J J Bluemink

Publications (2)5.93 Total impact

• Article: Improved RF performance of travelling wave MR with a high permittivity dielectric lining of the bore.

  A Andreychenko, J J Bluemink, A J E Raaijmakers, J J W Lagendijk, P R Luijten, C A T van den Berg
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  ABSTRACT: Application of travelling wave MR to human body imaging is restricted by the limited peak power of the available RF amplifiers. Nevertheless, travelling wave MR advantages like a large field of view excitation and distant location of transmit elements would be desirable for whole body MRI. In this work, improvement of the B 1+ efficiency of travelling wave MR is demonstrated. High permittivity dielectric lining placed next to the scanner bore wall effectively reduces attenuation of the travelling wave in the longitudinal direction and at the same time directs the radial power flow toward the load. First, this is shown with an analytical model of a metallic cylindrical waveguide with the dielectric lining next to the wall and loaded with a cylindrical phantom. Simulations and experiments also reveal an increase of B 1+ efficiency in the center of the bore for travelling wave MR with a dielectric lining. Phantom experiments show up to a 2-fold gain in B 1+ with the dielectric lining. This corresponds to a 4-fold increase in power efficiency of travelling wave MR. In vivo experiments demonstrate an 8-fold signal-to-noise ratio gain with the dielectric lining. Overall, it is shown that dielectric lining is a constructive method to improve efficacy of travelling wave MR. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
  Magnetic Resonance in Medicine 10/2012; · 2.96 Impact Factor
• Article: High-resolution MRI of the carotid arteries using a leaky waveguide transmitter and a high-density receive array at 7 T.

  W Koning, J J Bluemink, E A J Langenhuizen, A J Raaijmakers, A Andreychenko, C A T van den Berg, P R Luijten, J J M Zwanenburg, D W J Klomp
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  ABSTRACT: A setup for 7T MRI of the carotid arteries in the neck was designed and constructed. Separate dedicated arrays were used for transmit and receive. For the transmit array, single-side adapted dipole antennas were mounted on a dielectric pillow, which was shown to serve as a leaky waveguide, efficiently distributing B(1) into the neck. Risk assessment was performed by simulations. Phantom measurements were performed to establish optimal positions of the antennas on the pillow. Using two antennas, a dual transmit setup was created. In vivo B(1) (+) maps with different shim configurations were acquired to assess transmit performance. This effective transmit array was used in combination with a dedicated 30 channel small element receive coil. High-resolution in vivo turbo spin echo images were acquired to demonstrate the excellent performance of the setup. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
  Magnetic Resonance in Medicine 07/2012; · 2.96 Impact Factor