Optimized radiofrequency coil setup for MR examination of living isolated rat hearts in a horizontal 9.4T magnet

Abstract

Purpose: (i) To optimize an MR-compatible organ perfusion setup for the nondestructive investigation of isolated rat hearts by placing the radiofrequency (RF) coil inside the perfusion chamber; (ii) to characterize the benefit of this system for diffusion tensor imaging and proton ( 1 H-) MR spectroscopy. Methods: Coil quality assessment was conducted both on the bench, and in the magnet. The benefit of the new RF-coil was quantified by measuring signal-to-noise ratio (SNR), accuracy, and precision of diffusion tensor imaging/error in metabolite amplitude estimation, and compared to an RF-coil placed externally to the perfusion chamber. Results: The new design provided a 59% gain in signal-to-noise ratio on a fixed rat heart compared to using an external resonator, which found reflection in an improvement of living heart data quality, compared to previous external resonator studies. This resulted in 14-29% improvement in accuracy and precision of diffusion tensor imaging. The Cramer-Rao lower bounds for metabolite amplitude estimations were up to 5-fold smaller. Conclusion: Optimization of MR-compatible perfusion equipment advances the study of rat hearts with improved signal-tonoise ratio performance, and thus improved accuracy/precision. Magn Reson Med 73:2398-2405,

Interrogation of living myocardium in multiple static deformation states with diffusion tensor and diffusion spectrum imaging

“…The SNR gain can be invested in reducing scan time, increasing the spatial resolution and/or increasing the number of diffusion directions used. Higher SNR improves the precision and accuracy of DTI estimates in fixed rat hearts ( Hales et al., 2010; Lohezic et al., 2014 ). This could be used to reduce the number of animals needed for studies.…”

“…Furthermore, the changes in FA and the ratios λ 1 / λ 2 and λ 2 / λ 3 between the three mechanical states were found to be significant, which was not the case in the previous study. The gain in SNR obtained by integrating the RF coil inside the perfusion chamber results in improved accuracy and precision of the DTI estimates ( Lohezic et al., 2014 ), which could explain the statistically significant changes.…”

“…The setup presented by Hales et al. ( Hales et al., 2012 ) was modified by integrating the RF coil inside the perfusion rig ( Lohezic et al., 2014 ), as close as possible around the heart ( Fig. 1 ), and by delivering oxygen-enriched, albumin-containing perfusate under constant flow and at body temperature to the heart inside the magnet.…”

“…Refinement of the RF coil technology can improve the SNR of the MRI experiments, leading to significant differences in the accuracy and precision of the measured DTI parameters ( Giannelli et al., 2011; Lohezic et al., 2014 ). Here, we introduce a novel perfusion rig that integrates the RF coil within the organ perfusion chamber.…”

Evaluation of metal plastic deformation using radio‐frequency reflection features

“…Li et al [25] proposed a spectral segmentation method for adaptively determining the optimal frequency of vibration signals. Radio‐frequency technology has been widely used in non‐destructive testing with the advantages including non‐contact, one‐sided, no need for couplet to transmit the signal into the material [26, 27]. However, there are few works on metal plastic deformation using radio‐frequency method.…”