Optical phantoms are widely used for evaluating the performance of biomedical optical modalities, and hence, absorbing and scattering materials are required for the construction of optical phantoms. Towards that aim, new readily available and inexpensive black Ink (Parker) as a simulating absorber as well as Intralipid 20% as a simulating scatterer are thoroughly investigated. Broadband Transmittance and Diffuse reflectance spectroscopic measurements were performed in the visible range 400 -700 nm. Optical properties of the phantom materials are determined. Analytical expressions for absorption and scattering coefficient related to the concentrations and wavelength of the Parker ink and Intralipid are also presented and discussed. The results show nonlinear trend in the absorption coefficient of Parker ink over the examined visible spectral range. Furthermore, Intralipid scattering coefficient variation across the mentioned spectral range shows a tissue-like scattering trend. The findings demonstrate the capability of the broadband transmission and diffuse reflectance for characterizing tissue-like phantom materials in the examined spectral range.

The aim of this study is to characterize the optical properties of Intralipid20% using two methods modified Kubelka-Munk model and Mie theory and to test the applicability of a modified Kubelka-Munk model with a single integrating sphere system over a wide wavelength range 470 – 725nm. Scattering coefficients which estimated by these two methods were matched and the absorption effect was observed and quantified. Finally, the imaginary part of the refractive index was estimated besides scattering, absorption and anisotropy coefficients. Full Text: PDF ReferencesB.W. Pogue, and M.S. Patterson, "Review of tissue simulating phantoms for optical spectroscopy, imaging and dosimetry", J. Biomed. Opt. 11, 4(2006). CrossRef J. Hwang, C. Ramella-Roman, and R. Nordstrom, "Introduction: Feature Issue on Phantoms for the Performance Evaluation and Validation of Optical Medical Imaging Devices", Biomed. Opt. Express. 3, 6(2012). CrossRef P. Ninni, F. Martelli, and G. Zaccanti, "Intralipid: towards a diffusive reference standard for optical tissue phantoms", Phys. Med. Biol 56, 2(2011). CrossRef S. Flock, S. Jacques, B. Wilson, W. Star, and J.C. van Gemert, "Optical properties of intralipid: A phantom medium for light propagation studies", Lasers. Surg. Med 4, 12(1992). CrossRef R. Michels, F. Foschum, and A. Kienle, "Optical properties of fat emulsions", Opt. Express. 16, 8(2008). CrossRef L. Spinelli et al. "Calibration of scattering and absorption properties of a liquid diffusive medium at NIR wavelengths. Time-resolved method", Opt. Express. 15, 11(2007). CrossRef L. Spinelli et al. "Determination of reference values for optical properties of liquid phantoms based on Intralipid and India ink", Biomed. Opt. Express. 5, 7(2014). CrossRef H. van Staveren, C. Moes, J. van Marle, S. Prahl, and J. van Gemert, "Light scattering in lntralipid-10% in the wavelength range of 400–1100 nm", Appl. Opt. 30, 31(1991). CrossRef B. Wilson, M. Patterson, and S. Flock, "Indirect versus direct techniques for the measurement of the optical properties of tissues", Photochem. Photobiol. 46, 5(1987). CrossRef H. Soleimanzad, H. Gurden, and F. Pain, "Optical properties of mice skull bone in the 455- to 705-nm range", J. Biomed. Opt. 22, 1(2017). CrossRef C. Holmer et al. "Optical properties of adenocarcinoma and squamous cell carcinoma of the gastroesophageal junction", J. Biomed. Opt. 12, 1(2007). CrossRef S. Thennadil, "Relationship between the Kubelka–Munk scattering and radiative transfer coefficients", OSA. 25, 7(2008). CrossRef L. Yang, and B. Kruse, "Qualifying the arguments used in the derivation of the revised Kubelka–Munk theory: reply", OSA. 21, 10(2004). CrossRef W. Vargas, and G. Niklasson, "Applicability conditions of the Kubelka–Munk theory", Appl. Opt. 36, 22(1997). CrossRef A. Krainov, A. Mokeeva, E. Segeeva, P. Agrba, and M. Kirillin, "Optical properties of mouse biotissues and their optical phantoms", Opt. Spec. 115, 2(2013). CrossRef H.C. van de Hulst, Light Scattering by Small Particles. (New York, Dover Publication 1981). CrossRef C. Matzler, Matlab Functions for Mie Scattering and Absorption. (Bern, Bern university 2002). DirectLink C. Matzler, Matlab Functions for Mie Scattering and Absorption, version 2 (Bern, Bern university 2002). DirectLink G. Segelstein, The complex refractive index of water [dissertation]. (Kansas, university of Missouri-Kansas city 1981). DirectLink A. Shahin, and W. Bachir, Pol. J. Med. Phys. Eng. 21, 4(2017). CrossRef

Introduction: The purpose of this project is to develop a mathematical model to investigate light distribution and study effective parameters such as laser power and irradiated time to get the optimal laser dosage to control hyperthermia. This study is expected to have a positive impact and a better simulation on laser treatment planning of biological tissues. Moreover, it may enable us to replace animal tests with the results of a COMSOL predictive model. Methods: We used in this work COMSOL5 model to simulate the light diffusion and bio-heat equation of the mouse tissue when irradiated by 980 nm laser diode and the effect of different parameters (laser power, and irradiated time) on the surrounding tissue of the tumor treatment in order to prevent damage from excess heat Results: The model was applied to study light propagation and several parameters (laser power, irradiated time) and their impact on light-heat distribution within the tumor in the mouse back tissue The best result is at laser power 0.5 W and time irradiation 0.5 seconds in order to get the maximum temperature hyperthermia at 52°C. Conclusion:The goal of this study is to simulate a mouse model to control excess heating of tissue and reduce the number of animals in experimental research to get the best laser parameters that was safe for use in living animals and in human subjects.

Debonding of the ceramic brackets with the aid of laser technology has become a certified technique in the field of orthodontics, as the use of a laser eliminates the problems of debonding that are associated with the traditional method. These problems may include enamel cracking and broken ceramic brackets, as well as the pain experienced by the patient during the removal of ceramic brackets [1]. Moreover, the use of a laser reduced the efforts and time needed for brackets debonding through thermal annealing of orthodontic brackets [2]. However, the effects of different lasers on the teeth and pulp tissue have not been fully determined. AbstractBackground. Deboning of ceramic brackets using a Er:YAG laser has become an acceptable method to facilitate the removal of such type of brackets. Therefore, research has been conducted to establish safer and more effective techniques. The pulse duration is one of the most critical parameters with respect to thermal effect on the pulp vitality. Objectives. The goal of the current research is to evaluate the thermal effect of different Er:YAG laser pulse durations in order to establish safe and effective protocols of debonding ceramic brackets. Material and Methods. The sample consisted of 45 premolars extracted for orthodontic purposes. A ceramic bracket was bonded to each tooth. The sample was divided into three groups: 15 teeth for pulse duration of 50 µs, 15 teeth for pulse duration of 100 µs, and 15 teeth for pulse duration of 300 µs. All the ceramic brackets were exposed to the Er:YAG laser for 6 s by laser scanning method, with the same air and water conditions, as well as the same pulse energy and repetition rate. The tooth temperature was monitored during debonding the brackets by a thermal camera, and the ceramic bracket was debonded after 18 s. Then, the samples were examined under a microscope to evaluate the presence of the adhesive material. Results. The results showed the absence of a statistically significant difference between the pulse duration of 50, 100 and 300 µs in relation to the rise in temperature of the tooth. However, a statistically significant difference was found in relation to the presence of adhesive materials between pulse duration 50 µs and both 100 and 300 µs, with no statistically significant difference between 100 and 300 µs. Conclusions. Within the limits of this study, both Er: YAG pulse durations of 100 and 300 µs are preferred during ceramic brackets debonding using the laser scanning method (Dent. Med. Probl. 2016, 53, 3, 352-357).

Estimating tissue hypoxia using diffuse reflectance spectroscopy has been a tough challenge. In this work, a novel approach for extracting tissue oxygen saturation (StO2) from diffuse reflectance spectra is presented. The devised method is based on the second derivative of visible light diffuse reflectance of tissue over 100 nm ranged from 500 nm to 600 nm. The theoretical predictions of the method were confirmed by estimating StO2 from simulated diffuse reflectance generated by Monte Carlo based look-up tables. Effect of scattering and blood volume fraction on the StO2 estimation are quantified. Validation was also tested on clinical measurements from oral mucosal tissue. The devised second derivative Diffuse reflectance spectroscopy (SD-DRS) shows a potential application for detecting tumor hypoxia, in particular, the differentiation between healthy and cancerous tissue.

No abstract

The optical properties of 1 μm polystyrene in the wavelength range of 500–750 nm were estimated by using a white light spectrophotometric transmittance spectroscopy and a single integrating sphere system. To retrieve the optical characteristics, two analytical methods, namely, diffusion approximation and Kubelka–Munk were used, and then their results were compared with Mie theory calculations. The correspondence of the Kubelka–Munk scattering coefficient with Mie was obvious, and relative errors varied between 6.73% and 2.66% whereas errors varied between 6.87% and 3.62% for diffusion theory. Both analytical methods demonstrated the absorption property of polystyrene over the abovementioned wavelength range. Although absorption coefficient turned out to be much lower than scattering, constructing a realistic optical phantom requires taking into account absorption property of polystyrene. Complex refractive index of polystyrene based on these two methods was determined. Inverse Mie algorithm with scattering coefficient was also used to retrieve the real part of refractive index and absorption coefficient for calculating the imaginary part of refractive index. The relative errors of the real part did not exceed 2.6%, and the imaginary part was in consistence with the prior works. Finally, the presented results confirm the validity of diffusion theory with a single integrating sphere system.

Fluorescence spectroscopy is widely used for biomedical optical diagnosis and surgical resection of tumours. is work investigates laserinduced fluorescence spectroscopy of fluorescence inclusions that are embedded in turbid media. 405 nm laser diode is used for exciting buried protoporphyrin-(PpIX) based inclusions in brain-like optical phantoms. Effects of scattering and absorption of the turbid medium on the recorded fluorescence signal and depth-resolved fluorescence were studied. Results show that optical properties of the surrounding turbid medium influence the intensity of the fluorescence signal. Absorption coefficient of the surrounding medium is the major contributor to the fluorescent signal. Analysis of the recorded fluorescence spectra shows that the effect of absorption coefficient is larger than the effect of scattering coefficient on the fluorescence intensity by nearly fivefold. e findings indicate that the fluorescence signal could be used as a biomarker of optical property variations through different stages of malignancy. is can enhance the detectability of malignant tissue for diagnostic and surgical purposes as well.