Eight‐channel transceiver RF coil array tailored for 1H/19F MR of the human knee and fluorinated drugs at 7.0 T |
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| Authors: | Lukas Winter Pavla Neumanova Daniela Hofmann Jan Rieger Ralf Mekle Sonia Waiczies Thoralf Niendorf |
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| Affiliation: | 1. Berlin Ultrahigh Field Facility (BUFF), Max Delbrück Center for Molecular Medicine, Berlin, Germany;2. MRI.TOOLS GmbH, Berlin, Germany;3. Physikalisch‐Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany;4. Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine, Berlin, Germany |
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| Abstract: | The purpose of this study was to evaluate the feasibility of an eight‐channel dual‐tuned transceiver surface RF coil array for combined 1H/19F MR of the human knee at 7.0 T following application of 19F‐containing drugs. The 1H/19F RF coil array includes a posterior module with two 1H loop elements and two anterior modules, each consisting of one 1H and two 19F elements. The decoupling of neighbor elements is achieved by a shared capacitor. Electromagnetic field simulations were performed to afford uniform transmission fields and to be in accordance with RF safety guidelines. Localized 19F MRS was conducted with 47 and 101 mmol/L of flufenamic acid (FA) – a 19F‐containing non‐steroidal anti‐inflammatory drug – to determine T1 and T2 and to study the 19F signal‐to‐dose relationship. The suitability of the proposed approach for 1H/19F MR was examined in healthy subjects. Reflection coefficients of each channel were less than ?17 dB and coupling between channels was less than ?11 dB. QL/QU was less than 0.5 for all elements. MRS results demonstrated signal stability with 1% variation. T1 and T2 relaxation times changed with concentration of FA: T1/T2 = 673/31 ms at 101 mmol/L and T1/T2 = 616/26 ms at 47 mmol/L. A uniform signal and contrast across the patella could be observed in proton imaging. The sensitivity of the RF coil enabled localization of FA ointment administrated to the knee with an in‐plane spatial resolution of (1.5 × 1.5) mm2 achieved in a total scan time of approximately three minutes, which is well suited for translational human studies. This study shows the feasibility of combined 1H/19F MRI of the knee at 7.0 T and proposes T1 and T2 mapping methods for quantifying fluorinated drugs in vivo. Further technological developments are necessary to promote real‐time bioavailability studies and quantification of 19F‐containing medicinal compounds in vivo. Copyright © 2015 John Wiley & Sons, Ltd. |
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| Keywords: | magnetic resonance MRI fluorine magnetic resonance ultrahigh field MRI RF coil non‐steroidal anti‐inflammatory drug drug monitoring |
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