摘要:
The invention provides a magnetic resonance imaging (MRI) device (21), comprising a diagnostic space (25), a main magnetic system (22) for generating a main magnetic field in said diagnostic space, a gradient magnetic coil system (23) comprising a gradient coil for generating at least one gradient of the main magnetic field, and noise reducing means (29, 32) for reducing noise that is generated as a result of vibrations of the gradient coil. The noise reducing means comprise a sound-absorbing panel (29) disposed between the gradient coil and the diagnostic space. The sound-absorbing panel (29) comprises channels having an open end and a closed end.
摘要:
The invention relates to a magnetic resonance imaging (MRI) system (1) comprising an examination volume (11), a main magnet system (17) for generating a magnetic field (B0) in the examination volume, and a gradient magnet system (25) for generating altering gradients of the magnetic field in the examination volume. The gradient magnet system is accommodated in a housing (31) having a main wall (33) facing the examination volume and a substantially conical wall (35) facing away from the examination volume. The main wall and the conical wall enclose a substantially angular tip portion (47) of the housing. In order to limit the level of the acoustic vibrations in and around the MRI system (1) caused by mechanical vibrations of the angular tip portion (47), the MRI system comprises a plurality of acoustic resonators (55) which each comprise an elongate resonance volume (57) with an open end (59) and a closed end (61) and a length (L) between the open end and the closed end. The open ends of the resonators are arranged near the angular tip portion, and the length of the resonators is substantially equal to 0.25 k*(, wherein k=1, 3, 5, 7, . . . , and wherein ( is the wavelength of an acoustic wave caused by mechanical vibrations of the angular tip portion. The resonators have the acoustic property of neutralizing acoustic waves having said wavelength (. Preferably, the length of the resonators is tuned to at least one of the wavelengths corresponding to the mechanical resonance frequencies of the vibrating angular tip portion, as the acoustic waves originating from the vibrations at these resonance frequencies constitute a main portion of the overall acoustic level of the MRI system.
摘要:
The present invention relates to a magnetic resonance imaging (MRI) device. The basic components of an MRI device are the main magnet system (2), the gradient system (3), the RF system and the signal processing system. According to the present invention, the magnetic resonance imaging (MRI) device has an eddy current shield system, wherein the eddy current shield system comprises at least one perforated eddy current screen (13, 14), and wherein the or each perforated eddy current screen (13, 14) is assigned to the main magnet system (2).