Strong gradients, cool performance: A 64-channel array coil with concurrent field monitoring and thermal control for ex vivo diffusion-weighted brain imaging using the 3T connectome 2.0 MRI scanner
Purpose
High-resolution ex vivo diffusion-weighted imaging (dMRI) with high 𝑏-values presents significant challenges, including low signal-to-noise ratio (SNR), magnetic field perturbations, and temperature-related measurement shifts. This work introduces a hardware-based solution to address these limitations in human ex vivo brain imaging.
Methods
A customized anatomically conformal 64-channel receive array coil with a dedicated Tx birdcage coil was developed for 3T diffusion-weighted imaging of whole human ex vivo brain specimens. Field monitoring capabilities were integrated to correct spatiotemporal field perturbations caused by gradient-induced eddy currents. Temperature stability throughout extended acquisition periods was achieved through an integrated stabilization system. Coil performance was validated through comprehensive measurement of SNR, g-factor maps, field camera free induction decays (FIDs), temperature, mean diffusivity, and fractional anisotropy across multiple diffusion-weighted scans.
Results
The system demonstrated 73% higher SNR compared with a 72-channel in vivo head coil. Integration of the field camera maintained its FID quality without SNR penalties or significant receive coil coupling effects. Temperature stabilization improved the reliability of quantitative diffusion-weighted measurements by eliminating measurement drift during a 13-hour acquisition, where mean diffusivity and mean kurtosis would have increased by 22% and decreased by 19%, respectively.
Conclusion
We describe an integrated hardware approach for addressing higher order field perturbations, thermal instability, and SNR challenges in human ex vivo whole brain dMRI under high-diffusion sensitizing gradient conditions. This approach combines an anatomically optimized multichannel receive array, concurrent field monitoring, and active temperature stabilization. Enhanced image quality and improved reliability of quantitative MR imaging were demonstrated with this comprehensive hardware solution.
