A review of parallel transmit arrays for ultra-high field MR imaging

Chang-Hoon Choi, Andrew Webb, Stephan Orzada, Mikheil Kelenjeridze, N. Jon Shah, Jörg Felder

14th February 2023

Parallel transmission (pTx) techniques are used in ultra-high field (UHF) MR imaging to reduce inhomogeneity in the distribution of the flip angle and to control for elevated specific absorption rate (SAR). Given the increasing availability of UHF MRI systems at 7 T and above, it is anticipated that interest in pTX applications will grow accordingly.

One of the key components in MR systems capable of pTX is the design of the transmit array, as this has a major impact on performance in terms of power requirements, SAR and RF pulse design. Consequently, this paper analyses transmit array concepts to determine the strengths and weaknesses of different types of design and provides a systematic review of individual antennas employed for UHF, their combination into pTX arrays and methods to decouple the individual elements. Figures-of-merit (FoMs) frequently employed to describe the performance of pTX arrays are also given, along with summaries of published array designs in terms of these FoMs.

Original publication: A review of parallel transmit arrays for ultra-high field MR imaging