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Poster

A Microstrip Resonator for Animal MRI at 16.4 T

MPG-Autoren
http://pubman.mpdl.mpg.de/cone/persons/resource/persons84213

Shajan,  G
Department High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons83793

Balla,  DZ
Department High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons83973

Hoffmann,  J
Department High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84145

Pohmann,  R
Department High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Zitation

Shajan, G., Balla, D., Hoffmann, J., & Pohmann, R. (2008). A Microstrip Resonator for Animal MRI at 16.4 T. Poster presented at ESMRMB 2008 Congress: 25th Annual Meeting, Valencia, Spain.


Zitierlink: http://hdl.handle.net/11858/00-001M-0000-0013-C6D1-1
Zusammenfassung
Introduction: MRI is increasingly moving towards higher magnetic field because of the inherent high sensitivity and greater spectroscopic resolution. To realize these advantages, the front end, the RF coil and the receive chain, needs to be optimized. A Quadrature Microstrip Transmission Line (MTL) resonator was built and SNR is compared with a commercially available shielded linear birdcage coil. This work also includes development of a TR switch module (consisting of T/R switch and preamplifier) and a Microstrip transmission line based Quadrature hybrid. Subjects and Methods: Experiments were performed on a 16.4T/26cm horizontal bore Magnex Magnet attached to a Bruker biospec Spectrometer. The imaging gradient system has an inner diameter of 12cms. The resonator (Figure 1) is built on Teflon cylinder with wall thickness 5mm. It consists of 8 equally spaced λ/2 MTL resonators. Electromagnetic coupling among the 8 resonators makes the entire MTL volume coil resonate at the desired frequency. In this case, each resonator is tuned to 725MHz to resonate the volume coil to 705MHz in the unloaded condition. The TR switch module consists of a diode network and a 2 stage low noise amplifier (LNA). The first stage of the LNA has PHEMT ATF35143 and the second stage has BJT BFR193. The TR switch module has a gain of 30dB and noise figure of 1.1dB at 698MHz. Results: The losses in the receive chain is reduced by connecting the TR switch module closer to the birdcage coil. An SNR gain of 1.4X is observed as shown in Table 1. The MTL resonator has double the volume of the birdcage resonator and has comparable SNR as that of the birdcage resonator (Table 1). The linear and combined phantom images are shown in Figure 2. Figure 3 shows in-vivo Axial and Sagittal rat brain RARE images with in-plane spatial resolution of 117μm. Conclusion: A Quadrature MTL resonator with good SNR and signal uniformity has been built. This paves the way for developing actively decoupled resonators and to use smaller receive only surface coils for improved Sensitivity at 16.4T.