Research Projects

Early Sepsis Detection and Monitoring

Sepsis, one of the leading causes of death worldwide, is an overreaction to infection which disproportionately affects vulnerable and low-resource populations. Since early intervention is crucial for survival, Rasa's primary research is focused on developing frugal approaches for early sepsis recognition using optical spectroscopy. 

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Publications:

Eskandari, R., Milkovich, S., Kamar, F., Welsh, D. G., Goldman, D., Ellis, C. G., & Diop, M. (2024, December). Non-invasive point-of-care optical technique for continuous in vivo assessment of microcirculatory function: Application to a preclinical model of early sepsis. The FASEB Journal, 38(23), e70204.

Eskandari, R., Milkovich, S., Kamar, F., Welsh, D. G., Goldman, D., Ellis, C. G., & Diop, M. (2024, April). Assessing Progressive Microvascular Dysfunction in Early Sepsis with Non-invasive Optical Spectroscopy. In Clinical and Translational Biophotonics (pp. TW1B-3). Optica Publishing Group. 

Eskandari, R., Milkovich, S., Kamar, F., Welsh, D. G., Goldman, D., Ellis, C. G., & Diop, M. (2024, April). Continuous monitoring of microvascular function and perfusion in early onset of sepsis with noninvasive optical spectroscopy. In Critical Care Canada Forum 2023 Forum Abstracts (Vol. 71, pp. 50-53). Canadian Journal of Anesthesia.  

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Publications:

Hyperspectral Time-Resolved Near-infrared Spectroscopy for Cerebral Metabolism Monitoring

Optical spectroscopy is a promising neuromonitoring technique due to its portability, safety, and sensitivity to blood oxygenation and metabolism; however, brain monitoring in adults is challenging due to the thickness of their scalp/skull layers. Natalie is currently developing an optical spectroscopy device that can accurately isolate the brain metabolism signal without contamination by the extracerebral tissue. 

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Publications:

Li, N. C., Ioussoufovitch, S., & Diop, M. (2024). HyperTRCSS: A hyperspectral time-resolved compressive sensing spectrometer for depth-sensitive monitoring of cytochrome-c-oxidase and blood oxygenation. Journal of Biomedical Optics, 29(1), 015002-015002.

Li, N. C., Ioussoufovitch, S., & Diop, M. (2023, March). Hyperspectral time-resolved compressive sensing spectroscopy for monitoring cytochrome-c-oxidase and blood oxygenation. In Optical Tomography and Spectroscopy of Tissue XV (Vol. 12376, pp. 96-107). SPIE.

Li, N. C., & Diop, M. (2022, April). Analysis of near-infrared spectroscopy measures of cerebral oxygen metabolism in infants. In Microscopy Histopathology and Analytics (pp. JM3A-60). Optica Publishing Group.

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Publications:

Hyperspectral Near-infrared Spectroscopy for Addressing Skin Pigmentation Bias in Oxygenation Monitoring

Melanin, the main pigment within the human skin, is widely known to introduce bias into tissue-oxygenation measurements made by commercial near-infrared spectroscopy (NIRS) devices. As clinical practices and standards are determined by reference values obtained from lighter-skinned patients, this can lead to delayed treatment outcomes in racialized patient populations. Sophie's work focuses on the validation of a hyperspectral NIRS approach for determining tissue oxygenation more accurately, regardless of skin tone. 

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Publications:

Brain Monitoring in Preterm Infants

In Canada, 8% of births occur prematurely. Preterm infants born with very low birth weights are at a high risk of neurodevelopmental impairment: 5-10% of these infants develop major disabilities such as cerebral palsy - a permanent movement disorder - and 40-50% show other cognitive and behavioural deficits. Although numerous factors influence the occurrence of brain injury, fluctuations in cerebral blood flow (CBF) are believed to play a significant role due to the immaturity of the cerebral vascular system.

The newborn brain is therefore vulnerable to periods of low CBF which can impair energy metabolism and ultimately cause irreversible brain damage. Surprisingly, in today’s neonatal intensive care unit (NICU) there is no standardized method of cerebral monitoring.

To address this issue, our group (Diop an St Lawrence Lab) has developed a unique optical brain monitor. NNeMo, the Neonatal NeuroMonitor, is a non-invasive cerebral monitor that provides real-time measurements of tissue oxygen saturation, CBF, and oxygen metabolism in preterm infants, at the bedside. NNeMo utilizes near-infrared optical techniques, which have proven extremely safe and cost-efficient, to quantify physiological changes in the developing brain [1]. NNeMo is currently being implemented in the NICU at Victoria Hospital. It is our goal to provide clinicians with greater insight into hemodynamic events that precede brain injury. This information could enable clinicians to make adjustments to patient management to avoid brain injury, ultimately improving long-term outcome in preterm infants.

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Publications:

Rajaram, A., Milej, D., Suwalski, M., Kebaya, L., Kewin, M., Yip, L., de Ribaupierre, S., Han, V., Diop, M., & St. Lawrence, K. (2022). Assessing cerebral blood flow, oxygenation and cytochrome c oxidase stability in preterm infants during the first 3 days after birth. Scientific Reports, 12(1), 181.

Ajay Rajaram, Gemma Bale, Matthew Kewin, Laura B. Morrison, Ilias Tachtsidis, Keith St. Lawrence, and Mamadou Diop, "Simultaneous monitoring of cerebral perfusion and cytochrome c oxidase by combining broadband near-infrared spectroscopy and diffuse correlation spectroscopy," Biomed. Opt. Express 9, 2588-2603 (2018)

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease whose management hinges on successful early treatment. Despite this, current monitoring methods—such as clinical examination—require 3–6 months to detect initial treatment failure experienced by 1 in 3 RA patients. Considering that this delay in effective treatment places patients at risk of irreversible joint damage and unnecessary disease proliferation, there is a need for more sensitive approaches that can detect treatment failure much earlier than current methods.

To this end, we are developing near-infrared spectroscopy and imaging techniques which may detect early treatment failure. Currently investigated approaches include quantification of joint blood flow with dynamic contrast-enhanced spectrscopy and characterizing optical properties of the joints through cost-effective time-resolved near-infrared imaging based on structured illumination and compressed sensing.

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Former Team Members:

Ajay Rajaram

Publications:

S. Ioussoufovitch, L. B. Morrison, L. Desjardins, et al., “Quantification of joint blood flow by dynamic contrast-enhanced near-infrared spectroscopy: Application to monitoring disease activity in a rat model of rheumatoid arthritis,” Journal of Biomedical Optics 25(01), 1 (2020).

A. Rajaram, S. Ioussoufovitch, L. B. Morrison, et al., “Joint blood flow is more sensitive to inflammatory arthritis than oxyhemoglobin, deoxyhemoglobin, and oxygen saturation,” Biomedical Optics Express 7(10), 3843 (2016).

In this project, we will developed a realistic model of the infant head that included extracerebral layers (scalp and skull), cerebrospinal fluid, grey matter, and white matter. The model was generated from a 3D MRI image of an infant head and was used to test several fitting algorithms. Optical properties was assigned to each tissue type, using published literature values, and in silico experiments were conducted to generate data that closely mimic in vivo measurements. This data set was then used to test different algorithms that are currently used to estimate tissue optical properties from NIRS measurements. Notably, we investigated several approaches for recovering tissue optical properties from hyperspectral (i.e., broadband) CW-NIRS data.

Current Team Members:

Publications:

N. Abayomi and M. Diop, “Improving the accuracy of continuous-wave hyperspectral near infrared spectroscopy with spatially-resolved measurements and tikhonov regularization,” in Biophotonics Congress: Biomedical Optics 2020 (Translational, Microscopy, OCT, OTS, BRAIN), (2020).

Phenylephrine is commonly administered intravenously to increase blood pressure, but its effects on the peripheral (i.e., skeletal muscle) and cerebral (i.e., brain) microcirculation are controversial. Despite its widespread application, studies using cerebral oximetry have associated this drug with oxygen desaturation in the brain. Laura's MSc work focused on investigating the microcirculatory effects of phenlypehrine using hyperspectral near-infrared spectroscopy and diffuse correlation spectroscopy.

Led by

Laura Mawdsley

Publications:

Mawdsley, L.¹, Eskandari, R.¹, Kamar, F., Rajaram, A., Yip, L. C. M., Abayomi, N., Milkovich, S., St. Lawrence, K., Carson, J. J. L., Ellis, C. G., & Diop, M. (2024, August). In vivo optical assessment of cerebral and skeletal muscle microvascular response to phenylephrine. FASEB BioAdvances, 6(9), 390.

Mawdsley, L., Rajaram, A., Yip, L., Abayomi, N., Li, N., Milkovich, S., Carson, J., St. Lawrence, K., Ellis, C. G., & Diop, M. (2021, May). Simultaneous Monitoring of the Cerebral and Skeletomuscular Microcirculation using Hyperspectral Near Infrared Spectroscopy and Intravital Video Microscopy. In The FASEB Journal, 35.

Mawdsley, L., Abayomi, N., Rajaram, A., Yip, L. C., Milkovich, S., Lawrence, K. S., Carson, J., Ellis, C. G., & Diop, M. (2021, March). Using hyperspectral near infrared spectroscopy and diffuse correlation spectroscopy to monitor the microvascular effects of phenylephrine in vivo. In Optical Tomography and Spectroscopy of Tissue XIV (Vol. 11639, pp. 141-150). SPIE.

Measuring adult oxygen saturation is more difficult than in neonates due to the increased skull thickness, which results in high absorption. By using Hyperspectral TR-NIRS, we hope to increase the accuracy and sensitivity to the adult brain. Monte-Carlo experiments were conducted to investigate the sensitivity of late-photons hyperspectral near-infrared spectroscopy (Lp-hNIRS) for assessing cerebral oxygenation (ScO2) in adults. Results suggest that Lp-hNIRS provides more accurate estimates of ScO2 than multispectral time-resolved NIRS.

Current Team Members:

Publications:

D. J. F. Cohen and M. Diop, “Late-photons hyperspectral near-infrared spectroscopy improves the sensitivity to cerebral oxygenation in adults,” in Biophotonics Congress: Biomedical Optics 2020 (Translational, Microscopy, OCT, OTS, BRAIN), (2020).