Magnetic resonance imaging method with reduced acoustic noise

• US 7,061,240 B2
• Filed: 11/20/2002
• Issued: 06/13/2006
• Est. Priority Date: 11/26/2001
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Harvey, Paul Royston, Ham, Cornelis Leonardus Gerardus
• Primary Examiner(s): Gutierrez, Diego
• Assistant Examiner(s): Vargas, Dixomara
• Application Number:
  US10/496,489
• Publication Number:
  US 20040245987A1
• Time in Patent Office: 1,301 Days
• Field of Search: 324/307, 324/309, 600/410
• US Class Current: 324/309
• CPC Class Codes: G01R 33/3415 comprising arrays of sub-coils , i.e. phased-array coils with flexible receiver channels
• CPC Class Codes: G01R 33/3854 means for active and/or passive vibration damping or acoustical noise suppression in gradient magnet coil systems
• CPC Class Codes: G01R 33/5611 Parallel magnetic resonance imaging, e.g. sensitivity encoding [SENSE], simultaneous acquisition of spatial harmonics [SMASH], unaliasing by Fourier encoding of the overlaps using the temporal dimension [UNFOLD], k-t-broad-use linear acquisition speed-up technique [k-t-BLAST], k-t-SENSE structural details of arrays of sub-coils G01R33/3415

Abstract

A magnetic resonance imaging method comprises application of a pulse sequence which includes one or more pulses. The pulse sequence having an intrinsic scan time based on a full sampling rate in k-space for a predetermined full ‘field-of-view’ and a reference temporal pulse shape of the magnetic gradient pulses. A series of magnetic resonance signals is acquired by means of a receiver antennae system having a spatial sensitivity profile. Undersampled signal acquisition is applied to acquire undersampled magnetic resonance signals at a predetermined reduced sampling rate in k-space, the sampling rate being reduced by a reduction factor relative the full sampling rate. The pulse sequence being is during an actual signal scan time is applied. The actual signal scan time being larger than the intrinsic signal scan time times the reduction factor. The undersampling allows a smaller acquisition rate of the magnetic resonance signals and smaller slew rates and amplitudes of the magnetic gradient pulses and lower peak RF-fields of the refocusing pulses. Hence, lower acoustic noise and lower specific absorption rate are achieved.

Claims

1. A magnetic resonance imaging method comprising

application of a pulse sequence which includes one or more pulses

the pulse sequence having an intrinsic scan time based on a full sampling rate in k-space for a predetermined full ‘

field-of-view’ and

a reference temporal pulse shape of the magnetic gradient pulses

acquisition of a series of magnetic resonance signals by means of a receiver antennae system having a spatial sensitivity profile, wherein

undersampled signal acquisition is applied to acquire undersampled magnetic resonance signals at a predetermined reduced sampling rate in k-space, the sampling rate being reduced by a reduction factor relative the full sampling rate

the pulse sequence being applied during an actual signal scan time, the actual signal scan time being larger than the intrinsic signal scan time times the reduction factor,

wherein the pulse sequence includes magnetic gradient pulses and the magnetic gradient pulses are applied with a slew rate that is less than the slew rate involved with the reference pulse shape.

2. A magnetic resonance imaging method as claimed in claim 1, wherein the actual signal scan time is substantially equal to the intrinsic signal scan time.

3. A magnetic resonance imaging method as claimed in claim 1, wherein the pulses are applied with a pulse shape having temporal variations that are more slowly than the temporal variations involved in the reference temporal pulse shape.

4. A magnetic resonance imaging method as claimed in claim 1, wherein the pulse sequence includes radiofrequent (RF) pulses and the radiofrequent (RF) pulses are applied with an RF-magnetic field component (B₁) that is less than the RF-magnetic field component (B₁) involved with the reference pulse shape.

5. A magnetic resonance imaging method as claimed in claim 1, wherein the pulse shape of the pulses is adjustable so as to adapt the actual signal scan time of the pulse sequence in the range between the intrinsic signal scan time times the reduction factor and the intrinsic signal scan time.