The experimental methods of Doppler optical coherence tomography are applied for two-dimensional flow mapping of highly scattering fluid in flow with complex geometry. Converging flow (die entry) is used to demonstrate non-invasive methods to map varying velocity profiles before and after the entry. Complex geometry flow is scanned with approximately 10 x 10 x 10 microm3 spatial resolution. Structural images of the phantom and specific velocity images are demonstrated. A variety of velocity profiles have been obtained before and after the entry. Concave, blunted, parabolic and triangular profiles are obtained at different distances after the entry. Application of the technique to the study of blood circulation is discussed.
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http://dx.doi.org/10.1088/0031-9155/49/7/014 | DOI Listing |
World Neurosurg
December 2024
Clinical and Translational Neuroscience Unit, Department of Neurology and Feil Brain and Mind Research Institute, Weill Cornell Medicine, New York, New York, USA. Electronic address:
The subspecialty of neurocritical care has grown significantly over the past 40 years along with advancements in the medical and surgical management of neurological emergencies. The modern neuroscience intensive care unit (neuro-ICU) is grounded in close collaboration between neurointensivists and neurosurgeons in the management of patients with such conditions as ischemic stroke, aneurysmal subarachnoid hemorrhage, intracerebral hemorrhage, subdural hematomas, and traumatic brain injury. Neuro-ICUs are also capable of specialized monitoring such as serial neurological examinations by trained neuro-ICU nurses; invasive monitoring of intracranial pressure, cerebral oxygenation, and cerebral hemodynamics; cerebral microdialysis; and noninvasive monitoring, including the use of pupillometry, ultrasound monitoring of optic nerve sheath diameters, transcranial Doppler ultrasonography, near-infrared spectroscopy, and continuous electroencephalography.
View Article and Find Full Text PDFBiomimetics (Basel)
November 2024
Ocean and Maritime Digital Technology Research Division, Korea Research Institute of Ships and Ocean Engineering, Daejeon 34103, Republic of Korea.
Although the Doppler velocity log is widely applied to measure underwater fluid flow, it requires high power and is inappropriate for measuring low flow velocity. This study proposes a fluid flow sensor that utilizes optical flow sensing. The proposed sensor mimics the neuromast of a fish by attaching a phosphor to two pillar structures (A and B) produced using ethylene propylene diene monomer rubber.
View Article and Find Full Text PDFJ Cereb Blood Flow Metab
December 2024
Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, NY, USA.
Alzheimer's disease (AD), a neurodegenerative disorder with progressive cognitive decline, remains clinically challenging with limited understanding of etiology and interventions. Clinical studies have reported vascular defects prior to other pathological manifestations of AD, leading to the "Vascular Hypothesis" for the disorder. However, assessments of cerebral vasculature in AD rodent models have been constrained by limited spatiotemporal resolution or field of view of conventional imaging.
View Article and Find Full Text PDFLab Chip
December 2024
College of Engineering and Applied Sciences, Nanjing University, Jiangsu 210093, China.
Acoustic waves provide an effective method for object manipulation in microfluidics, often requiring high-frequency ultrasound in the megahertz range when directly handling microsized objects, which can be costly. Micro-air-bubbles in water offer a solution toward low-cost technologies using low-frequency acoustic waves. Owing to their high compressibility and low elastic modulus, these bubbles can exhibit significant expansion and contraction in response to even kilohertz acoustic waves, leading to resonances with frequencies determined and tuned by air-bubble size.
View Article and Find Full Text PDFPhotoacoustics
August 2024
Department of Physics, University of Auckland, Private Bag 92019, Auckland, 1010, New Zealand.
We present a technique called photoacoustic vector-flow (PAVF) to quantify the speed and direction of flowing optical absorbers at each pixel from acoustic-resolution PA images. By varying the receiving angle at each pixel in post-processing, we obtain multiple estimates of the phase difference between consecutive frames. These are used to solve the overdetermined photoacoustic Doppler equation with a least-squares approach to estimate a velocity vector at each pixel.
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