Initial Experience of Challenge-Free MRI-Based Oxygen Extraction Fraction Mapping of Ischemic Stroke at Various Stages: Comparison With Perfusion and Diffusion Mapping

No clue what use this is for. But your doctor needs a protocol to deliver as much oxygen as possible immediately. 

Is your doctor doing any of these? You only have 24 hours.

Possible solutions: Obviously not vetted coming from me. Don't do them. 

Normobaric oxygen (10)

How to Improve Your Brain Function with An Oxygen Concentrator April 2018 

Or is it more important to increase the loading ability of red blood cells to carry more oxygen? 

Like this?

University of Glasgow Study Demonstrates the Ability of Oxycyte® to Supply Oxygen to Critical Penumbral Tissue in Acute Ischemic Stroke  August 2012

Or like this?

chronic cannabis users have higher cerebral blood flow and extract more oxygen from brain blood flow than nonusers. August 2017  

The latest here:

Initial Experience of Challenge-Free MRI-Based Oxygen Extraction Fraction Mapping of Ischemic Stroke at Various Stages: Comparison With Perfusion and Diffusion Mapping

Shun Zhang¹, Junghun Cho^2,3, Thanh D. Nguyen², Pascal Spincemaille², Ajay Gupta², Wenzhen Zhu^1* and Yi Wang^2,3*

• ¹Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
• ²Department of Radiology, Weill Cornell Medicine, New York, NY, United States
• ³Department of Biomedical Engineering, Cornell University, Ithaca, NY, United States

MRI-based oxygen extraction fraction imaging has a great potential benefit in the selection of clinical strategies for ischemic stroke patients. This study aimed to evaluate the performance of a challenge-free oxygen extraction fraction (OEF) mapping in a cohort of acute and subacute ischemic stroke patients. Consecutive ischemic stroke patients (a total of 30 with 5 in the acute stage, 19 in the early subacute stage, and 6 in the late subacute stage) were recruited. All subjects underwent MRI including multi-echo gradient echo (mGRE), diffusion weighted imaging (DWI), and 3D-arterial spin labeling (ASL). OEF maps were generated from mGRE phase + magnitude data, which were processed using quantitative susceptibility mapping (QSM) + quantitative blood oxygen level-dependent (qBOLD) imaging with cluster analysis of time evolution. Cerebral blood flow (CBF) and apparent diffusion coefficient (ADC) maps were reconstructed from 3D-ASL and DWI, respectively. Further, cerebral metabolic rate of oxygen (CMRO₂) was calculated as the product of CBF and OEF. OEF, CMRO₂, CBF, and ADC values in the ischemic cores (absolute values) and their contrasts to the contralateral regions (relative values) were evaluated. One-way analysis of variance (ANOVA) was used to compare OEF, CMRO₂, CBF, and ADC values and their relative values among different stroke stages. The OEF value of infarct core showed a trend of decrease from acute, to early subacute, and to late subacute stages of ischemic stroke. Significant differences among the three stroke stages were only observed in the absolute OEF (F = 6.046, p = 0.005) and relative OEF (F = 5.699, p = 0.009) values of the ischemic core, but not in other measurements (absolute and relative CMRO₂, CBF, ADC values, all values of p > 0.05). In conclusion, the challenge-free QSM + qBOLD-generated OEF mapping can be performed on stroke patients. It can provide more information on tissue viability that was not available with CBF and ADC and, thus, may help to better manage ischemic stroke patients.

Introduction

Ischemic stroke due to impaired blood flow to the brain is one of the leading causes of mortality and morbidity all over the world (Benjamin et al., 2017; Wang et al., 2017). A major therapy objective is to salvage tissue in the ischemic penumbra, a region with perfusion below a functional threshold but above a preservation threshold (Dirnagl et al., 1999; Pushie et al., 2018; Thirugnanachandran et al., 2018). The penumbra is estimated using MRI according to the mismatch between perfusion weighted imaging (PWI, indicating a functional threshold) and diffusion weighted imaging (DWI, non-hyperintensity indicating a preservation threshold). However, the difficulty in perfusion quantification makes it problematic to define a PWI threshold (Wouters et al., 2017; Zaro-Weber et al., 2017). The PWI–DWI mismatch may overestimate the penumbral tissue with the mismatch volume varying with quantification methods (Sobesky et al., 2005).

Penumbra evolves rapidly within the first few hours (Dirnagl et al., 1999; Pushie et al., 2018; Thirugnanachandran et al., 2018), and 24 h may be the threshold time window beyond which ischemic lesion becomes irreversible (Bonova et al., 2013). Accordingly, therapy of ischemic stroke is guided by the time from stroke onset. In current guidelines, intravenous administration of thrombolytic tissue plasminogen activator can be performed within 4.5 h (Davis and Donnan, 2009), and endovascular thrombectomy guided by advanced imaging of penumbral pattern can be performed within 24 h (Saver et al., 2016; Albers et al., 2018; Nogueira et al., 2018; Powers et al., 2018; Adeoye et al., 2019). Additionally, about 14% of strokes are wake-up types without known onset time (Mackey et al., 2011). Therefore, it is important for stroke therapy to assess tissue viability in ischemic lesions and differentiate stroke stages (Allen et al., 2012).

Oxygen extraction fraction (OEF) mapping reflects tissue metabolic state and is regarded as a very sensitive parameter in characterizing neural damage as tissue evolves from oligemia, to penumbra, and finally to death during ischemia (Powers, 1991; Leigh et al., 2018). The ¹⁵O positron emission tomography (¹⁵O-PET) is the gold standard for quantitatively assessing OEF and cerebral metabolic rate of oxygen (CMRO₂). However, the 2 min half-life of ¹⁵O requires a cyclotron in the PET room, which is not available in almost all clinical practices, and PET is too expensive for routine use (Heiss, 2012; Leigh et al., 2018).

MRI-based OEF and CMRO₂ mapping techniques have recently been developed to evaluate oxygen consumption in tissue using quantitative blood oxygenation level-dependent (BOLD) contrast (He and Yablonskiy, 2007; Yablonskiy et al., 2013a), quantitative imaging of extraction of oxygen and tissue consumption (QUIXOTIC) (Bolar et al., 2011), calibrated BOLD (Davis et al., 1998; Gauthier and Hoge, 2012; Hoge, 2012; Blockley et al., 2013), and quantitative susceptibility mapping (QSM) (Zhang et al., 2015, 2017, 2018; Cho et al., 2018, 2020). In QSM, post-processing of complex 3D multi-echo gradient echo (mGRE) data (de Rochefort et al., 2010), tissue iron (ferritin, diffuse), and blood deoxyheme iron (in venioles, cylinders) can be separated using vascular challenges or prior knowledge (Zhang et al., 2015, 2017, 2018). Recently, OEF mapping can be achieved by combining QSM processing of phase and quantitative blood oxygen level-dependent (qBOLD) modeling of magnitude (Ogawa et al., 1990; Yablonskiy and Haacke, 1994b) of mGRE data without any vascular challenge administration (Cho et al., 2018, 2020), making it ready for routine use in imaging acute ischemic patients. When 3D OEF is multiplied by cerebral blood flow (CBF) from 3D arterial spin labeling (ASL) images, CMRO₂ can be generated from MRI examinations.

In this work, we report an initial experience using challenge-free OEF mapping from mGRE (Cho et al., 2020) in a cohort of acute and subacute ischemic stroke patients, and compared it with apparent diffusion coefficient (ADC), CBF, and CMRO₂ mapping.