scholarly journals Basal Cerebral Blood Volume during the Poststimulation Undershoot in BOLD MRI of the Human Brain

2010 ◽  
Vol 31 (1) ◽  
pp. 82-89 ◽  
Author(s):  
Peter Dechent ◽  
Gunther Schütze ◽  
Gunther Helms ◽  
Klaus Dietmar Merboldt ◽  
Jens Frahm
Keyword(s):  
Contrast Agent ◽  
Blood Volume ◽  
Animal Studies ◽  
Cerebral Blood Volume ◽  
Visual Stimulation ◽  
Three Dimensional ◽  
Blood Pool ◽  
Blood Oxygenation ◽  
Bold Mri ◽  
Oxygenation Level

One of the characteristics of the blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) response to functional challenges of the brain is the poststimulation undershoot, which has been suggested to originate from a delayed recovery of either cerebral blood volume (CBV) or cerebral metabolic rate of oxygen to baseline. Using bolus-tracking MRI in humans, we recently showed that relative CBV rapidly normalizes after the end of stimulation. As this observation contradicts at least part of the blood-pool contrast agent studies performed in animals, we reinvestigated the CBV contribution by dynamic T1-weighted three-dimensional MRI (8 seconds temporal resolution) and Vasovist at 3 T (12 subjects). Initially, we determined the time constants of individual BOLD responses. After injection of Vasovist, CBV-related T1-weighted signal changes revealed a signal increase during visual stimulation (1.7%±0.4%), but no change relative to baseline in the poststimulation phase (0.2%±0.3%). This finding renders the specific nature of the contrast agent unlikely to be responsible for the discrepancy between human and animal studies. With the assumption of normalized cerebral blood flow after stimulus cessation, a normalized CBV lends support to the idea that the BOLD MRI undershoot reflects a prolonged elevation of oxidative metabolism.

scholarly journals Physiological origin for the BOLD poststimulus undershoot in human brain: Vascular compliance versus oxygen metabolism

2011 ◽  
Vol 31 (7) ◽  
pp. 1599-1611 ◽  
Author(s):  
Jun Hua ◽  
Robert D Stevens ◽  
Alan J Huang ◽  
James J Pekar ◽  
Peter CM van Zijl
Keyword(s):  
Cerebral Blood Volume ◽  
Visual Stimulation ◽  
Oxygen Metabolism ◽  
Blood Oxygenation ◽  
Biophysical Model ◽  
Breath Hold ◽  
Signal Recovery ◽  
Vascular Compliance ◽  
Oxygenation Level ◽  
Bold Undershoot

The poststimulus blood oxygenation level-dependent (BOLD) undershoot has been attributed to two main plausible origins: delayed vascular compliance based on delayed cerebral blood volume (CBV) recovery and a sustained increased oxygen metabolism after stimulus cessation. To investigate these contributions, multimodal functional magnetic resonance imaging was employed to monitor responses of BOLD, cerebral blood flow (CBF), total CBV, and arterial CBV (CBVa) in human visual cortex after brief breath hold and visual stimulation. In visual experiments, after stimulus cessation, CBVa was restored to baseline in 7.9 ± 3.4 seconds, and CBF and CBV in 14.8 ± 5.0 seconds and 16.1 ± 5.8 seconds, respectively, all significantly faster than BOLD signal recovery after undershoot (28.1 ± 5.5 seconds). During the BOLD undershoot, postarterial CBV (CBVpa, capillaries and venules) was slightly elevated (2.4 ± 1.8%), and cerebral metabolic rate of oxygen ( CMRO2) was above baseline (10.6 ± 7.4%). Following breath hold, however, CBF, CBV, CBVa and BOLD signals all returned to baseline in ∼20 seconds. No significant BOLD undershoot, and residual CBVpa dilation were observed, and CMRO2 did not substantially differ from baseline. These data suggest that both delayed CBVpa recovery and enduring increased oxidative metabolism impact the BOLD undershoot. Using a biophysical model, their relative contributions were estimated to be 19.7 ± 15.9% and 78.7 ± 18.6%, respectively.

High-resolution cerebral blood volume imaging in humans using the blood pool contrast agent ferumoxytol

2012 ◽  
Vol 70 (3) ◽  
pp. 705-710 ◽  
Author(s):  
Thomas Christen ◽  
Wendy Ni ◽  
Deqiang Qiu ◽  
Heiko Schmiedeskamp ◽  
Roland Bammer ◽  
...  
Keyword(s):  
High Resolution ◽  
Contrast Agent ◽  
Blood Volume ◽  
Cerebral Blood Volume ◽  
Blood Pool ◽  
Blood Pool Contrast Agent ◽  
Volume Imaging

In Vivo Determination of Absolute Cerebral Blood Volume Using Hemoglobin as a Natural Contrast Agent: An MRI Study Using Altered Arterial Carbon Dioxide Tension

1999 ◽  
Vol 19 (7) ◽  
pp. 809-817 ◽  
Author(s):  
John A. Ulatowski ◽  
Joni M. E. Oja ◽  
Jose I. Suarez ◽  
Risto A. Kauppinen ◽  
Richard J. Traystman ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Carbon Dioxide ◽  
White Matter ◽  
Magnetic Resonance ◽  
Contrast Agent ◽  
Blood Volume ◽  
Cerebral Blood Volume ◽  
Spin Echo ◽  
Blood Oxygenation ◽  
Resonance Imaging

The ability of the magnetic resonance imaging transverse relaxation time, R2 = 1/T2, to quantify cerebral blood volume (CBV) without the need for an exogenous contrast agent was studied in cats (n = 7) under pentobarbital anesthesia. This approach is possible because R2 is directly affected by changes in CBF, CBV, CMRO2, and hematocrit (Hct), a phenomena better known as the blood-oxygenation-level-dependent (BOLD) effect. Changes in CBF and CBV were accomplished by altering the carbon dioxide pressure, Paco2, over a range from 20 to 140 mm Hg. For each Paco2 value, R2 in gray and white matter were determined using MRI, and the whole-brain oxygen extraction ratio was obtained from arteriovenous differences (sagittal sinus catheter). Assuming a constant CMRO2, the microvascular CBV was obtained from an exact fit to the BOLD theory for the spin-echo effect. The resulting CBV values at normal Paco2 and normalized to a common total hemoglobin concentration of 6.88 mmol/L were 42 ±18 μL/g (n = 7) and 29 ±19 μL/g (n = 5) for gray and white matter, respectively, in good agreement with the range of literature values published using independent methodologies. The present study confirms the validity of the spin-echo BOLD theory and, in addition, shows that blood volume can be quantified from the magnetic resonance imaging spin relaxation rate R2 using a regulated carbon dioxide experiment.

scholarly journals Modelling the depth-dependent VASO and BOLD responses in human primary visual cortex

2021 ◽  
Author(s):  
Atena Akbari ◽  
Saskia Bollmann ◽  
Tonima Ali ◽  
Markus Barth
Keyword(s):  
Visual Cortex ◽  
Blood Volume ◽  
Primary Visual Cortex ◽  
Cerebral Blood Volume ◽  
Blood Oxygenation ◽  
Physiological Variables ◽  
Oxygenation Level ◽  
Signal Specificity ◽  
Experimental Findings ◽  
Spatial Specificity

Functional magnetic resonance imaging (fMRI) using blood-oxygenation-level-dependent (BOLD) contrast is a common method for studying human brain function non-invasively. Gradient-echo (GRE) BOLD is highly sensitive to the blood oxygenation change in blood vessels; however, the signal specificity can be degraded due to signal leakage from the activated lower layers to the superficial layers in depth-dependent (also called laminar or layer-specific) fMRI. Alternatively, physiological variables such as cerebral blood volume using VAscular-Space-Occupancy (VASO) measurements have shown higher spatial specificity compared to BOLD. To better understand the physiological mechanisms (e.g., blood volume and oxygenation change) and to interpret the measured depth-dependent responses we need models that reflect vascular properties at this scale. For this purpose, we adapted a cortical vascular model previously developed to predict the layer-specific BOLD signal change in human primary visual cortex to also predict layer-specific VASO response. To evaluate the model, we compared the predictions with experimental results of simultaneous VASO and BOLD measurements in a group of healthy participants. Fitting the model to our experimental findings provided an estimate of CBV change in different vascular compartments upon neural activity. We found that stimulus-evoked CBV changes mainly occur in intracortical arteries as well as small arterioles and capillaries and that the contribution from venules is small for a long stimulus (~30 sec). Our results confirm the notion that VASO contrast is less susceptible to large vessel effects compared to BOLD.

scholarly journals Temporal Dynamics and Spatial Specificity of Arterial and Venous Blood Volume Changes during Visual Stimulation: Implication for Bold Quantification

2010 ◽  
Vol 31 (5) ◽  
pp. 1211-1222 ◽  
Author(s):  
Tae Kim ◽  
Seong-Gi Kim
Keyword(s):  
Blood Volume ◽  
Cerebral Blood Volume ◽  
Temporal Dynamics ◽  
Visual Stimulation ◽  
Magnetization Transfer ◽  
Venous Blood ◽  
Cortical Layer ◽  
Blood Oxygenation ◽  
Order Of Magnitude ◽  
The Difference

Determination of compartment-specific cerebral blood volume ( CBV) changes is important for understanding neurovascular physiology and quantifying blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI). In isoflurane-anesthetized cats, we measured the spatiotemporal responses of arterial CBV ( CBVa) and total CBV ( CBVt) induced by a 40-second visual stimulation, using magnetization transfer (MT)-varied BOLD and contrast-agent fMRI techniques at 9.4 T. To determine the venous CBV ( CBVv) change, we calculated the difference between CBVt and CBVa changes. The dynamic response of CBVa was an order of magnitude faster than that of CBVv, while the magnitude of change under steady-state conditions was similar between the two. Following stimulation offset, Δ CBVa showed small poststimulus undershoots, while Δ CBVv slowly returned to baseline. The largest CBVa and CBVt response occurred after 10 seconds of simulation in cortical layer 4, which we identified as the stripe of Gennari by T1-weighted MRI. The CBVv response, however, was not specific across the cortical layers during the entire stimulation period. Our data indicate that rapid, more-specific arterial vasodilation is followed by slow, less-specific venous dilation. Our finding implies that the contribution of CBVv changes to BOLD signals is significant for long, but not short, stimulation periods.

scholarly journals Carbogen-induced increases in tumor oxygenation depend on the vascular status of the tumor: A multiparametric MRI study in two rat glioblastoma models

2016 ◽  
Vol 37 (6) ◽  
pp. 2270-2282 ◽  
Author(s):  
Ararat Chakhoyan ◽  
Aurélien Corroyer-Dulmont ◽  
Marine M Leblond ◽  
Aurélie Gérault ◽  
Jérôme Toutain ◽  
...  
Keyword(s):  
Oxygen Saturation ◽  
Blood Volume ◽  
Cerebral Blood Volume ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Blood Oxygen ◽  
Blood Oxygen Saturation ◽  
Blood Oxygenation Level ◽  
Oxygenation Level ◽  
Volume Blood

The alleviation of hypoxia in glioblastoma with carbogen to improve treatment has met with limited success. Our hypothesis is that the eventual benefits of carbogen depend on the capacity for vasodilation. We examined, with MRI, changes in fractional cerebral blood volume, blood oxygen saturation, and blood oxygenation level dependent signals in response to carbogen. The analyses were performed in two xenograft models of glioma (U87 and U251) recognized to have different vascular patterns. Carbogen increased fractional cerebral blood volume, blood oxygen saturation, and blood oxygenation level dependent signals in contralateral tissues. In the tumor core and peritumoral regions, changes were dependent on the capacity to vasodilate rather than on resting fractional cerebral blood volume. In the highly vascularised U87 tumor, carbogen induced a greater increase in fractional cerebral blood volume and blood oxygen saturation in comparison to the less vascularized U251 tumor. The blood oxygenation level dependent signal revealed a delayed response in U251 tumors relative to the contralateral tissue. Additionally, we highlight the considerable heterogeneity of fractional cerebral blood volume, blood oxygen saturation, and blood oxygenation level dependent within U251 tumor in which multiple compartments co-exist (tumor core, rim and peritumoral regions). Finally, our study underlines the complexity of the flow/metabolism interactions in different models of glioblastoma. These irregularities should be taken into account in order to palliate intratumoral hypoxia in clinical trials.

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