scholarly journals Using BOLD Imaging to Measure Renal Oxygenation Dynamics in Rats Injected with Diuretics

2010 ◽  
Vol 9 (4) ◽  
pp. 187-194 ◽  
Author(s):  
Yoshinori KUSAKABE ◽  
Taro MATSUSHITA ◽  
Saori HONDA ◽  
Sakie OKADA ◽  
Kenya MURASE
Keyword(s):  
Bold Imaging

Myocardial BOLD Imaging with T2 Relaxation

2012 ◽  
Vol 6 (1) ◽  
pp. 18-30 ◽  
Author(s):  
Nilesh R. Ghugre
Keyword(s):  
T2 Relaxation ◽  
Bold Imaging

scholarly journals Artifacts-reduced 2D cine SSFP with flow compensation for myocardial BOLD imaging

2010 ◽  
Vol 12 (S1) ◽  
Author(s):  
Xiangzhi Zhou ◽  
Sotirios A Tsaftaris ◽  
Ying Liu ◽  
Richard Tang ◽  
Rachel Klein ◽  
...  
Keyword(s):  
Cine Ssfp ◽  
Bold Imaging ◽  
Flow Compensation

scholarly journals The Cumulative Influence of Hyperoxia and Hypercapnia on Blood Oxygenation and R2*

2015 ◽  
Vol 35 (12) ◽  
pp. 2032-2042 ◽  
Author(s):  
Carlos C Faraco ◽  
Megan K Strother ◽  
Jeroen CW Siero ◽  
Daniel F Arteaga ◽  
Allison O Scott ◽  
...  
Keyword(s):  
Venous Blood ◽  
Quantitative Information ◽  
Blood Oxygenation ◽  
Cerebrovascular Reactivity ◽  
Resonance Imaging ◽  
Tissue Water ◽  
Bold Mri ◽  
Bold Imaging ◽  
Complex Interactions ◽  
Oxygenation Level

Cerebrovascular reactivity (CVR)-weighted blood-oxygenation-level-dependent magnetic resonance imaging (BOLD-MRI) experiments are frequently used in conjunction with hyperoxia. Owing to complex interactions between hyperoxia and hypercapnia, quantitative effects of these gas mixtures on BOLD responses, blood and tissue R2∗, and blood oxygenation are incompletely understood. Here we performed BOLD imaging (3T; TE/TR = 35/2,000 ms; spatial resolution = 3×3×3.5 mm3) in healthy volunteers ( n = 12; age = 29±4.1 years) breathing (i) room air (RA), (ii) normocapnic-hyperoxia (95% O2/5% N2, HO), (iii) hypercapnic-normoxia (5% CO2/21% O2/74% N2, HC-NO), and (iv) hypercapnic-hyperoxia (5% CO2/95% O2, HC-HO). For HC-HO, experiments were performed with separate RA and HO baselines to control for changes in O2. T2-relaxation-under-spin-tagging MRI was used to calculate basal venous oxygenation. Signal changes were quantified and established hemodynamic models were applied to quantify vasoactive blood oxygenation, blood–water R∗2, and tissue-water R∗2. In the cortex, fractional BOLD changes (stimulus/baseline) were HO/RA = 0.011 ± 0.007; HC-NO/RA = 0.014±0.004; HC-HO/HO = 0.020±0.008; and HC-HO/RA = 0.035 ±0.010; for the measured basal venous oxygenation level of 0.632, this led to venous blood oxygenation levels of 0.660 (HO), 0.665 (HC-NO), and 0.712 (HC-HO). Interleaving a HC-HO stimulus with HO baseline provided a smaller but significantly elevated BOLD response compared with a HC-NO stimulus. Results provide an outline for how blood oxygenation differs for several gas stimuli and provides quantitative information on how hypercapnic BOLD CVR and R∗2 are altered during hyperoxia.

scholarly journals Transcranial alternating current stimulation attenuates BOLD adaptation and increases functional connectivity

2020 ◽  
Vol 123 (1) ◽  
pp. 428-438 ◽  
Author(s):  
Kohitij Kar ◽  
Takuya Ito ◽  
Michael W. Cole ◽  
Bart Krekelberg
Keyword(s):  
Functional Connectivity ◽  
Electric Fields ◽  
Full Range ◽  
Region Of Interest ◽  
Alternating Current ◽  
Human Motion ◽  
Dependent Manner ◽  
Bold Imaging ◽  
Transcranial Alternating Current Stimulation ◽  
The Brain

Transcranial alternating current stimulation (tACS) is used as a noninvasive tool for cognitive enhancement and clinical applications. The physiological effects of tACS, however, are complex and poorly understood. Most studies of tACS focus on its ability to entrain brain oscillations, but our behavioral results in humans and extracellular recordings in nonhuman primates support the view that tACS at 10 Hz also affects brain function by reducing sensory adaptation. Our primary goal in the present study is to test this hypothesis using blood oxygen level-dependent (BOLD) imaging in human subjects. Using concurrent functional magnetic resonance imaging (fMRI) and tACS, and a motion adaptation paradigm developed to quantify BOLD adaptation, we show that tACS significantly attenuates adaptation in the human motion area (hMT+). In addition, an exploratory analysis shows that tACS increases functional connectivity of the stimulated hMT+ with the rest of the brain and the dorsal attention network in particular. Based on field estimates from individualized head models, we relate these changes to the strength of tACS-induced electric fields. Specifically, we report that functional connectivity (between hMT+ and any other region of interest) increases in proportion to the field strength in the region of interest. These findings add support for the claim that weak 10-Hz currents applied to the scalp modulate both local and global measures of brain activity. NEW & NOTEWORTHY Concurrent transcranial alternating current stimulation (tACS) and functional MRI show that tACS affects the human brain by attenuating adaptation and increasing functional connectivity in a dose-dependent manner. This work is important for our basic understanding of what tACS does, but also for therapeutic applications, which need insight into the full range of ways in which tACS affects the brain.

Comparison of 8-Channel Versus 32-Channel Coils for BOLD Imaging at 3T

NeuroImage ◽  
2009 ◽  
Vol 47 ◽  
pp. S196
Author(s):  
M.S. Worden ◽  
E. Nixon ◽  
L. Fanella
Keyword(s):  
Bold Imaging

scholarly journals Multiple sclerosis-related white matter microstructural change alters the BOLD hemodynamic response

2016 ◽  
Vol 36 (11) ◽  
pp. 1872-1884 ◽  
Author(s):  
Nicholas A Hubbard ◽  
Monroe Turner ◽  
Joanna L Hutchison ◽  
Austin Ouyang ◽  
Jeremy Strain ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
White Matter ◽  
Diffusion Tensor ◽  
Hemodynamic Response ◽  
Blood Oxygen Level Dependent ◽  
Bold Signal ◽  
Hemodynamic Response Function ◽  
Related Factors ◽  
Bold Imaging ◽  
Microstructural Integrity

Multiple sclerosis (MS) results in inflammatory damage to white matter microstructure. Prior research using blood-oxygen-level dependent (BOLD) imaging indicates MS-related alterations to brain function. What is currently unknown is the extent to which white matter microstructural damage influences BOLD signal in MS. Here we assessed changes in parameters of the BOLD hemodynamic response function (HRF) in patients with relapsing-remitting MS compared to healthy controls. We also used diffusion tensor imaging to assess whether MS-related changes to the BOLD-HRF were affected by changes in white matter microstructural integrity. Our results showed MS-related reductions in BOLD-HRF peak amplitude. These MS-related amplitude decreases were influenced by individual differences in white matter microstructural integrity. Other MS-related factors including altered reaction time, limited spatial extent of BOLD activity, elevated lesion burden, or lesion proximity to regions of interest were not mediators of group differences in BOLD-HRF amplitude. Results are discussed in terms of functional hyperemic mechanisms and implications for analysis of BOLD signal differences.

Assessment of impaired vascular reactivity in a rat model of diabetic nephropathy: effect of nitric oxide synthesis inhibition on intrarenal diffusion and oxygenation measured by magnetic resonance imaging

2013 ◽  
Vol 305 (10) ◽  
pp. F1428-F1435 ◽  
Author(s):  
Katja Hueper ◽  
Dagmar Hartung ◽  
Marcel Gutberlet ◽  
Faikah Gueler ◽  
Holger Sann ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Diabetic Nephropathy ◽  
Diffusion Tensor Imaging ◽  
Mean Arterial Pressure ◽  
Vascular Reactivity ◽  
Diffusion Tensor ◽  
Vascular Conductance ◽  
Synthesis Inhibition ◽  
Bold Imaging ◽  
Before And After

Diabetes is associated with impaired vascular reactivity and the development of diabetic nephropathy. In a rat model of streptozotocin-induced diabetic nephropathy, the effects of systemic nitric oxide (NO) synthesis inhibition on intrarenal diffusion and oxygenation were determined by noninvasive magnetic resonance diffusion tensor imaging and blood O2 level-dependent (BOLD) imaging, respectively. Eight weeks after the induction of diabetes, 21 rats [ n = 7 rats each in the untreated control group, diabetes mellitus (DM) group, and DM with uninephrectomy (DM UNX) group] were examined by MRI. Diffusion tensor imaging and BOLD sequences were acquired before and after NO synthesis inhibition with N-nitro-l-arginine methyl ester (l-NAME). In the same rats, mean arterial pressure and vascular conductance were determined with and without the influence of l-NAME. In control animals, NO synthesis inhibition was associated with a significant increase of mean arterial pressure of 33.8 ± 4.3 mmHg ( P < 0.001) and a decrease of vascular conductance of −17.8 ± 2.0 μl·min−1·100 mmHg−1 ( P < 0.001). These changes were attenuated in both DM and DM UNX groups with no significant difference between before and after l-NAME measurements in DM UNX animals. Similarly, l-NAME challenge induced a significant reduction of renal transverse relaxation time (T2*) at MRI in control animals, indicating reduced renal oxygenation after l-NAME injection compared with baseline. DM UNX animals did not show a significant T2* reduction after NO synthesis inhibition in the renal cortex and attenuated T2* reduction in the outer medulla. MRI parameters of tissue diffusion were not affected by l-NAME in all groups. In conclusion, BOLD imaging proved valuable to noninvasively measure renal vascular reactivity upon NO synthesis inhibition in control animals and to detect impaired vascular reactivity in animals with diabetic nephropathy.

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