scholarly journals The Significance of Echo Time in fMRI BOLD Contrast: A Clinical Study during Motor and Visual Activation Tasks at 1.5 T

Tomography ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 333-343
Author(s):  
Themistoklis Boursianis ◽  
Georgios Kalaitzakis ◽  
Katerina Nikiforaki ◽  
Emmanouela Kosteletou ◽  
Despina Antypa ◽  
...  
Keyword(s):  
Gray Matter ◽  
Brain Function ◽  
Blood Oxygen Level Dependent ◽  
Small Scale ◽  
Blood Oxygen Level ◽  
Specific Sequence ◽  
Visual Cortices ◽  
Echo Time ◽  
Sequence Parameters ◽  
Larger Sample

Blood Oxygen Level Dependent (BOLD) is a commonly-used MR imaging technique in studying brain function. The BOLD signal can be strongly affected by specific sequence parameters, especially in small field strengths. Previous small-scale studies have investigated the effect of TE on BOLD contrast. This study evaluates the dependence of fMRI results on echo time (TE) during concurrent activation of the visual and motor cortex at 1.5 T in a larger sample of 21 healthy volunteers. The experiment was repeated using two different TE values (50 and 70 ms) in counterbalanced order. Furthermore, T2* measurements of the gray matter were performed. Results indicated that both peak beta value and number of voxels were significantly higher using TE = 70 than TE = 50 ms in primary motor, primary somatosensory and supplementary motor cortices (p < 0.007). In addition, the amplitude of activation in visual cortices and the dorsal premotor area was also higher using TE = 70 ms (p < 0.001). Gray matter T2* of the corresponding areas did not vary significantly. In conclusion, the optimal TE value (among the two studied) for visual and motor activity is 70 ms affecting both the amplitude and extent of regional hemodynamic activation.

scholarly journals Similarities and Differences in Arterial Responses to Hypercapnia and Visual Stimulation

2010 ◽  
Vol 31 (2) ◽  
pp. 560-571 ◽  
Author(s):  
Yi-Ching Lynn Ho ◽  
Esben Thade Petersen ◽  
Ivan Zimine ◽  
Xavier Golay
Keyword(s):  
Blood Volume ◽  
Transit Time ◽  
Gray Matter ◽  
Visual Stimulation ◽  
Vascular System ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen Level ◽  
Functional Studies ◽  
Arterial Blood ◽  
Arterial Blood Volume

Despite the different origins of cerebrovascular activity induced by neurogenic and nonneurogenic conditions, a standard assumption in functional studies is that the consequence on the vascular system will be mechanically similar. Using a recently developed arterial spin labeling method, we examined arterial blood volume, arterial-microvascular transit time, and cerebral blood flow (CBF) in the gray matter and in areas with large arterial vessels under hypercapnia, visual stimulation, and a combination of the two. Spatial heterogeneity in arterial reactivity was observed between conditions. During hypercapnia, large arterial volume changes contributed to CBF increase and further downstream, there were reductions in the gray matter transit time. These changes were not significant during visual stimulation, and during the combined condition they were moderated. These findings suggest distinct vascular mechanisms for large and small arterial segments that may be condition specific. However, the power relationships between gray matter arterial blood volume and CBF in hypercapnia (α = 0.69 ± 0.24) and visual stimulation (α = 0.68 ± 0.20) were similar. Assuming consistent capillary and venous volume responses across these conditions, these results offer support for a consistent total CBV–flow relationship typically assumed in blood oxygen-level dependent calibration techniques.

scholarly journals Cortical Depth-Dependent Temporal Dynamics of the BOLD Response in the Human Brain

2011 ◽  
Vol 31 (10) ◽  
pp. 1999-2008 ◽  
Author(s):  
Jeroen CW Siero ◽  
Natalia Petridou ◽  
Hans Hoogduin ◽  
Peter R Luijten ◽  
Nick F Ramsey
Keyword(s):  
Human Brain ◽  
Gray Matter ◽  
Animal Studies ◽  
Temporal Dynamics ◽  
Onset Time ◽  
Neurovascular Coupling ◽  
Blood Oxygen Level Dependent ◽  
Peak Time ◽  
Blood Oxygen Level ◽  
Coupling Mechanisms

Recent animal studies at high field have shown that blood oxygen level-dependent (BOLD) contrast can be specific to the laminar vascular architecture of the cortex, by differences in its temporal dynamics in reference to cortical depth. In this study, we characterize the temporal dynamics of the hemodynamic response (HDR) across cortical depth in the human primary motor and visual cortex, at 7T and using very short stimuli and with high spatial and temporal resolution. We find that the shape and temporal dynamics of the HDR changed in an orderly manner across cortical depth. Compared with the pial vasculature, HDRs in deeper gray matter are significantly faster in onset time (by ∼ 0.5 second) and peak time (∼2 seconds), and are narrower (by ∼1 second) and with smaller amplitude, in line with the known vascular organization across cortical depth and the transit of deoxygenated blood through the vasculature. The width of the HDR in deeper gray matter was as short as 2.1 seconds, indicating that neurovascular coupling takes place at a shorter timescale than previously reported in the human brain. These findings open the possibility to probe layer-specific hemodynamics and neurovascular coupling mechanisms in human gray matter.

scholarly journals Simultaneous mesoscopic Ca2+ imaging and fMRI: Neuroimaging spanning spatiotemporal scales

2018 ◽  
Author(s):  
Evelyn MR Lake ◽  
Xinxin Ge ◽  
Xilin Shen ◽  
Peter Herman ◽  
Fahmeed Hyder ◽  
...  
Keyword(s):  
Brain Function ◽  
Brain Activity ◽  
Blood Oxygen Level Dependent ◽  
Optical Measurements ◽  
Wide Field ◽  
Blood Oxygen Level ◽  
Neural Basis ◽  
Novel Approach ◽  
Transgenic Murine Model ◽  
Spatiotemporal Scales

ABSTRACTTo achieve a more comprehensive understanding of brain function requires simultaneous measurement of activity across a range of spatiotemporal scales. However, the appropriate tools to perform such studies are largely unavailable. Here, we present a novel approach for concurrent wide-field optical and functional magnetic resonance imaging (fMRI). By merging these two modalities, we are for the first time able to simultaneously acquire whole-brain blood-oxygen-level-dependent and whole-cortex calcium-sensitive fluorescent measures of brain activity. We describe the developments that allow us to combine these modalities without compromising the fidelity of either technique. In a transgenic murine model, we examine correspondences between activity measured using these modalities and identify unique and complementary features of each. Our approach links cell-type specific optical measurements of neural activity to the most widely used method for assessing human brain function. These data and approach directly establish the neural basis for the macroscopic connectivity patterns observed with fMRI.

scholarly journals Distinct patterns of brain activity in young carriers of theAPOE-ε4 allele

2009 ◽  
Vol 106 (17) ◽  
pp. 7209-7214 ◽  
Author(s):  
Nicola Filippini ◽  
Bradley J. MacIntosh ◽  
Morgan G. Hough ◽  
Guy M. Goodwin ◽  
Giovanni B. Frisoni ◽  
...  
Keyword(s):  
Brain Function ◽  
Brain Activity ◽  
Memory Performance ◽  
Blood Oxygen Level Dependent ◽  
Brain Morphology ◽  
Blood Oxygen Level ◽  
Prefrontal Cortical ◽  
Ε4 Allele ◽  
Brain Changes ◽  
Age Range

TheAPOEε4 allele is a risk factor for late-life pathological changes that is also associated with anatomical and functional brain changes in middle-aged and elderly healthy subjects. We investigated structural and functional effects of theAPOEpolymorphism in 18 young healthyAPOEε4-carriers and 18 matched noncarriers (age range: 20–35 years). Brain activity was studied both at rest and during an encoding memory paradigm using blood oxygen level-dependent fMRI. Resting fMRI revealed increased “default mode network” (involving retrosplenial, medial temporal, and medial-prefrontal cortical areas) coactivation in ε4-carriers relative to noncarriers. The encoding task produced greater hippocampal activation in ε4-carriers relative to noncarriers. Neither result could be explained by differences in memory performance, brain morphology, or resting cerebral blood flow. TheAPOEε4 allele modulates brain function decades before any clinical or neurophysiological expression of neurodegenerative processes.

scholarly journals A Study of Brain Neuronal and Functional Complexities Estimated Using Multiscale Entropy in Healthy Young Adults

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 995
Author(s):  
Sreevalsan S. Menon ◽  
K. Krishnamurthy
Keyword(s):  
Young Adults ◽  
Brain Function ◽  
Fluid Intelligence ◽  
Blood Oxygen Level Dependent ◽  
Multiscale Entropy ◽  
Blood Oxygen Level ◽  
Neurologically Impaired ◽  
Wide Range ◽  
Healthy Control ◽  
Functional Complexity

Brain complexity estimated using sample entropy and multiscale entropy (MSE) has recently gained much attention to compare brain function between diseased or neurologically impaired groups and healthy control groups. Using resting-state functional magnetic resonance imaging (rfMRI) blood oxygen-level dependent (BOLD) signals in a large cohort (n = 967) of healthy young adults, the present study maps neuronal and functional complexities estimated by using MSE of BOLD signals and BOLD phase coherence connectivity, respectively, at various levels of the brain’s organization. The functional complexity explores patterns in a higher dimension than neuronal complexity and may better discern changes in brain functioning. The leave-one-subject-out cross-validation method is used to predict fluid intelligence using neuronal and functional complexity MSE values as features. While a wide range of scales was selected with neuronal complexity, only the first three scales were selected with functional complexity. Fewer scales are advantageous as they preclude the need for long BOLD signals to calculate good estimates of MSE. The presented results corroborate with previous findings and provide a baseline for other studies exploring the use of MSE to examine changes in brain function related to aging, diseases, and clinical disorders.

scholarly journals Evaluation of Renal Tissue Oxygenation Using Blood Oxygen Level-Dependent Magnetic Resonance Imaging in Chronic Kidney Disease

2021 ◽  
pp. 1-11
Author(s):  
Fen Chen ◽  
Han Yan ◽  
Fan Yang ◽  
Li Cheng ◽  
Siwei Zhang ◽  
...  
Keyword(s):  
Renal Function ◽  
Tissue Oxygenation ◽  
Blood Oxygen Level Dependent ◽  
Renal Tissue ◽  
Selection Method ◽  
Resonance Imaging ◽  
Blood Oxygen Level ◽  
Bold Mri ◽  
Function Group ◽  
Renal Function Group

<b><i>Background:</i></b> Blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) has been widely used to assess renal oxygenation changes in different kidney diseases in recent years. This study was designed to evaluate and compare renal tissue oxygenation using 2 BOLD-MRI analysis methods, namely, the regional and whole-kidney region of interest (ROI) selection methods. <b><i>Methods:</i></b> The study ended up with 10 healthy controls and 40 chronic kidney disease (CKD) patients without dialysis. Their renal BOLD-MRI data were analyzed using whole-kidney ROI selection method and compared with regional ROI selection method. <b><i>Results:</i></b> We found the cortical, medullary, and whole-kidney R2* values were significantly higher in CKD patients than those in controls. Compared with the regional ROI selection method, the whole-kidney ROI selection method yielded higher cortical R2* values in both controls and CKD patients. The whole-kidney R2* values of deteriorating renal function group were significantly higher than those in stable renal function group. <b><i>Conclusions:</i></b> Cortical and medullary oxygenation was decreased significantly in CKD patients compared with the healthy controls, particularly in the medulla. The whole-kidney R2* values were positively correlated with kidney function and inversely correlated with the estimated glomerular filtration rate and effective renal plasma flow. Whole-Kidney R2* value might effectively predict the progression of renal function in patients with CKD.

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