Emerging research suggests the addition of relative oxygen ejection fraction (rOEF) — derived from dynamic susceptibility contrast (DSC) MRI — to apparent diffusion coefficient (ADC) mapping may significantly improve infarct prediction in patients treated for acute ischemic stroke (AIS).
For the retrospective study, recently published in Radiology, researchers reviewed pre- and post-treatment MRI data for 70 patients (mean age of 72.2) who had successful reperfusion (defined as a modified Thrombolysis in Cerebral Infarction score of > 2c) after suffering an anterior circulation large vessel occlusion stroke. The study authors compared the use of ADC mapping to the combination of ADC mapping with rOEF, which was calculated with DSC perfusion. Employing an ADC threshold of 620 x 10-6 mm2/sec or less, the researchers obtained ischemic core masks from baseline MRI and infarct masks from final diffusion-weighted imaging (DWI).
What New Brain MRI Research Reveals About Diffusion Reversal and Infarct Prediction in Acute Stroke Survivors
The study authors found that out of a total brain tissue volume of 819 mL originally described as ischemic core, follow-up MRI findings revealed diffusion reversal in 289 mL (35 percent) that was redesignated as surviving tissue.
For infarct prediction, the combined ADC/rOEF model in comparison to ADC alone provided significantly improved AUC (80 percent vs. 65 percent), sensitivity (74 percent vs. 60 percent) and specificity (76 percent vs. 63 percent).
“For voxel-level analysis, a combined rOEF-ADC model (AUC, 0.80) outperformed ADC for voxel-fate prediction and significantly improved true infarct estimation and reduced core volume overestimation compared with ADC alone,” noted lead study author Mona Asghariahmadabad, MD, who is affiliated with the Department of Radiology and Biomedical Imaging at the University of California-San Francisco (UCSF), and colleagues.
Is the Prognostic Benefit of Relative Oxygen Ejection Fraction Time-Dependent?
The researchers emphasized the time-dependent value of rOEF, noting that 71 percent of overestimated ischemic core was observed in patients with a last known well time of 120 minutes or less.
“This finding supports the concept of stunned brain, in which early ischemia and hemodynamic impairment can be compensated for by metabolic factors such as elevated OEF; however, as time passes, this elevation in OEF may eventually progress to metabolic exhaustion, reducing the protective potential of OEF in later stages,” pointed out Asghariahmadabad and colleagues.
Three Key Takeaways
• Combining rOEF with ADC substantially improves infarct prediction accuracy. Adding relative oxygen ejection fraction (derived from DSC-MRI) to standard ADC mapping raised AUC from 65 percent to 80 percent with meaningful gains in both sensitivity (60 percent to 74 percent) and specificity (63 percent to 76 percent), meaning ADC alone likely overestimates final infarct core in a clinically significant number of patients (35 percent diffusion reversal seen in this cohort).
• ADC-only ischemic core estimates should be interpreted cautiously, especially early after symptom onset. The overestimation of ischemic core was concentrated in patients presenting within 120 minutes of last known well (71 percent of overestimated ischemic core), reflecting a "stunned brain" phenomenon where elevated OEF temporarily compensates for ischemia before metabolic exhaustion sets in.
• rOEF's protective/predictive value appears time-dependent, which has triage implications. Incorporating rOEF into imaging protocols could help avoid excluding otherwise treatable patients from reperfusion therapy based on ADC-defined ischemic core alone, particularly in early-presenting patients where the risk of ischemic core overestimation is highest.
(Editor’s note: For related content, see “Can Brain MRI Help Predict Spinal Cord Stimulation Response for Treating Urinary Incontinence in Stroke Survivors?,” “AI in Neuroradiology: Keys to Workflow Integration, Governance and Facilitating Improved Outcomes” and “MRI Study Reveals Potentially Severe Impact of NAC Upon Heart and Brain Function in Breast Cancer Patients.”)
Beyond the inherent limitations of a single-center retrospective study, the authors acknowledged the small cohort size and noted that the majority of the cohort presented in an early time window.
