# Acousto-optical RF field sensors for safer diagnostic and interventional MRI

> **NIH NIH R01** · GEORGIA INSTITUTE OF TECHNOLOGY · 2021 · $415,692

## Abstract

Although adverse events related to MRI are rare, safety concerns due to RF induced heating have a significant
impact in clinical use especially for a growing number of patients with medical implants. Current regulations
based on estimated whole body absorption rate (SAR) impose unnecessary restrictions on RF power levels,
sometimes reducing the diagnostic efficacy, while even these low levels can create safety issues for specific
patients. Miniature sensors with local E-field and temperature measurement capability on individual patients
during the scans can alleviate these limitations while improving safety. These sensors can also have an impact
on interventional MRI applications where active markers, essentially miniature coils that locally measure the RF
signal, provide the best device visibility. These markers, however suffer from RF induced heating over conductive
transmission lines, an issue that gets exacerbated in higher field MR systems and does not currently have a
solution that satisfies all mechanical and electrical constraints. We recently developed a miniature acousto-
optical (AO) RF field sensor which detects and transmits the RF signal over an optical fiber instead of conductive
transmission lines, and therefore is totally free of RF induced heating and electromagnetic interference. The
same device has the potential to measure temperature as well as the local E/H field for SAR evaluation when
coupled with a properly designed antenna. In this application, we aim to optimize the design of the AO sensor
using unique mechanical resonances of optical fibers at Larmor frequencies of 0.55T, 1.5T and 3T systems and
use microfabrication techniques to make device with thin film piezoelectric transducers. We also propose a novel
packaging strategy to embed these AO RF field sensors in sleeves that can conform to any commercially
available MRI compatible catheter, to significantly increase the device options for interventional MRI. These
active markers and multi-parameter E/H field sensors will be rigorously tested according to the latest MRI safety
standards and evaluated in vivo for several challenging cardiovascular interventional MRI procedures.
Successful demonstration of the AO sensor as an active MRI marker with a non-conducting transmission line
will be a significant development for more effective, more efficient, safer, novel, and radiation-free interventional
procedures. The combined quantitative RF field and temperature sensing capability for local RF dosimetry has
the potential to impact clinical practice by broadening the MRI safety envelope as well as contributing to the
fundamental understanding of coupling effects such as B-field coupling, standing waves and gradient coil effects
on local SAR.

## Key facts

- **NIH application ID:** 10093044
- **Project number:** 5R01EB029331-02
- **Recipient organization:** GEORGIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** F. Levent Degertekin
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $415,692
- **Award type:** 5
- **Project period:** 2020-02-01 → 2023-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10093044

## Citation

> US National Institutes of Health, RePORTER application 10093044, Acousto-optical RF field sensors for safer diagnostic and interventional MRI (5R01EB029331-02). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10093044. Licensed CC0.

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