Other

Case Western Reserve University

Jeremiah A Heilman

Mark A Griswold

Matthew Riffe

Natalia Gudino

Markus Vester

Oliver Heid

Franz Schmitt

David Bina

Systems, methods, and other embodiments associated with controlling the specific absorption rate (SAR) in a patient associated with a conductor are described. The conductor may be, for example, a wire associated with a pacemaker, a wire associated with a neurostimulator, an orthopaedic device, and so on. One example method includes calibrating a multi-channel transmitter associated with a magnetic resonance imaging (MRI) apparatus imaging the patient. The example method also includes controlling the MRI apparatus to transmit radio frequency (RF) energy to image the patient in a manner where the RF energy will only influence the SAR near the conductor in the patient less than a desired threshold amount.

Controlling multi-channel transmitter effects on specific absorption rate

Example systems, apparatus, circuits, and so on described herein concern a Hall effect current sensor that includes a planar portion of a conductor that is oriented perpendicular to a base magnetic field in which it is located. In the presence of the magnetic field, a differential voltage is produced across the planar portion that is proportional to a strength of the magnetic field and the amount of current flowing through the conductor.

Hall effect current sensor

Example systems, apparatus, circuits, and so on described herein concern parallel transmission in high field MRI. One example apparatus includes a balun network that produces out-of-phase signals that are amplified to drive current-mode class-D (CMCD) field effect transistors (FETs) that are connected by a coil that includes an LC (inductance-capacitance) leg. The LC leg is to selectively alter the output analog RF signal and the analog RF signal is used in high field parallel magnetic resonance imaging (MRI) transmission.

On-coil current mode class D RF power amplifier in high field parallel transmission MRI

Example systems, apparatus, circuits, and so on described herein concern parallel transmission in MRI with on-coil current-mode (CMCD) amplifiers. One example apparatus includes switched voltage-mode class D (VMCD) pre-amplifiers. Another example apparatus includes amplitude modulation of the output of the CMCD amplifiers using feedback control based, at least in part, on a comparison of an envelope of transmit coil current to an envelope of an input RF pulse.

Switched mode pre-amplification and am feedback for on-coil switched mode amplifiers in parallel transmission MRI

Systems, methods, and other embodiments associated with mitigating off-resonance angle in steady-state coherent magnetic resonance imaging (MRI) are described. One example method includes accessing a B0 map and a coil sensitivity profile associated with an MRI apparatus configured to produce a steady-state coherent MRI sequence to image an object. The MRI apparatus is configured with a multi-channel transmission array having individually controllable transmission channels. The method includes computing transmission control parameters for individual transmission channels as a function of the B0 map and the coil sensitivity profile. The transmission control parameters are configured to facilitate controlling the transmission array to create a spatially varying phase profile using a single dimensional radio frequency (RF) pulse.

Mitigating off-resonance angle in steady-state coherent imaging

Systems, methods, and other embodiments associated with MRI excitation are described. One example method includes performing a calibration to determine a set of transmission parameters for a set of excitation pulses for transmission channels available on a multi-channel MRI transmitter. The set of excitation pulses are configured to produce a resulting nuclear magnetic resonance (NMR) signal from an object exposed to the set of excitation pulses. The resulting NMR signal comprises NMR signal associated with a first NMR resonance associated with the object and NMR signal associated with a second NMR resonance associated with the object.

Excitation uniformity

Devices, systems, methods, and other embodiments associated with magnetic resonance imaging (MRI) are described. In one embodiment, an apparatus includes an RF coil for use in multi-nuclear excitation in magnetic resonance imaging (MRI). The RF coil includes a set of two or more L-C coils. Members of the set of two or more L-C coils have individual resonance frequencies. An RF amplifier is placed near the RF coil. The RF amplifier is controllable to selectively produce the individual resonance frequency of a member of the set of two or more L-C coils based, at least in part, on a digital input provided to the RF amplifier.

Multi-frequency excitation coils for MRI

Systems, methods, and other embodiments associated with dynamically selectively configuring wireless transmitters associated with MRI detector coils are described. One example apparatus includes a detector coil to receive an NMR signal. The apparatus includes a dynamically configurable transmitter to transmit an RF transmission according to a configurable set of transmission parameters. The RF transmission is based on the NMR signal received by the MRI detector coil. The apparatus includes a tuning logic that cycles between an active state and a passive state under the control of a tuning program. While in the passive state, the tuning logic is to generate substantially no RF that could interfere with receiving the NMR signal at the MRI detector coil. While in the active state, the tuning logic is to configure the dynamically configurable transmitter to transmit according to the set of transmission parameters.

Dynamically selectively configuring wireless transmitter associated with MRI detector coil

Example systems, apparatus, circuits, and so on described herein concern parallel transmission in MRI. One example apparatus includes at least two field effect transistors (FETs) that are connected by a coil that includes an LC (inductance-capacitance) leg. The apparatus includes a controller that inputs a digital signal to the FETs to control the production of an output analog radio frequency (RF) signal. The LC leg is to selectively alter the output analog RF signal and the analog RF signal is used in parallel magnetic resonance imaging (MRI) transmission.

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Shaker Heights, OH, United States of America

Jeremiah A Heilman