Abstract: Systems and methods are described for phase-sensitive magnetic resonance imaging using an efficient and robust phase correction algorithm. A method includes obtaining a plurality of MRI data signals, such as two-point Dixon data, one-point Dixon data, or inversion recovery prepared data. The method further includes implementing a phase-correction algorithm, that may use phase gradients between the neighboring pixels of an image. At each step of the region growing, the method uses both the amplitude and phase of pixels surrounding a seed pixel to determine the correct orientation of the signal for the seed pixel. The method also includes using correlative information between images from different coils to ensure coil-to-coil consistency, and using correlative information between two neighboring slices to ensure slice-to-slice consistency.

Abstract: Systems and methods are described for chemical shift magnetic resonance imaging in the presence of multiple chemical species. A method includes obtaining a plurality of MRI data signals using a Dixon technique in combination with partially parallel imaging techniques and/or inversion recovery techniques, and processing the plurality of MRI data signals using a Dixon reconstruction technique to create a chemical specific shift image. An apparatus includes a MRI scanner for obtaining images, a controller configured to provide input to the scanner to acquire images using a Dixon technique in combination with partially parallel imaging techniques and/or inversion recovery techniques to produce a plurality of MRI data signals, and processing the plurality of MRI data signals using a Dixon reconstruction technique to create a chemical specific shift image, and an output device to display the resulting image.

Abstract: Automatic coil selection is based on determining an index gauge for a corresponding k-space data line acquired for each preselected coil during a prescan. Reliance on manual coil selection and markers is eliminated by adaptively determining the coils of an MR system that produce a preferred sensitivity to a desired field-of-view (FOV). The fast scan data is used to determine those coils most sensitive to the FOV and reject coil(s) least sensitive. Using only data acquired with the most sensitive coils, SNR is increased and unwanted artifacts are reduced in the final data acquisition and image reconstruction. Through automatic and adaptive selection/deselection, the invention reduces the susceptibility to human error, and therefore results in higher quality images.

Abstract: An automatic and adaptive MR data selection technique for use with a multi-receiver coil assembly in an MR imaging device is disclosed. The invention includes acquiring image data from a plurality of receiver coils and determining an index gauge for each of the images. The index gauge is a representation of the position of a given receiver coil within a desired field-of-view (FOV). The index gauges are compared and any image data set having an index gauge demonstrating a less than optimal position of the given receiver coil with respect to the desired FOV is removed based on the index gauges and the comparison. A final image can be reconstructed using the remaining image data sets. The final image is reconstructed from data having overall reduced noise, and therefore reduced artifacts.

Abstract: An automatic and adaptive MR data selection technique for use with a multi-receiver coil assembly in an MR imaging device is disclosed. The invention includes acquiring image data from a plurality of receiver coils and determining an index gauge for each of the images. The index gauge is a representation of the position of a given receiver coil within a desired field-of-view (FOV). The index gauges are compared and any image data set having an index gauge demonstrating a less than optimal position of the given receiver coil with respect to the desired FOV is removed based on the index gauges and the comparison. A final image can be reconstructed using the remaining image data sets. The final image is reconstructed from data having overall reduced noise, and therefore reduced artifacts.

Abstract: Automatic coil selection is based on determining an index gauge for a corresponding k-space data line acquired for each preselected coil during a prescan. Reliance on manual coil selection and markers is eliminated by adaptively determining the coils of an MR system that produce a preferred sensitivity to a desired field-of-view (FOV). The fast scan data is used to determine those coils most sensitive to the FOV and reject coil(s) least sensitive. Using only data acquired with the most sensitive coils, SNR is increased and unwanted artifacts are reduced in the final data acquisition and image reconstruction. Through automatic and adaptive selection/deselection, the invention reduces the susceptibility to human error, and therefore results in higher quality images.

Abstract: An improved technique is described for acquiring MR image data such as needed for FSE-based Dixon imaging techniques. A gradient-induced echo shift is produced in the pulse sequences by a small gradient applied along the readout axis prior to a readout pulse. When necessary, another small pulse is applied along the readout axis, equal in area and opposite in polarity to the first, to compensate for the shifting effect. Similar pulses are applied for each acquisition window. While data with non-zero phase shifts between water and fat signals are collected as fractional echoes, no increase in echo spacing is necessary with the modified acquisition strategy. Images corresponding to different phase shifts are reconstructed using phase-sensitive partial Fourier reconstruction algorithms whenever necessary. These images are then used to separate different chemical species (such as water and fat) in the object to be imaged.

Abstract: Artifacts in MR images caused by signals emanating from outside the design spherical volume (DSV) of the system are suppressed using customized spatial saturation pulse sequences interleaved with imaging pulse sequences. The spatial saturation pulse sequences are each customized to a specific region and are stored in a library for selective use when needed to suppress artifact producing signals emanating from specific regions outside the DSV.

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: Automatic coil selection is based on determining an index gauge for a corresponding k-space data line acquired for each preselected coil during a prescan. Reliance on manual coil selection and markers is eliminated by adaptively determining the coils of an MR system that produce a preferred sensitivity to a desired field-of-view (FOV). The fast scan data is used to determine those coils most sensitive to the FOV and reject coil(s) least sensitive. Using only data acquired with the most sensitive coils, SNR is increased and unwanted artifacts are reduced in the final data acquisition and image reconstruction. Through automatic and adaptive selection/deselection, the invention reduces the susceptibility to human error, and therefore results in higher quality images.

Abstract: An automatic and adaptive MR data selection technique for use with a multi-receiver coil assembly in an MR imaging device is disclosed. The invention includes acquiring image data from a plurality of receiver coils and determining an index gauge for each of the images. The index gauge is a representation of the position of a given receiver coil within a desired field-of-view (FOV). The index gauges are compared and any image data set having an index gauge demonstrating a less than optimal position of the given receiver coil with respect to the desired FOV is removed based on the index gauges and the comparison. A final image can be reconstructed using the remaining image data sets. The final image is reconstructed from data having overall reduced noise, and therefore reduced artifacts.

Abstract: Image artifacts produced by NMR signals emanating from outside the designed spherical volume in an MRI system are suppressed by interleaving preparatory pulse sequences with image pulse sequences performed during a scan. Each preparatory pulse sequence includes a pair of RF pulses having equal, but opposite flip angles. Spins in the image field of view are tipped and then restored by the pair of RF pulses and spins outside the designed spherical volume are saturated.

Abstract: Three MRI acquisitions are performed to acquire data from which separate water and fat images may be reconstructed using a three-point Dixon technique. The NMR data is acquired with a phased array coil having four separate coil elements. Low resolution images are reconstructed from the acquired NMR data sets and used to calculate phase corrections which are used to correct reconstructed high resolution images. The corrected high resolution images are processed using the Dixon technique to produce fat and water images for each coil element which are combined into a single fat and a single water image.

Abstract: MRI acquisitions are performed to acquire data from which separate water and fat images may be reconstructed using a Dixon technique. Fat signal components intermixed with the water image are suppressed by shifting the pixels in the fat image and subtracting a fraction of this pixel shifted fat image from the water image.

Abstract: A prescan process for an MR fast spin echo (FSE) pulse sequence adjusts the phases of the RF excitation pulse and RF refocusing pulses in the FSE pulse sequence to reduce the spatially invariant phase errors (zeroth order). The prescan process also calculates the value of a readout gradient compensation pulse, a phase-encoding gradient compensation pulse and a slice-select gradient compensation pulse to reduce the first order phase shifts along the readout, phase-encoding, and slice-select gradient axes.

Abstract: A phase-sensitive method of inversion recovery MR imaging is provided, which is directed to a specified object. The method comprises the steps of applying an inversion-recovery MR sequence to the object to acquire a set of MR data for an initial image, wherein the initial image comprises a pixel matrix of specified size, each of the initial image pixels having an associated MR signal and a phase vector. The method further comprises generating a phase vector image from information provided by respective initial image pixels, the phase vector image having a matrix size which is substantially less than the matrix size of the initial image. A region-growing procedure is applied to the phase vector image to remove phase errors therefrom. Thereupon, the phase vector image is zoomed or expanded to a matrix of the same size as the initial image matrix. For multi-slice imaging where TI time is comparatively long, the method may employ a distributed interleave mode of data acquisition to reduce total imaging time.

Abstract: An MRI system includes a gradient compensation system which appends magnetization reset gradient waveforms to imaging gradient waveforms produced during a scan. The magnetization compensation gradients maintain the residual magnetization in the MRI system at a constant level which reduces image artifacts.

Abstract: A system and method for improved water and fat separation in magnetic resonance imaging (MRI) is disclosed using a set of low-resolution images to correct phase errors with overall reduced scan time and post-processing time and enhanced reliability. Several embodiments are disclosed whereby reliable water and fat separation is achieved in nearly one NEX, Two NEX, or Three NEX regular imaging times. In the one embodiment, a regular image data set having water and fat phase-shifted by 90.degree. is acquired, along with two low-resolution image data sets where water and fat are phase-shifted by 0.degree. and 180.degree. are acquired. In another embodiment, two regular image data sets having water and fat phase-shifted by 0.degree. and 180.degree. are acquired, and a low-resolution imaging data set having water and fat phase-shifted by 90.degree. is acquired.

Abstract: A technique for accurately measuring two different spin configurations of transverse magnetization from which the reversible dephasing rate constant R.sub.2 ' can be calculated. Such reversible dephasing may be caused by magnetic field inhomogeneity such as arising from intravascular changes in the oxidation state of hemoglobin, from brain iron, or from cancellous bone, which allows these characteristics to be measured. The different spin configurations can be measured in a single scan by deriving a small R.sub.2 ' through independent and separate measurements of the two magnetization configurations generated by two RF pulses. The two configurations can be recalled independently of each other since they are affected differently by respective gradients flanking the .beta.-pulse which permit one spin configuration to decay with T.sub.2 while the other decays with T.sub.2 * from the same RF pulse.