Detection of low-frequency oscillations in neonatal piglets with speckle contrast diffuse correlation tomography

Abstract

Significance: Low-frequency oscillations (LFOs) (<0.1 Hz) with respect to cerebral blood flow (CBF) have shown promise as an indicator of altered neurologic activity in the abnormal brain. Portable optical instruments have evolved to offer a noninvasive alternative for continuous CBF monitoring at the bedside compared with many large neuroimaging modalities. However, their utilization for acquiring LFOs of CBF has only been studied to a limited extent.Aim: We aim to optimize an innovative speckle contrast diffuse correlation tomography (scDCT) system for the detection of LFOs within CBF variations. Approach:The scDCT was optimized to achieve a higher sampling rate and a faster image reconstruction using a moving window 3D reconstruction algorithm with parallel computation. Power spectral density (PSD) analysis was performed to investigate altered LFOs during transient global cerebral ischemia in neonatal piglets.Results: Transient global cerebral ischemia resulted in reductions in both CBF and PSD compared with their baseline values.Conclusions: Spontaneous LFOs, combined with CBF, provide a more comprehensive assay with the potential to clarify pathological mechanisms involved in brain injury. These results support scDCT's inclusion and application in the growing area of LFO analysis and demonstrate its inherent advantage for neurological studies in preclinical and clinical settings, such as neonatal intensive care units.

Depth-sensitive diffuse speckle contrast topography for high-density mapping of cerebral blood flow in rodents

“…A highperformance long-pass filter (>750 nm; #84-761, EdmundOptics) was used to minimize the influence of ambient light on DSCT measurements. 26 No obvious influence of ambient light was observed on the obtained raw intensity images or reconstructed BFI maps from the experiments. A pair of polarizers (LPNIRE050-B and LPNIRE200-B, Thorlabs) crossing the source and detection paths were added to reduce the specular reflection directly from the scanning light sources on the tissue surface.…”

“…Following our established method, 20,26 raw intensity images were prescreened to ensure that the detected light intensities (counts) were within the linear range of our camera and above the minimal SNR requirement (i.e., SNR > 3). The DSCT method first converted each of the raw intensity images taken at different source locations within the ROI into a speckle contrast image based on the fast LSCI analysis utilizing the Image Processing Toolbox™ and Parallel Computing Toolbox™ (Sec.…”

“…The DSCT data analysis requires the input of source locations. Following our established method, 26 the intensity image captured at each source location was analyzed to precisely determine its location. This method enabled accounting for the potential shift of each source location caused by tissue geometric factor.…”

“…Using a conventional 2D mapping method with 441 sources (21 × 21), the total sampling time to generate one 2D map of CBF was 60 s. In this study, a new method based on a moving window was adapted to improve the sampling rate, in which the topographic reconstruction of each CBF map was obtained when one new source position data point became available. 4,26 As a result, the total sampling time was reduced ∼440 times (i.e., from 60 to 0.136 s).…”

“…4,16,17 We have developed an innovative speckle contrast diffuse correlation tomography (scDCT; US Patent #9/861,319, 2018 18 ) method, which provides a noncontact, inexpensive, and portable tool for 3D imaging of blood flow distributions over a large FOV in relatively deep tissue volumes (up to ∼10 mm depth). [19][20][21][22][23][24][25][26][27][28] These advanced CCD/CMOS-based techniques are inherently founded upon the same concept despite differences in nomenclature and technological evolution.…”