Characterization of paramagnetic effects of molecular oxygen on blood oxygenation level‐dependent‐modulated hyperoxic contrast studies of the human brain

Pilkinton, David T.; Gaddam, Santosh R.; Reddy, Ravinder

doi:10.1002/mrm.22870

Cited by 21 publications

(38 citation statements)

References 20 publications

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“…Interestingly, 24 hours after VDA treatment, some of the tumors showed a negative change in BOLD signal at carbogen challenge. Although the precise reason for this observation is unclear, similar observations previously have been reported in the literature, in which the negative BOLD responses have been attributed to an increase in extravascular oxygen concentration due to a reduction in oxygen extraction fraction (29)(30)(31). It should be pointed out that in our study, we performed BOLD MR imaging with a T2-weighted spin-echo sequence.…”

Section: Discussionsupporting

confidence: 86%

Photoacoustic Imaging of Vascular Hemodynamics: Validation with Blood Oxygenation Level–Dependent MR Imaging

Rich¹,

Seshadri²

2015

Radiology

125

115

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).q RSNA, 2014 Purpose:To noninvasively assess vascular hemodynamics with photoacoustic imaging (PAI) and blood oxygenation level-dependent (BOLD) magnetic resonance (MR) imaging in phantoms and in an animal model. Materials and Methods:In vivo studies were performed with institutional animal care and use committee approval. In vitro experiments were performed by using a tissue-mimicking phantom in multiple oxygenation conditions (n = 6) to compare PAI measurements and BOLD MR imaging measurements. PAI and T2-weighted spin-echo-based BOLD MR imaging were performed to assess tumor response to carbogen (95% O 2 , 5% CO 2 ) in mice with head and neck tumors before (n = 11) and after (n = 9) treatment with a vascular disrupting agent (VDA). Two-tailed Pearson correlation analysis was performed to determine the correlation between the parameters measured with PAI and BOLD MR imaging in vitro. Two-tailed paired t tests were used to compare change in tumor hemoglobin oxygen saturation (sO 2 ) levels and BOLD signal in response to carbogen. Changes in PAI and BOLD signal intensity before and after VDA treatment were analyzed for significance by using analysis of variance with repeated measures. Results:Phantom measurements yielded good correlation between photoacoustically derived sO 2 levels and BOLD signal intensity (r = 0.937, P = .005) and partial pressure of oxygen (r = 0.981, P = .005). In vivo hemodynamic response to carbogen was characterized by a significant increase in tumor sO 2 levels (P = .003) and BOLD signal (P = .001).When compared with pretreatment estimates, treatment with VDA resulted in a significant reduction in the tumor hemodynamic response to carbogen at PAI (P = .030). Conclusion:Carbogen-based functional imaging with PAI and BOLD MR imaging enables monitoring of early changes in tumor hemodynamics after vascular targeted therapy.q RSNA, 2014

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Section: Discussionsupporting

confidence: 86%

Photoacoustic Imaging of Vascular Hemodynamics: Validation with Blood Oxygenation Level–Dependent MR Imaging

Rich¹,

Seshadri²

2015

Radiology

125

115

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“…This is a reasonable assumption given that molecular oxygen is very small relative to gadolinium complexes, and thus likely to be less affected by viscosity and macromolecules on the tumbling frequencies. Indeed, no significant differences in oxygen relaxivity were observed amongst phosphate buffered saline, 5% bovine serum albumin in phosphate buffered saline, and in vivo blood, 17 between buffered saline with and without 0.3 g/L human serum albumin, 18 or between balanced salt solution and vitreous samples. 16 In contrast, gadolinium agents show enhanced relaxivity in plasma and whole blood compared to water.…”

Section: Methodsmentioning

confidence: 92%

MRI of brain tissue oxygen tension under hyperbaric conditions

Muir

Cardenas²,

Duong³

2016

NeuroImage

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The brain depends on a continuous supply of oxygen to maintain its structural and functional integrity. This study measured T1 from MRI under normobaric air, normobaric oxygen, hyperbaric air, and hyperbaric oxygen (HBO) conditions as a marker of tissue pO2 since dissolved molecular oxygen acts as an endogenous contrast agent. Brain tissue T1 decreased corresponding to increased pO2 with increasing inhaled oxygen concentrations, and tissue oxygenation was estimated from the T1 changes between different inhaled oxygen levels. Tissue pO2 difference maps between different oxygen conditions showed heterogeneous pO2 changes in the brain. MRI-derived tissue pO2 was markedly lower than the arterial pO2 but was slightly higher than venous pO2. Additionally, for comparison with published extracellular tissue pO2 data obtained using oxygen electrodes and other invasive techniques, a model was used to estimate extracellular and intracellular pO2 from the MRI-derived mean tissue pO2. This required multiple assumptions, and so the effects of the assumptions and parameters used in modeling brain pO2 were evaluated. MRI-derived pO2 values were strongly dependent on assumptions about the extra- and intracellular compartments but were relatively less sensitive to variations in the relaxivity constant of oxygen and contribution from oxygen in the cerebral blood compartment. This approach may prove useful in evaluating tissue oxygenation in disease states such as stroke.

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“…1 shows the results of applying each of these filter sizes to phase data collected at normoxia. The spatial filter removes large-scale phase changes due to external sources and is particularly relevant for data collected at hyperoxia, where increased oxygen in the oral cavity and frontal sinus leads to an increased field inhomogeneity across the brain (Pilkinton et al, 2011). Therefore, the finest filter (D = 64) was applied to both hyperoxia and normoxia phase data for Method III .…”

Section: Methodsmentioning

confidence: 99%

Global intravascular and local hyperoxia contrast phase-based blood oxygenation measurements

et al. 2014

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The measurement of venous cerebral blood oxygenation (Yv) has potential applications in the study of patient groups where oxygen extraction and/or metabolism are compromised. It is also useful for fMRI studies to assess the stimulus-induced changes in Yv, particularly since basal Yv partially accounts for inter-subject variation in the haemodynamic response to a stimulus. A range of MRI-based methods of measuring Yv have been developed recently. Here, we use a method based on the change in phase in the MR image arising from the field perturbation caused by deoxygenated haemoglobin in veins. We build on the existing phase based approach (Method I), where Yv is measured in a large vein (such as the superior sagittal sinus) based on the field shift inside the vein with assumptions as to the vein's shape and orientation. We demonstrate two novel modifications which address limitations of this method. The first modification (Method II), maps the actual form of the vein, rather than assume a given shape and orientation. The second modification (Method III) uses the intra and perivascular phase change in response to a known change in Yv on hyperoxia to measure normoxic Yv in smaller veins. Method III can be applied to veins whose shape, size and orientation are not accurately known, thus allowing more localised measures of venous oxygenation. Results demonstrate that the use of an overly fine spatial filter caused an overestimation in Yv for Method I, whilst the measurement of Yv using Method II was less sensitive to this bias, giving Yv = 0.62 ± 0.03. Method III was applied to mapping of Yv in local veins across the brain, yielding a distribution of values with a mode of Yv = 0.661 ± 0.008.

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Characterization of paramagnetic effects of molecular oxygen on blood oxygenation level‐dependent‐modulated hyperoxic contrast studies of the human brain

Cited by 21 publications

References 20 publications

Photoacoustic Imaging of Vascular Hemodynamics: Validation with Blood Oxygenation Level–Dependent MR Imaging

Photoacoustic Imaging of Vascular Hemodynamics: Validation with Blood Oxygenation Level–Dependent MR Imaging

MRI of brain tissue oxygen tension under hyperbaric conditions

Global intravascular and local hyperoxia contrast phase-based blood oxygenation measurements

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