Dr. Alexander Ruesch Profile

Dr. Alexander Ruesch

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Publications (18)

Proceedings Article | 9 August 2023 Paper

Simulation of light propagation through the maternal abdomen: towards transabdominal fetal pulse oximetry

Jingyi Wu, Alexander Ruesch, Gopika Satish, Erin Anand, Martin Debreczeny, Eric Johansson, Neil Ray, Jana Kainerstorfer

Proceedings Volume 12628, 126281E (2023) https://doi.org/10.1117/12.2671002

KEYWORDS: Fetus, 3D modeling, Oximetry, Abdomen, Magnetic resonance imaging, Brain, Tissues, Muscles, 3D metrology, Monte Carlo methods

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SPIE Journal Paper | 13 July 2023 Open Access

Evaluating feasibility of functional near-infrared spectroscopy in dolphins

Alexander Ruesch, Deepshikha Acharya, Eli Bulger, Jiaming Cao, Christopher McKnight, Mercy Manley, Andreas Fahlman, Barbara Shinn-Cunningham, Jana Kainerstorfer

JBO, Vol. 28, Issue 07, 075001, (July 2023) https://doi.org/10.1117/12.10.1117/1.JBO.28.7.075001

KEYWORDS: Brain, Near infrared spectroscopy, Brain tissue, Muscles, Tissues, Animals, Optical properties, Absorption, Animal model studies, Skin

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SignificanceUsing functional near-infrared spectroscopy (fNIRS) in bottlenose dolphins (Tursiops truncatus) could help to understand how echolocating animals perceive their environment and how they focus on specific auditory objects, such as fish, in noisy marine settings.AimTo test the feasibility of near-infrared spectroscopy (NIRS) in medium-sized marine mammals, such as dolphins, we modeled the light propagation with computational tools to determine the wavelengths, optode locations, and separation distances that maximize sensitivity to brain tissue.ApproachUsing frequency-domain NIRS, we measured the absorption and reduced scattering coefficient of dolphin sculp. We assigned muscle, bone, and brain optical properties from the literature and modeled light propagation in a spatially accurate and biologically relevant model of a dolphin head, using finite-element modeling. We assessed tissue sensitivities for a range of wavelengths (600 to 1700 nm), source–detector distances (50 to 120 mm), and animal sizes (juvenile model 25% smaller than adult).ResultsWe found that the wavelengths most suitable for imaging the brain fell into two ranges: 700 to 900 nm and 1100 to 1150 nm. The optimal location for brain sensing positioned the center point between source and detector 30 to 50 mm caudal of the blowhole and at an angle 45 deg to 90 deg lateral off the midsagittal plane. Brain tissue sensitivity comparable to human measurements appears achievable only for smaller animals, such as juvenile bottlenose dolphins or smaller species of cetaceans, such as porpoises, or with source–detector separations ≫100 mm in adult dolphins.ConclusionsBrain measurements in juvenile or subadult dolphins, or smaller dolphin species, may be possible using specialized fNIRS devices that support optode separations of >100 mm. We speculate that many measurement repetitions will be required to overcome hemodynamic signals originating predominantly from the muscle layer above the skull. NIRS measurements of muscle tissue are feasible today with source–detector separations of 50 mm, or even less.

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Proceedings Article | 15 March 2023 Presentation + Paper

Non-invasive estimation of intracranial pressure using near-infrared spectroscopy

William Scammon, Filip Relander, Syeda Tabassum, Deepshikha Acharya, Alexander Ruesch, Jason Yang, Michael Wolf, Jaskaran Rakkar, Robert S. Clark, Michael McDowell, Jana Kainerstorfer

Proceedings Volume 12364, 123640J (2023) https://doi.org/10.1117/12.2652974

KEYWORDS: Near infrared spectroscopy, Intracranial pressure, Electrocardiography, Windows, Machine learning, Medicine, Heart, Sensors, Sampling rates, Injuries

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Proceedings Article | 15 March 2023 Presentation + Paper

Monitoring cerebral autoregulation at the respiration rate using near-infrared spectroscopy

N. Kedia, M. Banerjee, D. Acharya, A. Ruesch, J. Yang, S. Schmitt, M. Smith, J. Kainerstorfer

Proceedings Volume 12364, 123640N (2023) https://doi.org/10.1117/12.2650835

KEYWORDS: Near infrared spectroscopy, Heart, Tunable filters, Signal to noise ratio, Sensors, Frequency response, Spectroscopy

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Cerebral autoregulation (CA) is a mechanism to maintain cerebral blood flow (CBF) in response to changes in cerebral perfusion pressure (CPP), through active vasoconstriction and vasodilation of arterioles in the brain. Dynamic CA is believed to act as a high-pass filter such that only low frequency changes in pressure are counteracted by an active vasculature response. With high frequency oscillations in pressure, such as those that occur at the heart rate (HR), the effects of dynamic CA are absent and changes in CPP are passively transmitted to CBF based on the cerebrovascular resistance (CVR) and compliance (CVC). These changes in CVR/CVC occur with steady-state changes in CA which can be described by Lassen’s curve. However, it is unclear what drives phase differences between pressure and flow at the respiration rate of around 0.2 Hz (12 breaths per minute). Quantifying phase differences at the physiologic respiration rate could be useful to gain a better understanding of the effects of CA and as a potential clinical monitoring tool. In this work, we looked at phase differences between arterial blood pressure (ABP) and intracranial pressure (ICP) measured with invasive pressure sensors, which serve as surrogates for CPP and CBF, to investigate how Arg(ABP)-Arg(ICP) change at the respiration rate as a function of the CPP. We quantify how Arg(ABP)-Arg(ICP) changes with respect to CPP after low-frequency oscillations, respiratory induced oscillations, and with oscillations driven by the heart rate. In each frequency regime, the trends in phase differences between Arg(ABP)-Arg(ICP) are unique with respect to CPP. At the respiration rate, the trends in Arg(ABP)-Arg(ICP) did not completely follow those predicted by a dynamic CA response or by CVC/CVR, thus we believe that there is a combination of effects influencing the phase difference between Arg(ABP)-Arg(ICP) at the respiration frequency. We also explore whether this response could be monitored completely non-invasively using near infrared spectroscopy (NIRS). We use Arg(ΔHbT)-Arg(ΔHbO) as surrogates for CPP and CBF and see a similar response of phase differences with respect to CPP at the respiration rate.

SPIE Journal Paper | 23 January 2023 Open Access

Cerebrovascular impedance estimation with near-infrared and diffuse correlation spectroscopy

Jason Yang, Alexander Ruesch, Jana Kainerstorfer

NPh, Vol. 10, Issue 01, 015002, (January 2023) https://doi.org/10.1117/12.10.1117/1.NPh.10.1.015002

KEYWORDS: Near infrared spectroscopy, Blood pressure, Blood, Blood circulation, Head, Hemodynamics, Neurophotonics, Electrocardiography, Autocorrelation, Windows

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SPIE Journal Paper | 11 October 2022 Open Access

Using near-infrared spectroscopy and a random forest regressor to estimate intracranial pressure

Filip A. Relander, Alexander Ruesch, Jason Yang, Deepshikha Acharya, Bradley Scammon, Samantha Schmitt, Emily Crane, Matthew Smith, Jana Kainerstorfer

NPh, Vol. 9, Issue 04, 045001, (October 2022) https://doi.org/10.1117/12.10.1117/1.NPh.9.4.045001

KEYWORDS: Near infrared spectroscopy, Feature extraction, Neurophotonics, Machine learning, Electronic filtering, Data modeling, Filtering (signal processing), Blood pressure, Sensors, Brain

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Proceedings Article | 7 March 2022 Presentation

Clinical translation of intracranial pressure sensing with diffuse correlation spectroscopy

Syeda Tabassum, Alexander Ruesch, Deepshikha Acharya, Jason Yang, Jaskaran Rakkar, Robert S. Clark, Michael McDowell, Jana Kainerstorfer

Proceedings Volume PC11945, PC119450A (2022) https://doi.org/10.1117/12.2610429

KEYWORDS: Spectroscopy, Signal processing, Pathology, Morphological analysis, Machine learning, Data acquisition, Cerebral blood flow, Animal model studies

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Proceedings Article | 9 December 2021 Paper

Application of near-infrared spectroscopy in human elite freedivers while deep diving on a single breath hold

Alexander Ruesch, J. Chris McKnight, Eric Mulder, Jingyi Wu, Steve Balfour, Barbara Shinn-Cunningham, Erika Schagatay, Jana Kainerstorfer

Proceedings Volume 11920, 119201D (2021) https://doi.org/10.1117/12.2615370

KEYWORDS: Hemodynamics, Near infrared spectroscopy, Heart, Brain, Environmental sensing, Tissue optics, Sensors, Ocean optics, Medical research, Lung

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Proceedings Article | 9 December 2021 Paper

Functional near-infrared spectroscopy in non-domesticated grey seals

Alexander Ruesch, J. Chris McKnight, Gordon Hastie, Barbara Shinn-Cunningham, Jana Kainerstorfer

Proceedings Volume 11920, 119201E (2021) https://doi.org/10.1117/12.2615372

KEYWORDS: Hemodynamics, Sensors, Near infrared spectroscopy, Head, Visualization, 3D modeling, Brain, Heart, Data processing, Magnesium

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Proceedings Article | 9 December 2021 Paper

Intracranial pressure driven cardiac pulsation waveform changes measured with diffuse correlation spectroscopy

Syeda Tabassum, Alexander Ruesch, Deepshikha Acharya, Jaskaran Rakkar, Robert S. Clark, Michael McDowell, Jana Kainerstorfer

Proceedings Volume 11920, 119200Q (2021) https://doi.org/10.1117/12.2615249

KEYWORDS: Electrocardiography, Spectroscopy, Algorithm development, Beam propagation method, Traumatic brain injury, Near infrared spectroscopy, Cerebral blood flow, Medicine, Linear filtering, Heart

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Proceedings Article | 9 March 2020 Presentation

Role of cerebrovascular autoregulation in neurovascular coupling (Conference Presentation)

Deepshikha Acharya, Alexander Ruesch, Jason Yang, Samantha Schmitt, Jana Kainerstorfer, Matthew Smith

Proceedings Volume 11226, 112260Y (2020) https://doi.org/10.1117/12.2546760

KEYWORDS: Neurovascular coupling, Brain, Cerebral blood flow, Pathology, Near infrared spectroscopy, Traumatic brain injury, Electroencephalography, Visualization, Spectroscopy, Hemodynamics

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Proceedings Article | 9 March 2020 Presentation

Intracranial pressure estimated non-invasively in non-human primates and pediatric critical care (Conference Presentation)

Alexander Ruesch, Samantha Schmitt, Jason Yang, Deepshikha Acharya, Jaskaran Rakkar, Michael Wolf, Michael Mcdowell, Elizabeth Tyler-Kabara, Robert S. Clark, Matthew Smith, Jana Kainerstorfer

Proceedings Volume 11226, 112261J (2020) https://doi.org/10.1117/12.2546761

KEYWORDS: Traumatic brain injury, Blood pressure, Skull, Transducers, Brain, Tissues, Near infrared spectroscopy, Machine learning, Analytical research, Cerebral blood flow

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Proceedings Article | 9 March 2020 Presentation

Optical methods for non-invasive assessment of arteriole flow impedance (Conference Presentation)

Jason Yang, Alexander Ruesch, Jana Kainerstorfer

Proceedings Volume 11226, 1122610 (2020) https://doi.org/10.1117/12.2547639

KEYWORDS: Near infrared spectroscopy, Head, Modulation, Blood, Blood circulation, Resistance, Blood pressure, Temporal resolution, Cerebral blood flow, Spectroscopy

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Proceedings Article | 11 July 2019 Paper

Diffuse correlation spectroscopy for intracranial pressure estimation through cardiac pulse waveform analysis

Alexander Ruesch, Jason Yang, Deepshikha Acharya, Samantha Schmitt, Deepa Issar, Matthew Smith, Jana Kainerstorfer

Proceedings Volume 11074, 110740Z (2019) https://doi.org/10.1117/12.2527187

KEYWORDS: Brain, Spectroscopy, Cerebral blood flow, Blood pressure, Machine learning, Traumatic brain injury, Blood circulation

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Proceedings Article | 4 March 2019 Presentation

Low-cost high temporal resolution diffuse correlation spectroscopy (Conference Presentation)

Jason Yang, Alexander Ruesch, Matthew Smith, Jana Kainerstorfer

Proceedings Volume 10874, 1087416 (2019) https://doi.org/10.1117/12.2510467

KEYWORDS: Temporal resolution, Spectroscopy, Blood circulation, Signal to noise ratio, Tissue optics, Optical correlators, Brain, Ionizing radiation, Speckle pattern, Laser scattering

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Proceedings Article | 1 March 2019 Presentation + Paper

Frequency dependent hemodynamic response to intracranial pressure changes

Alexander Ruesch, Jason Yang, Samantha Nelson, Matthew Smith, Jana Kainerstorfer

Proceedings Volume 10874, 108741E (2019) https://doi.org/10.1117/12.2510113

KEYWORDS: Hemodynamics, Near infrared spectroscopy, Brain, Blood circulation, Blood, Diffusion, Blood pressure

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Proceedings Article | 15 March 2018 Presentation

Combined NIRS and DCS measurements of cerebral hemodynamics during intracranial and blood pressure changes (Conference Presentation)

Alexander Ruesch, Samantha Schmitt, Matthew Smith, Jana Kainerstorfer

Proceedings Volume 10493, 104930H (2018) https://doi.org/10.1117/12.2300031

KEYWORDS: Blood pressure, Near infrared spectroscopy, Hemodynamics, Blood circulation, Brain mapping, Traumatic brain injury, Cerebral blood flow, Microfluidics, Sensors, Brain

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Proceedings Article | 17 February 2017 Paper

Correlation between cerebral hemodynamic and perfusion pressure changes in non-human primates

A. Ruesch, M. Smith, G. Wollstein, I. Sigal, S. Nelson, J. Kainerstorfer

Proceedings Volume 10059, 100591P (2017) https://doi.org/10.1117/12.2252550

KEYWORDS: Near infrared spectroscopy, Hemodynamics, Brain, Blood, Blood pressure, Optical spectroscopy, Spectroscopy, Blood circulation, Oxygen, Tissues, Data modeling, Blood vessels

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Showing 5 of 18 publications

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