Abstract: Described here is a system and method for estimating apparent transverse relaxation rate, R2*, while simultaneously performing chemical species separation (e.g., water-fat separation) using magnetic resonance imaging (“MRI”). A homodyne reconstruction of k-space datasets acquired using a partial k-space acquisition is used and the chemical species separation of the resultant images takes into account the spectral complexity of the chemical species in addition to magnetic resonance signal decay associated with transverse relaxation. Full resolution maps of R2* are thus capable of being produced while also allowing for the production of images depicting the separated chemical species that are corrected for transverse relaxation associated signal decays.

Abstract: A method for producing parametric maps using a magnetic resonance imaging (MRI) system is provided. The MRI system is used to acquire k-space data from a field-of-view. A series of images is reconstructed from the acquired k-space data, and a confidence map is produced using the k-space data. The confidence map depicts regions in the field-of-view that are affected by error sources. A parametric map is produced using the reconstructed series of images and the produced confidence map. Values in the parametric map associated with regions in the field-of-view depicted in the confidence map as being affected by error sources are not computed, thereby reducing errors in the parametric map.

Abstract: A system and method for assessing magnetic susceptibility of tissue of a subject using a magnetic resonance imaging (MRI) system to acquire chemical-shift-encoded, water-fat separated data. From the water-fat separated data, separated water and fat images, as well as a magnetic field inhomogeneity map are used to estimate the magnetic susceptibility within tissue.

Abstract: A magnetic resonance imaging (“MRI”) system and method for producing an image of a subject with the MRI system in which signal contributions of water and fat are separated are provided. A plurality of in-phase echoes formed at a plurality of different echo times are sampled to acquire k-space data. The in-phase echoes include signal contributions from water and fat that are in-phase with each other. The signal contributions from water and fat are then separated by fitting only those echo signals that are in-phase echo signals to a signal model that models a fat spectrum as including multiple resonance peaks. From these signal contributions, an image of the subject depicting a desired amount of signal contribution from water and a desired amount of signal contribution is produced.

Abstract: A method for correcting motion-induced phase errors in diffusion-weighted k-space data acquired with a magnetic resonance imaging (MRI) system is provided. The MRI system is directed to acquire the following data from an imaging volume: three-dimensional diffusion-weighted k-space data, three-dimensional diffusion-weighted navigator data, three-dimensional non-diffusion-weighted k-space data, and three-dimensional non-diffusion-weighted navigator data. Initial estimates of k-space shift values and a constant phase offset value are calculated using the three-dimensional diffusion-weighted navigator data and the three-dimensional non-diffusion-weighted navigator data. These initial k-space shift values and constant phase offset value are then updated by iteratively minimizing a cost function that relates the phase of the diffusion-weighted k-space data to the phase of the non-diffusion-weighted k-space data, as shifted by the initial k-space shift values and constant phase offset value.

Abstract: A method for producing an image of a subject with a magnetic resonance imaging (“MRI”) system, in which relative signal contributions from a plurality of different chemical species are separated, is provided. A plurality of different echo signals occurring at a respective plurality of different echo times are acquired with the MRI system and a signal model that accounts for relative signal components for each of a plurality of different chemical species is formed for each echo signal. Those echo signals containing errors, such as phase errors, magnitude errors, or errors indicative of a corrupted echo signal, are identified. The relative signal components for each of the plurality of different chemical species are then determined by fitting the echo signals with the signal model. Particularly, those echo signals identified as containing errors are fitted to the signal models in a manner that discards the error-containing information.

Abstract: A method for measuring transverse relaxation rate, R2*, corrected for the presence of macroscopic magnetic field inhomogeneities with a magnetic resonance imaging (MRI) system is provided. The method accounts for additional signal decay that occurs as a result of macroscopic variations in the main magnetic field, B0, of the MRI system, and also mitigates susceptibility-based errors and introduction of increased noise in the R2* measurements. Image data are acquired by sampling multiple different echo signals occurring at respectively different echo times. A B0 field inhomogeneity map is estimated by fitting the acquired image data to an initial signal model. Using the estimated field map, a revised signal model that accounts for signal from multiple different chemical species and for signal decay resulting from macroscopic variations in the B0 field is formed. Corrected R2* values for the different chemical species are then estimated by fitting the acquired image data to the revised signal model.

Abstract: An apparatus and method for reconstructing multi-spectral 3D MR images includes a magnetic resonance (MRI) apparatus that includes an MRI system having a plurality of gradient coils positioned about a bore of a magnet, and an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly to acquire MR images. The MRI apparatus also includes a computer programmed to acquire a plurality of three-dimensional (3D) MR data sets, wherein each 3D MR data set is acquired using a central transmit and receive frequency set to an offset frequency value that is distinct for each 3D MR data set. The computer is also programmed to simultaneously generate a composite image and a magnetic field map based on the plurality of 3D MR data sets.

Abstract: An apparatus and method for reconstructing multi-spectral 3D MR images includes a magnetic resonance (MRI) apparatus that includes an MRI system having a plurality of gradient coils positioned about a bore of a magnet, and an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly to acquire MR images. The MRI apparatus also includes a computer programmed to acquire a plurality of three-dimensional (3D) MR data sets, wherein each 3D MR data set is acquired using a central transmit and receive frequency set to an offset frequency value that is distinct for each 3D MR data set. The computer is also programmed to simultaneously generate a composite image and a magnetic field map based on the plurality of 3D MR data sets.