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Eight‐channel transceiver RF coil array tailored for 1 H/ 19 F MR of the human knee and fluorinated drugs at 7.0 T
Author(s) -
Ji Yiyi,
Waiczies Helmar,
Winter Lukas,
Neumanova Pavla,
Hofmann Daniela,
Rieger Jan,
Mekle Ralf,
Waiczies Sonia,
Niendorf Thoralf
Publication year - 2015
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3300
Subject(s) - radiofrequency coil , nuclear magnetic resonance , electromagnetic coil , transceiver , radio frequency , physics , coupling (piping) , analytical chemistry (journal) , chemistry , materials science , nuclear medicine , electrical engineering , optoelectronics , cmos , chromatography , quantum mechanics , engineering , medicine , metallurgy
The purpose of this study was to evaluate the feasibility of an eight‐channel dual‐tuned transceiver surface RF coil array for combined 1 H/ 19 F MR of the human knee at 7.0 T following application of 19 F‐containing drugs. The 1 H/ 19 F RF coil array includes a posterior module with two 1 H loop elements and two anterior modules, each consisting of one 1 H and two 19 F 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 19 F MRS was conducted with 47 and 101 mmol/L of flufenamic acid (FA) – a 19 F‐containing non‐steroidal anti‐inflammatory drug – to determine T 1 and T 2 and to study the 19 F signal‐to‐dose relationship. The suitability of the proposed approach for 1 H/ 19 F 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. Q L / Q U was less than 0.5 for all elements. MRS results demonstrated signal stability with 1% variation. T 1 and T 2 relaxation times changed with concentration of FA: T 1 / T 2 = 673/31 ms at 101 mmol/L and T 1 / T 2 = 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) mm 2 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 1 H/ 19 F MRI of the knee at 7.0 T and proposes T 1 and T 2 mapping methods for quantifying fluorinated drugs in vivo . Further technological developments are necessary to promote real‐time bioavailability studies and quantification of 19 F‐containing medicinal compounds in vivo . Copyright © 2015 John Wiley & Sons, Ltd.