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PAPOTI, D. Development of RF transmitter coils and receivers NMR phased arrays for magnetic resonance imaging experiments on rats . 2011. 142 p. Tese (Doutorado) – Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, 2011. Magnetic Resonance Imaging (MRI) experiments on small animals, as well as in human, require a specific RF coil set in order to maximize the Radiofrequency (RF) field homogeneity during transmission and Signal-to-Noise Ratio (SNR) during reception. The most common geometries of RF transmitter coil used in human systems are the well known Birdcage resonators. Among the receiver coil’s geometry the concept of NMR Phased Arrays or multi channel coils is widely employed in applications that need a high SNR in a large region of interest (ROI), further allowing parallel imaging acquisition methodologies. The work reported here describes the development of a transmit-only and receive-only RF coil set actively detuned specifically designed to MRI acquisition of rat’s brain for purposes of neuroscience studies. The transmitter geometries developed were two Birdcages with 8 and 16 rungs and our proposed geometry named Double Crossed Saddle (DCS). For reception we developed one common surface coil made of two turn loops and a 2-channel Phased Array, both actively detuned during reception. The results have confirmed that the 16 rungs Birdcage are superior among other transmit coils in producing homogeneous RF field inside a ROI of 80% of coil ́s inner diameter. However, the simplicity and reduced number of capacitors makes the DCS coil a good choice in experiments with different samples and load conditions. Among the receive coils developed, the surface coil showed a better SNR in comparison with the 2-channel Phased array, which has the advantage of producing a large area with high SNR. The SNR of both surface coil and 2-channel array was compared with a transceiver Saddle Crossed coil, available at our lab, specific designed to obtain rat brain images. These results have corroborated that transmit-only and receive-only RF coils have best performance than transceiver volume coils for obtain MRI images of rat’s brain, allowing image acquisition with same resolution and reduced scan time.

Desenvolvimento de bobinas de RF transmissoras e receptoras do tipo >i<phased arrays>/i< para experimentos de imagens por ressonância magnética em ratos

Desenvolvimento de bobinas de RF transmissoras e receptoras do tipo >i/i< para experimentos de imagens por ressonância magnética em ratos