Magnetic resonance imaging apparatus

• US 6,567,685 B2
• Filed: 01/19/2001
• Issued: 05/20/2003
• Est. Priority Date: 01/21/2000
• Status: Expired due to Term

• Current Assignee: Toshiba Medical Systems Corporation (Canon Inc.)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Machida, Yoshio, Suzuki, Takeshiro, Katsunuma, Ayumi, Kanazawa, Hitoshi, Yamanaka, Masaaki, Yui, Masao, Takamori, Hiromitsu, Nozaki, Seiji, Hanawa, Masatoshi
• Primary Examiner(s): Walberg, Teresa
• Assistant Examiner(s): ROBINSON, DANIEL LEON
• Application Number:
  US09/764,215
• Publication Number:
  US 20010010464A1
• Time in Patent Office: 851 Days
• Field of Search: 600/407, 600/410, 600/411, 600/412, 600/423, 324/307, 436/173
• US Class Current: 600/410
• CPC Class Codes: G01R 33/3854 means for active and/or passive vibration damping or acoustical noise suppression in gradient magnet coil systems

Abstract

A magnetic resonance imaging apparatus generates an MR signal from an object by applying a gradient field pulse generated by a gradient field coil and a high-frequency magnetic field pulse generated by a high-frequency coil to the object in a static field, and reconstructs an image on the basis of the MR signal. The gradient field coil is housed in a sealed vessel. The internal air in the sealed vessel is exhausted by the pump to prevent noise. By controlling the operation of the pump using a control circuit, noise in imaging operation can be reduced more effectively.

Claims

1. A magnetic resonance imaging apparatus which generates an MR signal from an object by applying a gradient field pulse generated by a gradient field coil and a high-frequency magnetic field pulse generated by a high-frequency coil to the object in a measurement space in which a static field is formed, and reconstructs an image on the basis of the MR signal, comprising:

a sealed vessel housing the gradient field coil;

a pump for exhausting internal air from said sealed vessel; and

a noise gage for detecting a noise level in the measurement space, wherein said noise gage is used for speech communication.

2. A magnetic resonance imaging apparatus which generates an MR signal from an object by applying a gradient field pulse generated by a gradient field coil and a high-frequency magnetic field pulse generated by a high-frequency coil to the object in a static field, and reconstructs an image on the basis of the MR signal, comprising:

a sealed vessel housing the gradient field coil;

a pump for exhausting internal air from said sealed vessel;

a control circuit for controlling operation of said pump;

a vibration meter for detecting vibrations due to driving of said gradient field coil; and

a circuit for stopping driving said gradient field coil when a vibration level detected by said vibration meter is not less than a predetermined value.

3. A magnetic resonance imaging apparatus which generates an MR signal from an object by applying a gradient field pulse generated by a gradient field coil and a high-frequency magnetic field pulse generated by a high-frequency coil to the object in a static field, and reconstructs an image on the basis of the MR signal, comprising:

a sealed vessel housing the gradient field coil;

a pump for exhausting internal air from said sealed vessel;

a gradient field power supply for supplying a current to said gradient field coil; and

a control circuit for controlling said gradient field power supply to change a gradient of a leading edge of the current or a rise time of the current, wherein said control circuit determines the gradient of the leading edge or the rise time on the basis of a designated allowable noise level.

4. A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, and a sealed vessel housing the gradient field coil, comprising:

a pump for exhausting internal air from said sealed vessel;

a vacuum meter for detecting a degree of vacuum in said sealed vessel; and

a correcting section for correcting data acquired through the high-frequency coil or an image generated from the data on the basis of the detected degree of vacuum.

5. An apparatus according to claim 4, wherein said correcting section estimates a resonance frequency shift on the basis of the detected degree of vacuum, performs phase correction and/or frequency shift for a plurality of spectra generated from data acquired through the high-frequency coil, and adds the spectra.

6. An apparatus according to claim 4, wherein said correcting section estimates a resonance frequency shift on the basis of the detected degree of vacuum, shifts each of a plurality of images generated from data acquired through the high-frequency coil in a phase encoding direction, and adds or subtracts the plurality of images.

7. An apparatus according to claim 4, wherein said correcting section estimates a resonance frequency shift on the basis of the detected degree of vacuum, and phase-shifts each of a plurality of phase images generated from data acquired through the high-frequency coil.

8. A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, and a sealed vessel housing the gradient field coil, comprising:

a pump for exhausting internal air from said sealed vessel;

means for driving the gradient field coil and high-frequency coil to generate an MR signal from an object in accordance with an arbitrarily set imaging condition and acquire the MR signal; and

a pump control section for changing a driving pattern of said pump in accordance with the imaging condition.

9. A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, and a sealed vessel housing the gradient field coil, comprising:

a pump for exhausting internal air from said sealed vessel;

a control section for driving the gradient field coil and high-frequency coil in accordance with a pulse sequence selected from a plurality of types of pulse sequences in order to generate an MR signal from an object and acquire the MR signal; and

a pump control section for changing an ON time of said pump in accordance with the selected pulse sequence.

10. A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, and a sealed vessel housing the gradient field coil, comprising:

a pump for exhausting internal air from said sealed vessel;

a control section for driving the gradient field coil and high-frequency coil in accordance with a pulse sequence selected from a plurality of types of pulse sequences in order to generate an MR signal from an object and acquire the MR signal; and

a pump control section for driving said pump when the selected pulse sequence is a first pulse sequence, and stopping said pump when the selected pulse sequence is a second pulse sequence.

11. An apparatus according to claim 10, further comprising a vacuum gage for detecting a degree of vacuum in the sealed vessel.

12. An apparatus according to claim 11, further comprising a processing section for correcting a phase and/or frequency of data from said high-frequency coil in accordance with the detected degree of vacuum.

13. An apparatus according to claim 10, further comprising a control section for stopping the gradient field coil, the high-frequency coil, and data acquisition when the detected degree of vacuum does not satisfy a predetermined condition.

14. A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, and a sealed vessel housing the gradient field coil, comprising:

a shim coil for correcting a strength distribution of the static field;

a vacuum gage for detecting a degree of vacuum in the sealed vessel; and

means for changing a current supplied to said shim coil, on the basis of the detected degree of vacuum.

15. A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, a sealed vessel housing the gradient field coil, and a shim coil for correcting magnetic field inhomogeneity, comprising:

a sensor for detecting a degree of vacuum in the sealed vessel; and

a control section for changing a driving condition for the shim coil on the basis of the detected degree of vacuum.

16. A magnetic resonance imaging apparatus which generates an MR signal from an object by applying a gradient field pulse generated by a gradient field coil and a high-frequency magnetic field pulse generated by a high-frequency coil to the object in a static field, and reconstructs an image on the basis of the MR signal, comprising:

a sealed vessel housing the gradient field coil;

a pump for exhausting internal air from said sealed vessel;

a control circuit for controlling operation of said pump;

a pressure sensor for detecting an internal pressure in said sealed vessel; and

a circuit for stopping driving said gradient field coil when the internal pressure in said sealed vessel which is detected by said pressure sensor is not less than a predetermined value.