Improved sensitivity and microvascular weighting of 3T laminar fMRI with GE-BOLD using NORDIC and phase regression

• Published in: NeuroImage (Orlando, Fla.) Fla.), 2023-05, Vol.271, p.120011-120011, Article 120011
• Main Authors: Knudsen, Lasse, Bailey, Christopher J., Blicher, Jakob U., Yang, Yan, Zhang, Peng, Lund, Torben E.
• Format: Article
• Language: English
• Subjects: 3 Tesla; Blood; Brain; Brain Mapping - methods; Contamination; Cortex (motor); Cortex (temporal); Cortical layers; Functional magnetic resonance imaging; Hand; Humans; Laminar fMRI; Magnetic Resonance Imaging - methods; Microvasculature; Motor task performance; NORDIC denoising; Phase regression; Primary motor cortex; Reproducibility of Results; Signal-To-Noise Ratio; Spatial discrimination; Time series; Upper Extremity; Veins & arteries
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2023.120011

•We tested the feasibility of laminar BOLD fMRI at 3T.•NORDIC denoising was used to improve tSNR by a factor of ∼3.•Phase regression reduced macrovascular contamination.•With these tools, layerprofiles could be obtained robustly within and across sessions.•Improved feasibility of 3T laminar fMRI is supported thus increasing its availability. Functional MRI with spatial resolution in the submillimeter domain enables measurements of activation across cortical layers in humans. This is valuable as different types of cortical computations, e.g., feedforward versus feedback related activity, take place in different cortical layers. Laminar fMRI studies have almost exclusively employed 7T scanners to overcome the reduced signal stability associated with small voxels. However, such systems are relatively rare and only a subset of those are clinically approved. In the present study, we examined if the feasibility of laminar fMRI at 3T could be improved by use of NORDIC denoising and phase regression. 5 healthy subjects were scanned on a Siemens MAGNETOM Prisma 3T scanner. To assess across-session reliability, each subject was scanned in 3–8 sessions on 3–4 consecutive days. A 3D gradient echo EPI (GE-EPI) sequence was used for BOLD acquisitions (voxel size 0.82 mm isotopic, TR = 2.2 s) using a block design finger tapping paradigm. NORDIC denoising was applied to the magnitude and phase time series to overcome limitations in temporal signal-to-noise ratio (tSNR) and the denoised phase time series were subsequently used to correct for large vein contamination through phase regression. NORDIC denoising resulted in tSNR values comparable to or higher than commonly observed at 7T. Layer-dependent activation profiles could thus be extracted robustly, within and across sessions, from regions of interest located in the hand knob of the primary motor cortex (M1). Phase regression led to substantially reduced superficial bias in obtained layer profiles, although residual macrovascular contribution remained. We believe the present results support an improved feasibility of laminar fMRI at 3T.