Medical College of Wisconsin
CTSICores SearchResearch InformaticsREDCap

Automatic tuned MRI RF coil for multinuclear imaging of small animals at 3T. J Magn Reson 2002 Mar;155(1):39-44 PMID: 11945031

Abstract

We have developed an MRI RF coil whose tuning can be adjusted automatically between 120 and 128 MHz for sequential spectroscopic imaging of hydrogen and fluorine nuclei at field strength 3 T. Variable capacitance (varactor) diodes were placed on each rung of an eight-leg low-pass birdcage coil to change the tuning frequency of the coil. The diode junction capacitance can be controlled by the amount of applied reverse bias voltage. Impedance matching was also done automatically by another pair of varactor diodes to obtain the maximum SNR at each frequency. The same bias voltage was applied to the tuning varactors on all rungs to avoid perturbations in the coil. A network analyzer was used to monitor matching and tuning of the coil. A Pentium PC controlled the analyzer through the GPIB bus. A code written in LABVIEW was used to communicate with the network analyzer and adjust the bias voltages of the varactors via D/A converters. Serially programmed D/A converter devices were used to apply the bias voltages to the varactors. Isolation amplifiers were used together with RF choke inductors to provide isolation between the RF coil and the DC bias lines. We acquired proton and fluorine images sequentially from a multicompartment phantom using the designed coil. Good matching and tuning were obtained at both resonance frequencies. The tuning and matching of the coil were changed from one resonance frequency to the other within 60 s.

Author List

Muftuler LT, Gulsen G, Sezen KD, Nalcioglu O

Author

Lutfi Tugan Muftuler PhD Associate Professor in the Neurosurgery department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Equipment Design
Magnetic Resonance Imaging
Phantoms, Imaging



View this publication's entry at the Pubmed website PMID: 11945031
jenkins-FCD Prod-158 788e756cee95f97989f23472575fc754037544be