Assessment of ischemic penumbra in patients with hyperacute stroke using amide proton transfer (APT) chemical exchange saturation transfer (CEST) MRI.
Chemical exchange saturation transfer (CEST)-derived, pH-weighted, amide proton transfer (APT) MRI has shown promise in animal studies for the prediction of infarction risk in ischemic tissue. Here, APT MRI was translated to patients with acute stroke (1-24 h post-symptom onset), and assessments of APT contrast, perfusion, diffusion, disability and final infarct volume (23-92 days post-stroke) are reported. Healthy volunteers (n = 5) and patients (n = 10) with acute onset of symptoms (0-4 h, n = 7; uncertain onset <24 h, n = 3) were scanned with diffusion- and perfusion-weighted MRI, fluid-attenuated inversion recovery (FLAIR) and CEST. Traditional asymmetry and a Lorentzian-based APT index were calculated in the infarct core, at-risk tissue (time-to-peak, TTP; lengthening) and final infarct volume. On average (mean ± standard deviation), control white matter APT values (asymmetry, 0.019 ± 0.005; Lorentzian, 0.045 ± 0.006) were not significantly different (p > 0.05) from APT values in normal-appearing white matter (NAWM) of patients (asymmetry, 0.022 ± 0.003; Lorentzian, 0.048 ± 0.003); however, ischemic regions in patients showed reduced (p = 0.03) APT effects compared with NAWM. Representative cases are presented, whereby the APT contrast is compared quantitatively with contrast from other imaging modalities. The findings vary between patients; in some patients, a trend for a reduction in the APT signal in the final infarct region compared with at-risk tissue was observed, consistent with tissue acidosis. However, in other patients, no relationship was observed in the infarct core and final infarct volume. Larger clinical studies, in combination with focused efforts on sequence development at clinically available field strengths (e.g. 3.0 T), are necessary to fully understand the potential of APT imaging for guiding the hyperacute management of patients.
['Tietze|Anna|A|', 'Blicher|Jakob|J|', 'Mikkelsen|Irene Klaerke|IK|', 'Østergaard|Leif|L|', 'Strother|Megan K|MK|', 'Smith|Seth A|SA|', 'Donahue|Manus J|MJ|']
D000328:Adult D000368:Aged D000465:Algorithms D000577:Amides D001921:Brain D002545:Brain Ischemia D005260:Female D006801:Humans D007090:Image Interpretation, Computer-Assisted D008279:Magnetic Resonance Imaging D008297:Male D008875:Middle Aged D011522:Protons D020521:Stroke
penumbra amide proton transfer chemical exchange saturation transfer (CEST) MRI acute stroke cerebrovascular disease lactate pH