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Empirical model of human blood transverse relaxation at 3?T improves MRI T2 oximetry.

ABSTRACT: We sought a human blood T2 -oximetery calibration curve over the wide range of hematocrits commonly found in anemic patients applicable with T2 relaxation under spin tagging (TRUST).Blood was drawn from five healthy control subjects. Ninety-three in vitro blood transverse relaxation (T2b ) measurements were performed at 37°C over a broad range of hematocrits (10-55%) and oxygen saturations (14-100%) at 3 Tesla (T). In vivo TRUST was performed on 35 healthy African American control subjects and 11 patients with chronic anemia syndromes.1/T2 rose linearly with hematocrit (r2 ?=?0.96), for fully saturated blood. Upon desaturation, 1/T2 rose linearly with the square of the oxygen extraction, (1-Y)2 , and the slope was linearly proportional to hematocrit (r2 ?=?0.88). The resulting bilinear model between 1/T2 , (1-Y)2 , and hematocrit had a combined r2 of 0.96 and a coefficient of variation of 6.1%. Using the in vivo data, the bilinear model had significantly lower bias and variability than existing calibrations, particularly for low hematocrits. In vivo Bland Altman analysis demonstrated clinically relevant bias that was -6% (absolute saturation) for hematocrits near 30% and rose to?+?6% for hematocrits near 45%.This work introduces a robust bilinear calibration model that should be used for MRI oximetry. Magn Reson Med 77:2364-2371, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

SUBMITTER: Bush A

PROVIDER: S-EPMC5218988 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Empirical model of human blood transverse relaxation at 3 T improves MRI T<sub>2</sub> oximetry.

Bush Adam A Borzage Matthew M Detterich John J Kato Roberta M RM Meiselman Herbert J HJ Coates Thomas T Wood John C JC

Magnetic resonance in medicine 20160706 6

<h4>Purpose</h4>We sought a human blood T<sub>2</sub> -oximetery calibration curve over the wide range of hematocrits commonly found in anemic patients applicable with T<sub>2</sub> relaxation under spin tagging (TRUST).<h4>Methods</h4>Blood was drawn from five healthy control subjects. Ninety-three in vitro blood transverse relaxation (T<sub>2b</sub> ) measurements were performed at 37°C over a broad range of hematocrits (10-55%) and oxygen saturations (14-100%) at 3 Tesla (T). In vivo TRUST wa ...[more]

PMID: 27385283

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Project description:Magnetic resonance imaging (MRI)-based quantification of the blood-oxygenation-level-dependent (BOLD) effect allows oxygen extraction fraction (OEF) mapping. The multi-parametric quantitative BOLD (mq-BOLD) technique facilitates relative OEF (rOEF) measurements with whole brain coverage in clinically applicable scan times. Mq-BOLD requires three separate scans of cerebral blood volume and transverse relaxation rates measured by gradient-echo (1/T2∗) and spin-echo (1/T2). Although the current method is of clinical merit in patients with stroke, glioma and internal carotid artery stenosis (ICAS), there are relaxation measurement artefacts that impede the sensitivity of mq-BOLD and artificially elevate reported rOEF values. We posited that T2-related biases caused by slice refocusing imperfections during rapid 2D-GraSE (Gradient and Spin Echo) imaging can be reduced by applying 3D-GraSE imaging sequences, because the latter requires no slice selective pulses. The removal of T2-related biases would decrease overestimated rOEF values measured by mq-BOLD. We characterized effects of T2-related bias in mq-BOLD by comparing the initially employed 2D-GraSE and two proposed 3D-GraSE sequences to multiple single spin-echo reference measurements, both in vitro and in vivo. A phantom and 25 participants, including young and elderly healthy controls as well as ICAS-patients, were scanned. We additionally proposed a procedure to reliably identify and exclude artefact affected voxels. In the phantom, 3D-GraSE derived T2 values had 57% lower deviation from the reference. For in vivo scans, the formerly overestimated rOEF was reduced by -27% (p < 0.001). We obtained rOEF = 0.51, which is much closer to literature values from positron emission tomography (PET) measurements. Furthermore, increased sensitivity to a focal rOEF elevation in an ICAS-patient was demonstrated. In summary, the application of 3D-GraSE improves the mq-BOLD-based rOEF quantification while maintaining clinically feasible scan times. Thus, mq-BOLD with non-slice selective T2 imaging is highly promising to improve clinical diagnostics of cerebrovascular diseases such as ICAS.

Dataset Information

Empirical model of human blood transverse relaxation at 3?T improves MRI T2 oximetry.

Publications

Empirical model of human blood transverse relaxation at 3 T improves MRI T<sub>2</sub> oximetry.

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