Novel 1H/19F double‐tuned coil using an asymmetrical butterfly coil

TL;DR

This paper introduces a new MRI coil design that efficiently captures both proton and fluorine signals, improving imaging quality for applications like cell tracking.

Contribution

The asymmetrical butterfly coil design enables dual-tuning for 1H and 19F without signal loss, offering higher efficiency than traditional methods.

Findings

The asymmetrical butterfly coil achieved higher quadrature efficiency at both 1H and 19F frequencies.

It demonstrated superior receive sensitivity and SNR compared to a single-tuned loop coil.

The split resonance peak effectively spanned the 19F to 1H frequency range without losses.

Abstract

Background: Fluorine‐19 (19F) magnetic resonance imaging (MRI) is a non‐invasive imaging tool for the targeted application of fluorinated agents, such as cell tracking, and for the demonstration of oximetry. However, as the SNR of 19F is significantly weaker than that of proton (1H) imaging, the 19F coil must be combined with 1H coils for anatomical co‐registration and B0 shimming. This is difficult due to the strong coupling between the coils when they are in proximity, and is problematic since the Larmor frequency of 19F is 94% that of 1H, further increasing the potential for coupling between the 1H and 19F elements.

Purpose: Conventional double‐tuned coil methods tend to generate loss compared to single‐tuned reference coils. The asymmetrical butterfly coil has a split resonance peak, which can cover frequencies of 1H and 19F without losses arising from lossy traps or switching circuits. In this study, the use of an asymmetrical butterfly coil was evaluated for 1H/19F applications.

Methods: To increase quadrature efficiency at both the 1H and 19F frequencies, the left and right loops of the butterfly coil were tuned asymmetrically. The coil's tuning and performance were evaluated in simulations and MR measurements, and the results were compared to a dimension‐matched single‐tuned loop coil.

Results: The split resonance peak of the asymmetrical butterfly coil successfully spanned the 19F to 1H frequency. It operated with higher quadrature efficiency at both 1H and 19F frequencies and demonstrated superior receive sensitivity and SNR compared to the dimension‐matched single‐tuned loop coil.

Conclusions: The split resonance peak of the asymmetrical butterfly coil supported both 1H and 19F frequencies, delivering a higher SNR than that of the single‐tuned loop coil. Since the asymmetrical butterfly coil can cover ¹H and ¹⁹F frequencies without loss and provides higher efficiency than the reference single‐tuned coil, it can be effectively utilized for ¹H/¹⁹F MRI applications.

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