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 resonant coil system with improved sensitivity and signal-to-noise performance is described. A primary coil is tuned to a first resonance frequency and inductively coupled to a secondary coil that is separately tuned to a second resonance frequency. The primary and secondary coils form a resonant system with a resonance frequency that is a function of the primary and secondary coil resonance frequencies. The resonance frequency of the coil system is less than both the primary resonance frequency and the secondary resonance frequency. The mutual inductance between the two coils is high and the resonance frequency of the coil system's parallel mode is well separated from that of the anti-parallel mode.

Abstract: A resonant coil system with improved sensitivity and signal-to-noise performance is described. A primary coil is tuned to a first resonance frequency and inductively coupled to a secondary coil that is separately tuned to a second resonance frequency. The primary and secondary coils form a resonant system with a resonance frequency that is a function of the primary and secondary coil resonance frequencies. The resonance frequency of the coil system is less than both the primary resonance frequency and the secondary resonance frequency. The mutual inductance between the two coils is high and the resonance frequency of the coil system's parallel mode is well separated from that of the anti-parallel mode.

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: An apparatus and method for triaging patients according to radiation exposure operates by measuring electron paramagnetic resonance spectra of fingernails, toenails, and/or teeth. A coil structure allows in vivo measurement of tooth enamel or fingernail keratin with reduced coupling to underlying tissue.

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: An apparatus and method for triaging patients according to radiation exposure operates by measuring electron paramagnetic resonance spectra of fingernails, toenails, and/or teeth. A coil structure allows in vivo measurement of tooth enamel or fingernail keratin with reduced coupling to underlying tissue.

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 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 uniform-field resonator includes a central cavity section having a cross-section which is set to the cutoff frequency for a particular microwave propagation mode and a pair of end sections which enclose the cavity to form a resonator in which the field is substantially uniform along the entire length of the central cavity—regardless of its length. A number of end section design strategies and resulting structures are described for supporting the uniform-field mode of operation in the central cavity section.

Abstract: A uniform-field resonator includes a central cavity section having a cross-section which is set to the cutoff frequency for a particular microwave propagation mode and a pair of end sections which enclose the cavity to form a resonator in which the field is substantially uniform along the entire length of the central cavity—regardless of its length. A number of end section design strategies and resulting structures are described for supporting the uniform-field mode of operation in the central cavity section.

Abstract: Time course MRI data is acquired from the hippocampal region of the brain and processed to produce an index which is a measure of the functional connectivity between locations therein. The MRI data is acquired while the brain is substantially at rest and the spontaneous low frequency component of the time course data at each location in the hippocampus is extracted and compared in a cross-correlation process.

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: A local RF and gradient coil for acquiring images of the human brain using fast NMR pulse sequences includes an end capped RF bird cage coil surrounded by a 3 axis gradient coil assembly. An RF shield is disposed between the RF coil and the gradient coils and it is divided into separate segments to reduce eddy currents induced by the changing gradient fields.

Abstract: A local RF and gradient coil for acquiring images of the human brain using fast NMR pulse sequences includes an end capped RF bird cage coil surrounded by a 3 axis gradient coil assembly. An RF shield is disposed between the RF coil and the gradient coils and it is divided into separate segments to reduce eddy currents induced by the changing gradient fields.

Abstract: An electron paramagnetic resonance (EPR) spectrometer employing a reference arm microwave bridge provides efficient, simultaneous generation of orthogonal I and Q signals. The simultaneous generation is enabled through the use of a field effect transistor (FET) microwave amplifier in the signal arm feeding a balanced quadrature mixer. The I and Q signals are then combined to produce a signal suitable for use as a discriminator in an automatic frequency control (AFC) circuit. An important characteristic of the discriminator signal is that it is independent of the relative phase angle .alpha. between the reference arm and signal arm of the bridge. In a further embodiment, an apparatus is disclosed which computes .alpha. from the I and Q signals, and uses the computed value for .alpha. to extract pure absorption and pure dispersion information from the I and Q signals regardless of the setting of .alpha. in the bridge.

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.