MR imaging quality and feasibility of a novel interleaved iTBS/fMRI setup

Abstract Introduction: Concurrent TMS/fMRI has become a promising technique for investigating the acute effects of rTMS on the brain. However, image quality in concurrent TMS/fMRI may still have its limitations. In this study, we aimed to explore the data quality before concluding the findings from this state-of-the-art setup to ensure the imaging quality was sufficient for analysis. Methods: Nineteen healthy participants participated in this study. In the first session, we performed baseline MRI scans with a 64-channel head coil in a 3T Magnetom Prisma scanner and measured individual resting-motor thresholds (rMT). From the second to the fourth session, we performed scans with ultrathin 14-channel MR receive coils with a standard iTBS protocol and randomized three conditions for each participant: 80% or 40% rMT over the left DLPFC and 80% rMT over the left M1 region. In these sessions, structural scans (MP2RAGE sequence) and three functional scans were acquired, resting-state fMRI (rsfMRI) immediately before and after stimulation, and interleaved iTBS/fMRI. All rsfMRI data was preprocessed with bias field correction, despiking, segmentation, coregistration, normalization, and smoothing. Results: The mean TMS coil framewise displacement (FD) from the original target showed no significant difference between conditions. However, three subjects in the DLPFC 80% condition had coil displacement more than 3mm (Figure 1) related to TMS intolerance. MP2RAGE sequence provides satisfactory image quality, but the SNR and CNR are still inferior to the baseline T1w image (Figure 2). For fMRI imaging, we compared the SNR on both rsfMRI and interleaved iTBS/fMRI; all improved significantly after preprocessing (Figure 3). Discussions: This result demonstrates that the novel concurrent TMS/fMRI setup provides high-quality structural and functional scans. Additionally, the TMS coil had an acceptable FD range confirmed for further analysis. This study was supported by the Federal Ministry of Education and Research: ERA-NET NEURON,FKZ:01EW1903View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT) Research Category and Technology and Methods Translational Research: 10. Transcranial Magnetic Stimulation (TMS) Keywords: TMS, fMRI, Concurrent TMS/fMRI