M. J. C. Van Gemert

Bio: M. J. C. Van Gemert is an academic researcher from University of Amsterdam. The author has contributed to research in topics: Laser & Scattering. The author has an hindex of 39, co-authored 97 publications receiving 6790 citations. Previous affiliations of M. J. C. Van Gemert include Academic Medical Center & University of California, Irvine.

Two-dimensional birefringence imaging in biological tissue by polarization-sensitive optical coherence tomography.

Abstract: Using a low-coherence Michelson interferometer, we measure two-dimensional images of optical birefringence in bovine tendon as a function of depth. Polarization-sensitive detection of the signal formed by interference of backscattered light from the sample and a mirror in the reference arm give the optical phase delay between light that is propagating along the fast and slow axes of the birefringent tendon. Images showing the change in birefringence in response to laser irradiation are presented. The technique permits rapid noncontact investigation of tissue structural properties through two-dimensional imaging of birefringence.

Skin optics

Abstract: The current status of tissue optics is reviewed, distinguishing among the cases of dominant absorption, dominant scattering, and scattering about equal to absorption. Previously published data as well as some current unpublished data on (human) stratum corneum, epidermis, and dermis are collected and/or (re)analyzed in terms of absorption coefficient, scattering coefficient, and anisotropy scattering factor. It is found that the individual skin layers show strongly forward scattering (anisotropy factors between 0.7 and 0.9). The absorption and scattering data show that for all wavelengths considered, scattering is much more important than absorption. Solutions to the transport equation for a multilayer skin model and finite beam laser irradiation that take this into account are not yet available. Hence, any quantitative dosimetry for skin treated with (laser) light is inaccurate. >

Determining the optical properties of turbid media by using the adding–doubling method

Abstract: A method is described for finding the optical properties (scattering, absorption, and scattering anisotropy) of a slab of turbid material by using total reflection, unscattered transmission, and total transmission measurements. This method is applicable to homogeneous turbid slabs with any optical thickness, albedo, or phase function. The slab may have a different index of refraction from its surroundings and may or may not be bounded by glass. The optical properties are obtained by iterating an adding–doubling solution of the radiative transport equation until the calculated values of the reflection and transmission match the measured ones. Exhaustive numerical tests show that the intrinsic error in the method is <3% when four quadrature points are used.

Double-integrating-sphere system for measuring the optical properties of tissue

Abstract: A system is described and evaluated for the simultaneous measurement of the intrinsic optical properties of tissue: the scattering coefficient, the absorption coefficient, and the anisotropy factor. This system synthesizes the theory of two integrating spheres and an intervening scattering sample with the inverse adding–doubling algorithm, which employs the adding–doubling solution of the radiative transfer equation to determine the optical properties from the measurement of the light flux within each sphere and of the unscattered transmission. The optical properties may be determined simultaneously, which allows for measurements to be made while the sample undergoes heating, chemical change, or some other external stimulus. An experimental validation of the system with tissue phantoms resulted in the determination of the optical properties with a <5% deviation when the optical density was between 1 and 10 and the albedo was between 0.4 and 0.95.

Minimal information for studies of extracellular vesicles 2018 (MISEV2018) : a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

Abstract: The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points.

Optical properties of biological tissues: a review.

Abstract: A review of reported tissue optical properties summarizes the wavelength-dependent behavior of scattering and absorption. Formulae are presented for generating the optical properties of a generic tissue with variable amounts of absorbing chromophores (blood, water, melanin, fat, yellow pigments) and a variable balance between small-scale scatterers and large-scale scatterers in the ultrastructures of cells and tissues.

MCML-Monte Carlo modeling of light transport in multi-layered tissues

Abstract: A Monte Carlo model of steady-state light transport in multi-layered tissues (MCML) has been coded in ANSI Standard C; therefore, the program can be used on various computers. Dynamic data allocation is used for MCML, hence the number of tissue layers and grid elements of the grid system can be varied by users at run time. The coordinates of the simulated data for each grid element in the radial and angular directions are optimized. Some of the MCML computational results have been verified with those of other theories or other investigators. The program, including the source code, has been in the public domain since 1992.

A review of the optical properties of biological tissues

Abstract: The known optical properties (absorption, scattering, total attenuation, effective attenuation, and/or anisotropy coefficients) of various biological tissues at a variety of wavelengths are reviewed. The theoretical foundations for most experimental approaches are outlined. Relations between Kubelka-Munk parameters and transport coefficients are listed. The optical properties of aorta, liver, and muscle at 633 nm are discussed in detail. An extensive bibliography is provided. >