High-Density Speckle Contrast Optical Tomography (HD-SCOT) is an optical technique with the potential to address the limitations of current techniques for imaging Cerebral Blood Flow (CBF). To evaluate HD-SCOT’s performance, we developed an anatomical-head-based simulation to obtain HD-SCOT measurements and reconstructed images. We observed that including longer source-detector distances can reduce localization errors. Even though speckle contrast decreases with increased exposure times, the System-to-Noise Ratio (SNR) can increase dramatically. For instrumentation, we evaluated statistics of speckles through a multi-mode fiber (MMF) bundle and demonstrated the feasibility of tracking pulsatile blood flow in a human subject using MMFs.
A limiting factor for personalizing therapies in stroke patients is the inability to continuously monitor the cerebral status of patients. In particular, potential impairment of cerebral autoregulation (CA) in these patients may incur certain risks during their mobilization. We have used hybrid diffuse optical techniques to measure new biomarkers related to CA status as well as metabolic health in a large cohort of stroke patients in order to determine biomarkers indicative of clinical improvement. If validated, these results can pave the way towards personalization of stroke therapy based on direct measures of cerebral health.
Cerebral autoregulation (CA) as a mechanism to protect the brain from ischemia or hypoperfusion may play an important role related to post-stroke interventions such as the physiotherapy and the outcome. Here, we present a non-invasive assessment of the CA status by diffuse correlation spectroscopy (DCS) measures calculating the DCS moving correlation coeffcient CBFx with arterial blood pressure (ABP). The measurements are performed during the first mobilization after the onset of the symptoms. The CBFx is compared to values obtained in a healthy population showing signicantly higher values in the stroke population. This may pave the way for personalized treatment.
High-density speckle contrast optical tomography (HD-SCOT) is a potentially attractive technique for bedside imaging of cerebral blood flow (CBF). To evaluate the performance of HD-SCOT, we built a pipeline with an anatomical head model for simulating measurements and reconstructed images. We observed that the cortical region is well represented by measurements with source-detector distance at least 29 mm. Including larger source-detector distances can reduce localization errors but with reduced signal-to-noise ratio (SNR). Imaging performance is highly dependent on the exposure time, with optimal exposure time dependent on the noise model. Future HD-SCOT systems will be designed using these results.
Standard techniques for detection of thyroid cancer (ultrasound screening and fine-needle aspiration biopsy) have limited sensitivity and specificity, leading to a very large number of unnecessary thyroid extraction surgeries. With the aim of improving diagnosis, hybrid diffuse optics and ultrasound were used on nodules patients to obtain tissue hemodynamic information. Nodules rated 4A or 4B in the thyroid imaging reporting and data system (TI-RADS) are of clinical relevance and were classified using a logistic regression model built on our results. Fourteen benign and four malignant nodules were classified with a sensitivity of 100% and specificity of 77%.
KEYWORDS: Monte Carlo methods, Diffuse optical tomography, Sensors, Near infrared spectroscopy, Spectroscopy, Oxygen, Injuries, Hybrid optics, Heart, Head
We present a simulation study on the design of a multi-modal high-density hybrid diffuse optical tomographic probe for monitoring infants with congenital heart disease (CHD) before, during, and after surgery. Different probe designs are evaluated based on the signal distribution and sensitivity profile generated using a Monte Carlo-based simulation toolbox. An optimal design was chosen after several iterations starting from the initial design. To cover a wide region of interest, this unit design was extended in a modular fashion, while respecting mechanical restrictions as well as the need for dense distribution of sources and detectors.
A variety of diffuse optical methods use laser speckle contrast and its statistics to non-invasively determine blood flow. In most cases, this implies very low detected count-rates which leads to systematic errors in determining the correct speckle statistics. We have developed a comprehensive method for simulating realistic speckle contrast resultant from light propagation in tissue taking into account experimental and fundamental sources of noise. Results of the simulation are used to determine the relationship of these parameters on the precision and accuracy of the speckle contrast signal.
We present a method for simulating speckle contrast signal, noise, and signal offset in speckle contrast optical spectroscopy and tomography. The simulations provide a realistic model by simulating custom system and tissue properties.
KEYWORDS: Hemodynamics, Cognitive informatics, Transparent conductors, Physiology, Neuroimaging, Data acquisition, Time resolved spectroscopy, Spectroscopy, Neuroscience, Medical research
We present a study investigating the effect of non-medical face masks (FFP2 and surgical) on cerebral hemodynamics measured by transcranial hybrid diffuse optics, and on systemic physiology in 13 healthy adults (age: 23-33 years).
We present an update on a clinical study on 200 stroke patients where hybrid diffuse optics is used to monitor microvascular cerebral hemodynamics and derived parameters during postural changes twenty-four hours after stroke onset.
Speckle contrast optical spectroscopy/tomography (SCOS/SCOT) is a low-cost, non-invasive, and real-time optical imaging modality for measuring cerebral blood flow with increased signal-to-noise ratio relative to diffuse correlation spectroscopy. However, the recent camera-based detector system is not ideal for imaging a large area of the human brain because of the limited area of focus over the contour of the head and hair occluding the field of view. Here we demonstrated the feasibility of using inexpensive multi-mode fiber bundles to build a SCOS system for mapping the flow of fluids, and we showed a statistical method for distinguishing noise and speckle signals.
High-density speckle contrast optical tomography (HD-SCOT) is attractive for imaging cerebral blood flow (CBF), with desirable cost and signal-to-noise ratio (SNR). Previous studies showed feasibility of HD-SCOT in rodent models using lab instruments. To investigate potential performance for a dedicated HD-SCOT instrument, we simulated HD-SCOT imaging for an anatomical head model. We evaluated potential imaging performance versus depth for varying exposure times and measurement availability. Results showed that an HD-SCOT system could have image resolution of 13 mm full-width-half-maximum at 12 mm depth, with instrument parameters affecting localization error and SNR. These results will guide design of future research instruments
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