Abstract: The present invention includes a technique for use with magnetic resonance imaging that includes the application of a non-linear, higher-order gradient field in the presence of a moving object to be scanned. MR data is acquired as the object moves through the non-linear gradient field. Resulting images are contiguous and do not require the patching together of data in either k-space or image space and result in an image with expanded FOV in a longitudinal direction of the moving object.

Abstract: Coil sensitivity of a receive coil to a gradient null location is measured and, from the measurements, a coil calibration value is determined and used to modify the MR data acquired with that receive coil to reduce the adverse effects of gradient nulling on MR images. Coil sensitivity values are determined for each coil of a coil array and the data for each coil is respectively weighted. An image that is substantially free of gradient null artifacts or ghosting is then reconstructed from the weighted data.

Abstract: A system and method are provided for designing RF pulses for multi-channel and/or multi-dimensional spatially-selective applications using a linear approximation. Embodiments of the system and method may use a generalized linear-class large tip angle approximation to design RF pulses for multi-channel and parallel transmission. Further, some of these approximations allow for the design of arbitrarily large flip angles, irregularly-shaped flip angle profiles, or arbitrary initial magnetization values. Embodiments of the system and method may also provide for the design of k-space trajectories which aid in maintaining assumptions of the various linear class approximations.

Abstract: A system and method are provided for adjusting RF pulses and gradient waveforms to reduce B1 field magnitude in MR imaging sequences. When an RF pulse is presented which has a high amplitude segment that would exceed a maximum B1 magnitude, the system and method provided herein can apply a variable slew rate design technique. A slew rate of at least one gradient waveform can be varied to reduce a B1 field magnitude during transmission of the high amplitude segment of the RF pulse. By controlling the slew rate of gradient waveforms for non-Cartesian k-space trajectories according to a calculated maximum allowable slew rate function, embodiments of the system and method can, in effect, reduce gradient amplitude.

Abstract: A system and method are provided for designing RF pulses which have improved magnetization profiles. By utilizing an optimal control approach as an alternative to, or in combination with, non-iterative approximations, RF pulses generated by the system and method described herein will exhibit less deviation from that of “ideal” Bloch solutions. Consequently, the magnetization profiles produced by the RF pulses generated by the system and method described herein will be closer to the desired profiles. In addition, limitations of non-iterative approximations, such as maximum tip angle limits and linearity constraints, can be avoided.

Abstract: Coil sensitivity of a receive coil to a gradient null location is measured and, from the measurements, a coil calibration value is determined and used to modify the MR data acquired with that receive coil to reduce the adverse effects of gradient nulling on MR images. Coil sensitivity values are determined for each coil of a coil array and the data for each coil is respectively weighted. An image that is substantially free of gradient null artifacts or ghosting is then reconstructed from the weighted data.

Abstract: A sensitivity encoding method (SENSE) is used to acquire an MR image having a reduced field of view. The number of aliased replicates caused by surrounding object boundaries is calculated for each image pixel location to obtain optimal aliasing artifact suppression without reducing image SNR.

Abstract: A system and method for MR imaging with coil sensitivity or calibration data acquisition for reducing wrapping or aliasing artifacts is disclosed. Low resolution MR data representative of coil sensitivity of a coil arrangement within an FOV is acquired prior to application of an imaging data acquisition scan and is used to reduce wrapping or aliasing artifacts in a reconstructed image.

Abstract: The present invention includes a technique for use with magnetic resonance imaging that includes the application of a non-linear, higher-order gradient field in the presence of a moving object to be scanned. MR data is acquired as the object moves through the non-linear gradient field. Resulting images are contiguous and do not require the patching together of data in either k-space or image space and result in an image with expanded FOV in a longitudinal direction of the moving object.

Abstract: A method and apparatus are disclosed for deriving an enhanced sensitivity matrix for describing coil sensitivity in a magnetic resonance imaging system. The enhanced sensitivity matrix provides sensitivity information for pixels near the edge of the imaged object such that pixels near the edge for which there was no sensitivity information are associated with a derived sensitivity. Likewise pixels near the edge for which there is measured sensitivity information are instead associated with a derived sensitivity to offset deficient sensitivity measurements near the edge of the object.

Abstract: A method and apparatus are disclosed for deriving an enhanced sensitivity matrix for describing coil sensitivity in a magnetic resonance imaging system. The enhanced sensitivity matrix provides sensitivity information for pixels near the edge of the imaged object such that pixels near the edge for which there was no sensitivity information are associated with a derived sensitivity. Likewise pixels near the edge for which there is measured sensitivity information are instead associated with a derived sensitivity to offset deficient sensitivity measurements near the edge of the object.

Abstract: The present invention includes a technique for use with magnetic resonance imaging that includes the application of a non-linear, higher-order gradient field in the presence of a moving object to be scanned. MR data is acquired as the object moves through the non-linear gradient field. Resulting images are contiguous and do not require the patching together of data in either k-space or image space and result in an image with expanded FOV in a longitudinal direction of the moving object.

Abstract: A technique is provided for characterizing and correcting for instabilities or variations in a magnet system of an MRI scanner. The technique makes use of a navigator pulse to read out navigator echo data in the absence of phase encode, or with phase encode effects rewound. The navigator data is used to characterize several potential effects of magnet system instabilities or variations, such as zeroth order phase shifts, first order (linear) phase shifts, bulk position shifts, and amplitude effects. The effects of the instabilities can be used, then, to correct image data acquired during an examination.

Abstract: Calibration data is acquired during a prescan in an MRI system from each local coil in a coil array. The calibration data is used to calculate a sensitivity matrix S which is employed in a SENSE technique to reconstruct an MR image acquired with the same local coils.

Abstract: A sensitivity encoding method (SENSE) is used to acquire an MR image having a reduced field of view. The number of aliased replicates caused by surrounding object boundaries is calculated for each image pixel location to obtain optimal aliasing artifact suppression without reducing image SNR.

Abstract: A method and apparatus for increasing the signal-to-noise ratio in a magnetic resonance image generated with a system including at least two receiver coils where the data acquisition period is reduced by increasing the space between k-space raster data rows such that image wrapping occurs and an unwrapping algorithm is required, the method including identifying a sensitivities matrix corresponding to the receiver coils, acquiring NMR signals and converting those signals to image pixel intensities, defining a correction matrix, altering the sensitivities matrix as a function of the correction matrix, combining the altered sensitivities matrix and the intensity matrix to generate an estimated spin density matrix and using a spin density matrix to generate the final image.

Abstract: Calibration data is acquired during a prescan in an MRI system from each local coil in a coil array. The calibration data is used to calculate a sensitivity matrix S which is employed in a SENSE technique to reconstruct an MR image acquired with the same local coils.

Abstract: A method and apparatus for increasing the signal-to-noise ratio in a magnetic resonance image generated with a system including at least two receiver coils where the data acquisition period is reduced by increasing the space between k-space raster data rows such that image wrapping occurs and an unwrapping algorithm is required, the method including identifying a sensitivities matrix corresponding to the receiver coils, acquiring NMR signals and converting those signals to image pixel intensities, defining a correction matrix, altering the sensitivities matrix as a function of the correction matrix, combining the altered sensitivities matrix and the intensity matrix to generate an estimated spin density matrix and using a spin density matrix to generate the final image.

Abstract: A magnetic resonance imaging system has a primary set of whole-body gradient coils and a supplemental set of gradient coils. The supplemental gradient coils are employed to produce imaging gradients when fast imaging pulse sequences are performed, and the primary set of gradient coils are employed when interleaved saturation or navigator signals pulse sequences are performed during a scan.

Abstract: An MRI system has two sets of gradient coils driven by two corresponding sets of gradient amplifiers. Logical gradient waveforms produced during a pulse sequence are rotated to produce corresponding physical gradient waveforms and these are distributed to drive both sets of coils simultaneously. Each distributed set of physical gradient waveforms is separately compensated for Eddy current errors, and a polarizing field Eddy current compensation signal is produced and used to modulate the RF reference frequency of the system transceiver.