Leland Stanford Junior University

Other

General Electric Company

Brian Rutt

Mihir Pendse

Michael M Thornton

Paul A Picot

Mohammad Mehdi Khalighi

Simone Winkler

Manojkumar Saranathan

James A Rioux

Obtaining minimum duration parallel transmit pulses for simultaneous multislice imaging that includes minimizing specific absorption rate hotspots, using an IMPULSE pTx optimization method to determine multiple spoke locations and multiple channel weights for multiple slices while enforcing a specified flip angle inhomogeneity tolerance over the multiple slices when excited, applying a control algorithm to conform a simultaneous multislice (SMS) pulse to the excited multiple slices to minimize a cost function having terms corresponding to an excitation accuracy and a pulse power, where a regularization term in the cost function is configured by the control algorithm for excitation accuracy while limiting a peak pulse power, and applying a time-optimal variable rate selective excitation (VERSE) to enforce a peak power constraint with a minimum pulse duration by reshaping a RF waveform and a gradient waveform without altering an excitation profile if the peak power limit on a channel is exceeded.

Methods for mitigating local SAR hotspots and flip angle uniformity in ultra-high field simultaneous multislice imaging using parallel transmission

A method for providing SAR focusing at a target in a body using an MRI system is provided. A computed pulse is provided at a lower power to the body. A MR thermometry is performed. A map is created from the MR thermometry to determine if a hotspot aligns with the target. If the target does not align with the hotspot, then the steps are performed comprising, recomputing the computed pulse, providing the computed pulse at a lower power to the body, performing MR thermometry, creating a map from the MR thermometry to determine if a hotspot aligns with the target, and repeating these steps until the hotspot aligns with the target. The computed pulse is applied at a higher power to the body to provide the desired SAR at the target. Temperature change is monitored with MR thermometry the previous two steps are repeated until desired temperature is achieved.

Method and apparatus for SAR focusing with an array of RF transmitters

A method and system for estimating a specific absorption rate of a tissue region prior to performing a magnetic resonance (MR) imaging scan on the tissue region. The method comprises radiating the tissue region with a plurality of short pulses, wherein the tissue region emits thermoacoustic signals responsive to the short pulses, receiving the thermoacoustic signals by at least one ultrasonic transducer, calculating a temperature rise of the tissue region based on the received thermoacoustic signals, scaling the temperature rise to estimate a temperature rise of the tissue region resulting from an MR imaging scan, and estimating the specific absorption rate of the tissue region based on the estimated temperature rise.

Method and system for estimating the specific absorption rate of a tissue region prior to a magnetic resonance imaging scan

A method for providing an image of a subject in a magnetic resonance imaging MRI system with parallel transmission (pTx) is provided. A localizer scan of the subject is provided. Body anatomy is determined from the localizer scan. The body anatomy is matched with at least one body model of a plurality of body models. Band Bmaps are calculated from the body anatomy. The electric fields from the at least one body model and constraints are used to simultaneously determine a plurality of excitation pulses for a pTx. MRI is performed on the subject using the determined excitation pulses. Global SAR is monitored in real time to ensure all time-averaged constraints are satisfied simultaneously.

Iterative minimization procedure with uncompressed local SAR estimate

A method for providing an image of a subject is provided. The plurality of Cartesian points is divided into a first group and a second group, wherein all of the Cartesian points in the first group have a kthat is less than or equal to kof all of the Cartesian points in the second group. The second group is divided into N subgroups. An inversion recovery radio frequency is applied to the subject. K-space data for the first group of Cartesian points for M different time periods is acquired, wherein k-space data is acquired for only one sub-group sequentially and cyclically for the M different time periods. For each time period i of the M different time periods, acquired k-space data for the first group of Cartesian points at time period i and k-space data from N consecutive subgroups of Cartesian points.

Method for rapid-multicontrast brain imaging

A magnetic resonance imaging (MRI) apparatus includes a magnetic resonance imaging (MRI) system having a plurality of gradient coils positioned about a bore of a magnet, and an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly to acquire MR images, and a computer programmed to generate an original image of an object, generate a proton density weighted image of the object, generate a B+ field map of the object, generate a transmit-corrected image based on the B+ field map and based on the proton density weighted image, electronically filter the transmit-corrected image to generate a receive sensitivity map, and revise the original image using the receive sensitivity map.

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Stanford, CA, United States of America

Brian Rutt