnet at room temperature (20, 30° C.), cooling is necessarily required. Considering efficiency, water cooling is generally used for cooling.

この常電導の電磁石ではコイル材料に銅かアルミニュー
ムを使用する。従ってコイルに温度変化を生ずると、コ
イル径も変化する。その結果、磁場の強さも変化する。This normally conducting electromagnet uses copper or aluminum as the coil material. Therefore, when a temperature change occurs in the coil, the coil diameter also changes. As a result, the strength of the magnetic field also changes.

コイル温度変化で生ずる磁場強さの変化は（１）式で示
される。Changes in magnetic field strength caused by changes in coil temperature are expressed by equation (1).

ΔＨ牟２αΔｔ　　　　　　・・・・・・（１）ΔＨ：
磁場強さの変化量 α：コイル材料の線膨張係数（ｐｐｍ／”Ｃ）Δｔ：コ
イルの変化温度（”Ｃ） （１）式から、Δｔが１℃変化すると、コイルをアルミ
ニュウムとして、αは２３ｐｐｍ／’Ｃであるから、磁
場強さの変化ＡＨは、４３ｐｐｍとなる。事実電磁石の
コイル温度変化による磁場の変化は計算値と良く一致す
る１以上のことから、磁場安定度を１１０ＰＰ以下とす
ると、冷却水温度の変化幅を０．２５　℃以下にする必
要があった。ΔH㉟2αΔt ・・・・・・(1) ΔH:
Amount of change in magnetic field strength α: Coefficient of linear expansion of coil material (ppm/''C) Δt: Change temperature of coil (''C) From equation (1), when Δt changes by 1°C, when the coil is made of aluminum, α becomes Since it is 23 ppm/'C, the change AH in magnetic field strength is 43 ppm. In fact, the change in the magnetic field due to the change in the electromagnet coil temperature is 1 or more, which is in good agreement with the calculated value, so if the magnetic field stability is set to 110PP or less, the range of change in the cooling water temperature needs to be 0.25 °C or less. .

第２図は従来例を示す。１は数ｐｐｍと高い安定度の励
磁電流工。を供給し得る定電流電源で、励磁電流工。に
より電磁石２は励磁される６電磁石２にはその熱エネル
ギーを吸収し、冷却するために、冷却水装置３から冷却
水Ｑが供給されている。定電流電源１においては、一定
の励磁電流工。FIG. 2 shows a conventional example. 1 is an excitation current generator with high stability of several ppm. A constant current power supply that can supply excitation current. The electromagnet 2 is excited by 6. Cooling water Q is supplied from a cooling water device 3 to the electromagnet 2 in order to absorb the thermal energy and cool it. In the constant current power supply 1, the excitation current is constant.

を出力するための、基準となる高安定な基準電圧源１ａ
と、励磁電流工。の出力点Ｐ２から電流を検出し、これ
を入力の加え合せ点Ｐ８へ帰還する帰還増幅器１ｃが設
けられ、加え合せ点Ｐ、で基準電圧源１ａの基準信号Ｅ
ｒｅｆと帰還増幅器１ｃからの帰還信号Ｅ、との偏差信
号ΔＥを得て、この偏差信号ΔＥを高い増幅度と大電力
容量を有する誤差増幅器１ｂにより増幅し、常に基準電
圧源１ａの基準信号Ｈｒｅｆに一定の増幅度を乗じた励
磁電流を得ている。かかる構成の磁界発生装置において
、温度に依存する磁場の変動、を極小化するために、冷
却水装置から供給される冷却水の安定化と電磁石の周囲
温度の安定化に努力が払われていた。従って、特に冷却
水装置は規模が大きく、かつ高価なものとなり、装置全
体のコストパーフォーマンスの低下を招く欠点を有して
いた。A highly stable reference voltage source 1a that serves as a reference for outputting
and excitation electrician. A feedback amplifier 1c is provided which detects a current from an output point P2 and returns it to an input summing point P8, and at the summing point P, a reference signal E of the reference voltage source 1a is
A deviation signal ΔE between ref and the feedback signal E from the feedback amplifier 1c is obtained, and this deviation signal ΔE is amplified by the error amplifier 1b having a high amplification degree and large power capacity, and the reference signal Href of the reference voltage source 1a is always The excitation current is obtained by multiplying by a certain amplification degree. In a magnetic field generator with such a configuration, efforts have been made to stabilize the cooling water supplied from the cooling water device and the temperature surrounding the electromagnet in order to minimize temperature-dependent fluctuations in the magnetic field. . Therefore, the cooling water system in particular becomes large in scale and expensive, which has the drawback of lowering the cost performance of the entire system.

従来の冷却水装置によれば、−次冷却器からの冷水を熱
交換器へ供給し、これにより、熱交換器二次側の、電磁
石へ供給される循環式の二次冷却水を冷却する。二次冷
却水の高度な温度安定性は、−次冷水の三方弁による流
量制御、二次冷却水のヒータによる加熱制御、さらには
二次冷却水系に設けられたバッファタンクによる積分効
果などの多重の温度制御によって達成されていた。第３
図は、その水温制御の一例を示したもので、１℃の安定
度を有する例である。しかし、冷却水装置の簡易化、高
経済性化、小形軽量化、高信頼化は、電磁石方式の核磁
気共鳴診断装置の大きな課題である。According to the conventional cooling water system, cold water from the secondary cooler is supplied to the heat exchanger, thereby cooling the circulating secondary cooling water that is supplied to the electromagnet on the secondary side of the heat exchanger. . The high temperature stability of the secondary cooling water is achieved by multiple factors, including flow rate control using a three-way valve for the secondary cooling water, heating control using the secondary cooling water heater, and an integral effect from the buffer tank installed in the secondary cooling water system. This was achieved through temperature control. Third
The figure shows an example of water temperature control, and is an example with stability of 1°C. However, simplifying the cooling water system, making it more economical, making it smaller and lighter, and making it more reliable are major challenges for electromagnetic nuclear magnetic resonance diagnostic equipment.

〔発明の目的〕[Purpose of the invention]

本発明の目的は電磁石の冷却に用いられる冷媒装置の冷
媒温度の安定度を緩和し、究極のところその精密な温度
調節によらずとも、簡単な冷媒装置で安定な磁場を得る
ことができる核磁気共鳴診断装置の磁界発生装置を提供
することにある。The purpose of the present invention is to alleviate the stability of the refrigerant temperature of a refrigerant device used to cool an electromagnet, and ultimately to create a core that can obtain a stable magnetic field with a simple refrigerant device without the need for precise temperature control. An object of the present invention is to provide a magnetic field generating device for a magnetic resonance diagnostic device.

〔発明の概要〕[Summary of the invention]

本発明の特徴は、電磁石のコイル温度変化と、磁場の変
化が実質的に比例的に良く対応していることを利用して
、電磁石の温度を検出して、これと基準温度との偏差を
得、そしてこの偏差を電磁石に予め定められた電流を与
えるように発生される基準値にフィードバックするよう
にした点にある。A feature of the present invention is that the temperature of the electromagnet is detected by utilizing the fact that changes in the coil temperature of the electromagnet and changes in the magnetic field substantially correspond in proportion to each other, and the deviation between this and the reference temperature is detected. and this deviation is fed back to a reference value generated to provide a predetermined current to the electromagnet.

〔発明の実施例〕[Embodiments of the invention]

第１図は本発明の一実施例を示す、定電流電源１、電磁
石２．及び冷却水装置３の基本構成は従来例の第１図と
同じである。FIG. 1 shows an embodiment of the present invention, including a constant current power supply 1, an electromagnet 2. The basic configuration of the cooling water device 3 is the same as that of the conventional example shown in FIG.

ここで、電磁石２のコイル２ａの適切な位置にコイル温
度を検出する温度検出器４を設ける。この温度検出器は
温度をこれに比例した電気量に変換し易い種類のものが
良く、測温抵抗体や熱電対が好ましい、測定温度は２０
〜４０℃程度の温度を計測するのに好適な種類のものを
選定する。温度検出器４のコイル温度信号Ｔ。は温度変
換器５で比例した電圧信号Ｅ０に変換される。一方、電
磁石２のコイル２ａの温度に等価な基準温度信号Ｅ？を
もつ、温度基準発生器を設け、前記コイル温度に比例し
た電圧信号Ｅ。と当該基準温度信号Ｅ？とを加え合せ点
Ｐ３で、それらの温度偏差信号ΔＥ、を得る。この温度
偏差信号−Ｅ、は、電磁石２の温度変化に対する磁場変
化の割合と、定電流電源の励磁電流工。の変化量に対す
る電磁石２の磁場変化量の割合、すなわち、定電流電源
１の基準電圧源１ａよりの基準信号Ｅｒａｆの変動量に
対する磁場変化量の割合が一致するよう、規準化した温
度偏差信号Ｅ１′　　に、バッファ増幅器７により変換
され、この信号Ｅ　ｔ’　　と基準信号Ｅｒａｆとを加
え合せ点Ｐ４で加算する。その結果１次の基準信号Ｅｒ
ａｆ　’は、　Ｅｒｅｆ’　＝ＩＥｒｅｆ＋　ＡＥ、’
　　となり。Here, a temperature detector 4 is provided at an appropriate position of the coil 2a of the electromagnet 2 to detect the coil temperature. This temperature sensor should be of a type that can easily convert temperature into an amount of electricity proportional to it, preferably a resistance temperature detector or thermocouple.The measurement temperature is 20
Select a type suitable for measuring temperatures of about ~40°C. Coil temperature signal T of temperature detector 4. is converted into a proportional voltage signal E0 by the temperature converter 5. On the other hand, the reference temperature signal E? equivalent to the temperature of the coil 2a of the electromagnet 2? a temperature reference generator having a voltage signal E proportional to the coil temperature; and the reference temperature signal E? By adding these, the temperature deviation signal ΔE is obtained at a point P3. This temperature deviation signal -E is the ratio of the magnetic field change to the temperature change of the electromagnet 2 and the excitation current of the constant current power supply. The temperature deviation signal E1 is normalized so that the ratio of the amount of change in the magnetic field of the electromagnet 2 to the amount of change in , that is, the ratio of the amount of change in the magnetic field to the amount of change in the reference signal Eraf from the reference voltage source 1a of the constant current power supply 1 is the same. ' is converted by the buffer amplifier 7, and this signal E t' and the reference signal Eraf are added at a summing point P4. As a result, the first-order reference signal Er
af' is Eref' = IEref + AE,'
Next door.

電磁石２のコイル温度で補正されたものとなる。It is corrected by the coil temperature of the electromagnet 2.

従って、基準信号Ｅｒｅｆ　’に対応して励磁電流■。Therefore, the excitation current ■ corresponds to the reference signal Eref'.

が出力される。第４図は、電磁石２のコイル温度の変化
率と磁場の変化率を、励磁電流工。一定下で、通電時間
に対して実測した一例を示したものである。この場合の
電磁石２の磁場強度は、０．０５Ｔ、コイルはアルミニ
ュウム製のものである。この結果から、コイル温度の変
化率ΔＴ／Ｔｏと、磁場の変化率ΔＨ０は通常時間ｔに
対して、傾斜がまったく同一であり、コイル温度Ｔｃｌ
と磁場の強さＨｏは、特定の係数で実質的に比例関係に
あることを示している。この特性から得られた、単位コ
イル温度変化に対する磁場強さの変化は４７　ｐ　ｐ　
ｍ／’Ｃであった。これは（１）式で、線膨張係数αを
アルミニウムとして得られる計算値４６ｐｐｍ／’Ｃと
良く一致する。is output. Figure 4 shows the rate of change of the coil temperature of electromagnet 2 and the rate of change of the magnetic field using the excitation current. This is an example of actual measurement of current application time under certain conditions. In this case, the magnetic field strength of the electromagnet 2 is 0.05T, and the coil is made of aluminum. From this result, the rate of change ΔT/To of the coil temperature and the rate of change ΔH0 of the magnetic field have exactly the same slope with respect to the normal time t, and the coil temperature Tcl
and the magnetic field strength Ho are shown to have a substantially proportional relationship with a specific coefficient. The change in magnetic field strength with respect to unit coil temperature change obtained from this characteristic is 47 p p
It was m/'C. This agrees well with the calculated value of 46 ppm/'C obtained by equation (1) and assuming that the linear expansion coefficient α is aluminum.

第５図は、第１図の実施例の制御ブロックダイヤグラム
を示す、Ｇ８は偏差増幅器１ｂに、Ｇ。FIG. 5 shows a control block diagram of the embodiment of FIG. 1, in which G8 is connected to the deviation amplifier 1b;

は電磁石２に、Ｇ、は温度検出器４と温度変換器５に、
Ｇ、はバッファ増幅器７に、Ｇ、はコイル２ａの温度変
化による磁場変動にそれぞれ対応し。is to the electromagnet 2, G is to the temperature detector 4 and temperature converter 5,
G corresponds to the buffer amplifier 7, and G corresponds to magnetic field fluctuations due to temperature changes in the coil 2a.

各々の伝達函数を示す。Ｔ、はコイル２ａを冷却する冷
却水装置３からの冷却水Ｑの冷却水温度である。θ・Ｐ
は、励磁電流工。でコイル２ａが消費する熱量に対応し
たコイル２ａの温度上昇分であり、θは冷却系までの熱
抵抗、Ｐは消費電力である。コイル２ａの温度上昇はθ
とＰの積で表わされる。従ってコイル温度Ｔ０は、Ｔ１
１１＝ＴＱ＋θ・Ｐとなる。Ｔｏは、コイル２ａの温度
変化がない場合の固定された温度で、温度変化のみを抽
出するための制御系操作のための要素で任意に選択でき
る０以上の制御構成で、冷却水Ｑの変動や、その水温Ｔ
、の変化は、コイル２ａの温度Ｔ。となって現われ、電
磁石２の駆動電流Ｉ０による安定な磁場Ｈ０に対し、磁
場変動ΔＨ０の外乱として。Each transfer function is shown. T is the cooling water temperature of the cooling water Q from the cooling water device 3 that cools the coil 2a. θ・P
is an excitation electrician. is the temperature rise of the coil 2a corresponding to the amount of heat consumed by the coil 2a, θ is the thermal resistance up to the cooling system, and P is the power consumption. The temperature rise of coil 2a is θ
It is expressed as the product of and P. Therefore, the coil temperature T0 is T1
11=TQ+θ·P. To is a fixed temperature when there is no temperature change in the coil 2a, and is a control configuration of 0 or more that can be arbitrarily selected as an element for control system operation to extract only temperature changes, and changes in the cooling water Q. Oh, that water temperature T
, is the temperature T of the coil 2a. This appears as a disturbance of magnetic field fluctuation ΔH0 with respect to the stable magnetic field H0 due to the drive current I0 of the electromagnet 2.

加えられ、不安定さを助長する要因となる。しかし、コ
イル２ａの温度Ｔ６を、定電流制御系の入力に帰還する
ことで、外乱を打消すことができる。This is a factor that promotes instability. However, the disturbance can be canceled by feeding back the temperature T6 of the coil 2a to the input of the constant current control system.

コイル温度Ｔ。の偏差信号ΔＥｔ’は次の（２）式％式
％ 基準電圧Ｅｒａｆとコイル温度の偏差信号ΔＥｔ’は加
え合せ点Ｐ、で加え合わされるが、この入力から電磁石
２の磁場Ｈ０までの伝達函数は、（３）式で示される。Coil temperature T. The deviation signal ΔEt' is expressed by the following equation (2). is expressed by equation (3).

Ｈ０＝Ｇｔ・Ｇ、（Ｅｒａｆ−Ｇ４（ＧａＴａ−Ｅ？）
）・　（３）一方、冷却水ＴＱの変化に伴う磁場変動Ａ
Ｈ０は（１）式の２α＝Ｇ、であり、これを代入すると
（４）式となる。H0=Gt・G, (Eraf-G4(GaTa-E?)
)・(3) On the other hand, magnetic field fluctuation A due to change in cooling water TQ
H0 is 2α=G in equation (1), and substituting this gives equation (4).

ＡＨ０＝２α（’ｒ　Ｑ＋θ・Ｐ　−Ｔｏ）　　　・・
・（４）結果として得られる磁場Ｈ０′　　は、（３）
と（４）式の和であり、（５）式となる。AH0=2α('r Q+θ・P −To) ・・
・(4) The resulting magnetic field H0' is (3)
and (4), resulting in equation (5).

Ｈａ’　＋＝Ｇｔ・Ｇ、・Ｈｒｅｆ　　Ｇｉ・Ｇｚ：Ｇ
４（ＧａＴａ　　Ｂｙ）＋２α（Ｔａ−Ｔｏ）　　　　
−（５）但し、Ｔ０＝ＴＱ十〇・Ｐ ここで、Ｇ１・Ｇ２・Ｇ３・Ｇ４＝２α、Ｇ１−Ｇ。Ha' +=Gt・G,・Href Gi・Gz:G
4 (GaTa By) + 2α (Ta-To)
-(5) However, T0=TQ10・P Here, G1・G2・G3・G4=2α, G1−G.

・Ｇ、・Ｅ？＝２αＴ０とすると（６）式を得る。・G, ・E? =2αT0, we obtain equation (6).

Ｈ０’　＝　Ｇ、　・Ｇ、　・Ｅｒ５ｆ　　　　　　　
−（６）以上述べたごとく、本実施例によれば、電磁石
２のコイルを冷却する冷却水の温度に変動があっても、
また流量に変動があっても、二次的にコイル２ａの温度
が変動しても、極めて安定な磁場を得ることができる。H0' = G, ・G, ・Er5f
-(6) As described above, according to this embodiment, even if there is a fluctuation in the temperature of the cooling water that cools the coil of the electromagnet 2,
Further, even if the flow rate fluctuates or secondarily the temperature of the coil 2a fluctuates, an extremely stable magnetic field can be obtained.

第６図は、応用例を示す図で、温度検出端４ａ。FIG. 6 is a diagram showing an application example, in which the temperature detection end 4a is shown.

４ｂのごとく検出位置を分散させて複数個設け、それぞ
れの位置の温度を温度変換器５ａ、５ｂにより電圧信号
に変換し、加え合せ点Ｐ、で加え合せ、平均化回路５Ｃ
により、より正確な温度に対応する電圧信号Ｅ。を得て
、さらに安定度の向上を図っている。4b, a plurality of detection positions are distributed and provided, and the temperature at each position is converted into a voltage signal by temperature converters 5a and 5b, and the signals are added at a summing point P, and an averaging circuit 5C
The voltage signal E corresponds to a more accurate temperature. We are working to further improve stability.

本発明の実施例によれば、磁場発生装置の磁場安定度を
確実に５ｐｐｍ以下を達成できると共に、電磁石を冷却
する冷却水温度安定度を１０℃程度まで緩和できるので
、精密温度調節装置の不要な、簡単な構造で、経済性の
高い、冷却水装置とすることができる。さらに小形、軽
量化を達成できる。According to the embodiment of the present invention, the magnetic field stability of the magnetic field generator can be reliably achieved at 5 ppm or less, and the temperature stability of the cooling water for cooling the electromagnet can be relaxed to about 10°C, so there is no need for a precision temperature control device. A cooling water device with a simple structure and high economic efficiency can be obtained. It is also possible to achieve smaller size and lighter weight.

具体的には、経済性、大きさ、重量などが従来品の１７
２以下にできる。加えて、磁場発生装置と同一室内に設
定も可能となり、保守性、信頼性の向上にも効果がある
。Specifically, the economy, size, weight, etc. of the conventional product 17
It can be reduced to 2 or less. In addition, it can be installed in the same room as the magnetic field generator, which has the effect of improving maintainability and reliability.

〔発明の効果〕〔Effect of the invention〕

本発明によれば、電磁石の冷却に用いられる冷媒装置の
冷媒温度の安定度を緩和し、特にその精密な温度調節に
上らずとも、簡単な冷媒装置で安定な磁場を得ることが
できる核磁気共鳴診断装置の磁界発生装置が提供される
。According to the present invention, the stability of the refrigerant temperature of a refrigerant device used for cooling an electromagnet is relaxed, and a stable magnetic field can be obtained with a simple refrigerant device without having to perform particularly precise temperature control. A magnetic field generating device for a magnetic resonance diagnostic apparatus is provided.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明の一実施例を示す核磁気共鳴診断装置の
磁界発生装置のブロック図、第２図は従来の核磁気共鳴
診断装置の磁界発生装置のブロック図、第３図は従来例
による冷却水温度安定度特性図、第４図は電磁石の温度
と磁場の変化率特性図、第５図は第１図の実施例の制御
ブロック図、第６図は本発明にもとづくもう一つの実施
例を示す核磁気共鳴診断装置の磁界発生装置の一部のブ
ロック図である。 １・・・定電流電源、２・・・電磁石、３・・・冷却水
装置、４・・・温度検出器、５・・・温度変換器、６・
・・温度標準発生器、７・・・バッファ増幅器、Ｐ４・
・・温度帰還信代理人　弁理士　小川勝男　　− 早　２図 時間ｔ Ｄ　　　　３６　　４６　　　？６　　１２６　　　　
ｒ５６遍を峙間１１員ｉｌｌFig. 1 is a block diagram of a magnetic field generator of a nuclear magnetic resonance diagnostic apparatus showing an embodiment of the present invention, Fig. 2 is a block diagram of a magnetic field generator of a conventional nuclear magnetic resonance diagnostic apparatus, and Fig. 3 is a conventional example. FIG. 4 is a characteristic diagram of the temperature stability of the cooling water according to the present invention, FIG. 4 is a characteristic diagram of the temperature of the electromagnet and the rate of change of the magnetic field, FIG. 1 is a block diagram of a part of a magnetic field generating device of a nuclear magnetic resonance diagnostic apparatus showing an embodiment. FIG. DESCRIPTION OF SYMBOLS 1... Constant current power supply, 2... Electromagnet, 3... Cooling water device, 4... Temperature detector, 5... Temperature converter, 6...
...Temperature standard generator, 7...Buffer amplifier, P4.
...Temperature Return Agent Patent Attorney Katsuo Ogawa - Early 2 Figure Time t D 36 46? 6 126
11 members of the 56th generation ill

Claims (1)

【特許請求の範囲】 １、核磁気共鳴現象を用い、生体の断層像を得るために
用いられる、電磁石を含む核磁気共鳴診断装置の磁界発
生装置において、前記電磁石を冷却する冷媒装置と、前
記電磁石の温度を検出し、その対応電気信号を発生する
手段と、基準温度電気信号を発生する手段と、前記検出
された温度の電気信号と前記基準温度電気信号との間の
偏差信号を発生する手段と、前記電磁石に予め定められ
た電流を与えるように予め定められた基準信号を発生す
る手段と、前記偏差信号を前記基準信号に加える手段と
を備えていることを特徴とする核磁気共鳴診断装置の磁
界発生装置。 ２、前記電磁石の温度を検出し、その対応電気信号を発
生する手段は前記磁石の異なる位置の温度を検出し、そ
れらの平均電気信号を発生するように構成されているこ
とを特徴とする特許請求の範囲第１項に記載された核磁
気共鳴診断装置の磁界発生装置。[Scope of Claims] 1. A magnetic field generating device for a nuclear magnetic resonance diagnostic apparatus including an electromagnet, which is used to obtain a tomographic image of a living body using a nuclear magnetic resonance phenomenon, comprising: a refrigerant device for cooling the electromagnet; means for detecting the temperature of the electromagnet and generating a corresponding electrical signal; means for generating a reference temperature electrical signal; and generating a deviation signal between the detected temperature electrical signal and the reference temperature electrical signal. nuclear magnetic resonance, comprising: means for generating a predetermined reference signal to apply a predetermined current to the electromagnet; and means for adding the deviation signal to the reference signal. Magnetic field generator for diagnostic equipment. 2. The patent characterized in that the means for detecting the temperature of the electromagnet and generating a corresponding electric signal is arranged to detect the temperature of different positions of the magnet and generate an average electric signal thereof. A magnetic field generating device for a nuclear magnetic resonance diagnostic apparatus according to claim 1.