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Magnetic Resonance An interactive open-access publication of the Groupement AMPERE
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https://doi.org/10.5194/mr-2020-20
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/mr-2020-20
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  01 Sep 2020

01 Sep 2020

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This preprint is currently under review for the journal MR.

Increased flow rate of hyperpolarized aqueous solution for DNP-enhanced MRI achieved by an open Fabry-Pérot type microwave resonator

Alexey Fedotov1, Ilya Kurakin1, Sebastian Fischer2, Thomas Vogl2, Thomas F. Prisner3, and Vasyl Denysenkov3 Alexey Fedotov et al.
  • 1Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, 603950, Russia
  • 2Institute of Diagnostic and Interventional Radiology, University Hospital Frankfurt, Frankfurt am Main, 60590, Germany
  • 3Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University, Frankfurt am Main, 60438, Germany

Abstract. A continuous flow dynamic nuclear polarization (DNP) employing the Overhauser effect at ambient temperatures can be used among other methods to increase sensitivity of magnetic resonance imaging (MRI). The hyperpolarized state of water protons can be achieved by flowing aqueous liquid through a microwave resonator placed directly in the bore of a 1.5 T MRI magnet. Here we describe a new open Fabry-Pérot resonator as DNP polarizer, which exhibits a larger microwave exposure volume for the flowing liquid in comparison with a cylindrical TE013 microwave cavity. The Fabry-Pérot resonator geometry was designed using quasi-optical theory and simulated by CST software. Performance of the new polarizer was tested by MRI DNP experiments on a TEMPOL aqueous solution using a blood-vessel phantom. The Fabry-Pérot resonator revealed a 2-fold larger DNP enhancement with a 4-fold increased flow rate compared to the cylindrical microwave resonator. This increased yield of hyperpolarized liquid allows MRI applications on larger target objects.

Alexey Fedotov et al.

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Alexey Fedotov et al.

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Short summary
The sensitivity of magnetic resonance imaging can be increased by coupling of the less sensitive nuclear spins which are excited at radio-frequencies to unpaired electron spins of radicals which are excited at microwave frequencies. Here we demonstrate how an Fabry-Perot type microwave resonance structure can be used to significantly enhance the polarization transfer from electron to water proton nuclear spins under constant flow conditions for imaging applications at 1.5 T.
The sensitivity of magnetic resonance imaging can be increased by coupling of the less sensitive...
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