title: Brain tissue oxygen evaluation by wireless near-infrared spectroscopy.
abstract: BACKGROUND
  Monitoring the partial pressure of oxygen in brain tissue (PbtO2) is an important tool for traumatic brain injury (TBI) but is invasive and inconvenient for real time monitoring. Near-infrared spectroscopy (NIRS), which can monitor hemoglobin parameters in the brain tissue, has been used widely as a noninvasive tool for assessing cerebral ischemia and hypoxia. Therefore, it may have the potential as a noninvasive tool for estimating the change of PbtO2. In this study, a novel wireless NIRS system was designed to monitor hemoglobin parameters of rat brains under different impact strengths and was used to estimate the change of PbtO2 noninvasively in TBI.
  
  
  METHODS
  The proposed wireless NIRS system and a PbtO2 monitoring system were used to monitor the oxygenation of rat brains under different impact strengths. Rats were randomly assigned to four different impact strength groups (sham, 1.6 atm, 2.0 atm, and 2.4 atm; n = 6 per group), and the relationships of concentration changes in oxyhemoglobin (HbO2), deoxyhemoglobin (HbR), and total hemoglobin (HbT), and PbtO2 during and after TBI with different impact strengths were investigated. Triphenyltetrazolium chloride (TTC) staining was also used to evaluate infarction volume.
  
  
  RESULTS
  Concentration changes in HbO2, HbR, and HbT dropped immediately after the impact, increased gradually, and then became stable. Changes in PbtO2 had a similar tendency with the hemoglobin parameters. There was significant correlation between changes in PbtO2 and HbO2 (correlation = 0.76) but not with changes in HbR (correlation = 0.06). In triphenyltetrazolium chloride staining, the infarction volume was highly but negatively associated with oxygen-related parameters like PbtO2 and HbO2.
  
  
  CONCLUSIONS
  Changes in HbO2 under TBI was highly and positively correlated with changes in PbtO2. By using the relative changes in HbO2 as a reference parameter, the proposed wireless NIRS system may be developed as a noninvasive tool for estimating the change of PbtO2 in brain tissue after TBI.
authors.affiliation: Institute of Photonic System, National Chiao-Tung University, Tainan, Taiwan; Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan; Division of Neurosurgery, Department of Surgery, Chi Mei Medical Center, Tainan, Taiwan; Department of Child Care, Southern Taiwan University of Science and Technology, Tainan, Taiwan.
authors.forename: Che-Chuan
authors.initials: CC
authors.lastname: Wang
authors.affiliation: Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan; Division of Neurosurgery, Department of Surgery, Chi Mei Medical Center, Tainan, Taiwan; Department of Biotechnology, Southern Taiwan University of Science and Technology, Tainan, Taiwan.
authors.forename: Jinn-Rung
authors.initials: JR
authors.lastname: Kuo
authors.affiliation: Institute of Imaging and Biomedical Photonics, National Chiao-Tung University, Tainan, Taiwan.
authors.forename: Yu-Chih
authors.initials: YC
authors.lastname: Chen
authors.affiliation: Division of Neurosurgery, Department of Surgery, Chi Mei Medical Center, Tainan, Taiwan.
authors.forename: Chung-Ching
authors.initials: CC
authors.lastname: Chio
authors.affiliation: Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan.
authors.forename: Jhi-Joung
authors.initials: JJ
authors.lastname: Wang
authors.affiliation: Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan; Institute of Imaging and Biomedical Photonics, National Chiao-Tung University, Tainan, Taiwan. Electronic address: borshyhlin@gmail.com.
authors.forename: Bor-Shyh
authors.initials: BS
authors.lastname: Lin
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D001930:Brain Injuries / Q000378:metabolism*; D008297:Male; D008991:Monitoring, Physiologic; D010100:Oxygen / Q000378:metabolism*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D059015:Wireless Technology
chemical_list: D015415:Biomarkers; D010100:Oxygen
keywords: Deoxyhemoglobin; Near-infrared spectroscopy; Oxyhemoglobin; Partial pressure of oxygen in brain tissue; Traumatic brain injury