Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2016 Sep 30;6:34180. doi: 10.1038/srep34180

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

Copyright © 2016, The Author(s)

This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

PMC Copyright notice

(a) Demonstration of improved gradiometer performance via fine “spatial-shimming” the cancellation coil (Rx2) location relative to the transmit coil (Tx). This has the effect of fine adjusting the Rx2-to-Tx coupling factor for improved inductive decoupling reaching up to −67 dB (10 kHz). (b) The gradiometer is capable of wideband feedthrough attenuation which is essential in the AWR’s wideband excitation context. (c) The very low drive coil inductance of 2.5 μH coupled with high coil efficiency of 1.06 mT/ampere enables high field amplitudes across an unprecedented DC – 400 kHz despite not using resonant circuits for reactive power handling. When compared to the safe scanning limits for a human⁵, we see that the AWR’s unprecedented drive-field flexibility allows for testing of almost any drive waveform that would be used in a safe human scanning context, enabling comprehensive drive waveform optimization. In contrast, conventional VSM⁷⁷ and AC Susceptometry⁷⁸ are unable to cover the MPI-relevant parameter space. We limit our device design to below 400 kHz because near zero-field, the delay from magnetic relaxation is expected to be >2 μs⁶², surpassing a half-period of the drive waveform and causing poor resolution.