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S. E. Hosseini:
"Development of a highly sensitive 8 channel receive-only radio frequency coil array for microscopic magnetic resonance imaging at 7 Tesla";
Betreuer/in(nen): G. Badurek, E. Laistler; Atominstitut und Med. Univ. Wien, 2017; Abschlussprüfung: 29.08.2017.

High resolution magnetic resonance imaging (MRI) strongly depends on the availability of highly sensitive radio frequency (RF) coils. The goal of this work is the development of a receiver coil array with high sensitivity and parallel imaging performance. We designed and constructed a tube-shaped eight-channel receive-only array. The inner and outer diameter of the coil tube is limited by the space available in the transmit coil and the desired sample diameter, respectively. The individual coil elements were arranged to cover the surface of the inner cylinder in two rows consisted of four elements. Elements within one row were mutually decoupled by transformer decoupling. Decoupling between rows was achieved by coil overlap. In addition, preamplifier decoupling was implemented. A double-layer flexible printed circuit board (PCB) was designed for each of the two rows. The coil conductors were deposited on one layer, the other layer contained solder pads for the circuitry required for tuning, matching, transformer decoupling, active detuning, and preamplifier decoupling. These PCBs were wrapped around the inner cylinder (phenolic paper) before soldering the components and could be moved with respect to each other to optimize overlap decoupling between the rows. Preamplifiers are placed directly at the coil to minimize losses. Performance of the coil was validated with bench and imaging measurements. Each element was successfully tuned to 297.2 MHz and matched to 75 ohms. Efficient mutual decoupling (< -14dB) was achieved by transformer and overlap decoupling and supplemented by preamplifier decoupling (< -17dB). Active detuning circuits provided an isolation > 40 dB between tuned and detuned state. A very good homogeneity over a large field of view (FOV) (> 90 mm) was achieved with different samples. Construction of the array has potential for applying parallel imaging (R=2) with a reasonable SNR. The use of thin flexible PCBs enables the incorporation of the coil circuitry and on-board preamplifiers despite the limited available space. Comparative investigations can be done between the receiver coil and other available coils for further evaluations.

NMR / 7Tesla / coil development