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Hyperpolarized C magnetic resonance spectroscopy in pig models enables metabolic activity mapping, providing a powerful tool for the study of the heart physiology, but requires the development of dedicated radiofrequency coils, capable of providing large field of view with high signal-to-noise ratio (SNR) data. This work describes the simulations and the tests of a transmit-only (TX) volume coil/receive-only (RX) surface coil both designed for hyperpolarized studies of pig heart with a clinical 3T scanner. The coil characterization is performed by developing an SNR model for coil performance in terms of coil resistance, sample-induced resistance and magnetic field pattern. In particular, coil resistances were calculated from Ohm's law, while magnetic field patterns and sample-induced resistances were calculated using a numerical finite-difference time-domain algorithm. Experimental phantom chemical shift image, showed good agreement with the theoretical SNR-vs-depth profiles and highlighted the advantage of the novel configuration over the single transmit-receive coils throughout the volume of interest for cardiac imaging in pig. Finally, the TX-birdcage/RX-circular configuration was tested by acquiring metabolic maps with hyperpolarized [1-13C] pyruvate injected i.v. in a pig. The results of the phantom and pig experiments show the ability of the coil configuration to image well the metabolites distribution. [ABSTRACT FROM AUTHOR]

ABSTRACT This work describes the design of a quadrature surface coil constituted by a circular loop and a butterfly coil, employed in transmit/receive (TX/RX) mode for hyperpolarized 13C studies of pig heart with a clinical 3T scanner. The coil characterization is performed by developing an SNR model for coil performance evaluation in terms of coil resistance, sample-induced resistance and magnetic field pattern. Experimental SNR-vs.-depth profiles, extracted from the [1-13C]acetate phantom chemical shift image (CSI), showed good agreement with the theoretical SNR-vs.-depth profiles. Moreover, the performance of the quadrature coil was compared with the single TX/RX circular and TX/RX butterfly coil, in order to verify the advantage of the proposed configuration over the single coils throughout the volume of interest for cardiac imaging in pig. Finally, the quadrature surface coil was tested by acquiring metabolic maps with hyperpolarized [1-13C]pyruvate injected i.v. in a pig. © 2013 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 43B: 69-77, 2013 [ABSTRACT FROM AUTHOR]

Radiofrequency coils in magnetic resonance systems are used to irradiate nuclear spins and to pick up the signals emitted by the nuclei with high signal-to-noise ratio and large sensitivity region. The quality of the obtained images strongly depends upon the coil performance. When used at low frequencies, a number of drawbacks arise that drastically reduce their overall performances. In this work, we describe and verify the accuracy of a coil sensitivity estimation method based on the perturbing sphere theory which permits characterization of coil performance in a short time and that can be useful for periodical coil quality controls. In particular, we describe the application of the method by testing two C birdcage coils tuned at 32.13 MHz and verifying its accuracy using theoretical and experimental approaches. [ABSTRACT FROM AUTHOR]

Cardiac metabolism assessment with hyperpolarized C magnetic resonance spectroscopy in pig models requires the design of dedicated coils capable of providing large field of view with high signal-to-noise ratio (SNR) data. This work presents a comparison between a commercial C quadrature birdcage coil and a homebuilt C circular coil both designed for hyperpolarized studies of pig heart with a clinical 3T scanner. In particular, the simulation of the two coils is described by developing an SNR model for coil performance prediction and comparison. While coil resistances were calculated from Ohm's law, the magnetic field patterns and sample-induced resistances were calculated using a numerical finite-difference time-domain algorithm. After the numerical simulation of both coils, the results are presented as SNR-versus-depth profiles using experimental SNR extracted from the [1-C]acetate phantom chemical shift image and with a comparison of metabolic maps acquired by hyperpolarized [1-C]pyruvate injected in a pig. The accuracy of the developed SNR models was demonstrated by good agreement between the theoretical and experimental coil SNR-versus-depth profiles. [ABSTRACT FROM AUTHOR]