Keywords: Task/Intervention Based fMRI, fMRI (task based), IGT, Neurofinance

Motivation: Neurofinance has shown great opportunity for researchers in the field of finance to understand the financial decision-making process at the neurological level.

Goal(s): To investigate the decision-making process through fMRI technique using IOWA Gambling task to understand the significance of education (financial management education in this study) for acquiring financial literacy skills for better financial decision making.

Approach: fMRI technique is used to identify the brain activation patterns for acquisition of financial literacy skills and further exploring the role of training on learning, memory.

Results: We identified areas with  association of memory and learning during financial decision-making via IGT task.

Impact: Neuroscience provides the foundation for comprehending affective influences on financial decisions. In recent years, neurological, behavioural and cognitive approaches have given economics and finance an impetus and has led to the emergence of the disciplines in Neurofinance and Neuroeconomics.

Keywords: fMRI Analysis, Epilepsy, Implanted Electrodes, intracranial EEG, fMRI, Susceptibility

Motivation: Model susceptibility-induced signal degradation in fMRI in patients with implanted electrodes and reduce imaging artifacts across electrodes. 

Goal(s): Develop a model to understand and mitigate susceptibility effects due to implanted electrodes in fMRI. 

Approach: Model electrode (platinum sphere) and brain activation contrast (cylinders representing blood vessels) at 3T. Calculate intravoxel dephasing and assess the impact of the electrode on signal amplitude and activation contrast. Investigate the impact of echo times on signal loss. 

Results: Key findings reveal signal enhancement with increased distance from the electrode and reduced contrast loss with shorter echo times.

Impact: This research could redefine future functional diagnostics in patients with implanted electrodes such as epilepsy or Parkinson’s disease patients, leading to more precise surgical interventions and improved patient care. Mitigating susceptibility-induced image artifacts will impact neuroscience research and clinical applications.

Keywords: fMRI Acquisition, Parallel Transmit & Multiband

Motivation: While pTx has been shown to improve the temporal signal-to-noise ratio (tSNR) in fMRI, it is not clear how variations in pulse fidelity between scans modulate tSNR and how this impacts fMRI studies using pTx.

Goal(s): To study whether the improved tSNR obtained with pTx in fMRI is reproducible across multiple scans of the same subject.

Approach: We scanned and rescanned two subjects using both traditional and pTx excitations, and examined the variation in tSNRs between the scans.

Results: Traditional and pTx excitations demonstrated comparable reproducibility in tSNR.

Impact: The improved tSNRs obtained using pTx were consistent across scans of the same subject, demonstrating inter-scan variations comparable with traditional single channel excitations. Collectively, these preliminary results suggest that pTx can be used with reproducibility confidence in fMRI studies.

Keywords: fMRI Acquisition, fMRI, B1-shim

Motivation: High-resolution MRI enables precise studies of specific brain regions but this comes at a cost of increased acquisition time.

Goal(s): We examined if calibration-free destructive interferences can be introduced with simple static B₁-shims for zoomed fMRI acquisitions.

Approach: We optimised destructive B₁ phase offsets and implemented these whilst assessing image quality in MPRAGE, tSNR in an EPI timeseries, flip angle distributions and |B₁|.

Results: Calibration-free destructive shims allowed reducing the field-of-view (50%) and acquisition-time (35%), while retaining good signal (higher B₁ and similar tSNR) in the target (visual cortex).

Impact: The calibration-free destructive B1 shims can be applied across brain regions with standard head coils and therefore translate across neuroscientific studies, while reducing acquisition-time and signal contributions from noise-prone areas. This may flexibly improve the spatial resolution and signal quality.

Keywords: fMRI Acquisition, fMRI, z-shim

Motivation: Combined fMRI acquisitions of human brainstem and cervical spinal cord helps to investigate their interaction, e.g., during pain processing.

Goal(s): To test whether combined T2*-weighted EPI of both regions is feasible at 7 Tesla.

Approach: EPI pulse sequence supporting region-wise geometry (FOV, slice thickness, voxel size), timing (echo spacing, echo time), and shim parameters (linear terms and frequency), and flip angles together with a region-wise shim algorithm extended to consider static third-order shim terms.

Results: A reasonable image quality could be obtained in both regions, but strategies to reduce ghosting artifacts in the spinal cord need to be investigated.

Impact: Being able to cover human brainstem and cervical spinal cord regions in a single EPI acquisition at 7 Tesla can help to investigate the interaction of both regions with improved spatial resolution.

Keywords: fMRI Acquisition, fMRI, z-shim

Motivation: Z-shimming ameliorates through-slice dephasing in T2*-weighted functional neuroimaging but, surprisingly, a linear fit to the field in slice direction may not provide z-shim settings yielding the maximum signal.

Goal(s): To demonstrate that optimum z-shim settings should be obtained from a reference acquisition stepping through a range of z-shims at the desired echo time.

Approach: Numerical simulations of the MR signal were performed for different through-slice field distributions, echo times, and z-shims.

Results: Z-shims derived from the linear fit minimize the dephasing but this is not equivalent to maximizing the signal. Furthermore, optimum z-shim settings may depend on the echo time.

Impact: The results could help to optimize z-shim settings in T2*-weighted acquisitions used for BOLD-based functional neuroimaging by using a reference acquisition stepping through a range of z-shims at the desired echo time rather than a fit to the field distribution.

Keywords: fMRI Acquisition, fMRI

Motivation: EPTI is a new highly-efficient imaging approach that addresses limitations of EPI by providing high-resolution distortion- and blurring-free imaging for fMRI. However, shot-to-shot phase-variations induced by physiological processes in conventional multi-shot EPTI can introduce instabilities into the reconstructed time-series data.

Goal(s): Improving physiology-induced temporal stability of multi-shot EPTI.

Approach: Combing multi-shot EPTI with the VFA-FLEET method, which minimizes shot-to-shot phase-variations by reordering the multi-shot acquisitions while maximizing the signal level by using a variable-flip-angle train and recursive RF pulse design.

Results: In vivo fMRI data acquired at 7T demonstrate that the physiological instabilities of multi-shot EPTI can be substantially reduced with proposed method.

Impact: Here we test whether temporal instabilities in conventional multi-shot EPTI time-series caused by physiological variability can be reduced by combining EPTI with the variable-flip-angle FLEET method. This combination can improve the usability and robustness of EPTI for high-resolution fMRI studies.

Keywords: fMRI Acquisition, fMRI, silent, Looping Star, pulse sequence design, non-cartesian reconstruction

Motivation: Silent Looping Star fMRI offers unique advantages for neuroscience investigation, but image quality is affected by undersampling artifacts. 

Goal(s): Here, we describe novel methods for improving the spatiotemporal encoding efficiency of Looping Star and thereby further advance its utility for silent fMRI.

Approach: A new Looping Star encoding scheme which adds extra out-of-plane oscillations and thereby improves overall encoding efficiency is introduced and combined with auto-calibrated cgSENSE parallel imaging reconstruction.  

Results: The sharpest, most intensity uniform images and lowest background noise are demonstrated by the combination of both enhancements while maintaining BOLD sensitivity in a simultaneous, combined visual and auditory fMRI task.

Impact: The combination of a new trajectory and auto-calibrated parallel imaging leads to sharper and more uniform silent fMRI images with reduced streaking artifacts as demonstrated visually and on a visual-auditory fMRI task.

Keywords: Neurotransmission, fMRI (resting state)

Motivation: To leverage the intrinsic multi-echo capabilities of Looping Star (ME-LS) for fMRI applications to minimize susceptibility-related signal loss to enhance sensitivity to underlying neurovascular changes.

Goal(s): Our objective is to demonstrate feasibility of detecting resting state networks using a silent multi-echo fMRI approach enabled by Looping Star

Approach: Resting-state Multi-echo Looping Star fMRI was implemented on MAGNUS and scanned in healthy volunteers.

Results: This feasibility study shows established resting-state networks and connectome matrixes for multi-echo Looping Star fMRI and highlights the impact of the broad parameter space accessible with MAGNUS for Looping Star.

Impact: Silent ME-fMRI has a multitude of advantages, ranging from increased sensitivity to neuro-correlates of sleep dysregulation, auditory-sensory studies, neurological disorders and to provide a more immersive experience by combining sound with visual stimuli in the MR environment.

Keywords: fMRI Acquisition, fMRI

Motivation:  
Zero-TE fMRI offers researchers a valuable tool for enabling more efficient and effective awake animal imaging. However, this has yet to be tested and validated in mice, a popular species in fMRI studies.

Goal(s): The goal of this study is to validate using zero-TE fMRI in a mouse model, through signal analysis and characterization, and later connectivity comparisons/analyses.

Approach: 10 anesthetized (1.1%iso) mice were scanned for resting-state and stimulation-based fMRI at 9.4T, acquired using EPI and ZTE; the reconstructed data were then characterized.

Results: This study presents evidence that though ZTE signal differs from EPI signal, there is still sufficient overlap in connectivity.

Impact: This study presents evidence that ZTE is an effective alternative to EPI in fMRI studies. If employed, this will address several issues researchers currently face (motion artifacts, signal loss, etc.), while still ensuring functional contrast is produced.

Keywords: fMRI Acquisition, fMRI, fMRI(Non-BOLD)

Motivation: To propose the novel spin-lock sequence employing phase modulation (self-resonance spin-lock: SR-SL). There is no report on self-resonance during the spin-lock pulse, and we would like to share this idea through this report.

Goal(s): To demonstrate the feasibility of SR-SL and characterize its pros and cons.

Approach: Mathematical analysis of the Bloch equation, numerical simulation, and phantom experiment.

Results: All the results of three approaches agreed. We confirmed the phase modulation could control the operating point of MR image contrast, which provides us with desired contrast change depending on the target magnetic field.

Impact: We proposed the novel spin-lock sequence named self-resonance spin-lock (SRSL), which can control the operating point of MR image contrast and provides desired contrasts. SR-SL has potential to improve sensitivity to magnetic fields and save saturation absorption rate.

Keywords: fMRI Acquisition, fMRI, inflow effects

Motivation: Most fMRI techniques infer neuronal activity from signal changes created by a complex interplay between hemodynamics and sequence design parameters.  

Goal(s): Investigate inflow effects in SE-BOLD fMRI signals at different field strengths and resolutions.

Approach: We placed PINS pulses to saturate the magnetization in all slice gaps. By turning them on or off, inflow contributions to the SE-BOLD signal were modulated. Both 3- and 1.5-mm data were collected using a visual stimulation paradigm at 3T and 7T.

Results: Inflow contributions to SE-BOLD varied by field strength and partial voluming effects. Even at 7T, non-negligible inflow contributions were observed.

Impact: Saturating the magnetization in slice-gaps allows investigation of inflow effects in SE-BOLD fMRI. Low-resolution 3T-data revealed differences in onset timing. Comparing low- and high-resolution 7T-data with and without slice-gap saturation, increased resolution retained more activation, suggesting reduced sensitivity to inflow. 

Keywords: fMRI Acquisition, High-Field MRI, Laminar fMRI, High-resolution fMRI

Motivation: Resolving distinct functional activation and connectivity within cerebral cortical layers requires high imaging resolutions and microvascular specificity along with sufficient sensitivity—a major challenge for current fMRI methodologies.

Goal(s): To measure capillary-weighted spin-echo-BOLD fMRI signals in human cerebral cortex, with 500-micron resolution in the radial direction (i.e., perpendicular to the cortical surface).

Approach: We used a novel “linescan” technique that samples a single spin echo with multiple gradient echoes.

Results: We provide the first demonstration of T₂-weighted BOLD activation via linescan fMRI in humans and show that the multiple gradient echoes can be combined in various ways to manipulate functional contrast and sensitivity.

Impact: Our novel LS-GESSE technique allows for controlled trade-offs between sensitivity and specificity and should help enable the measurement of microvascular fMRI signals at spatial resolutions approaching the thickness of individual cortical layers, facilitating noninvasive studies of cortical dynamics and circuitry.

Keywords: fMRI Acquisition, Blood vessels, SE-BOLD EPI

Motivation: Macrovascular contributions to the BOLD signal reduce microvascular specificity, which can be alleviated by using SE sequences -refocusing local field inhomogeneities near large veins. Thus, the microvascular specificity of SE-EPI scan will rely on ETL duration, however, this dependence is not well-characterized in humans at 7T. 

Goal(s): Determining how microvascular-specific SE-EPI BOLD responses vary with ETL in humans at 7T.

Approach: A biophysical model was developed and a validation experiment was conducted during a hyperoxic gas-challenge aiming at determining this goal.

Results: Both our simulations and measurements indicate an increase in macrovascular contamination with longer ETL-durations, leading to a decrease in microvascular specificity.

Impact: Through biophysical simulations and measurements, we show an increase in macrovascular contamination with longer ETL durations, leading to a substantial decrease in microvascular SE-BOLD specificity

Keywords: fMRI Acquisition, fMRI (task based), diffusion

Motivation: Addressing the uncertainty of dfMRI's spatial specificity compared to BOLD-fMRI, considering the influence of perfusion and potential for more localized brain activation mapping.

Goal(s): To evaluate whether six-directional MPG dfMRI enhances the localization of brain activity in response to visual stimulation versus standard BOLD-fMRI.

Approach: Employed high-resolution 7T MRI with dfMRI and BOLD protocols, analyzing data with advanced pre-processing and statistical methods to compare spatial activation patterns.

Results: dfMRI demonstrated more confined activation regions, especially at higher b-values, suggesting improved spatial specificity, although complete isolation from BOLD-fMRI's T2* changes remains challenging.

Impact: Enhanced dfMRI specificity could refine our understanding of neural activity patterns, crucial for advancing cognitive neuroscience and developing targeted brain-based interventions.

Keywords: fMRI Acquisition, fMRI (task based), non-BOLD fMRI; diffusion tensor encoding; white matter

Motivation: Diffusion fMRI (dfMRI) has the potential to overcome some of the limitations of BOLD fMRI. However, acquisitions with linear diffusion encoding are sensitive to the underlying fibre orientations and may therefore give variable sensitivity, particularly in white matter.

Goal(s): To assess the utility of isotropic b-tensor encoding in a diffusion fMRI acquisition (iso-dfMRI).

Approach: We acquired iso-dfMRI data during a visual stimulation task. We compared this to dfMRI with linear diffusion encoding (dir-dfMRI) and to BOLD.

Results: Iso-dfMRI detected activity in the visual system with a larger spatial extent than dir-dfMRI and was less dependent on underlying fibre orientations.

Impact: We highlight the utility of isotropic b-tensor encoding dfMRI for detecting activity independently of underlying fibre arrangement. Thus, temporal resolution can be increased compared to acquiring multiple linear encoding directions and fMRI sensitivity in white matter boosted compared to BOLD.