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

Patent metadata

Field	Value
Publication number	US-11679254-B2
Application number	US-201715811588-A
Country	US
Kind code	B2
Filing date	Nov 13, 2017
Priority date	Nov 11, 2016
Publication date	Jun 20, 2023
Grant date	Jun 20, 2023

Abstract

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.

First claim

What is claimed is:

1. An imaging system comprising: a magnet system configured to generate a static magnetic field about at least a region of interest (ROI) of a subject arranged in the imaging system; at least one gradient coil configured to establish at least one magnetic gradient field with respect to the static magnetic field; a radio frequency (RF) system configured to deliver excitation pulses to the subject; a computer system programmed to: receive coil parameters that include current related to at least one radio frequency (RF) coil identified in an imaging pulse sequence to be performed in the imaging system; obtain a first model including a plurality of tissue types and corresponding electromagnetic properties in the ROI; obtain a second model indicating at least one of location, orientation, and physiological properties of one or more nerve tracks in the ROI, estimate a plurality of Peripheral Nerve Stimulation (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; estimate an extra concomitant field that reduces electric fields induced in the ROI by performing the pulse sequence using the coil parameters to be below at least a selected one of the PNS threshold during the imaging pulse sequence; and performing the imaging pulse sequence while generating the extra concomitant field that reduces electric fields induced in the ROI to maintain the electric fields produced in the ROI below at least a selected one of the PNS threshold.

2. The system of claim 1 wherein the first model comprises an anatomical tetrahedral mesh that models a plurality of tissue types and corresponding electromagnetic properties.

3. The system of claim 1 wherein the second model comprises a nerve fiber atlas that encodes location, orientation, and physiological properties of nerve tracks in a human body.

4. The system of claim 1 wherein the computer system is further programmed to compute electromagnetic fields in the ROI produced by the at least one gradient coil.

5. The system of claim 1 wherein the at least one gradient coil is a magnetic particle imaging (MPI) gradient coil, and the computer system is further programmed to compute electromagnetic fields in the ROI produced by the MPI gradient coil.

6. The system of claim 1 wherein the computer system is further programmed to estimate the plurality of the PNS thresholds by modulating electromagnetic fields, using the at least one RF coil, in amplitude in a first range and frequency in a second range until an action potential is detected by a membrane depolarization in the nerve membrane model.

7. The system of claim 6 wherein the first range is OmT to 100mT and the second range is 10 kHz to 200 kHz for the at least one gradient coil, wherein the at least one gradient coil is a magnetic particle imaging (MPI) gradient coil; and
wherein the first range is determined by a threshold of a magnetic resonance imaging (MRI) scanner and the second range is 0.1 kHz to 5 kHz for the at least one gradient coil.

8. The system of claim 1 wherein the computer system is programmed to generate magnetic and electric fields in the first model from a time-varying current applied to the at least one RF coil using an electromagnetic field simulation.

9. The system of claim 8 wherein the computer system is programmed to obtain an effective electric potential along a nerve fiber present in the one or more nerve tracks by projecting the electric fields onto the nerve fiber.

10. The system of claim 9 wherein the computer system is programmed to evaluate the nerve membrane model by providing the effective electric potential to the nerve membrane model; and
wherein the computer system is programmed to determine whether an action potential is initiated by analyzing an output of the nerve membrane model.

11. A method for assessing Peripheral Nerve Stimulation (PNS) in an imaging system, comprising:
receiving an imaging pulse sequence to be applied to at least a region of interest (ROI) of a subject arranged in the imaging system, the imaging pulse sequence identifying coil parameters that include current related to at least one coil;
obtaining a first model including a plurality of tissue types and corresponding electromagnetic properties in the ROI;
obtaining a second model indicating at least one of location, orientation, and physiological properties of one or more nerve tracks in the ROI;
estimating 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;
estimating an extra concomitant field that reduces electric fields induced by performing the pulse sequence using the coil parameters to be below at least a selected one of the PNS threshold when performing the imaging pulse sequence using the coil parameters; and
reporting the extra concomitant field that reduces electric fields induced using the coil parameters below at least the selected one of the PNS threshold when performing the imaging pulse sequence using the coil parameters.

12. The method as recited in claim 11 , wherein the first model comprises an anatomical tetrahedral mesh that models a plurality of tissue types and corresponding electromagnetic properties.

13. The method as recited in claim 11 , wherein the second model comprises a nerve fiber atlas that encodes location, orientation, and physiological properties of nerve tracks in a human body.

14. The method of claim 11 , wherein the at least one coil includes a magnetic resonance imaging (MM) gradient coil, and further comprising computing electromagnetic fields in the ROI produced by the magnetic resonance imaging (Mill) gradient coil.

15. The method of claim 11 , wherein the at least one coil includes a magnetic resonance imaging (MM) gradient coil, and further comprising computing electromagnetic fields in the ROI produced by the magnetic particle imaging (MPI) gradient coil.

16. The method of claim 11 , further comprising:
estimating the plurality of the PNS thresholds by modulating electromagnetic fields in amplitude in a first range and frequency in a second range using the at least one coil until an action potential is detected in the nerve membrane model.

17. The method of claim 16 , wherein the first range is OmT to 100mT and the second range is 10 kHz to 200 kHz for the at least one coil, wherein the at least one coil is a magnetic particle imaging (MPI) gradient coil; and
wherein the first range is determined by a threshold of a magnetic resonance imaging (Mill) scanner and the second range is 0.1 kHz to 5 kHz for the at least one coil.

18. The method of claim 11 , further comprising:
generating magnetic and electric fields in the first model from a time-varying current applied to the at least one coil using an electromagnetic field simulation.

19. The method of claim 18 , further comprising:
obtaining an effective electric potential along a nerve fiber present in the one or more nerve tracks by projecting the electric fields onto the nerve fiber.

20. The method of claim 19 , further comprising:
evaluating the nerve membrane model by providing the effective electric potential to the nerve membrane model; and
determining whether an action potential is initiated by analyzing an output of the nerve membrane model.

Assignees

• Massachusetts Gen Hospital

Inventors

• Wald Lawrence
• Guerin Bastien
• Davids Mathias

Classifications

• A61N2/006

  for magnetic stimulation of nerve tissue · CPC title

• A61B6/469

  for selecting a region of interest [ROI] · CPC title

• A61N1/3605

  Implantable neurostimulators for stimulating central or peripheral nerve system · CPC title

• A61N2/02

  using magnetic fields produced by coils, including single turn loops or electromagnets (A61N2/12 takes precedence) · CPC title

• A61N1/086 Primary

  Magnetic resonance imaging [MRI] compatible leads · CPC title