Design and construction of an actively frequency-switchable RF coil for field-dependent Magnetisation Transfer Contrast MRI with fast field-cycling

Magnetisation Transfer Contrast (MTC) is an important MR contrast-generating mechanism to characterise the MR-invisible macromolecular protons using an off-resonance pre-saturation RF irradiation pulse (or MT pulse). MTC MRI is normally implemented at a fixed magnetic field; however, it may be usefu...

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Bibliographic Details
Published in:Journal of magnetic resonance (1997) 2010-11, Vol.207 (1), p.134-139
Main Authors: Choi, Chang-Hoon, Hutchison, James M.S., Lurie, David J.
Format: Article
Language:English
Subjects:
Coiling
Construction
Design engineering
Electromagnetic Fields
Electronics
Equipment Design
Field-cycling
Irradiation
Magnetic fields
Magnetic resonance
Magnetic Resonance Imaging - instrumentation
Magnetisation transfer
Multi-tunable coil
Phantoms, Imaging
PIN diode switch
PIN diodes
Protons
Radio frequencies
Radio Waves
Switching
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Summary:Magnetisation Transfer Contrast (MTC) is an important MR contrast-generating mechanism to characterise the MR-invisible macromolecular protons using an off-resonance pre-saturation RF irradiation pulse (or MT pulse). MTC MRI is normally implemented at a fixed magnetic field; however, it may be useful to evaluate changes of the MT effect as a function of external magnetic field strength (B0). In order to conduct field-dependent MTC experiments with a single MR system, two techniques are crucially needed. B0 should be able to be switched between levels during irradiation of the MT pulse. At the same time, the resonance frequency of the RF coil (f0) should also be able to be shifted to the corresponding value. Switching B0 is attained by the fast field-cycling technique, while in order to switch f0, a specially designed multi-tunable RF coil is required. Here, we designed and constructed an actively frequency-switchable RF coil for frequencies at and below 2.5MHz. The design employed PIN diodes, and enabled switching f0 between five different values, with excellent impedance matching (approximately −37dB S11 reflection) and Q-factor of about 100 at each configuration.
ISSN:1090-7807
1096-0856
DOI:10.1016/j.jmr.2010.08.018