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Benchmarking transverse spin relaxation based oxygenation measurements in the brain during hypercapnia and hypoxia.

ABSTRACT: PURPOSE:To simultaneously assess reproducibility of three MRI transverse relaxation parameters ( R2', R2*, and R2 ) for brain tissue oxygenation mapping and to assess changes in these parameters with inhalation of gases that increase and decrease oxygenation, to identify the most sensitive parameter for imaging brain oxygenation. MATERIALS AND METHODS:Forty-eight healthy subjects (25 male, ages 35?±?8 years) were scanned at 3.0 Tesla, each with one of four gases (mildly and strongly hypercapnic and hypoxic) administered in a challenge paradigm, using a gas delivery setup designed for patient use. Cerebral blood flow mapping with arterial spin labeling, and simultaneous R2', R2*, and R2 mapping with gradient-echo sampling of free induction decay and echo (GESFIDE) were performed. Reproducibility in air and gas-induced changes were evaluated using nonparametric analysis with correction for multiple comparisons. RESULTS:Our gas delivery setup achieved stable gas challenges as shown by physiological monitoring. Test-retest variability of R2', R2*, and R2 were found to be 0.24 s-1 (8.6% of mean), 0.24 s-1 (1.3% of mean), and 0.15 s-1 (1.0% of mean), respectively. Strong hypoxia produced the most conclusive oxygenation-driven relaxation change, inducing increases in R2' (25?±?13%, P?=?0.03), R2* (5?±?2%, P?=?0.02), and R2 (2?±?2%, NS). CONCLUSION:We benchmarked the intra-scan test-retest variability in GESFIDE-based transverse relaxation rate mapping. Using a reliable framework for gas challenge paradigms, we recommend strong hypoxia for validating oxygenation mapping methods, and the use of tissue R2' change, instead of R2* or R2 , as a metric for studying brain tissue oxygenation using transverse relaxation methods. LEVEL OF EVIDENCE:1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:704-714.

SUBMITTER: Ni WW

PROVIDER: S-EPMC5555840 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Benchmarking transverse spin relaxation based oxygenation measurements in the brain during hypercapnia and hypoxia.

Ni Wendy W WW Christen Thomas T Zaharchuk Greg G

Journal of magnetic resonance imaging : JMRI 20170317 3

<h4>Purpose</h4>To simultaneously assess reproducibility of three MRI transverse relaxation parameters ( R2', R2*, and R<sub>2</sub> ) for brain tissue oxygenation mapping and to assess changes in these parameters with inhalation of gases that increase and decrease oxygenation, to identify the most sensitive parameter for imaging brain oxygenation.<h4>Materials and methods</h4>Forty-eight healthy subjects (25 male, ages 35 ± 8 years) were scanned at 3.0 Tesla, each with one of four gases (mildly ...[more]

PMID: 28306210

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Project description:Therapeutic hypercapnia has the potential for neuroprotection after global cerebral ischemia. Here we further investigated the effects of different degrees of acute systemic hypoxia in combination with hypercapnia on brain damage in a rat model of hypoxia and ischemia. Adult wistar rats underwent unilateral common carotid artery (CCA) ligation for 60 min followed by ventilation with normoxic or systemic hypoxic gas containing 11%O2,13%O2,15%O2 and 18%O2 (targeted to PaO2 30-39 mmHg, 40-49 mmHg, 50-59 mmHg, and 60-69 mmHg, respectively) or systemic hypoxic gas containing 8% carbon dioxide (targeted to PaCO2 60-80 mmHg) for 180 min. The mean artery pressure (MAP), blood gas, and cerebral blood flow (CBF) were evaluated. The cortical vascular permeability and brain edema were examined. The ipsilateral cortex damage and the percentage of hippocampal apoptotic neurons were evaluated by Nissl staining and terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling (TUNEL) assay as well as flow cytometry, respectively. Immunofluorescence and western blotting were performed to determine aquaporin-4 (AQP4) expression. In rats treated with severe hypoxia (PaO2 < 50 mmHg), hypercapnia augmented the decline of MAP with cortical CBF and damaged blood-brain barrier permeability (p < 0.05). In contrast, in rats treated with mild to moderate hypoxia (PaO2 > 50 mmHg), hypercapnia protected against these pathophysiological changes. Moreover, hypercapnia treatment significantly reduced brain damage in the ischemic ipsilateral cortex and decreased the percentage of apoptotic neurons in the hippocampus after the CCA ligated rats were exposed to mild or moderate hypoxemia (PaO2 > 50 mmHg); especially under mild hypoxemia (PaO2 > 60 mmHg), hypercapnia significantly attenuated the expression of AQP4 protein with brain edema (p < 0.05). Hypercapnia exerts beneficial effects under mild to moderate hypoxemia and augments detrimental effects under severe hypoxemia on brain damage in a rat model of hypoxia-ischemia.

Dataset Information

Benchmarking transverse spin relaxation based oxygenation measurements in the brain during hypercapnia and hypoxia.

Publications

Benchmarking transverse spin relaxation based oxygenation measurements in the brain during hypercapnia and hypoxia.

Similar Datasets

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