OHBM 2024 Brainhack: Hack your RF coil

This hackathon project is part of the series, Hack your Scanner, following contributions of previous years. 2022 VASO mosaic, 2021 visual exporting scanner data with QR Modem, 2020 viewing data with ASCII art on MARS with LN_INFO. This year is about hacking your RF-coil.

Contributors: Renzo Huber¹, Tyler Morgan¹, Alessandra Pizzuti², Benedikt Poser², Barbara Dymerska³, Dario Bosch⁴, Yuhui Chai⁵, Natalia Gudino¹, Joelle Sarlls¹, Amir Seginer⁶, Sebastian Dresbach^2,7, Jen Evans¹, Joseph (An Thanh) Vu⁸, Salvatore Torrisi⁸, Rüdiger Stirnberg⁹, Monique Tourell¹⁰, Saskia Bollmann¹⁰, Monique Tourell¹⁰, Chia-Yin Wu¹⁰, Luca Vizioli¹¹, Essa Yacoub¹¹, Nikos Priovoulos¹², Emma Bouwer¹², Wietske van Der Zwaag¹², Hendrik Mattern¹³, Jin Jin¹⁴, Daniel Gomez¹⁵, Anna Blazejewska¹⁵, Jonathan Polimeni¹⁵, Peter Bandettini¹

NIH, Bethesda, USA
University Maastricht, Netherlands
UCL, London, UK
MPI for Biological Cybernetics, Tübingen, Germany
University of Illinois Urbana-Chaimpaign, USA
Weizmann Institute of Science, Israel
Max-Planck Leipzig, Germany
UCSF, VA, USA
DZNE Bonn, Germany
Centre for Advanced Imaging, University of Queensland, Australia
CMRR, Minneapolis, USA
Spinoza, Amsterdam, Netherlands
Magdeburg, Germany
Siemens Healthineers, Australia
Martinos Center, MGB, USA

Project summary

Brainhack Project Description

There are more than 100 7T scanners installed around the world and virtually all of them are equipped with an 32ch RF coils from Nova Medical. In the last decade, this coil model has evolved from a niche engineering challenge for prototype scanners to a mainstream FDA-approved medical product. Despite the current abundance of this coil, there are no public quality metrics about it’s stability, consistency across sites, nor across models of single channel transmit (sTx) and multi-channel transmit (pTx).

However, these QA metrics are vital for the upcoming transition of most 7T scanners. Namely, until now almost all 7T scanners were used as single-channel transit systems (e.g. SIEMENS Magentom 7T, classic and Terra). But the new generation of FDA-approved 7T scanners that are solely used as parallel transmit systems (e.g. SIEMENS Terra.X). While the common pTx Nova coil has been successfully validated for a number of clinical imaging protocols, it has never been compared with the sTX coil for highly accelerated fMRI protocols.

Pilot experiments suggest that the pTx coil performs worse in tSNR limited fMRI protocols. This is despite the fact that the transmit performance is improved.

Example of worse quality on pTx compared to sTx. These examples of highly accelerated fMRI protocols indicate elevated G-Factor noise amplification for pTx coils compared to sTx coils. Data taken from [Huber 2024]. This project, we aim to reproduce these results.

The goals of this project is to:

We want to learn and describe basic QA procedures of 7T RF-coils.
We want to characterize the differences of noise characteristics in fMRI protocols across different coil models; pTx and sTx.
We want to engage with the community to gather and compare basic QA metrics across scanners.

We hope that these results will be informative as reference data for any 7T sights that are unsure if their SNR is at the optimal level. Furthermore, we hope that findings of this project will pave the way for cross-site large neuroimaging studies.

Tutorial: switch back and forth sTx and pTx on SIEMENS Terra

Learning how to switch between pTx and sTx mode on a 7T Terra and 7T plus, respectively.

sTx to pTx

Push green power button

Unplug sTx coil
RFPA-cabinet in machine room, middle button to “set mode”, select 8-channel fbr

Then turn off and turn back on and waiting for the knocking sound
Plug in pTX head coil

pTx to sTx

Plug single channel coil on table
Push blue button to turn off PTX
RFPA to “set mode” it to combine mode, reboot RFPA and wait for the knocking sound

common issue of switching at 7T plus: E-Shim error, booting failed.

If you encounter this error you can, go back to the console that was previously activated, open MARS terminal, login as root, execute: restart mr, if this does not work, try to execute: reboot mars.

Good first issue: execute basic Coil QA

On all SIEMENS scanners, there is a standardized protocol that conveniently generates the most basic quality metric of any receive coil: coil_utils.

It can be found in the Dot-Cockpit under: default, Sequence region, Service Sequences, Default, coil_util. This sequence is designed to test the receive coil. For the pTx coil, this sequence us executed in CP (trueform) mode.