Abstract
Slow sinusoidal, hemodynamic oscillations (SSHOs) around 0.1 Hz are frequently seen in mammalian and human brains. In four patients undergoing epilepsy surgery, subtle but robust fluctuations in oxy‐ and deoxyhemoglobin were detected using hyperspectral imaging of the cortex. These SSHOs were stationary during the entire 4 to 10 min acquisition time. By Fourier filtering the oxy‐ and deoxyhemoglobin time signals with a small bandwidth, SSHOs became visible within localized regions of the brain, with distinctive frequencies and a continuous phase variation within that region. SSHOs of deoxyhemoglobin appeared to have an opposite phase and 11% smaller amplitude with respect to the oxyhemoglobin SSHOs. Although the origin of SSHOs remains unclear, we find indications that the observed SSHOs may embody a local propagating hemodynamic wave with velocities in line with capillary blood velocities, and conceivably related to vasomotion and maintenance of adequate tissue perfusion. Hyperspectral imaging of the human cortex during surgery allow in‐depth characterization of SSHOs, and may give further insight in the nature and potential (clinical) use of SSHOs.
Highlights
Background correction no yes yes yesNumber of wavelength blocksTime per wavelength block [ms]Total acquisition time [mins:secs] 06:07 04:17 10:24 10:16|4NOORDMANS et al.NOORDMANS 3ET56AL1.FI G URE 2 (a) Plots of changes in oxy and deoxy concentrations of patient 3 at location 1. (b) Corresponding power spectra
We provide a thorough description of the observed SSHOs in four patients with epilepsy who underwent epilepsy surgery in the UMC Utrecht
Peaks are seen for the SSHOs around 0.1 Hz, and the respiration and heart rate, the latter two corresponding to the rates reported by the anesthesia machine of 12 and 56 min21, respectively. (c) Zooming on the curves of (a)
Summary
Background correction no yes yes yesNumber of wavelength blocksTime per wavelength block [ms]Total acquisition time [mins:secs] 06:07 04:17 10:24 10:16|4NOORDMANS et al.NOORDMANS 3ET56AL1.FI G URE 2 (a) Plots of changes in oxy (red) and deoxy (blue) concentrations of patient 3 at location 1 (indicated by the plus symbol in Figure 6E, near retractor). (b) Corresponding power spectra. Total acquisition time [mins:secs] 06:07 04:17 10:24 10:16. FI G URE 2 (a) Plots of changes in oxy (red) and deoxy (blue) concentrations of patient 3 at location 1 (indicated by the plus symbol, near retractor). Peaks are seen for the SSHOs around 0.1 Hz, and the respiration and heart rate, the latter two corresponding to the rates reported by the anesthesia machine of 12 and 56 min, respectively. A phase shift of about 180 degrees can clearly be seen between the changes in concentration of oxygenation and deoxygenation [Color figure can be viewed at wileyonlinelibrary.com]. The Delta-t method results in a set of DcHbO and DcHbR images, where the change in HbO and HbR concentrations are known per pixel at each moment in time (with respect to the situation at t50)
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