Omnia Hamdy

Adequate understanding of tissue optical characteristics is the foundation of laser-based diagnostics and phototherapy. This paper introduces an integrated experimental-computational-engineering framework for laser-based characterization of biological tissues, bridging the gap between biophysical measurement and medical device design. Ex vivo tissues, including chicken skin (native, boiled, dry), chicken liver (native, coagulated), bovine muscle, and rabbit skull, were measured at clinically relevant wavelengths (635, 650, and 808 nm) using both integrating sphere and distant-detector configurations. Parameters were extracted using the Kubelka–Munk model and the Beer–Lambert law. The Diffusion Approximation, which was solved using the Finite Element Method in COMSOL Multiphysics, was used to generate high-resolution fluence rate distributions. Typical engineering design criteria for diffuse reflectance probe systems, such as optimal source–detector separation, fiber numerical aperture, operating wavelength selection, and an exploratory ex vivo tissue-state index (CDI) whose in vivo applicability remains to be established, are subsequently obtained from the resulting optical property database. The proposed method shows how the hardware design of non-invasive biomedical sensing devices is influenced directly and optimized by a systematic optical characterization workflow, which minimizes empirical trial-and-error in prototype development. This multidisciplinary approach offers a consistent methodology that may be used with image-guided surgical equipment, phototherapy planning systems, and optical biopsy probes.

Fluoride treatment has long been recognized as an important method for treating dental decay. Silver Diamine Fluoride (SDF) treatment has emerged as a low-cost and simple approach, combining silver’s antimicrobial properties with fluoride’s caries-inhibiting activities. The present study compares the effects of two lasers, diode-pumped solid-state frequency-doubled Nd: YAG (DPSS, 532 nm) and diode (980 nm), on fluoride absorption in dentin when used with SDF. Following treatment with 38% SDF, the prepared dentin specimens were exposed to radiation for 3, 5, and 10 s using either a frequency-doubled Nd: YAG laser (532 nm, 1 W, free-space beam, 3 mm diameter) or a diode laser (980 nm, continuous wave) at 1 W and 3 W power with a 300 μm optical fiber scanned tangentially across the surface at a speed of 1 mm/s. The equivalent energy densities for 1 W and 3 W diode irradiation were approximately 1,414.7 J/cm² and 4,244.1 J/cm², while for Nd: YAG exposure, it ranged from 42.4 to 141.4 J/cm². Evaluation methods included scanning electron microscopy (SEM) to assess dentinal tubule openness and energy-dispersive X-ray (EDX) analysis to quantify fluoride uptake. Statistical analyses included the Kruskal-Wallis test and Mann-Whitney comparisons, with Spearman’s correlation coefficient used to examine relationships between image analysis and EDX results. Results indicated that the combination of SDF treatment with laser irradiation significantly increased fluoride uptake and decreased open dentinal tubules compared to SDF treatment alone (overall P < 0.001). The SDF + diode 3 W group exhibited the highest mean fluoride wt% and the lowest mean% open tubules (significant compared to SDF alone, P < 0.05). The fd-Nd: YAG 10 s group exhibited fluoride levels comparable to diode 3 W. There was a significant negative correlation (ρ = -0.78, P < 0.001) between fluoride wt% and percentage of open tubules. Laser irradiation with Diode at 3 W or fd-Nd: YAG Laser-assisted SDF treatment enhances tubule blockage and boosts surface fluoride retention in a laboratory context. These findings support the use of lasers to optimize the effectiveness of SDF in caries prevention and dentinal tubule sealing. However, more in-vivo and thermal safety research is required before making a clinical recommendation.

Osteoporosis is a widespread chronic metabolic bone disease. It has developed into a severe public health problem, especially for older people. Preventing fractures caused by osteoporosis and enhancing patient experiences require early identification of bone mineral loss. The commercially available technologies for diagnosing osteoporosis are costly and may trigger cell mutation. Therefore, non-invasive treatments have received great attention. This work explores the potential of employing optical collimated transmittance at 660, 785, and 980 nm to monitor progressive mineral loss in EDTA-treated chicken bone samples. Over the course of six weeks, 20 samples (10 diaphysis and 10 epiphysis) were measured weekly. Transmittance was elevated following demineralisation, particularly at 980 nm, which increased by 190%. The receiver operating characteristic (ROC) analysis produced area under the curve (AUC) values ranging from 0.834 to 0.996 (95% CI), demonstrating strong discrimination between baseline and demineralised states. These results show that near-infrared optical transmission is sensitive to mineral loss and has the potential to be used for low-cost bone assessments. Although EDTA-induced demineralisation does not fully recreate the complicated pathophysiology of clinical osteoporosis, this simplified model serves as a preliminary platform for assessing optical signals associated with mineral loss.

The sensitivity of laser-induced fluorescence (LIF) to slight biochemical changes has made it an effective tool for non-invasive biomedical diagnostics. Since milk is a biological fluid that is both optically and biochemically complex, we employed it as a model sample to evaluate how effectively LIF senses thermally induced molecular changes. Full-fat and skimmed milk samples were systematically examined under 405 nm excitation both before and after controlled heating. The collected fluorescence spectra were then subjected to chemometric analysis using Principal Component Analysis (PCA) for unsupervised classification and Partial Least Squares Regression (PLSR), Support Vector Classifier (SVC), and Random Forest (RF) for predictive modeling. The statistical significance of the observed spectral changes was validated using paired t-tests. Following thermal processing, the emission band at around 533 nm, which corresponds to riboflavin, was significantly reduced, based on fluorescence spectra. The statistical significance of this decrease was validated by paired t-tests (p R² >0.95) achieved by PLSR. Excellent classification performance was achieved by the SVM classifier with RBF kernels, correctly classifying 100% of data sets. Good model generalization without overfitting is indicated by the close agreement between the test set and cross-validation accuracies. Furthermore, the robustness and generalizability of the model were confirmed by the low out-of-bag error rate in RF implementations. These results show the potential of LIF as a sensitive, non-destructive method for assessing thermal and metabolic changes in biomedical contexts and validate milk as a practical surrogate system for comparing fluorescence-based methods.

This work demonstrates that heating porcine skin promotes thermal optical clearing (TOC), increasing 660-nm laser transmittance by 35%. This highlights TOC's potential to enhance light penetration for improved optical imaging and diagnostics.