A Pi-Shaped Compact Dual Tuned 1H/23Na Microstripline-Based Switch for 7-Tesla MRI

Abstract

In this article, a compact transmitting/receiving switch is designed with concentric microstriplines on the top and bottom faces of a coupler to handle RF signals to/from 1H and 23Na RF coils working specifically at 7-Tesla magnetic resonance imaging machines. A pi-shaped equivalent circuit, from the transmission line theory, has been used with outer and inner microstriplines to compact them in size. The switch has been designed using an electromagnetic wave simulator in order to transmit/receive RF signals to/from the RF coils at the specified resonance frequencies that match with the same speeds of precession of the 1H and 23Na atomic nuclei to support imaging as well as spectroscopic features that are used to monitor the metabolism changes as a measure to the existence of tumors. The proposed pi-shaped equivalent circuit has miniaturized the size of the designed dual tuned switch by around 70% compared to classical fabricated microstripline-based switch. This work adds promising benefits to multi-tuned switches in terms of capability to be integrated with multichannel RF coils. The proposed miniaturized dual tuned switch has revealed high isolation between inner and outer couplers and excellent insertion losses during transmit and receive modes for both 1H and 23Na MRI.