Abstract: Systems and methods for designing and fabricating three-dimensional objects with precisely computed material compositions for use in enhancing electromagnetic fields for magnetic resonance imaging (“MRI”) are provided. As examples, the fabricated object can be designed to reduce magnetic field inhomogeneities in the main magnetic field of an MRI system, or to reduce inhomogeneities in a transmit radio frequency (“RF”) field (i.e., a B1 field). As examples, the object can be a shim; a housing or other part of an RF coil; a medical device, such as a surgical implant; or component used in a medical device, such as a housing for an implantable medical device.

Abstract: Systems and methods for designing and fabricating three-dimensional objects with precisely computed material compositions for use in enhancing electromagnetic fields for magnetic resonance imaging (“MRI”) are provided. As examples, the fabricated object can be designed to reduce magnetic field inhomogeneities in the main magnetic field of an MRI system, or to reduce inhomogeneities in a transmit radio frequency (“RF”) field (i.e., a B1 field). As examples, the object can be a shim; a housing or other part of an RF coil; a medical device, such as a surgical implant; or component used in a medical device, such as a housing for an implantable medical device.

Abstract: A method for reconstructing a plurality of images depicting a subject from image data that is simultaneously acquired from a corresponding plurality of slice locations with a magnetic resonance imaging (MRI] system is provided. Image data is acquired following the application of radio frequency (RF] energy to the plurality of slice locations. The RF energy is tailored to provide a different phase to each of the plurality of slice locations. Reference image data is also acquired for each slice location following the application of RF energy that has the same phase as is used to excite the respective slice location for the acquisition of the image data. Aliased images are reconstructed from the image data, and reference images are reconstructed from the reference image data. Using both of these image sets, an unaliased image is produced for each of the plurality of slice locations.

Abstract: Described here are systems and methods for improved magnetic resonance imaging (“MRI”} using a radio frequency (“RF”} system that establishes a Larmor frequency using a clock signal generated by the RF system to provide phase coherency and improved spectral quality among the RF pulses generated by the RF system. With this system, the conventionally relied-upon reference signal is no longer needed to maintain phase coherency. Instead, the system clock of the RF system is used to create the Larmor frequency used for pulse formation in the RF transmitter and for signal demodulation in the RF receiver.

Abstract: A method for reconstructing a plurality of images depicting a subject from image data that is simultaneously acquired from a corresponding plurality of slice locations with a magnetic resonance imaging (MRI] system is provided. Image data is acquired following the application of radio frequency (RF] energy to the plurality of slice locations. The RF energy is tailored to provide a different phase to each of the plurality of slice locations. Reference image data is also acquired for each slice location following the application of RF energy that has the same phase as is used to excite the respective slice location for the acquisition of the image data. Aliased images are reconstructed from the image data, and reference images are reconstructed from the reference image data. Using both of these image sets, an unaliased image is produced for each of the plurality of slice locations.

Abstract: A magnetic resonance imaging (MRI) system includes a transmitter that produces an RF excitation pulse that is applied to a subject positioned in the MRI system to induce emission of at least one of an NMR signal and an ESR signal therefrom, and that produces a reference signal indicative of the phase of the RF excitation pulse. A first analog-to-digital converter has an input for receiving the reference signal that is synchronous with the RF excitation pulse. One or more additional analog-to-digital converters/processors have inputs for receiving the at least one of NMR signals and ESR signals produced by a subject placed in the MRI system and produce one or more complex digital signals therefrom. A normalizer is connected to receive and normalize the digital reference signal and a mixer is connected to receive the normalized digital reference signal and the digital signal. Accordingly, the mixer is operable to multiply the normalized complex digital reference signal with the complex digital signal.

Abstract: A magnetic resonance imaging (MRI) system includes a transmitter that produces an RF excitation pulse that is applied to a subject positioned in the MRI system to induce emission of at least one of an NMR signal and an ESR signal therefrom, and that produces a reference signal indicative of the phase of the RF excitation pulse. A first analog-to-digital converter has an input for receiving the reference signal that is synchronous with the RF excitation pulse. One or more additional analog-to-digital converters/processors have inputs for receiving the at least one of NMR signals and ESR signals produced by a subject placed in the MRI system and produce one or more complex digital signals therefrom. A normalizer is connected to receive and normalize the digital reference signal and a mixer is connected to receive the normalized digital reference signal and the digital signal. Accordingly, the mixer is operable to multiply the normalized complex digital reference signal with the complex digital signal.

Abstract: A magnetic resonance imaging (MRI) system includes a transmitter that produces an RF excitation pulse that is applied to a subject positioned in the MRI system to induce emission of at least one of an NMR signal and an ESR signal therefrom, and that produces a reference signal indicative of the phase of the RF excitation pulse. A first analog-to-digital converter has an input for receiving the reference signal that is synchronous with the RF excitation pulse. One or more additional analog-to-digital converters/processors have inputs for receiving the at least one of NMR signals and ESR signals produced by a subject placed in the MRI system and produce one or more complex digital signals therefrom. A normalizer is connected to receive and normalize the digital reference signal and a mixer is connected to receive the normalized digital reference signal and the digital signal. Accordingly, the mixer is operable to multiply the normalized complex digital reference signal with the complex digital signal.

Abstract: A technique for acquiring magnetic field maps simultaneously with the images they affect allows improved correction of shimming and/or geometric distortions in the image and allows imaging techniques where subject motion is inevitable or required.

Abstract: A perfusion image is produced by acquiring a series of time course MR images from an imaging slice. During the acquisition spins flowing into the slice are repeatedly tagged with an RF tagging pulse having a flip angle that is modulated according to a tagging pattern. Voxels in the series of reconstructed MR images having signals which vary according to the tagging pattern indicate perfusion. Perfusion images indicating either flow or velocity are produced.

Abstract: A magnetic resonance imaging (MRI) system includes a transmitter that produces an RF excitation pulse that is applied to a subject positioned in the MRI system to induce emission of at least one of an NMR signal and an ESR signal therefrom, and that produces a reference signal indicative of the phase of the RF excitation pulse. A first analog-to digital converter has an input for receiving the reference signal that is synchronous with the RF excitation pulse. One or more additional analog-to-digital converters/processors have inputs for receiving the at least one of NMR signals and ESR signals produced by a subject placed in the MRI system and produce one or more complex digital signal therefrom. A normalizer is connected to receive and normalize the digital reference signal and a mixer is connected to receive the normalized digital reference signal and the digital signal. Accordingly, the mixer is operable to multiply the normalized complex digital reference signal with the complex digital signal.

Abstract: A technique for acquiring magnetic field maps simultaneously with the images they affect allows improved correction of shimming and/or geometric distortions in the image and allows imaging techniques where subject motion is inevitable or required.

Abstract: A perfusion image is produced by acquiring a series of time course MR images from an imaging slice. During the acquisition spins flowing into the slice are repeatedly tagged with an RF tagging pulse having a flip angle that is modulated according to a tagging pattern. Voxels in the series of reconstructed MR images having signals which vary according to the tagging pattern indicate perfusion. Perfusion images indicating either flow or velocity are produced.

Abstract: An EPI pulse sequence is performed by an NMR system which acquires images of the brain over a time interval during which the subject performs a function or is stimulated in a pattern. The voxel size of acquired images corresponds to the anatomy of cortical microcirculation structures which range from 1 to 2 mm along all three axes. A centric view order is employed and one-half of k-space is sampled to reduce scan time for each image.

Abstract: A local head coil for an MRI system includes a passive shim assembly having ferroshims placed to reduce B0 field inhomogeneities caused by susceptibility effects in the subject being imaged. A prescan is performed with the subject in place to measure B0 field inhomogeneities and the passive shim assembly is tailored to the subject by attaching ferroshim inserts based on these measurements.

Abstract: An EPI pulse sequence is performed by an NMR system which acquires 128 images of the brain over a time interval during which the subject performs a function or is stimulated. The acquired time course NMR data is displayed in different ways for analysis. Four different methods for producing brain function images from the NMR data are described.

Abstract: Counter Rotating Current (CRC) pairs of loop-gap resonators are combined with planar pairs of loop-gap resonators to form networks of NMR local coils. A first embodiment is a quadrature probe in which a planar pair is sandwiched between the loop-gap resonators of the CRC pair. In a plurality of other embodiments, CRC pairs, planar pairs, and other types of local coils are arranged adjacent to one another to form networks of NMR local coils with an enlarged net region of sensitivity. In a further embodiment of the invention, an excitation coil operated in an excite/receive mode is combined with intrinsically isolated local detectors to form an NMR detection network.

Abstract: A local coil for use in NMR imaging includes a pair of loop-gap resonators which are geometrically arranged to be intrinsically isolated. The local coil also includes passive decoupling means to completely decouple the local coil during excitation. In a first embodiment, the pair of loop-gap resonators are disposed axially and the passive decoupling means comprises a pair of back-to-back diodes across the loop-gap resonators. In a second embodiment, the pair of loop-gap resonators are disposed in a plane and the passive decoupling means comprises two single turn loops inside each loop-gap resonator with back-to-back diodes across an open segment of each single turn loop. During excitation, the diodes fire thereby lowering the Q and shifting the resonant frequency of the local coil. Using a combination of intrinsic isolation and passive decoupling, the local coil is completely decoupled from the excitation field.

Abstract: A local probe for use in nuclear magnetic resonance imaging includes a pair of loop-gap resonators which are connected together and positioned adjacent a region of interest. FID signals produced in the region of interest induce signals in coupling loops mounted near each loop-gap resonator, and these connect to a transmission line leading to the receiver. Three embodiments are disclosed, one best suited for imaging appendages, a second best suited for imaging the head and neck, and a third best suited for the spine.

Abstract: Counter Rotating Current (CRC) pairs of loop-gap resonators are combined with planar pairs of loop-gap resonators to form networks of NMR local coils. A first embodiment is a quadrature probe in which a planar pair is sandwiched between the loop-gap resonators of the CRC pair. In a plurality of other embodiments, CRC pairs, planar pairs, and other types of local coils are arranged adjacent to one another to form networks of NMR local coils with an enlarged net region of sensitivity.