Alexandre Douplik

Toronto Metropolitan University · Physics

Background: Tissue oxygenation is a critical marker of tissue status and can be used to evaluate and track wound progress, the viability of transplanted tissue, and burns. Thus, the determination of tissue oxygenation (preferably remotely) is of great importance. Aim: Explore the impact of oxygenation changes on tissue color. Material and metho...

This study focused on the use of Non-Invasive Transcranial Alternating Current Stimulation (NITACS) to induce and map phosphenes (spark-like percepts in the visual field) in healthy individuals. The study found optimal stimulation parameters to induce reliable phosphenes without skin irritation or pain. The results suggest NITACS can be used as a t...

Non-Invasive Transcranial Alternating Current Stimulation (NITACS) is a method that applies weak electrical currents to the scalp or face to modulate brain activity. A fascinating application of NITACS is the induction of phosphenes — visual phenomena where individuals perceive light without external stimuli. These phosphenes have been observed and...

The ongoing coronavirus pandemic requires more effective disinfection methods. Disinfection using ultraviolet light (UV), especially longer UVC wavelengths, such as 254 and 270/280 nm, has been proven to have virucidal properties, but its adverse effects on human skin and eyes limit its use to enclosed, unoccupied spaces. Several studies have shown...

Photoplethysmography (PPG) is a noninvasive optical technology with applications including vital sign extraction and patient monitoring. However, its current use is primarily limited to heart rate and oxygenation monitoring. This study aims to demonstrate the utility of PPG for physiological investigations. In particular, we sought to demonstrate t...

Unlabelled: A non-invasive, contactless, inexpensive and easy-to-operate perfusion imaging method using a consumer-grade mobile camera (iPhone 8) developed in our group can visualise blood flow in tissue. Methods: Ischemia was induced in one hand using a blood pressure cuff inflated over the systolic blood pressure to stop the blood flow. Using...

Purpose: Visualization and monitoring of capillary loops in dermis and mucosa are interesting for various clinical applications, including rheumatology, early cancer, and shock detection. However, the limitations of existing imaging technologies are not well understood. Therefore, this study aimed to elucidate peculiarities of the subsurface defect...

Diabetic foot ulceration is a major complication of diabetes.If untreated, diabetic foot ulcers may become infected and require total or partial amputation of the affected limb. In this Chapter, we briefly overview the pathophysiology of diabetic foot, including microbial burden, current “gold standard” diagnostics, prediction of development, and n...

Photoplethysmography (PPG) is a noninvasive optical technology, with applications including vital sign extraction and patient monitoring. The PPG acquisition skin type may be of importance. Skin is either non‐glabrous (~90%) or glabrous (~10%). Clinical PPG collection is typically from glabrous (fingerpad), while proliferating wearables collecting...

p>The ongoing coronavirus pandemic requires more effective disinfection methods. The disinfection using ultraviolet light (UV), especially longer UVCs such as 254 nm, 270/280 nm have been proved to have virucidal properties, but its adverse effects on human skin and eyes limit its use to enclosed unoccupied spaces. Several studies conducted the in...

p>The ongoing coronavirus pandemic requires more effective disinfection methods. The disinfection using ultraviolet light (UV), especially longer UVCs such as 254 nm, 270/280 nm have been proved to have virucidal properties, but its adverse effects on human skin and eyes limit its use to enclosed unoccupied spaces. Several studies conducted the in...

Specular reflection from tissue is typically considered as undesirable, and managed through device design. However, we believe that specular reflection is an untapped light-tissue interaction, which can be used for imaging subcutaneous blood flow. To illustrate the concept of subcutaneous blood flow visualization using specular reflection from the...

Cardiovascular disease (CVD) is a leading cause of death worldwide and was responsible for 31% of all deaths in 2015. Changes in fluid pressures within the vessels of the circulatory system reflect the mechanical function of the heart. The jugular venous (JV) pulse waveform is an important clinical sign for assessing cardiac function. However, tech...

Introduction: The PPG signal contains important information about microvascular hemodynamics, including endothelial-related metabolic, neurogenic, myogenic, respiratory, and cardiac activities. The present goal of is to explore the utility of a consumer-grade smartphone camera as an investigational tool to study such activities. Traditional PPG is...

Little is known about differences in the photoplethysmogram (PPG) across glabrous and non-glabrous skin, which is crucial given emerging PPG modalities. Using remote PPG in four subjects, we detected changes in amplitude and temporal lag.

Introduction: Pulse wave velocity imaging (PWVi) is a novel technology developed by our group for real-time assessment of ischemia. The objectives of this proof-of-concept study included (1) remote detection of blood flow pulse and (2) assessing the feasibility of pulse wave velocity (PWV) imaging. Methods: PWVi is based on a 12-bit RGB camera (...

Oxygen supply to tissues can be seriously impacted during wound healing. Edema (accumulation of fluids in interstitial space) can increase the distance between capillaries, thus decreasing oxygen supply to cells. There is no standard clinical tool for quantification of edema, and early edema detection (preferably preclinical) is of great clinical n...

Interpretation of tissue fluorescence spectra can be complicated due to interplay with tissue optics. We have developed a photon propagation approach for correction of fluorescence on absorption in two realistic scenarios: when fluorophores are located a) on the surface of the turbid tissue and b) in a layer inside the turbid tissue. The approach t...

Multispectral/hyperspectral imaging is one of the imaging modalities to visualize and quantify blood supply in surface tissues such as skin or mucosa. The results of visualization can be potentially affected by various factors, for instance by elevated methemoglobin (MetHb) content (e.g., methemoglobinemia). The scope of the current study is to dev...

Optical microscopy is limited to shallow interrogation depths as high-resolution imaging in scattering media is challenging. Current methods require complex and expensive experimental setup or suffer from low resolution. Through gating of photons exiting the scattering media using a restricted numerical aperture (NA) fiber optic plate (FOP), we est...

In this study, we present facile fabrication of a miniaturized remote sensing SERS platform using highly tunable Nano-Sphere Lithography (NSL) technique. Using 200 μm diameter optical fibers with high numerical aperture (0.5NA), the SERS enhancement of remote sensing was found to be 98% of direct sensing configuration. Standard silica optical fiber...

Methemoglobin (MetHb) is an important biomolecule, which is involved in a number of pathways associated with reactive oxygen species (ROS). Thus, MetHb has a potential to be used as a surrogate measure of ROS activity. Unfortunately, most of the existing clinical modalities used for MetHb concentration measurements determine the systemic MetHb leve...

Introduction: Visualization and monitoring of capillary loops in dermis and mucosa are of interest for a number of clinical applications, such as capillaroscopy, early cancer, or shock detection. For historical reasons, an unaided eye is still a primary aide to diagnostics in visual examinations for many medical specializations. However, the abili...

Radio frequency (RF) catheter ablation is commonly used to eliminate dysfunctional cardiac tissue by heating via an alternating current. Clinical outcomes are highly dependent on careful anatomical guidance, electrophysiological mapping, and careful RF power titration during the procedure. Yet, current treatments rely mainly on the expertise of the...

We demonstrate a setup based on lensless, minimally invasive micro-endoscope to image biological samples through scattering medium. We present in-vitro results of Polydimethylsiloxane micro-channels filled with Hemoglobin covered by intralipid mimicking epidermis of human skin.

Aluminium sulphonated phthalocyanine (AlPs) photosensitiser mixed with Hemoglobin (Hb) was used to create patterned oxygenation states of Hb in tissue mimicking gelatin phantoms. Temporal study of Hb conversion and an oxygenation patterned phantom is presented.

Raman spectroscopy (RS) can provide a molecular vibrational fingerprint of an analyte. In this study, RS was used to distinguish normal tissues from tumor tissues using ex-vivo and deparaffinized breast tissues.

We describe an imaging approach based on an optical setup made up of a miniature, lensless, minimally invasive endoscope scanning a sample and matching post processing techniques that enables enhanced imaging capabilities. The main scopes of this article are that this approach enables imaging beyond highly scattering medium and increases the resolu...

Optical properties (μa, μs and g) of certain human tissue types such as skin and blood have been very well investigated. However until today, for internal body organs such as the esophagus they are not well characterized. For ex-vivo measurements “Inverse Adding Doubling” (IAD) and Inverse Monte-Carlo-Simulation (IMCS) are state of the art. Both me...

Red blood cell (RBC) transfusion is a critical component of the health care services. RBCs are stored in blood bags in hypothermic temperatures for a maximum of 6 weeks post donation. During this in vitro storage period, RBCs have been documented to undergo changes in structure and function due to mechanical and biochemical stress. Currently, there...

Gas microbubbles (MBs) are investigated as intravascular optical coherence tomography (OCT) contrast agents. Agar + intralipid scattering tissue phantoms with two embedded microtubes were fabricated to model vascular blood flow. One was filled with human blood, and the other with a mixture of human blood + MB. Swept-source structural and speckle va...

In this paper we present gold nanoparticles coated with silicon that switch the order between the scattering and the absorption magnitude at the resonance peak and tune the plasmon resonance over the spectrum. This is obtained by modifying the refractive index of the silicon coating of the nanoparticle by illuminating it with a pumping light due to...

In this study gas microbubbles are investigated as intravascular OCT contrast agents. Agar+Intralipid scattering tissue-like phantoms with two embedded microtubes were fabricated to model vascular blood flow. One was filled with human blood, and the other with a mixture of human blood and microbubbles. Swept-source structural and speckle variance O...

A portable, spatially resolved diffuse reflectance (SRDR) lensless imaging technique based on the charge coupled device (CCD), or complementary metal-oxide semiconductor (CMOS) sensor directly coupled with fiber optic bundle can be proposed for visualization of subsurface structures such as intrapapillary capillary loops (IPCLs). In this article, w...

We developed a 2D multi-agent stochastic model of interaction between cellular debris, bacteria and neutrophils in the surface cutaneous wound with local hypoxia. Bacteria, which grow logistically with a maximum carrying capacity, and debris are phagocytosed by neutrophils with probability determined by the partial pressure of oxygen in the tissue,...

Microbubble contrast agents can potential improve optical imaging diagnostics based on increasing light scattering. Detection and quantification of microcirculation have been improved in diffuse reflectance imaging by administrating microbubbles

This chapter considers mechanisms of pressure ulcer development, its possible clinical scenarios, and contemporary care guidelines, including photonic methods of diagnosis and treatment. We also consider how these optical methods are integrated into the recent clinical routines. A review of the modern techniques available on the market and analysis...

Utilizing the localized surface plasmon resonance (LSPR) effect of metallic nanoparticles enables their usage as contrast agents in a variety of applications for medical diagnostics and treatment. Those applications can use both the very strong absorption and scattering properties of the metallic nanoparticle due to their LSPR effects. There are ce...

A portable, spatially resolved diffuse reflectance (SRDR) lensless imaging technique based on the charge coupled device (CCD), or complementary metal-oxide semiconductor (CMOS) sensor directly coupled with fiber optic bundle can be proposed for visualization of subsurface structures such as intrapapillary capillary loops (IPCLs). In this article, w...

We have collected Raman spectral libraries for obtaining operator independent diagnostics under ex-vivo and in-vivo conditions and we have tested this approach using multivariate analysis on known solutions with Raman active components. Article not available.

The group of editors would like to express their thankfulness to all the contributing authors for submitting their valuable and informative manuscripts. We would like to wish all the authors success in their researches.

This chapter considers the interaction of high-power lasers with tissue. Laser surgery market and trends are considered, as well as the main laser surgery domains including photothermolysis, photocoagulation, thermal ablation, photoablation, and photodisruption. However, photochemical/photodynamic or low-level power domains are not touched. The his...

To assess superficial epithelial microcirculation, a diagnostic tool should be able to detect the heterogeneity of microvasculature, and to monitor qualitative derangement of perfusion in a diseased condition. Employing a lensless CMOS imaging chip with an RGB Bayer filter, experiments were conducted with a microfluidic platform to obtain diffuse r...

We evaluated diffuse reflectance spectroscopy implemented as a small field-of-view technique for discrimination of dysplasia from metaplasia in Barrett's esophagus as an adjuvant to autofluorescence endoscopy. Using linear discriminant analysis on 2579 spectra measured in 54 patients identified an optimum a 4-wavelength classifier (at 485, 513, 598...

In imaging, contrast agents are utilized to enhance sensitivity and specificity of diagnostic modalities. In ultrasound imaging, microbubbles (MBs)—a gas-core shell-encapsulated agent—are used clinically as contrast agents. The working hypothesis of this study is that microbubbles can be employed as an intravascular contrast agent in optical imagin...

In this paper we present a special fiber based endoscope with an inflatable lens. This endoscope is designed for photodynamic therapy (PDT), while reducing the external diameter of the treatment device. When the endoscope is inserted into the human body, a latex water fillable balloon attached to the endoscope is inflated in front of scope's tip ac...

Various scenarios of light propagation paths in turbid media (single backward scattering, multiple backward scattering, banana shape) are discussed and their contributions to reflectance spectra are estimated. It has been found that a single backward or multiple forward scattering quasi-1D paths can be the major contributors to reflected spectra in...

Lack of sensory feedback during laser surgery prevents surgeons from keeping track of the exact lesion profile and cutting depth. As a result, duration and complexity of the treatments are significantly increased. In this study we propose a new method for enabling three-dimensional tracking of the exact lesion profile, based on detection of shock w...

Microvascular pattern was estimated via lens-less image acquisition from intralipid/microfluidic phantom. The CMOS chip provided proficient images of subsurface structures - microchannels filled out by haemoglobin disguised under layer of Intralipid.

Optical contrast agents introduce distinct features to induce detectable changes in native tissue properties [1]. In ultrasound imaging, microbubbles (MBs) - a gas-core shell-encapsulated agent - are used clinically as contrast agents. The working hypothesis of this study is that microbubbles can be employed as an intravascular contrast agent in op...

Lack of sensory feedback during laser surgery prevents surgeons from discerning the exact location of the incision, which increases duration and complexity of the treatment. In this study we demonstrate a new method for monitoring of laser ablation procedures. Real-time tracking of the exact three dimensional (3D) lesion profile is accomplished by...

Successful laser surgery is characterized by a precise cut and effective hemostasis with minimal collateral thermal damage to the adjacent tissues. Consequently, the surgeon needs to control several parameters, such as power, pulse repetition rate, and velocity of movements. In this study we propose utilizing optoacoustics for providing the necessa...

In our chapter we describe the main mechanisms of interaction between laser light and biological tissues including both diagnostic and therapeutical applications. Various types of biotissue have been considered in terms of the tissue structure, light distribution in biostructures and tissue properties modification under laser irradiation.

Developing minimally invasive methodologies for imaging of internal organs is an emerging field in the biomedical examination research. This paper introduces a new multi-functional microendoscope device capable of imaging of internal organs with a minimal invasive intervention. In addition, the developed microendoscope can also be employed as a mon...

Imaging of high resolution targets

Supplementary Information

Magnetic micro particles imaged inside a phantom

Laser-tissue interaction during laser surgery can be classified into two biophysical processes: tissue removal in the focal zone of the laser beam and heating in the surrounding tissue. In order to ensure a precise cut and minimal collateral thermal damage, the surgeon has to control several parameters, such as power, repetition rate and fiber move...

Bladder biopsy with optical coherence tomography (OCT) assisting the surgeon in the decision-making process on the fly and delineating normal and malignant tissues is briefly considered in this chapter.

Optical coherence tomography (OCT) modalities are considered in this chapter as intraoperative tools assisting the surgeon in decision-making processes, guiding surgery near sensitive structures such as vessels and nerves, and delineating normal and pathologic tissue. Basic principles and modalities of OCT are briefly provided without details as th...

In this work we present the operation principle as well as the preliminary experimental results of a new type of micro size multicore fiber that enables imaging through drilled phantoms. Imaging of a manipulated micro wire through a drilled phantom is presented. Superresolution technique for enhancing the resolution of the constructed image is also...

Background & Aims: This study was performed to improve the autofluorescence imaging (AFI) in the upper GI tract by applying a new method of normalized autofluorescence (NAFI) obtained via tri-modal imaging. NAFI may provide lower false positive rate to achieve ultimately better specificity at acceptable sensitivity. This is a prospective, controlle...

The efficient electric field enhancement due to coating a dielectric wedge by plasmon-carrying nanowires has been demonstrated numerically within the framework of the finite-difference frequency-domain method. The numerical simulations show increasing of electric field intensity in the near-field region of the dielectric wedge coated by silver nano...

Because direct measurements of the refractive index of hemoglobin over a large wavelength range are challenging, indirect methods deserve particular attention. Among them, the Kramers-Kronig relations are a powerful tool often used to derive the real part of a refractive index from its imaginary part. However, previous attempts to apply the relatio...

A technical feasibility of autofluorescence ductoscopy in breast milk ducts as blood vessels phantoms has been assessed as successful. Malignant tumor can be clearly identified through the milk ducts. We also present the operation principle as well as the preliminary experimental results of a new type of microsize multicore fiber that enables imagi...

We developed a novel method for real-time monitoring of alteration of the local epithelium vessel/capillary and blood oxygenation spatial pattern in epithelium exploiting a compact fibre sensor system based on spatially and spectrally resolved diffuse reflectance. The method is based on collection of spatially resolved diffuse reflectance R(λ) by f...

Objectives: Laser surgery requires feedback to avoid the accidental destruction of critically important tissues. It was the aim of the authors to identify different tissue types in vivo by diffuse reflectance spectroscopy to set the basis for tissue-specific control of laser surgery. Methods: Tissue differentiation was performed on in vivo tissu...

Because the refractive index of hemoglobin in the visible range is sensitive to the hemoglobin concentration, optical investigations of hemoglobin are important for medical diagnostics and treatment. Direct measurements of the refractive index are, however, challenging; few such measurements have previously been reported, especially in a wide wavel...

We report the synthesis of novel inorganic contamination-free photosensitizers based on colloidal silicon nanoparticles prepared by laser ablation in pure deionized water. We show that such nanoparticles are capable of generating singlet oxygen 1 O 2 under laser irradiation with a yield estimated at 10% of that of photofrin, which makes them a pote...