title: Continuous correction of differential path length factor in near-infrared spectroscopy.
abstract: In continuous-wave near-infrared spectroscopy (CW-NIRS), changes in the concentration of oxyhemoglobin and deoxyhemoglobin can be calculated by solving a set of linear equations from the modified Beer-Lambert Law. Cross-talk error in the calculated hemodynamics can arise from inaccurate knowledge of the wavelength-dependent differential path length factor (DPF). We apply the extended Kalman filter (EKF) with a dynamical systems model to calculate relative concentration changes in oxy- and deoxyhemoglobin while simultaneously estimating relative changes in DPF. Results from simulated and experimental CW-NIRS data are compared with results from a weighted least squares (WLSQ) method. The EKF method was found to effectively correct for artificially introduced errors in DPF and to reduce the cross-talk error in simulation. With experimental CW-NIRS data, the hemodynamic estimates from EKF differ significantly from the WLSQ (p < 0.001). The cross-correlations among residuals at different wavelengths were found to be significantly reduced by the EKF method compared to WLSQ in three physiologically relevant spectral bands 0.04 to 0.15 Hz, 0.15 to 0.4 Hz and 0.4 to 2.0 Hz (p < 0.001). This observed reduction in residual cross-correlation is consistent with reduced cross-talk error in the hemodynamic estimates from the proposed EKF method.
authors: Thayer School of Engineering at Dartmouth, Hanover, NH 03755, USA. tanveer@dartmouth.edu
authors: Tanveer
authors: T
authors: Talukdar
authors: Jason H
authors: JH
authors: Moore
authors: Solomon G
authors: SG
authors: Diamond
mesh_terms: D000465:Algorithms; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D016018:Least-Squares Analysis; D010108:Oxyhemoglobins / Q000032:analysis; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin
references: Arch Phys Med Rehabil. 2006 Dec;87(12 Suppl 2):S12-9
references: 17140875
references: J Biomed Opt. 2006 Sep-Oct;11(5):054007
references: 17092156
references: Anesth Analg. 2007 Feb;104(2):341-6
references: 17242091
references: Appl Opt. 2003 Jun 1;42(16):2881-7
references: 12790436
references: Neurocrit Care. 2010 Apr;12(2):173-80
references: 19908166
references: J Biomed Opt. 2010 Mar-Apr;15(2):026006
references: 20459251
references: Adv Exp Med Biol. 1988;222:183-9
references: 3129910
references: Phys Med Biol. 1993 Dec;38(12):1859-76
references: 8108489
references: J Clin Monit. 1995 Mar;11(2):109-17
references: 7760083
references: J Biomed Opt. 2009 Sep-Oct;14(5):054038
references: 19895139
references: J Biomed Opt. 2002 Jan;7(1):51-9
references: 11818012
references: Ann Biomed Eng. 2012 Feb;40(2):398-407
references: 21971964
references: Top Stroke Rehabil. 2008 Sep-Oct;15(5):427-50
references: 19008203
references: Appl Opt. 2003 Jun 1;42(16):2906-14
references: 12790439
references: Anesthesiology. 2007 Mar;106(3):458-62
references: 17325503
references: J Biomed Opt. 2012 May;17(5):056002
references: 22612125
references: IEEE Trans Biomed Eng. 2010 Jun;57(6):1377-87
references: 20172809
references: Phys Med Biol. 1992 Jul;37(7):1531-60
references: 1631197
references: Appl Opt. 1997 Jan 1;36(1):21-31
references: 18250644
references: Circulation. 1996 Mar 1;93(5):1043-65
references: 8598068
references: Appl Opt. 2009 Apr 1;48(10):D280-98
references: 19340120
references: Phys Med Biol. 1995 Feb;40(2):295-304
references: 7708855
references: J Biomed Opt. 2006 Jul-Aug;11(4):044008
references: 16965165
references: Math Biosci. 1991 Nov;107(1):73-82
references: 1806109
references: Phys Med Biol. 1988 Dec;33(12):1433-42
references: 3237772
references: Neurocrit Care. 2009;11(2):288-95
references: 19649749
references: Phys Med Biol. 2002 Jun 21;47(12):2075-93
references: 12118602
references: Neuroimage. 2003 Apr;18(4):865-79
references: 12725763
references: J Biomed Opt. 2005 Jan-Feb;10(1):11015
references: 15847581