Patient safety concept for multichannel transmit coils
✍ Scribed by Frank Seifert; Gerd Wübbeler; Sven Junge; Bernd Ittermann; Herbert Rinneberg
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 816 KB
- Volume
- 26
- Category
- Article
- ISSN
- 1053-1807
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
Purpose
To propose and illustrate a safety concept for multichannel transmit coils in MRI based on finite‐differences time‐domain (FDTD) simulations and validated by measurements.
Materials and Methods
FDTD simulations of specific absorption rate (SAR) distributions in a cylindrical agarose phantom were carried out for various radio frequency (RF) driving conditions of a four‐element coil array. Additionally, maps of transmit amplitude, signal phase, and temperature rise following RF heating were measured by MRI.
Results
Quantitative agreement was achieved between simulated and measured field distributions, thus validating the numerical modeling. When applying the same RF power to each element of the coil array but systematically varying the RF phase between its elements, the maximum of the SAR distribution was found to vary by a factor of about 15.
Conclusion
Our results demonstrate that current RF safety approaches are inadequate to deal with the new challenge of multichannel transmit coils. We propose a new concept based on a systematic investigation of the parameter space for RF phases and amplitudes. In this way the driving conditions generating the highest local SAR values per unit power can be identified and appropriately considered in the RF safety concept of a given MRI system. J. Magn. Reson. Imaging 2007;26:1315–1321. © 2007 Wiley‐Liss, Inc.