title: Spectral analysis of near-infrared spectroscopy signals measured from prefrontal lobe in subjects at risk for stroke.
abstract: OBJECTIVE
  The objective of this study was to assess the spontaneous cerebral oscillations based on the wavelet transform of near-infrared spectroscopy (NIRS) signals in subjects at risk for atherosclerotic stroke.
  
  
  METHODS
  A total of 32 subjects were recruited from the university to participate in this study: 20 were normal subjects (age = 59.6 ± 10.2 year) and the other 12 were subjects at risk for ischemic stroke (age = 60.2 ± 10.1 year).The cerebral oxygenation signal was monitored for 10 min from the left prefrontal lobe using NIRS.
  
  
  RESULTS
  With spectral analysis based on wavelet transform, five frequency intervals were identified (I, 0.005-0.02 Hz; II, 0.02-0.06 Hz; III, 0.06-0.15 Hz; IV, 0.15-0.40 Hz; and V, 0.40-2.0 Hz). The amplitude of the [Hb] in the frequency intervals from I to V and of the [HbO(2)] in frequency intervals I and V in subjects at risk for stroke were found to be significantly lower compared to the amplitudes in normal subjects.
  
  
  CONCLUSIONS
  The reduction of spontaneous oscillations in these subjects suggests an increased stiffness in the cerebral artery. This indicates the possibility of applying spontaneous oscillations, based on the wavelet transform of NIRS signals, to assess the risk in subjects with atherosclerosis.
authors.affiliation: School of Mechanical Engineering, Shandong University, Jinan, People's Republic of China. zyongli@sdu.edu.cn
authors.forename: Zengyong
authors.initials: Z
authors.lastname: Li
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
authors.forename: Qing
authors.initials: Q
authors.lastname: Xin
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Chen
authors.forename: Feifei
authors.initials: F
authors.lastname: Liu
authors.forename: Jianping
authors.initials: J
authors.lastname: Li
mesh_terms: D000465:Algorithms; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000378:metabolism*; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D020521:Stroke / Q000097:blood* / Q000175:diagnosis*
chemical_list: D006454:Hemoglobins