26 December 2017 High-speed spatial frequency domain imaging of rat cortex detects dynamic optical and physiological properties following cardiac arrest and resuscitation
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Abstract
Quantifying rapidly varying perturbations in cerebral tissue absorption and scattering can potentially help to characterize changes in brain function caused by ischemic trauma. We have developed a platform for rapid intrinsic signal brain optical imaging using macroscopically structured light. The device performs fast, multispectral, spatial frequency domain imaging (SFDI), detecting backscattered light from three-phase binary square-wave projected patterns, which have a much higher refresh rate than sinusoidal patterns used in conventional SFDI. Although not as fast as “single-snapshot” spatial frequency methods that do not require three-phase projection, square-wave patterns allow accurate image demodulation in applications such as small animal imaging where the limited field of view does not allow single-phase demodulation. By using 655, 730, and 850 nm light-emitting diodes, two spatial frequencies ( f x = 0 and 0.3    mm 1 ), three spatial phases (120 deg, 240 deg, and 360 deg), and an overall camera acquisition rate of 167 Hz, we map changes in tissue absorption and reduced scattering parameters ( μ a and μ s ) and oxy- and deoxyhemoglobin concentration at 14    Hz . We apply this method to a rat model of cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) to quantify hemodynamics and scattering on temporal scales ( Δ t ) ranging from tens of milliseconds to minutes. We observe rapid concurrent spatiotemporal changes in tissue oxygenation and scattering during CA and following CPR, even when the cerebral electrical signal is absent. We conclude that square-wave SFDI provides an effective technical strategy for assessing cortical optical and physiological properties by balancing competing performance demands for fast signal acquisition, small fields of view, and quantitative information content.
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Robert H. Wilson, Robert H. Wilson, Christian Crouzet, Christian Crouzet, Mohammad Torabzadeh, Mohammad Torabzadeh, Afsheen K. Bazrafkan, Afsheen K. Bazrafkan, Maryam Hosseini-Farahabadi, Maryam Hosseini-Farahabadi, Babak Jamasian, Babak Jamasian, Dishant Donga, Dishant Donga, Juan Alcocer, Juan Alcocer, Shuhab Mohammed Zaher, Shuhab Mohammed Zaher, Bernard Choi, Bernard Choi, Yama Akbari, Yama Akbari, Bruce J. Tromberg, Bruce J. Tromberg, } "High-speed spatial frequency domain imaging of rat cortex detects dynamic optical and physiological properties following cardiac arrest and resuscitation," Neurophotonics 4(4), 045008 (26 December 2017). https://doi.org/10.1117/1.NPh.4.4.045008 . Submission: Received: 21 August 2017; Accepted: 29 November 2017
Received: 21 August 2017; Accepted: 29 November 2017; Published: 26 December 2017
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