The General Hospital Corporation

Massachusetts Institute of Technology

Massachusetts General Hospital Corporation

Siemens Aktiengesellschaft

Siemens Healthcare Gmbh

Bastien Guerin

Lawrence Leroy Wald

Elfar Adalsteinsson

Markus Vester

Luca Daniel

Mathias Davids

Zohaib Mahmood

Matthew Scot Rosen

Bruce R Rosen

Jason Stockmann

Boris Keil

Clarissa Z Cooley

A method for assessing peripheral nerve stimulation (PNS) for a coil geometry includes retrieving a PNS Huygens' P-matrix for a body model. The PNS Huygens' P-matrix is defined on a Huygens' surface enclosing the body model. The method further includes generating a coil specific PNS P-matrix for the coil geometry based on at least the PNS Huygens' P-matrix for the body model, determining at least one PNS threshold for the coil geometry based on the coil specific PNS P-matrix, and storing the at least one PNS threshold in a storage device.

System for and method of rapid peripheral nerve stimulation assessment of gradient coils

Systems and methods for designing and manufacturing electromagnetic coils for use with a magnetic resonance imaging ('MRI') system are described. More particularly, described here are methods for designing and manufacturing gradient coils for producing magnetic field gradients with greater peripheral nerve stimulation (“PNS”) thresholds relative to conventional gradient coils. The gradient coil design is constrained using an oracle penalty that is computed to account for a PNS requirement for the coil. In other applications, the oracle penalty can be used to optimize driving patterns for an electromagnetic stimulation system, such that a target PNS requirement is achieved.

Method for designing electromagnetic coils with explicit peripheral nerve stimulation constraint based on an oracle penalty

A system and method is provided for assessing Peripheral Nerve Stimulation (PNS). The system receives an imaging pulse sequence to be applied to a region of interest (ROI) of a subject arranged in the imaging system, where the imaging pulse sequence identifies coil parameters related to at least one coil. The system obtains a first model including a plurality of tissue types and corresponding electromagnetic properties in the ROI. The system then obtains a second model indicating location, orientation, and/or physiological properties of one or more nerve tracks in the ROI. The system estimates a plurality of PNS thresholds in the ROI caused by the imaging pulse sequence applied in the imaging system using the first model, the second model, a nerve membrane model, and the coil parameters.

System and method for using concomitant fields to control peripheral nerve stimulation (PNS) in MRI image encoding

Described here are systems and methods for performing magnetic resonance imaging ('MRI') using radio frequency ('RF') phase gradients to provide spatial encoding of magnetic resonance signals rather than the conventional magnetic field gradients. Particularly, the systems and methods described here implement swept RF pulses (e.g., wideband, uniform rate, and smooth transition (&#x201c;WURST&#x201d;) RF pulses) and a quadratic phase correction to enable RF phase gradient encoding in inhomogeneous background (B) magnetic fields.

Methods for spatially encoding magnetic resonance signals with swept radio frequency (RF) pulses applied with RF spatial phase gradients

Systems and methods for designing parallel transmission radiofrequency (RF) pulses for use in a RF treatment. The methods include selecting a target region in a subject, and providing a plurality of specific absorption rate (SAR) matrices for estimation of SAR at locations within the subject. The methods also include determining a first set of SAR matrices for locations in the target region using the provided SAR matrices, and determining a second set of SAR matrices for locations not in the target region using the provided SAR matrices. The methods further include designing a plurality of RF pulses for achieving a target power deposition in the target region by using the first set of SAR matrices and the second set of SAR matrices in an optimization that determines a set of RF waveforms that produce a target average local SAR using the first set of SAR matrices while minimizing a local SAR and a global SAR using the second set of SAR matrices.

System and method for hyperthermia treatment using radiofrequency phased arrays

Described here are a system and method for designing radio frequency ('RF') pulses for parallel transmission ('pTx') applications, and particularly pTx applications in magnetization transfer (&#x201c;MT&#x201d;) magnetic resonance imaging (&#x201c;MRI&#x201d;). The concept of &#x201c;SAR hopping&#x201d; is implemented using a constrained optimization problem that simultaneously designs multiple RF sub-pulses to maximize power deposition in a bound proton pool while also minimizing local SAR across multiple bound proton pool excitation frequencies. This results in the set of RF waveforms that yield the best excitation profiles for all pulses while ensuring that the local SAR of the average of all pulses is below the regulatory limit imposed by the FDA. Pulses are designed simultaneously while constraining local SAR, global SAR, and peak voltage, explicitly.

System and method for reducing specific absorption rate in magnetization transfer magnetic resonance imaging

A method of determining a decoupling matrix of a decoupling system for an array of coils of a parallel transmission magnetic resonance imaging (MRI) system includes obtaining impedance matrix data for the array of coils without the decoupling system, determining, based on the impedance matrix data for the array of coils, an objective function representative of deviation from a decoupled operating condition for the array of coils in which the array of coils are decoupled via the decoupling system, and defining, with a processor, a decoupling matrix representative of a set of impedances of the decoupling system with an iterative procedure that optimizes elements of the decoupling matrix to minimize the objective function and reach the decoupled operating condition.

Decoupling of parallel transmission arrays in magnetic resonance imaging

A magnetic resonance imaging (MRI) system includes a plurality of transmitters to generate a parallel transmission radio frequency (RF) pulse, an array of coils coupled to the plurality of transmitters to apply the parallel transmission RF pulse to a subject, and a decoupling system connected to the plurality of transmitters and the array of coils. The decoupling system includes a plurality of hybrid couplers, each hybrid coupler of the plurality of hybrid couplers being coupled to a respective pair of the plurality of transmitters and to a respective pair of the array of coils. The plurality of hybrid couplers are configured to diagonalize an impedance matrix of the plurality of coils.

Described here are a system and method for designing radio frequency ('RF') pulses for parallel transmission ('pTx') applications, and particularly pTx applications in multislice magnetic resonance imaging (&#x201c;MRI&#x201d;). The concept of &#x201c;SAR hopping&#x201d; is implemented by framing the concept between slice-selective excitations as a constrained optimization problem that attempts designing multiple pulses simultaneously subject to an overall local SAR constraint. This results in the set of RF waveforms that yield the best excitation profiles for all pulses while ensuring that the local SAR of the average of all pulses is below the regulatory limit imposed by the FDA. Pulses are designed simultaneously while constraining local SAR, global SAR, and peak power, and average power explicitly.

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Cambridge, MA, United States of America

Bastien Guerin