摘要:
An MRI system (1) comprises a housing (10) defining an examination space (2) for receiving a body for examination, a patient table (3) being displaceable into and out of the examination space (2), a magnetic field generating system (4) for generating a magnetic field in the examination space (2), and an electromagnetic resonance receive system (5) which comprises a set of dedicated receive coils (20). According to the invention at least one dedicated receive coil (20) is fixedly attached to the housing (10).
摘要:
The invention relates to a magnetic resonance imaging (MRI) apparatus comprising an electrical coil system (17) for transmitting and receiving a radio-frequent (RF) magnetic field from an examination volume (3) of the MRI apparatus. The electrical coil system (17) comprises at least one surface coil (35) which substantially extends in a plane. The surface coil serves for transmitting and/or receiving an RF magnetic field which is substantially oriented perpendicular to the plane of the surface coil (35). The surface coil (35) has a main coil axis (37). When the MRI apparatus is in use the main coil axis (37) extends substantially parallel to a main magnetic field in the examination volume (3) of the MRI apparatus. On both sides of the main coil axis (37) the surface coil (35) comprises an electrically conducting element (39) which extends substantially parallel to the main coil axis (37). To provide a surface coil (35) which transmits more homogeneous RF magnetic fields and/or has a more homogeneous sensitivity for received RF magnetic fields than known surface coils, at least one of the electrically conducting elements (39) of the surface coil (35) comprises at least two electrical conductors (41). With respect to their distance to the main coil axis (37) these electrical conductors (41) are positioned at a relatively short distance from each other. In the plane of the surface coil (35) the electrical conductors (41) substantially extend parallel to the main coil axis (37) of the surface coil (35).
摘要:
A combiner/splitter device (100) comprises two transmission lines (23, 24), wound to form a helical coil (55), this helical coil being bent to a toroidal shape. Furthermore, a capacitor (51) is provided, connected in parallel with the two outer conductors (25, 26) of the two transmission lines (23, 24). The combination of the wound transmission lines and said capacitor forms a parallel resonator (56). The combiner/splitter device is suitable for use in a magnetic resonance imaging (MRI) system to combine the output signals of a receiver coil system and/or to split the input signal of a transmission coil system used in the MRI system.
摘要:
The invention relates to a treatment room (7) suitable for recording images of a human or animal body on the basis of a magnetic resonance (MR) imaging technique, the walls (7a), the ceiling (7b) and the floor (7c) of the treatment room forming an electromagnetic shield for a magnetic resonance (MR) imaging system (1) arranged in the treatment room, which MR imaging system comprises at least a target area (5) in which a human or animal body can be placed, a housing (2, 3, 4) comprising at least one main magnetic unit and at least one gradient magnetic unit for generating one or more magnetic fields in the target area (5), and at least one radio-frequency (RF) pulse unit (6) for generating an electromagnetic RF pulse in the target area (5). The invention further relates to a magnetic resonance imaging system comprising a target area in which a human or animal body can be placed, a housing comprising at least one main magnetic unit and at least one gradient magnetic unit for generating one or more magnetic fields in the target area, and at least one radio-frequency (RF) pulse unit for generating an electromagnetic RF pulse in the target area. In accordance with the invention, means (10, 11, 12, 13, 14, 15, 16, 17) are present which, in operation, counteract the electromagnetic effects (8) of the RF pulse in the treatment room (7) outside the target area (5).
摘要:
The invention relates to a radio-frequent (RF) coil system (17, 17′) for use in a magnetic resonance imaging (MRI) system. The RF coil system comprises at least one main coil (35) for transmitting an RF magnetic field (B1) into and/or receiving an RF magnetic field (B1′) from an examination volume (3) of the MRI system. The main coil has a main coil axis (37), which is or is to be oriented parallel to a main magnetic field (B0) in the examination volume, and at least one electrical conductor (39, 41) which extends mainly parallel to the main coil axis. According to the invention, the RF coil system comprises at least two electrical auxiliary coils (51, 53, 55, 57) which are assigned to said conductor of the main coil. The auxiliary coils are arranged on opposite sides of said conductor of the main coil. Each auxiliary coil has a coil axis (59, 61, 63, 65) which extends substantially parallel to the main coil axis at a distance from the conductor of the main coil to which the respective auxiliary coil is assigned, said distance being small relative to a main dimension (L) of the main coil. The auxiliary coils constitute passive electrical coils in which electrical currents are generated under the influence of an RF magnetic field (B11, B11′) present at the location of the auxiliary coils. The RF magnetic field (B12, B34) generated by the auxiliary coils as a result of said currents in the auxiliary coils suppresses said RF magnetic field present at the location of the auxiliary coils. Thus, the auxiliary coils provide a sensitivity reducing effect of the RF coil system in local regions (47, 49) which are at relatively small distances from the conductor of the main coil. For regions at a distance from the conductor of the main coil comparable to the main dimension of the main coil, said sensitivity reducing effect is negligible.
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 method for determination of spatial sensitivity profiles of RF transmit and/or receive coils (7, 8, 9) in an examination volume (17) of a magnetic resonance (MR) imaging device (1). In accordance with the method of the invention, nuclear magnetization is excited within the examination volume (17) by a sequence of RF pulses and switched magnetic field gradients, wherein the sequence comprises RF pulses with at least two different excitation flip angles. MR signals are acquired and processed so as to form at least two MR images, each corresponding to one of these flip angles. The spatial sensitivity profiles are then computed in the positions of the pixels or voxels of the MR images based upon the dependence of the pixel or voxel values on the respective flip angles. Alternatively, a plurality of instances of a sequence of RF pulses and switched magnetic field gradients is applied and MR signals are acquired, wherein a different combination of transmit and receive coils (7, 8, 9) is used for each instance of the sequence. The spatial sensitivity profiles are then computed in the positions of the pixels or voxels of the MR images formed from the acquired MR signals by taking the logarithm of the pixel or voxel values and by solving a linear system of equations for each pixel or voxel.