KEYWORDS: Brain, Ischemia, Simulation of CCA and DLA aggregates, Windows, Speckle, 3D image reconstruction, Sampling rates, Tissues, Reconstruction algorithms, Neuroimaging
SignificanceLow-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.AimWe aim to optimize an innovative speckle contrast diffuse correlation tomography (scDCT) system for the detection of LFOs within CBF variations.ApproachThe 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.ResultsTransient global cerebral ischemia resulted in reductions in both CBF and PSD compared with their baseline values.ConclusionsSpontaneous 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.
The purpose of this study is to investigate the effects of external factors – including environmental conditions (e.g., ambient temperature, ambient relative humidity), and deployment parameters (e.g., working distance, viewing angle, setting temperature of external temperature reference source (ETRS)) – on the use of infrared thermographs (IRTs) for elevated body temperature (EBT) detection. These effects were theoretically evaluated through computer simulation and experimentally evaluated through bench tests. Overall, the insights into the influence of these factors provided by this study may improve IRT performance and thus enhance the potential of IRTs as countermeasures for high-quality point-of-care EBT screening.
An innovative camera-based speckle contrast diffuse correlation tomography (scDCT) technology has been developed recently, which enables noncontact, noninvasive, high-density, 3D imaging of cerebral blood flow (CBF) distributions. This study demonstrated the capability and safety of scDCT technique for imaging of CBF distributions in a neonatal piglet model of transient ischemic stroke. Moreover, power spectral density analyses of low-frequency oscillations (LFOs) and the network connections over the brain were assessed before and after the induction of acute ischemic stroke. The stroke resulted in a substantial decrease in CBF, attenuations in resting-state LFOs, and functional connectivity disruptions in motor and somatosensory cortices.
KEYWORDS: Ischemia, Optical sensors, Simulation of CCA and DLA aggregates, Semiconductor lasers, Detector arrays, Spectroscopy, Speckle, Neuroscience, Laser tissue interaction, Head
We report an innovative, wearable, multiscale diffuse speckle contrast flowmetry (DSCF) probe for continuous transcranial imaging of cerebral blood flow (CBF) in animal s. Significant reductions in CBF during transient ligation of bilateral common carotid arteries were detected by DSCF (-35±13% in two mice and -59% in a piglet), meeting clinical expectations. Results from DSCF and an established CBF measurement device, diffuse correlation spectroscopy, were consistent and significantly correlated. With further optimization and validation in animals and humans, we expect to ultimately offer a unique, noninvasive, low-cost, and fast brain imaging tool for basic neuroscience research and clinical applications.
Intraventricular hemorrhage (IVH) is the most common neurological complication of prematurity. IVH is a bleeding inside or around ventricles, spaces in the brain containing the cerebrospinal fluid, which occurs as a result of the fragility and immaturity of blood vessels in premature brains. Severe IVH disrupts development of structural and functional connectivity networks, leading to impairments of cerebral development and neurologic deficits. Preterm infants with IVH are prone to alterations in cerebral blood flow (CBF) and associated spontaneous low-frequency fluctuations. However, there are no established noninvasive imaging methods for continuous monitoring of CBF alterations at the bedside in neonatal intensive care units. An innovative CCD/CMOS based speckle contrast diffuse correlation tomography (scDCT) technology has been recently developed in our laboratory, which enables noncontact, noninvasive, and high-density 3D imaging of CBF distributions in deep brain cortex. In the present study, the capability of scDCT technique for noncontact 3D imaging of CBF distributions in a neonatal piglet model of IVH was demonstrated. Moreover, power spectral density analyses of scDCT data were performed to assess alterations in spontaneous low frequency fluctuations in the resting brain, before and after inducing IVH. IVH resulted in a CBF decrease in deep brain cortex. Resting-state spontaneous low-frequency fluctuations after IVH showed attenuations in all frequencies (0.009– 0.08 Hz) compared to the baseline before IVH. In conclusion, scDCT is capable of detecting brain hemodynamic disruptions (reduction in CBF and attenuation in spontaneous low-frequency fluctuations) after IVH, which might be useful for instant management of IVH and associated complications.
A noncontact electron multiplying charge-coupled-device (EMCCD)-based speckle contrast diffuse correlation tomography (scDCT) technology has been recently developed in our laboratory, allowing for noninvasive three-dimensional measurement of tissue blood flow distributions. One major remaining constraint in the scDCT is the assumption of a semi-infinite tissue volume with a flat surface, which affects the image reconstruction accuracy for tissues with irregular geometries. An advanced photometric stereo technique (PST) was integrated into the scDCT system to obtain the surface geometry in real time for image reconstruction. Computer simulations demonstrated that a priori knowledge of tissue surface geometry is crucial for precisely reconstructing the anomaly with blood flow contrast. Importantly, the innovative integration design with one single-EMCCD camera for both PST and scDCT data collection obviates the need for offline alignment of sources and detectors on the tissue boundary. The in vivo imaging capability of the updated scDCT is demonstrated by imaging dynamic changes in forearm blood flow distribution during a cuff-occlusion procedure. The feasibility and safety in clinical use are evidenced by intraoperative imaging of mastectomy skin flaps and comparison with fluorescence angiography.
We report a low-cost compact diffuse speckle contrast flowmeter (DSCF) consisting of a small laser diode and a bare charge-coupled-device (CCD) chip, which can be used for contact measurements of blood flow variations in relatively deep tissues (up to ∼8 mm). Measurements of large flow variations by the contact DSCF probe are compared to a noncontact CCD-based diffuse speckle contrast spectroscopy and a standard contact diffuse correlation spectroscopy in tissue phantoms and a human forearm. Bland–Altman analysis shows no significant bias with good limits of agreement among these measurements: 96.5%±2.2% (94.4% to 100.0%) in phantom experiments and 92.8% in the forearm test. The relatively lower limit of agreement observed in the in vivo measurements (92.8%) is likely due to heterogeneous reactive responses of blood flow in different regions/volumes of the forearm tissues measured by different probes. The low-cost compact DSCF device holds great potential to be broadly used for continuous and longitudinal monitoring of blood flow alterations in ischemic/hypoxic tissues, which are usually associated with various vascular diseases.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.