title: Altered resting-state FMRI signals in acute stroke patients with ischemic penumbra.
abstract: BACKGROUND
  Identifying the ischemic penumbra in acute stroke subjects is important for the clinical decision making process. The aim of this study was to use resting-state functional magnetic resonance singal (fMRI) to investigate the change in the amplitude of low-frequency fluctuations (ALFF) of these subjects in three different subsections of acute stroke regions: the infarct core tissue, the penumbra tissue, and the normal brain tissue. Another aim of this study was to test the feasilbility of consistently detecting the penumbra region of the brain through ALFF analysis.
  
  
  METHODS
  Sixteen subjects with first-ever acute ischemic stroke were scanned within 27 hours of the onset of stroke using magnetic resonance imaging. The core of infarct regions and penumbra regions were determined by diffusion and perfusion-weighted imaging respectively. The ALFF were measured from resting-state blood oxygen level dependent (BOLD) fMRI scans. The averaged relative ALFF value of each regions were correlated with the time after the onset of stroke.
  
  
  RESULTS
  Relative ALFF values were significantly different in the infarct core tissue, penumbra tissue and normal brain tissue. The locations of lesions in the ALFF maps did not match perfectly with diffusion and perfusion-weighted imagings; however, these maps provide a contrast that can be used to differentiate between penumbra brain tissue and normal brain tissue. Significant correlations between time after stroke onset and the relative ALFF values were present in the penumbra tissue but not in the infarct core and normal brain tissue.
  
  
  CONCLUSIONS
  Preliminary results from this study suggest that the ALFF reflects the underlying neurovascular activity and has a great potential to estimate the brain tissue viability after ischemia. Results also show that the ALFF may contribute to acute stroke imaging for thrombolytic or neuroprotective therapies.
authors.affiliation: Department of Diagnostic Radiology, Chang Gung Memorial Hospital at Chiayi, College of Medicine and School of Medical Technology, Chang-Gung University, Taoyuan, Taiwan.
authors.forename: Yuan-Hsiung
authors.initials: YH
authors.lastname: Tsai
authors.affiliation: Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States of America.
authors.forename: Rui
authors.initials: R
authors.lastname: Yuan
authors.affiliation: Department of Neurology, Chang Gung Memorial Hospital at Chiayi, College of Medicine and School of Medical Technology, Chang-Gung University, Taoyuan, Taiwan.
authors.forename: Yen-Chu
authors.initials: YC
authors.lastname: Huang
authors.affiliation: Department of Diagnostic Radiology, Chang Gung Memorial Hospital at Chiayi, College of Medicine and School of Medical Technology, Chang-Gung University, Taoyuan, Taiwan.
authors.forename: Hsu-Huei
authors.initials: HH
authors.lastname: Weng
authors.affiliation: Department of Diagnostic Radiology, Chang Gung Memorial Hospital at Chiayi, College of Medicine and School of Medical Technology, Chang-Gung University, Taoyuan, Taiwan.
authors.forename: Mei-Yu
authors.initials: MY
authors.lastname: Yeh
authors.affiliation: Department of Biomedical Imaging and Radiological Sciences, National Yang Ming University, Taipei, Taiwan; Institute of Neuroscience, National Yang Ming University, Taipei, Taiwan.
authors.forename: Ching-Po
authors.initials: CP
authors.lastname: Lin
authors.affiliation: Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States of America.
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Biswal
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020521:Stroke / Q000503:physiopathology*