Boris Majaron

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Verified

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• Professor of Physics
• Scientific Advisor at Jožef Stefan Institute

In this proof-of-concept study we combine two optical techniques to enable assessment of structure and composition of human skin in vivo: Pulsed photothermal radiometry (PPTR), which involves measurements of transient dynamics in mid-infrared emission from sample surface after exposure to a light pulse, and diffuse reflectance spectroscopy (DRS) in...

Upconverting nanoparticles (UCNPs) are being extensively investigated for applications in bioimaging because of their ability to emit ultraviolet, visible, and near-infrared light. NaYF4 is one of the most suitable host matrices for producing high-intensity upconversion fluorescence; however, UCNPs based on NaYF4 are not chemically stable in aqueou...

Optical microcavities and microlasers were recently introduced as probes inside living cells and tissues. Their main advantages are spectrally narrow emission lines and high sensitivity to the environment. Despite numerous novel methods for optical imaging in strongly scattering biological tissues, imaging at single-cell resolution beyond the balli...

We analyze the influence of a person’s age on the thicknesses and reduced scattering coefficients of the epidermis and dermis in visible part of the spectrum. Their values were assessed using a non-invasive technique which combines pulsed photothermal radiometry and diffuse reflectance spectroscopy with Monte Carlo modeling of light transport in a...

Objectives: Assess the suitability of the technique for objective monitoring of laser tattoo removal by an extended treatment protocol. Materials and methods: One half of the tattoo in the first volunteer was treated with nanosecond and the other half with picosecond laser pulses at 1064 nm. In the second subject, four test areas were treated re...

Our group has recently introduced a methodology for noninvasive assessment of structure and composition of human skin in vivo by combining two optical techniques. First, diffuse reflectance spectra in visible part of the spectrum are measured using a compact integrating sphere with internal light source. The second technique, pulsed photothermal ra...

Our group has recently presented a novel technique for noninvasive assessment of the structure and composition of human skin in vivo. The approach combines two optical techniques, photothermal radiometry and diffuse reflectance spectroscopy in visible part of the spectrum with numerical modeling of light transport in a four-level model of human ski...

The concept of photothermal tomography (PTT) involves spatially and temporally resolved detection of blackbody emission from the sample surface after irradiation with a short light pulse. In principle, this allows reconstruction of the light-induced temperature field inside the sample, thus enabling three-dimensional imaging of absorbing structures...

Controlled poration of lipid membranes is crucial for numerous biomimetic applications such as targeted drug delivery. Although several chemical and physical mechanisms have been proposed for the poration of synthetic membranes, achieving good temporal and spatial control remains a challenge. In this study, we introduce a novel method for membrane...

We investigate age-related changes of the dermal reduced scattering coefficient in human skin using a recently introduced methodology for non-invasive characterization of structure and composition of skin in vivo. The approach combines pulsed photothermal radiometry (PPTR) with diffuse reflectance spectroscopy (DRS) in visible part of the spectrum....

Pulsed photothermal radiometry involves measurements of transient changes in blackbody emission from a sample surface after irradiation with a short light pulse. From such a radiometric record, light-induced temperature field inside the sample can be econstructed by solving the inverse problem of heat diffusion and radiation. In principle, this ena...

Pulsed photothermal radiometry (PPTR) involves analysis of transient changes in mid-infrared (IR) emission from a sample surface after irradiation with a short light pulse. From a radiometric record obtained with a fast IR camera, light-induced temperature field inside the sample can be reconstructed in three dimensions (3D) by solving the inverse...

NaYF 4 nanoparticles codoped with Yb 3+ and Tm 3+ exhibit upconversion fluorescence in near-infrared and visible spectral range. Consequently, such upconverting nanoparticles (UCNPs) can be used as contrast agents in medical diagnos-tics and bioassays. However, they are not chemically stable in aqueous dispersions, especially in phosphate solutions...

Four distinct tungsten suboxide (WO 3-x ) nanomaterials were synthesized via chemical vapour transport reaction and the role of their crystal structures on the optical properties was studied. These materials grow either as thin, quasi-2D crystals with the W n O 3n-1 formula (in shape of platelets or nanotiles), or as nanowires (W 5 O 14 , W 18 O 49...

The increasing interest in upconverting nanoparticles (UCNPs) in biodiagnostics and therapy fuels the development of biocompatible UCNPs platforms. UCNPs are typically nanocrystallites of rare-earth fluorides codoped with Yb³⁺ and Er³⁺ or Tm³⁺. The most studied UCNPs are based on NaYF4 but are not chemically stable in water. They dissolve significa...

We have developed a novel methodology for noninvasive assessment of structure and composition of human skin in vivo by combining two optical techniques [1]. The approach combines pulsed photothermal radiometry (PPTR), involving time-resolved measurements of mid-infrared emission with a fast infrared camera (SC7500, FLIR Systems; λ = 3.5–5.1 μm) aft...

Titanium foils of different thicknesses were anodized, and the photocatalytic activity of the resulting TiO2 nanotube (NT) layers was determined. All of the titanium foils were anodized simultaneously under identical experimental conditions to avoid the influence of the aging of the anodizing electrolyte and other anodization parameters, such as vo...

Abstract published in: Lasers Surg. Med., 53 (S33), p. S34, May 2021

We have augmented a recently introduced method for noninvasive analysis of skin structure and composition and applied it to monitoring of dynamical processes in traumatic bruises. The approach combines diffuse reflectance spectroscopy in visible spectral range and pulsed photothermal radiometry. Data from both techniques are analyzed simultaneously...

We explore the potential for noninvasive monitoring of laser tattoo removal treatment by adapting a recently introduced methodology for quantitative assessment of structure and composition of human skin in vivo. 1 The approach combines diffuse reflectance spectroscopy in visible part of the spectrum with pulsed photothermal radiometry, involving ti...

We have recently introduced a novel methodology for the noninvasive analysis of the structure and composition of human skin in vivo. The approach combines pulsed photothermal radiometry (PPTR), involving time-resolved measurements of mid-infrared emission after irradiation with a millisecond light pulse, and diffuse reflectance spectroscopy (DRS) i...

Background and Objectives The aim of this study was to determine the temperature depth profiles induced in human skin in vivo by using a pulsed 975 nm diode laser (with 5 ms pulse duration) and compare them with those induced by the more common 532 nm (KTP) and 1,064 nm (Nd:YAG) lasers. Quantitative assessment of the energy deposition characteristi...

Diffusion approximation (DA) of the radiative transport equation allows derivation of enclosed solutions for diffuse reflectance from multi-layer scattering structures, such as human skin. Although the DA is known to be inadequate near tissue boundaries and light sources, analytical tractability makes such solutions very attractive for use in nonin...

We have recently introduced a novel methodology for noninvasive assessment of structure and composition of human skin in vivo. The approach combines pulsed photothermal radiometry (PPTR), involving time-resolved measurements of midinfrared emission after irradiation with a millisecond light pulse, and diffuse reflectance spectroscopy (DRS) in visib...

Pulsed dye laser irradiation in the wavelength range of 585 to 600 nm is currently the gold standard for treatment of port-wine stains (PWSs). However, this treatment method is often ineffective for deeply seated blood vessels and in individuals with moderate to heavy pigmentation. Use of optical particles doped with the FDA-approved near-infrared...

We are combining two optical techniques, pulsed photothermal radiometry (PPTR) and diffuse reflectance spectroscopy (DRS), for noninvasive assessment of the structure and composition of human skin in vivo. The analysis involves simultaneous multidimensional fitting of the measured PPTR signals and DRS spectra with predictions of a numerical model o...

We are combining two optical techniques, pulsed photothermal radiometry (PPTR) and diffuse reflectance spectroscopy (DRS), for noninvasive assessment of structure and composition of human skin in vivo. The analysis involves simultaneous multi-dimensional fitting of the measured PPTR signals and DRS spectra with predictions of a numerical model of l...

We present a novel methodology for quantitative analysis of hemodynamics in human skin in vivo. Our approach combines pulsed photothermal radiometry (i.e., time-resolved measurements of midinfrared emission from sample surface after exposure to a short light pulse) and diffuse reflectance spectroscopy in visible part of the spectrum. Experimental d...

Upconverting nanoparticles (UCNPs) of β-NaYF4, co-doped with Yb³⁺ and Tm³⁺ and 21–36 nm large, were synthesized using a modified thermal decomposition method. The as-synthesized UCNPs were coated with oleic acid and dispersible in nonpolar media. Their morphology, size and crystal structure were analysed with transmission electron microscopy and X-...

Light-activated theranostic materials offer a potential platform for optical imaging and phototherapeutic applications. We have engineered constructs derived from erythrocytes, which can be doped with the FDA-approved near infrared (NIR) chromophore, indocyanine green (ICG). We refer to these constructs as NIR erythrocyte-mimicking transducers (NET...

We investigate the effect of shear flow applied during the drying of aqueous suspension of cellulose nanocrystals on optical reflective properties and structural characteristics of the resulting solidified films. Shear flow can significantly improve internal structural homogeneity of the films, while its effect on optical reflective properties is r...

Dissolution of upconverting AYF4:Yb,Tm (A = Na or K) nanoparticles (UCNPs) in aqueous media was systematically studied. UCNPs with a cubic structure and sizes between 10 and 33 nm were synthesized solvothermally in ethylene glycol at 200 °C. The UCNPs of both compositions showed an upconversion fluorescence-emission characteristic for Tm(3+). The e...

Background and Objectives: Dynamical processes in traumatic bruises (hematomas) involve mass diffusion of extravasated hemoglobin (Hb), enzymatic decomposition of the Hb into bilirubin, and removal of both species by lymphatic drainage. As demonstrated recently, combining diffuse reflectance spectroscopy (DRS) and photothermal radiometric (PTR) mea...

In simulations of light transport in biological tissues and organs knowledge of tissue optical properties is imperative for realism of the predicted effects. One factor which is commonly overlooked is the choice of appropriate scattering phase function. Henyey-Greenstein phase function (PF) is often applied due to its suitability for analytical der...

Fluorescent nanoparticles, especially fluorides, have received a great deal of interest due to their optical properties, making them suitable for applications in bio-imaging. For this reason they need to exhibit a superior chemical stability in aqueous media. We have studied the influence of the synthesis parameters on the chemical stability of NaY...

Pulsed photothermal radiometry (PPTR) allows noninvasive measurement of laser-induced temperature depth profiles, providing useful information on depth distribution of specific absorbers in optically scattering biological tissues. In the present study, PPTR profiling is combined with numerical modeling of light transport in human skin to analyze he...

We combine pulsed photothermal radiometry (PPTR) depth profiling with diffuse reflectance spectroscopy (DRS) measurements for a comprehensive analysis of bruise evolution in vivo. While PPTR enables extraction of detailed depth distribution and concentration profiles of selected absorbers (e.g. melanin, hemoglobin), DRS provides information in a wi...

The chemical stability of upconverting, lanthanide-doped, fluoride nanoparticles in aqueous media, which shows great potential in bioimaging, was studied. The partial dissolution of selected nanoparticles (NaYF4, LaF3 and GdF3) co-doped with Yb3+ and Tm3+ was detected and compared with respect to their size, chemical composition and structure.

We apply diffuse reflectance spectroscopy (DRS) and pulsed photothermal radiometry (PPTR) for characterization of the bruise evolution process. While DRS provides information in a wide range of visible wavelengths, the PPTR enables extraction of detailed depth distribution and concentration profiles of selected absorbers (e.g. melanin, hemoglobin)....

In three-dimensional (3-D) modeling of light transport in heterogeneous biological structures using the Monte Carlo (MC) approach, space is commonly discretized into optically homogeneous voxels by a rectangular spatial grid. Any round or oblique boundaries between neighboring tissues thus become serrated, which raises legitimate concerns about the...

Pulsed photothermal radiometry (PPTR) allows noninvasive determination of laser-induced temperature depth profiles in optically scattering layered structures. The obtained profiles provide information on spatial distribution of selected chromophores such as melanin and hemoglobin in human skin. We apply the described approach to study time evolutio...

Light propagation in highly scattering biological tissues is often treated in the so-called diffusion approximation (DA). Although the analytical solutions derived within the DA are known to be inaccurate near tissue boundaries and absorbing layers, their use in quantitative analysis of diffuse reflectance spectra (DRS) is quite common. We analyze...

Diffuse reflectance spectra (DRS) of biological samples are commonly measured using an integrating sphere (IS). To account for the incident light spectrum, measurement begins by placing a highly reflective white standard against the IS sample opening and collecting the reflected light. After replacing the white standard with the test sample of inte...

Pulsed photothermal radiometry (PPTR) allows noninvasive measurement of laser-induced temperature depth profiles. The obtained profiles provide information on depth distribution of absorbing chromophores, such as melanin and hemoglobin. We apply this technique to objectively characterize mass diffusion and decomposition rate of extravasated hemoglo...

Perceived color of traumatic bruise depends strongly on depth of the spilled blood, natural skin tone, ambient light conditions, etc., which prevents an accurate and reliable determination of the time of the injury. Pulsed photothermal radiometry (PPTR) allows noninvasive determination of the laser-induced temperature depth profile in human skin. W...

Measurement of diffuse reflectance spectra (DRS) is a common experimental approach for non-invasive determination of tissue optical properties, as well as objective monitoring of various tissue malformations. Propagation of light in scattering media is often treated in diffusion approximation (DA). The major advantage of this approach is that it le...

Manuscript of Chapter 23 in: Optical-Thermal Response of Laser-Irradiated Tissue Ashley J. Welch and MartinJ.C. van Gemert, editors 2nd edition, Springer Science, 2011

Pulsed photothermal radiometry (PPTR) enables noninvasive determination of temperature depth profiles induced in strongly scattering biological tissues and organs, including human skin, by pulsed laser irradiation. In the present study, we evaluate the potential of this technique for objective characterization of a laser tattoo removal procedure....

An analytical model of mass diffusion and biochemical transformation kinetics in bruise development and healing process was recently developed in order to simulate bruised skin color at various time points and enable objective determination of the time of injury. However, parameters of the model were not determined directly. Instead, biologically p...

Pulsed photothermal radiometry (PPTR) allows for noninvasive determination of the laser-induced temperature depth profile in strongly scattering samples, including human skin. In a recent experimental study, we have demonstrated that such information can be used to derive rather accurate predictions of the maximal safe radiant exposure on an indivi...

In customary implementation of three-dimensional (3D) Monte Carlo (MC) numerical model of light transport in heterogeneous biological structures, the volume of interest is divided into voxels by a rectangular spatial grid. Each voxel is assumed to have homogeneous optical properties and curved boundaries between neighboring tissues inevitably becom...

Background and objectives: Nd:YAP laser emitting at 1,342 nm appears promising for nonablative skin rejuvenation treatment, based on favorable absorption properties of water and melanin in this part of the spectrum. A quantitative determination of energy deposition characteristics of Nd:YAP in normal human skin should enable design of a safe and e...

Diffuse reflectance spectra (DRS) of biological samples are commonly measured using an integrating sphere (IS), in which spectrally broad illumination light is multiply scattered and homogenized. The measurement begins by placing a highly reflective white standard against the IS sample opening and collecting the reflected light at the signal output...

Current laser therapy of port wine stain (PWS) birthmarks with a single laser pulse (SLP) does not produce complete lesion removal in the majority of patients. To improve PWS therapeutic efficacy, we evaluated the performance of an approach based on multiple laser pulses (MLP) to enhance blood vessel photocoagulation. The hamster dorsal window cham...

Pulsed photothermal radiometry (PPTR) allows noninvasive determination of temperature depth profiles induced by pulsed laser irradiation of strongly scattering biological tissues and organs, including human skin. In present study, we evaluate the potential of this technique for investigational characterization and possibly quantitative evaluation o...

We present a three-dimensional Monte Carlo model of optical transport in skin with a novel approach to treatment of side boundaries of the volume of interest. This represents an effective way to overcome the inherent limitations of "escape" and "mirror" boundary conditions and enables high-resolution modeling of skin inclusions with complex geometr...

Despite application of cryogen spray (CS) precooling, customary treatment of port wine stain (PWS) birthmarks with a single laser pulse does not result in complete lesion blanching for a majority of patients. One obvious reason is nonselective absorption by epidermal melanin, which limits the maximal safe radiant exposure. Another possible reason f...

Port wine stain (PWS), also called nevus flammeus, is a congenital, cutaneous vascular malformation involving post-capillary venules which produce a light pink to red to dark-red-violet discoloration of human skin [1]. PWS occurs in an estimated 3 children per 1000 live births, affecting males and females and all racial groups equally [2]. There ap...

We have developed a three-dimensional Monte Carlo (MC) model of optical transport in skin and applied it to analysis of port wine stain treatment with sequential laser irradiation and intermittent cryogen spray cooling. Our MC model extends the approaches of the popular multi-layer model by Wang et al.1 to three dimensions, thus allowing treatment...

Pulsed photothermal profiling involves reconstruction of temperature depth profile induced in a layered sample by single-pulse laser exposure, based on transient change in mid-infrared (IR) emission from its surface. Earlier studies have indicated that in watery tissues, featuring a pronounced spectral variation of mid-IR absorption coefficient, an...

We present an experimental comparison of pulsed photothermal (PPT) profiling in collagen-based tissue phantoms utilizing different midinfrared spectral bands. Laser-induced temperature profiles are reconstructed using a custom optimization code within the customary monochromatic approximation. Both experimental results and a detailed numerical simu...

p>In experiments and numerical simulations of pulsed photothermal temperature profiling, we compare three signal binning approaches. In uniform binning n subsequent signal data points are averaged, quadratic binning follows from the characteristic of thermal diffusion, and geometrical binning utilizes geometric progression. Our experiment was perf...

We report on the first experimental evaluation of pulsed photothermal radiometry (PPTR) using a spectrally composite kernel matrix in signal analysis. Numerical studies have indicated that this approach could enable PPTR temperature profiling in watery tissues with better accuracy and stability as compared to the customary monochromatic approximati...

We present a systematic experimental comparison of pulsed photothermal temperature profiling utilizing the customary spectral band of the InSb radiation detector (lambda=3.0 to 5.6 microm) and a narrowed acquisition band (4.5 to 5.6 microm). We use custom tissue phantoms composed of agar gel layers separated by thin absorbing layers. The laser-indu...

Although photothermal radiometric (PTR) measurements commonly employ broad-band signal acquisition to increase the signal-to-noise ratio, all reported studies apply a fixed infrared (IR) absorption coefficient to simplify the involved signal analysis. In samples with large spectral variation of micro(lambda) in mid-IR, which includes most biologica...

We determine experimentally the accuracy of pulsed photothermal radiometric (PPTR) temperature depth profiling in water-based samples. We use custom tissue phantoms composed of agar gel layers separated by very thin absorbing layers. Two configurations of the acquisition system are compared, one using the customary spectral band of the InSb radiati...