Abstract: Tracer kinetic models are utilized as temporal constraints for highly under-sampled reconstruction of DCE-MRI data. In one embodiment, a method for improving dynamic contrast enhanced imaging. The method includes steps of administering a magnetic resonance contrast agent to a subject and then collecting magnetic resonance contrast agent from the subject. A tracer kinetic model (i.e. eTofts or Patlak) is selected to be applied to the magnetic resonance imaging data. The tracer kinetic model is applied to the magnetic resonance imaging data. Tracer kinetic maps and dynamic images are simultaneously reconstructed and a consistency constraint is applied. The proposed method allows for easy use of different tracer kinetic models in the formulation and estimation of patient-specific arterial input functions jointly with tracer kinetic maps.

Abstract: Tracer kinetic models are utilized as temporal constraints for highly under-sampled reconstruction of DCE-MRI data. In one embodiment, a method for improving dynamic contrast enhanced imaging. The method includes steps of administering a magnetic resonance contrast agent to a subject and then collecting magnetic resonance contrast agent from the subject. A tracer kinetic model (i.e. eTofts or Patlak) is selected to be applied to the magnetic resonance imaging data. The tracer kinetic model is applied to the magnetic resonance imaging data. Tracer kinetic maps and dynamic images are simultaneously reconstructed and a consistency constraint is applied. The proposed method allows for easy use of different tracer kinetic models in the formulation and estimation of patient-specific arterial input functions jointly with tracer kinetic maps.

Abstract: A magnetic resonance imaging system may include: a magnet; gradient coils; an RF pulse transmitter; an RF receiver that receives MR signals from tissue that has been exposed to RF pulses from the RF pulse generator, gradient fields from the gradient coils, and a magnetic field from the magnet; a system controller that controls the magnet, gradient coils, RF pulse transmitter, and RF receiver so as to generate data representative of at least a portion of the composition of an object, including controlling the gradient coils and RF receiver so as to cause MRI data to be acquired that includes information about at least one attribute of the object at different points in time and that represents an incomplete sample of a portion of k-space that is a Fourier transform of the object; and a data processing system that generates one or more images of at least a portion of the object based on the MRI data.

Abstract: A magnetic resonance imaging system may include a magnet, gradient coils, an RF pulse transmitter, an RF receiver that receives MR signals from tissue that has been exposed to RF pulses, gradient fields, and a magnetic field, and a computer that includes a processor. The computer may have a configuration that: causes the RF pulse transmitter and gradient coils to emit multiple labeling pulses at predetermined labeling times directed to blood in a subject; causes the RF pulse transmitter, gradient coils, and magnet to generate MR signals directed to tissue at one or more spatial locations within the subject that receives the blood; causes the RF receiver to receive MR signals emitted by the tissue at predetermined imaging times; generates an image of the tissue based on the received MR signals; repeats the foregoing four actions one or more times; and generates information indicative of perfusion within the tissue based on the generated images.

Abstract: An MRI scanner may include one or more gradient waveform generators, gradient amplifiers, gradient coils, an RF waveform generator, an RF amplifier, an RF coil, a superconducting magnet, an RF detector; a digitizer, and a computer system that controls the one or more gradient waveform generators and the RF waveform generator so as to generate a magnetization saturation preparation pulse sequence that includes a tip-down pulse that is insensitive to RF field inhomogeneity followed by a tip-back pulse that employs a conjugate symmetry constraint in its energy spectrum.

Abstract: A magnetic resonance imaging system may include: a magnet; gradient coils; an RF pulse transmitter; an RF receiver that receives MR signals from tissue that has been exposed to RF pulses from the RF pulse generator, gradient fields from the gradient coils, and a magnetic field from the magnet; a system controller that controls the magnet, gradient coils, RF pulse transmitter, and RF receiver so as to generate data representative of at least a portion of the composition of an object, including controlling the gradient coils and RF receiver so as to cause MRI data to be acquired that includes information about at least one attribute of the object at different points in time and that represents an incomplete sample of a portion of k-space that is a Fourier transform of the object; and a data processing system that generates one or more images of at least a portion of the object based on the MRI data.

Abstract: A method implemented in a graphics engine for decoding image blocks to derive an original image is provided. The method comprises receiving at least one encoded image data block at a block decoder, the at least one encoded image data block comprising a plurality of codewords and a bitmap. The method further comprises determining a block type based on the plurality of codewords and selecting a decoder unit among a plurality of decoder units in accordance with the block type.

Abstract: A method implemented in a graphics engine for decoding image blocks to derive an original image is provided. The method comprises receiving at least one encoded image data block at a block decoder, the at least one encoded image data block comprising a plurality of codewords and a bitmap. The method further comprises determining a block type based on the plurality of codewords and selecting a decoder unit among a plurality of decoder units in accordance with the block type.

Abstract: Embodiments of the present disclosure are directed to systems and methods for providing tailored RF pulse trains, based on estimated B0 and B1 profiles, for uniform saturation for MRI techniques. The tailored pulse trains are optimized to minimize residual longitudinal magnetization in target tissue. The B0 and B1 profiles can be measured a priori over a desired region of a patient, e.g., the heart, and can overcome or mitigate SAR and B1 inhomogeneity constraints. In exemplary embodiments, the tailored pulse trains can include hard pulses with unequal weighting. In other embodiments, the tailored pulse trains can include BIR-4 pulse trains that are optimized to minimize residual longitudinal magnetization in target tissue. The tailored pulse train designs can improve the immunity to B1 variation while maintaining low RF power. MRI systems, methods, and controllers for providing tailored pulse trains are described.

Abstract: Magnetic resonance imaging techniques are described that utilize bSSFP sequences in which two or more gradient waveforms are interleaved in a “groupwise” fashion, i.e., each waveform is executed consecutively two or more times before switching to the other waveform, where “N” counts the number of times each waveform is executed consecutively. As a result, embodiments of the present disclosure can mitigate steady-state signal distortions or artifacts in interleaved balanced steady-state free precession (bSSFP) caused by slightly unbalanced eddy-current fields. Related MRI systems are also described.

Abstract: Techniques and systems for magnetic resonance imaging. In one aspect, preparatory pulse sequences precede alternating repetition time steady state free precession (ATR SSFP) pulse sequences to enable image acquisition before reaching a steady-state equilibrium. The design of the preparatory sequences is based on a two step process: First an oscillatory residue is expressed in terms of a window (e.g., a Kaiser-Bessel window) and scale parameters. Second the oscillatory residue is minimized to determine the scale parameters according to a desired application (e.g. ATR SSFP, optimized for fat, water, etc.) The preparation scheme described in this specification can be applied to arbitrary repetition times and RF phase cycling combinations.

Abstract: Referenceless techniques for flow imaging are described that exploit a refocusing property of balanced steady state free precession (“SSFP”) magnetic resonance imaging (“MRI”), and achieve up to approximately a 50% reduction in total scan time. With the echo time set to one half of the sequence repetition time (TE=TR/2), non-flow-related image phase tends to vary smoothly across the field-of-view, and can be estimated from static tissue regions to produce a phase reference for nearby voxels containing flowing blood. These approaches produce accurate in vivo one-dimensional velocity estimates in half the scan time compared with conventional balanced SSFP phase-contrast methods. The feasibility of referenceless time-resolved 3D flow imaging (called “7D” flow) is demonstrated for a carotid bifurcation application from just three acquisitions. Related systems are also described. Other attributes such as blood acceleration can also be imaged with such techniques.

Abstract: A method implemented in a graphics engine for decoding image blocks to derive an original image is provided. The method comprises receiving at least one encoded image data block at a block decoder, the at least one encoded image data block comprising a plurality of codewords and a bitmap. The method further comprises determining a block type based on the plurality of codewords and selecting a decoder unit among a plurality of decoder units in accordance with the block type.

Abstract: An image processing system including an image encoder and image decoding system is provided. The image encoder system includes an image decomposer, a block encoder, and an encoded image composer. The image decomposer decomposes the image into blocks. The block encoder, which includes a selection module, a codeword generation module and a construction module, processes the blocks. Specifically, the selection module computes a set of parameters from image data values of a set of image elements in the image block. The codeword generation module generates codewords, which the construction module uses to derive a set of quantized image data values. The construction module then maps each of the image element's original image data values to an index to one of the derived image data values. The image decoding system reverses this process to reorder decompressed image blocks in an output data file.

Abstract: Embodiments of the present disclosure are directed to systems and methods for providing tailored RF pulse trains, based on estimated B0 and B1 profiles, for uniform saturation for MRI techniques. The tailored pulse trains are optimized to minimize residual longitudinal magnetization in target tissue. The B0 and B1 profiles can be measured a priori over a desired region of a patient, e.g., the heart, and can overcome or mitigate SAR and B1 inhomogeneity constraints. In exemplary embodiments, the tailored pulse trains can include hard pulses with unequal weighting. In other embodiments, the tailored pulse trains can include BIR-4 pulse trains that are optimized to minimize residual longitudinal magnetization in target tissue. The tailored pulse train designs can improve the immunity to B1 variation while maintaining low RF power. MRI systems, methods, and controllers for providing tailored pulse trains are described.

Abstract: Referenceless techniques for flow imaging are described that exploit a refocusing property of balanced steady state free precession (“SSFP”) magnetic resonance imaging (“MRI”), and achieve up to approximately a 50% reduction in total scan time. With the echo time set to one half of the sequence repetition time (TE=TR/2), non-flow-related image phase tends to vary smoothly across the field-of-view, and can be estimated from static tissue regions to produce a phase reference for nearby voxels containing flowing blood. These approaches produce accurate in vivo one-dimensional velocity estimates in half the scan time compared with conventional balanced SSFP phase-contrast methods. The feasibility of referenceless time-resolved 3D flow imaging (called “7D” flow) is demonstrated for a carotid bifurcation application from just three acquisitions. Related systems are also described. Other attributes such as blood acceleration can also be imaged with such techniques.

Abstract: Magnetic resonance imaging techniques are described that utilize bSSFP sequences in which two or more gradient waveforms are interleaved in a “groupwise” fashion, i.e., each waveform is executed consecutively two or more times before switching to the other waveform, where “N” counts the number of times each waveform is executed consecutively. As a result, embodiments of the present disclosure can mitigate steady-state signal distortions or artifacts in interleaved balanced steady-state free precession (bSSFP) caused by slightly unbalanced eddy-current fields. Related MRI systems are also described.

Abstract: Techniques and systems for magnetic resonance imaging. In one aspect, preparatory pulse sequences precede alternating repetition time steady state free precession (ATR SSFP) pulse sequences to enable image acquisition before reaching a steady-state equilibrium. The design of the preparatory sequences is based on a two step process: First an oscillatory residue is expressed in terms of a window (e.g., a Kaiser-Bessel window) and scale parameters. Second the oscillatory residue is minimized to determine the scale parameters according to a desired application (e.g. ATR SSFP, optimized for fat, water, etc.) The preparation scheme described in this specification can be applied to arbitrary repetition times and RF phase cycling combinations.

Abstract: For in vivo magnetic resonance imaging at high field (?3 T) it is essential to consider the homogeneity of the active B1 field (B1+), particularly if surface coils are used for RF transmission. A new method is presented for highly rapid B1+ magnitude mapping. It combines the double angle method with a B1-insensitive magnetization-reset sequence such that the choice of repetition time (TR) is independent of T1 and with a multi-slice segmented (spiral) acquisition to achieve volumetric coverage with adequate spatial resolution in a few seconds.

Abstract: For in vivo magnetic resonance imaging at high field (?3 T) it is essential to consider the homogeneity of the active B1 field (B1+), particularly if surface coils are used for RF transmission. A new method is presented for highly rapid B1+ magnitude mapping. It combines the double angle method with a B1-insensitive magnetization-reset sequence such that the choice of repetition time (TR) is independent of T1 and with a multi-slice segmented (spiral) acquisition to achieve volumetric coverage with adequate spatial resolution in a few seconds.