Near-infrared spectroscopy and imaging for investigating stroke rehabilitation: Test-retest reliability and review of the literature

Objectives: To review the use of near-infrared spectroscopy (NIRS) in stroke rehabilitation and to evaluate NIRS test-retest reliability within-session on a motor control task commonly used in neuroimaging of stroke recovery. Design: Cohort study. Setting: Hospital-based research laboratory. Participants: Nineteen healthy control subjects (age range, 22-55y). Interventions: Subjects performed 2 experimental runs of a finger-opposition task in a block-design paradigm (finger opposition alternated with a fixation rest period) while undergoing multichannel NIRS and physiologic monitoring. Main Outcome Measure: Reliability coefficients (Pearson r) for oxyhemoglobin (O(2)Hb) and deoxyhemoglobin (HHb) correlated amplitude modulations across measurement channels during individual blocks and block averages. Results: Correlations between single blocks (ie, 16-s slices of data) exhibited a correlation intercept of 33 +/- .09 for O(2)Hb. This value was minimally decreased by increasing lag between compared blocks (slope, -.012; P=.019) but was substantially enhanced by averaging across blocks (within-run slope, 11: between-run slope, .044). Correlations using 64 seconds of data reached 0.6. Results for HHb were virtually identical. Conclusions: NIRS modulations were repeatable even when comparing very short segments of data. When averaging longer data segments, the test-retest correspondences compared favorably to neuroimaging using other modalities. This suggests that NIRS is a reliable tool for longitudinal stroke rehabilitation and recovery studies.