JPS63214249A - Power source apparatus for nuclear magnetic resonance imaging apparatus - Google Patents
Power source apparatus for nuclear magnetic resonance imaging apparatusInfo
- Publication number
- JPS63214249A JPS63214249A JP62047577A JP4757787A JPS63214249A JP S63214249 A JPS63214249 A JP S63214249A JP 62047577 A JP62047577 A JP 62047577A JP 4757787 A JP4757787 A JP 4757787A JP S63214249 A JPS63214249 A JP S63214249A
- Authority
- JP
- Japan
- Prior art keywords
- magnetic resonance
- nuclear magnetic
- power supply
- switching
- frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000013421 nuclear magnetic resonance imaging Methods 0.000 title claims description 10
- 230000003068 static effect Effects 0.000 claims description 15
- 238000005481 NMR spectroscopy Methods 0.000 claims description 13
- 238000001514 detection method Methods 0.000 claims description 6
- 230000000007 visual effect Effects 0.000 claims 1
- 230000000694 effects Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 230000010355 oscillation Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000009499 grossing Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Magnetic Resonance Imaging Apparatus (AREA)
Abstract
(57)【要約】本公報は電子出願前の出願データであるた
め要約のデータは記録されません。(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は核磁気共鳴イメージング装置に係り、特にその
大電力を要求される静磁場、傾斜磁場。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a nuclear magnetic resonance imaging apparatus, particularly for static magnetic fields and gradient magnetic fields that require large amounts of power.
高周波磁場の発生に必要な各種電源に好適な電源装置に
関する。The present invention relates to a power supply device suitable for various power supplies necessary for generating high-frequency magnetic fields.
従来の核磁気共鳴イメージング装置の電源部の構成例を
第２図に示す。これは良く知られている様に直列制御形
の定電圧（流）電源である。この方式による電源は、比
較的精度が良く、またリップルが少ないという利点があ
る。しかしながら直列制御部で消費する電力が大きく、
効率が悪い。FIG. 2 shows an example of the configuration of a power supply section of a conventional nuclear magnetic resonance imaging apparatus. As is well known, this is a series controlled constant voltage (current) power supply. This type of power supply has the advantage of relatively high accuracy and low ripple. However, the power consumed by the series control section is large,
ineffective.
このため大出力のときは水冷方式の電源となる。Therefore, when the output is high, it becomes a water-cooled power source.
一方、効率の良い定電圧（流）電源としてのスイッチン
グ方式のものは、スイッチングによるノイズのため、磁
気共鳴信号のような微少信号の検出用には用いられてい
なかった。On the other hand, switching type power supplies as efficient constant voltage (current) power supplies have not been used for detecting minute signals such as magnetic resonance signals due to noise caused by switching.
従来より用いられている代表的な定電圧（流）電源は第
２図に示したように、直列（並列でも同様）制御方式を
用いている。この方式は、出力電圧（流）と基準電圧と
の差を検出し、直列制御回路の抵抗を制御することによ
り、常に一定の出方電圧（流）となるように負帰還がが
がっている。Typical constant voltage (current) power supplies conventionally used use a series (or parallel) control system, as shown in FIG. This method detects the difference between the output voltage (current) and the reference voltage and controls the resistance of the series control circuit to create negative feedback so that the output voltage (current) is always constant. There is.
このような方式は実績があり、かつリップルが少なく、
精度の良い安定化電源である。しかしながら、直列制御
部で消費する電力が大きく、効率が悪いという欠点があ
った。このために出方電力が大きい安定化出力を得る時
に、直列制御部で消費される電力のために発熱し、水冷
の冷却手段を必要としていた。したがって電源の構成が
複雑となり、大形、高価となる欠点があった。This method has a proven track record and has low ripple.
It is a highly accurate stabilized power supply. However, there was a drawback that the series control section consumed a large amount of power and was inefficient. For this reason, when a stabilized output with a large output power is obtained, heat is generated due to the power consumed in the series control section, and water-cooling cooling means is required. Therefore, the configuration of the power supply is complicated, and the disadvantage is that it is large and expensive.
一方、スイッチング方式の安定化電源は効率が良い利点
を持っているが、リップルが大きく、かつスイッチング
による影響を他回路に及ぼすため、特に微少信号を取り
扱う核磁気共鳴イメージング装置では、雑音が増加する
という問題点があり、一部の電源を除いて殆んど実用さ
れてぃなかった。On the other hand, switching-type stabilized power supplies have the advantage of high efficiency, but they have large ripples and the effects of switching affect other circuits, resulting in increased noise, especially in nuclear magnetic resonance imaging systems that handle minute signals. Due to this problem, it was rarely put into practical use except for some power supplies.
本発明の目的は、前記従来の電源の後者の方式のスイッ
チング方式の電源を、静磁場発生用電源など核磁気共鳴
イメージング装置用の主電源として用いても実用−に問
題の無いノイズレベルに抑えるよう改良した電源装置を
提供することにある。It is an object of the present invention to suppress the noise level of the latter switching type power supply of the above-mentioned conventional power supply to a level that does not pose a practical problem even when used as a main power supply for a nuclear magnetic resonance imaging apparatus such as a power supply for generating a static magnetic field. An object of the present invention is to provide an improved power supply device.
上記目的はスイッチング方式の定電圧（流）電源に用い
るスイッチング周波数を所望の核磁気共鳴信号の帯域外
にシフトさせるよう構成することにより達成される。す
なわち、核磁気共鳴信号の周波数をｆｏとしてその帯域
をΔｆとすると、スイッチング電源用のスイッチング周
波数ｆ ｓｗは、ｆ、ｗ＞ΔＪを満足させる。さらにｆ
ｓｗの高調波が、核磁気共鳴信号や中間周波の各波に影
響しないよう、スイッチング周波数ｆ ｓｗを制御する
必要がある。一般に核磁気共鳴信号の検出回路には、ヘ
テロダイン検波の方式を採用しており、局部発振器や、
中間周波数など、種々の周波数が存在するが、これらの
周波数にスイッチング周波数ｆ ｓｗのｎ倍の高調波が
影響しないようにｆ ｓｗを制御する。このことにより
、スイッチング周波数ｆ Ｓｗとｎ・ｊ’ ＳＷによる
影響が所望の帯域外にくるようにして。The above object is achieved by configuring the switching frequency of the constant voltage (current) power supply to be shifted out of the band of the desired nuclear magnetic resonance signal. That is, if the frequency of the nuclear magnetic resonance signal is fo and its band is Δf, the switching frequency f sw for the switching power supply satisfies f,w>ΔJ. Further f
It is necessary to control the switching frequency f sw so that the harmonics of sw do not affect the nuclear magnetic resonance signal or the intermediate frequency waves. Generally, the nuclear magnetic resonance signal detection circuit uses a heterodyne detection method, which uses a local oscillator,
Although there are various frequencies such as intermediate frequencies, fsw is controlled so that these frequencies are not affected by harmonics that are n times higher than the switching frequency fsw. This causes the effects of the switching frequencies f Sw and n·j' SW to be outside the desired band.
目的の視野内にこの影響をなくさせることが可能となる
。It becomes possible to eliminate this influence within the target field of view.
以下、本発明の一実施例を第１図により説明する。１は
被検者、２はベッド、３は静磁場発生用のコイルである
。静磁場発生コイル３は静磁場発生用定電流回路により
供給される電流により、静磁場Ｈｏを体軸方向に均一に
発生する。ここで傾斜コイル４を用いて傾斜磁場を体軸
方向にかけながら、かつ照射コイル５によりＲＦ波を照
射することにより、体軸のある特定断面に核磁気共鳴現
象を起こさせる。この時の核磁気共鳴現象の信号を検出
コイル６を用いて検出する。この時の核磁気共鳴の周波
数ｉｏは静磁場の強さをＨｏ とすると、良く知られた
ω＝２πｆｏ ＝γＨＯ−−（１）
の関係がある。γは磁気回転比であり、機種により決ま
る定数であり、プロトンの時、この値は、ｒｑ）
ｙ＝４２．５７ ＭＨｚ／１ｅｓｎａである。従って
Ｈａとして、０ 、２ ｔｅｓ Ｑ ａとすると核磁気
共鳴の中心周波数ｆｏは８．５ＭＨｚである。ここでイ
メージングの視野と周波数帯域との関係は、傾斜磁場の
強さの関数となる。この傾斜磁場の強さを０ 、２ Ｇ
ａｕｓｓ／ ｃｍとし、視野を３０（１）とすれば、式
（１）の関係より要求される帯域は２５．５ＫＨｚであ
る。すなわち、前述の系ではＮＭＲ信号としては中心周
波数ｆ ｏ ＝ ８ 、５ Ｍ Ｈｚでその帯域幅は、
２５．５ＫＨｚとなる。An embodiment of the present invention will be described below with reference to FIG. 1 is a subject, 2 is a bed, and 3 is a coil for generating a static magnetic field. The static magnetic field generating coil 3 generates a static magnetic field Ho uniformly in the body axis direction using a current supplied by a constant current circuit for static magnetic field generation. Here, by applying a gradient magnetic field in the body axis direction using the gradient coil 4 and irradiating RF waves with the irradiation coil 5, a nuclear magnetic resonance phenomenon is caused in a specific cross section of the body axis. The signal of the nuclear magnetic resonance phenomenon at this time is detected using the detection coil 6. The frequency io of nuclear magnetic resonance at this time has the well-known relationship ω=2πfo=γHO−(1), where Ho is the strength of the static magnetic field. γ is the gyromagnetic ratio, which is a constant determined by the model; in the case of protons, this value is rq) y=42.57 MHz/1 esna. Therefore, if Ha is 0 and 2 tes Q a, the center frequency fo of nuclear magnetic resonance is 8.5 MHz. Here, the relationship between the imaging field of view and the frequency band is a function of the strength of the gradient magnetic field. The strength of this gradient magnetic field is 0, 2 G
auss/cm and the field of view is 30(1), the required band is 25.5 KHz from the relationship in equation (1). That is, in the above system, the NMR signal has a center frequency f o = 8, 5 MHz, and a bandwidth of
It becomes 25.5KHz.
第１図の点線で囲まれたＡは静磁場用の安定化電源のブ
ロックである。整流、平滑回路７により得られた電圧は
パワードライバ８に印加される。A, surrounded by a dotted line in FIG. 1, is a block of a stabilized power supply for the static magnetic field. The voltage obtained by the rectifying and smoothing circuit 7 is applied to the power driver 8.
この出力はフィルタ９を通り、静磁場用コイル３に印加
される。一方この電流は誤差検出器１０により基準信号
と比較され、パルス幅変調器１１のパルス幅を制御する
。このパルス幅変調器への入力信号は可変周波発振器１
２からの出力を得ている。このような負帰還ループによ
り、常に基準信号と比例した電流を高精度に安定に静磁
場コイルに供給することができる。This output passes through a filter 9 and is applied to the static magnetic field coil 3. This current, on the other hand, is compared with a reference signal by an error detector 10 to control the pulse width of the pulse width modulator 11. The input signal to this pulse width modulator is the variable frequency oscillator 1
I am getting the output from 2. With such a negative feedback loop, a current proportional to the reference signal can always be stably supplied to the static magnetic field coil with high precision.
次に点線で囲まれたＢのブロックはＮＭＲ信号の検出系
である。核磁気共鳴信号ｆｏは受信コイル６により、検
知され、増幅器１３により増幅される。この信号は第１
のミキサー１４ａに印加され、図示されていない局部発
振器からの信号ｆＬｉとミキシングされてｆＨ１＝ｆｏ
＋ｆｂ１の周波数に変換される。このｆＭｌは第２のミ
キサ１４ｂに接続されて、第２の局部発振器からの出力
ｆ夏、２とミキシングされてｆＭ２＝ｆＭ１−ｆＬ２の
周波数の信号を得る。この１Ｍ２は最終段のミキサ１４
ｃによりｆし３とミキシングされて、Δｆ＝ｆＭ２ ｆ
ｐｓの周波数の信号となる。この信号はＡ／Ｄ変換器１
５でＡ／Ｄ変換されたのち像再構成部に送られ、像再生
用生データとして利用される。このようにＮＭＲ信号は
微少信号のため、妨害波の干渉を受けにくいように何段
かの周波数変換をうけて最終出力を得る構成をとる。以
上のような構成において、静磁場用の電源がスイッチン
グ方式のため、フィルタ９が高性能の特性をもつもので
も、リップルを極度に減少させることは困難である。こ
れが回路のアース系の不完全、実装方法等により、わず
かにＡ／Ｄ変換器１５のところに誘起される。Next, block B surrounded by a dotted line is an NMR signal detection system. The nuclear magnetic resonance signal fo is detected by the receiving coil 6 and amplified by the amplifier 13. This signal is the first
is applied to the mixer 14a and mixed with a signal fLi from a local oscillator (not shown) to form
It is converted to a frequency of +fb1. This fMl is connected to the second mixer 14b and mixed with the output fX,2 from the second local oscillator to obtain a signal with a frequency of fM2=fM1-fL2. This 1M2 is the final stage mixer 14
Mixed with f and 3 by c, Δf=fM2 f
It becomes a signal with a frequency of ps. This signal is sent to A/D converter 1
After being A/D converted in step 5, the data is sent to the image reconstruction section and used as raw data for image reproduction. In this way, since the NMR signal is a very small signal, it is configured to undergo several stages of frequency conversion so as to be less susceptible to interference from interference waves, and then to obtain the final output. In the above configuration, since the power source for the static magnetic field is of a switching type, it is difficult to reduce ripples to an extreme extent even if the filter 9 has high performance characteristics. This is slightly induced at the A/D converter 15 due to imperfections in the circuit's grounding system, mounting method, etc.
しかしながら、この不要周波数が所望の帯域Δｆより大
きい時には、この雑音は、結果的に視野の外に追い出す
ことができる。これを満足させるために、スイッチング
周波数ｆ ｓｗはｆｓ、＞Δｆの条件を満たすように可
変発振器１２の発振周波数ｆ ｓｗを制御する。また、
スイッチング信号は一般的に矩形波を用い、その幅を制
御するため、非常に多くの高調波を含んでおり、これが
、局部発振。However, when this unnecessary frequency is larger than the desired band Δf, this noise can eventually be pushed out of the field of view. In order to satisfy this, the oscillation frequency f sw of the variable oscillator 12 is controlled so that the switching frequency f sw satisfies the condition of fs,>Δf. Also,
The switching signal generally uses a rectangular wave, and because its width is controlled, it contains a large number of harmonics, which is called local oscillation.
中間周波に影響を与える。このために、ｎ’ｆｓＷがｆ
Ｌｘ＋ ｆシ２ツＪＬ３．ｆＭ１ツＪＭ２の各々の帯域
Δｆ内に存在しない様に可変発振器１２の発振周波数ｆ
ｓｗを制御する。然るにこのような手段により、スイ
ッチング方式の電源を用いても、そのスイッチング周波
数を前記条件にあるように制御する、或いは、出力信号
を観測しながら、ｆ ｓｗの周波数を制御することによ
り、その雑音としての影響が軽減でき、核磁気共鳴イメ
ージング装置用電源として実用できるのである。また、
静磁場の強さを変化させる時には、その中心周波数も比
例して変化するため、前記条件になるよう可変発振器１
２の周波数を変える必要がある。Affects intermediate frequencies. For this reason, n'fsW is f
Lx+ f shi2tsu JL3. The oscillation frequency f of the variable oscillator 12 is set so that it does not exist within each band Δf of fM1 and JM2.
Control sw. However, with such means, even if a switching power supply is used, the noise can be reduced by controlling its switching frequency to meet the above conditions, or by controlling the frequency of fsw while observing the output signal. This makes it possible to reduce the effects of this, and it can be put to practical use as a power source for nuclear magnetic resonance imaging equipment. Also,
When changing the strength of the static magnetic field, the center frequency also changes proportionally, so the variable oscillator 1 is adjusted to meet the above conditions.
It is necessary to change the frequency of 2.
なお、以上の実施例は静磁場用電源について説明したが
、傾斜磁場、照射磁場等の全ての電源についても適用で
きる。Although the above embodiments have been described with respect to a static magnetic field power source, the present invention can also be applied to all power sources such as a gradient magnetic field and an irradiation magnetic field.
以上説明した如く、本発明によれば、効率の良いスイッ
チング方式の核磁気共鳴イメージング装置用電源を実現
せしめ、かつ従来必要とされていた水冷による水冷手段
を不要とする。また装置の構成を大幅に簡略化でき、ノ
」）形、軽量化が計れ、安価に製作可能となる。更に、
保守、運転経費も節約できる効果があり、工業上大いに
有益である。As described above, according to the present invention, an efficient switching type power source for a nuclear magnetic resonance imaging apparatus is realized, and water cooling means conventionally required is not required. In addition, the configuration of the device can be greatly simplified, its shape and weight can be reduced, and it can be manufactured at low cost. Furthermore,
This has the effect of saving maintenance and operating costs, and is of great industrial benefit.
第１図は、本発明の一実施例を示す構成図、第２図は、
従来方式の直列制御方式による定電圧（流）源の構成図
である。
３・・・静磁場用コイル、８・・・パワードライバ、９
・・・フィルタ、１０・・・誤差検出器、１１・・・パ
ルス幅変調器、１２・・・可変発振器、１４・・・ミキ
サ、１５・・・Ａ／Ｄ変換器。FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 2 is a configuration diagram of a constant voltage (current) source using a conventional series control method. 3... Static magnetic field coil, 8... Power driver, 9
... Filter, 10 ... Error detector, 11 ... Pulse width modulator, 12 ... Variable oscillator, 14 ... Mixer, 15 ... A/D converter.
Claims (1)
めの核磁気共鳴イメージング装置用電源装置において、
前記電源装置がスイッチング手段を有するスイッチング
方式の電源によつて構成されたものであり、かつ前記ス
イッチング手段のスイッチング周波数を、所望の視野の
帯域外にシフトさせる手段を備えていることを特徴とす
る核磁気共鳴イメージング備置用電源装置。 ２、前記シフト手段が前記スイッチング周波数の高調波
成分が、核磁気共鳴信号検出回路の各種局部発振器や中
間周波数信号と一致しないように制御する手段を有し、
検出信号のノイズが最小となるように前記スイッチング
手段のスイッチング周波数を制御することを特徴とする
特許請求範囲第１項記載の核磁気共鳴イメージング装置
用電源装置。[Claims] 1. In a power supply device for a nuclear magnetic resonance imaging apparatus for generating magnetic fields of a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field,
The power supply device is configured by a switching type power supply having switching means, and is characterized in that it is equipped with means for shifting the switching frequency of the switching means out of the band of a desired visual field. Power supply for nuclear magnetic resonance imaging equipment. 2. The shifting means has means for controlling harmonic components of the switching frequency so that they do not coincide with various local oscillators or intermediate frequency signals of the nuclear magnetic resonance signal detection circuit,
2. The power supply device for a nuclear magnetic resonance imaging apparatus according to claim 1, wherein the switching frequency of the switching means is controlled so that noise in the detection signal is minimized.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62047577A JPS63214249A (en) | 1987-03-04 | 1987-03-04 | Power source apparatus for nuclear magnetic resonance imaging apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62047577A JPS63214249A (en) | 1987-03-04 | 1987-03-04 | Power source apparatus for nuclear magnetic resonance imaging apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS63214249A true JPS63214249A (en) | 1988-09-06 |
| JPH0377739B2 JPH0377739B2 (en) | 1991-12-11 |
Family
ID=12779100
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62047577A Granted JPS63214249A (en) | 1987-03-04 | 1987-03-04 | Power source apparatus for nuclear magnetic resonance imaging apparatus |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS63214249A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013240592A (en) * | 2012-05-14 | 2013-12-05 | General Electric Co <Ge> | System and method for noise control in medical imaging system |
| JP2015039428A (en) * | 2013-08-20 | 2015-03-02 | 株式会社東芝 | Magnetic resonance imaging device |
| JP2015517864A (en) * | 2012-05-30 | 2015-06-25 | コーニンクレッカ フィリップス エヌ ヴェ | Switching power supply unit controlled by switching frequency to supply power to magnetic resonance gradient coil |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60207045A (en) * | 1984-03-30 | 1985-10-18 | Shimadzu Corp | Nmr tomography apparatus |
| JPS61285518A (en) * | 1985-06-12 | 1986-12-16 | Toshiba Corp | High frequency power unit for magnetic resonance imaging device |
-
1987
- 1987-03-04 JP JP62047577A patent/JPS63214249A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60207045A (en) * | 1984-03-30 | 1985-10-18 | Shimadzu Corp | Nmr tomography apparatus |
| JPS61285518A (en) * | 1985-06-12 | 1986-12-16 | Toshiba Corp | High frequency power unit for magnetic resonance imaging device |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013240592A (en) * | 2012-05-14 | 2013-12-05 | General Electric Co <Ge> | System and method for noise control in medical imaging system |
| JP2015517864A (en) * | 2012-05-30 | 2015-06-25 | コーニンクレッカ フィリップス エヌ ヴェ | Switching power supply unit controlled by switching frequency to supply power to magnetic resonance gradient coil |
| JP2015039428A (en) * | 2013-08-20 | 2015-03-02 | 株式会社東芝 | Magnetic resonance imaging device |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0377739B2 (en) | 1991-12-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |