Search Results (127)

According to the International Diabetes Federation, 589 million adults worldwide live with diabetes in 2025 (approximately 1 in 9 adults). The development of convenient noninvasive blood glucose monitoring systems has been a central focus in diabetes management. Optical spectroscopy has advanced significantly among all noninvasive glucose detection techniques. A photoacoustic system has been developed using a single-wavelength near-infrared laser, operating at 1625 nm, where glucose exhibits an overtone absorption band with relatively low water interference. The noninvasive system has been evaluated using artificial skin phantoms, with different glucose concentrations, covering both normoglycemic and hyperglycemic blood glucose levels. The detection sensitivity of the developed system has been enhanced to ±15 mg/dL across the entire clinically relevant glucose range. K-nearest neighbours and wide neural network machine learning models were developed for noninvasive glucose classification. The models achieved prediction accuracies of 80.0% and 81.5%, respectively, with 100% of the predicted data located within zones A and B of Clarke’s error grid analysis. These findings satisfy the regulatory requirements for glucose monitors established by Health Canada and the U.S. Food and Drug Administration. Full article

Background and Objectives: Individuals with lower limb amputation are at increased risk of developing post-amputation complications that may affect rehabilitation outcomes. Assessing thermal symmetry between the residual and intact limbs, as well as activity-related temperature changes, represents a non-invasive and cost-effective approach for preliminary clinical evaluation. This study aimed to investigate regional skin temperature symmetry between residual and intact limbs at rest and following activity, and to examine whether the presence of phantom limb sensation or pain influences thermal patterns. Methods: Twenty-three individuals with unilateral lower limb amputation (mean age: 42.2 ± 15.1 years) participated in this cross-sectional study. The presence of phantom limb sensation and pain was recorded. Skin temperature measurements were obtained using a non-contact infrared thermometer under two conditions: “resting” and “post-activity” following a 10 min self-selected walking task, conducted after prosthetic removal. Measurements were acquired from the patella, tibialis anterior, and distal points of both the residual and intact limbs in both conditions. Results: Significant inter-limb differences were observed in the patellar and tibialis anterior regions, with higher temperatures at the patella and lower temperatures at the tibialis anterior on the residual limb. No significant differences were detected at the distal regions under either condition. Post-activity temperature increases were observed in the tibialis anterior and distal regions of the intact limb, whereas no comparable adaptation was observed on the residual limb. Thermal profiles did not differ between participants with and without phantom limb pain or sensation. Conclusions: These findings demonstrate that skin temperature dynamics in individuals with amputation are region-specific and influenced by functional activity. The absence of post-activity thermal adaptation in the residual limb may have clinical implications for rehabilitation monitoring. Incorporating regional thermal assessment into routine evaluation may support individualized rehabilitation strategies following lower limb amputation. Full article

This work presents a novel compact size and sensitive band-stop filter, whose notch frequency is 5.5 GHz, and it is suggested to estimate the concentration of blood glucose non-invasively. The filter is made on FR-4, with the size of the entire structure being 15 mm × 25 mm × 1.6 mm. A human finger-phantom model, comprising layers of skin, fat, blood, and bone, is built in an EM simulation environment (HFSS) to assess the sensing performance of the human finger-phantom. The glucose content in the blood layer is kept at a range of 0 to 500 mg/dL, with the ratio of the resonant frequency shift being assessed by placing the finger phantom on the proposed filter structure. The sensing principle is based on the fact that the resonant frequency of the microwave sensor changes with changes in glucose concentration in the tissue, and this is due to the changes in the dielectric properties of the tissue. The shifts obtained in the study are used for the evaluation of glucose concentration in blood as a non-invasive technique. This work explores five microstrip band-stop filters noted as Designs I, II, III, IV, and V. In these filters, better results of minimum and maximum frequency shifts of 0.1 and 1.4 MHz in Design I and 0.1 and 2 MHz in Design IV are observed. The simulated results of Design IV are verified with measured results. Good matching is also noted at the lower frequencies. The filters are compact, cost-effective, and give better sensitivity performance. Hence, the proposed design can be used for glucose monitoring in blood samples involving a non-invasive method. Full article

This study presents a computational, simulation-based investigation of the dielectric response of human hand tissues, skin, fat, muscle, and bone to radiofrequency (RF) electromagnetic fields emitted by mobile devices. The widespread adoption of handheld devices and the deployment of fifth-generation (5G) networks, including millimetre-wave (mmWave) bands, have intensified concerns regarding localized human exposure to RF radiation, particularly in the hand, which serves as the primary interface during device operation. Using validated dielectric property datasets, numerical simulations were performed across the frequency range of 0.5–40 GHz, employing the Finite-Difference Time-Domain (FDTD) method to solve Maxwell’s equations, with analytical evaluations conducted in Maple-18. A heterogeneous multilayer hand phantom was developed, and simulations were conducted under controlled exposure conditions, including a transmitted power of 1 W, antenna gain of 2 dBi, and incident power density of 5 W/m², consistent with ICNIRP and NCC safety guidelines. Tissue responses were assessed over a temperature range of 10–40 °C to account for thermal variability. The results demonstrate strong frequency- and temperature-dependent behaviour of dielectric properties, intrinsic impedance, reflection coefficient, attenuation, and specific absorption rate (SAR). At lower frequencies (<1 GHz), RF energy penetrated more deeply with distributed absorption and relatively low SAR values, whereas higher frequencies (3–40 GHz) produced highly localized absorption in superficial tissues, particularly skin and muscle. Increasing temperature led to significant increases in permittivity, conductivity, and SAR, with up to a twofold enhancement observed between 10 °C and 40 °C. These findings confirm that 5G and mmWave exposures result in predominantly surface-confined energy deposition in hand tissues. The study provides a robust computational framework for evaluating hand device electromagnetic interactions and offers quantitative insights relevant to antenna design, exposure compliance assessment, and the development of evidence-based safety guidelines. Full article

Current diagnostic modalities for rheumatoid arthritis (RA), such as Magnetic Resonance Imaging (MRI) and ultrasound (US), excel at visualizing structural pathology but are either resource-intensive or often limited to morphological assessment. In this work, we present the design and technical validation of a low-cost continuous-wave near-infrared (NIR) dual-mode optical probe for functional monitoring of joint inflammation. Unlike superficial imaging, NIR light penetrates approximately 3–5 cm and is tissue and wavelength dependent, enabling trans-illumination of the synovial volume. The system combines reflectance and transmission geometries to resolve the ambiguity between disease presence and disease severity. To validate the diagnostic logic, we employed mcxyzn Monte Carlo (MC) simulations to model the optical signature of RA progression from early onset to EULAR-OMERACT grade 2 pannus hypertrophy on a simplified finger model, based on several tissue models in the literature and supported by physical measurements on a multilayer silicone phantom and in vivo signal verification on human volunteers. Our results demonstrate a distinct functional dichotomy: reflectance geometry serves as a binary discriminator of synovial turbidity onset, while transmission flux serves as a monotonic proxy for pannus volume, exhibiting a quantifiable signal decay consistent with the Beer–Lambert law. Signal verification on a subject with confirmed RA pathology demonstrated a significant increase in the effective attenuation coefficient (${\mu }_{eff} ~ 0.59$ mm⁻¹) compared to the healthy baseline (${\mu }_{eff} ~ 0.47$ mm⁻¹). Furthermore, simulation analysis revealed a critical “metric inversion” in darker skin phenotypes (Fitzpatrick V–VI), where the standard beam-broadening signature of inflammation is artificially suppressed by epidermal absorption. We conclude that while transmission flux remains a robust grading metric across diverse skin tones, morphological beam-shape metrics are not robust, particularly in high-absorption populations. By targeting the hemodynamic precursors of structural damage, this dual-mode probe design offers a potential pathway for longitudinal, quantitative monitoring of disease activity at the point of care, while the systematic use of the Monte Carlo framework provides insight into the measurement geometry most suitable for a given clinical endpoint, whether that be detecting the presence or severity of rheumatoid arthritis. Full article

The role of microneedles (MNs) in enhancing tissue permeability has long been established. Their capacity to serve as drug-delivery vehicles or biosensing platforms makes them ideal candidates for applications in which tissue serves as the primary pathway. Such potential can only be thoroughly validated through tissue-dependent tests. Although MNs are not limited to human tissues, humans remain the most relevant target group. This highlights the need to develop platforms that closely replicate the structure of human tissue for the intended applications. To date, many studies have addressed the limited availability of human samples, constrained by ethical concerns and other challenges, by using artificial, human-like tissue mimics. These models have been widely used to evaluate various aspects of MN performance, including penetrability, drug delivery, and biosensing. Despite limitations, artificial tissues provide a practical assessment tool in MN development. This review offers new insights into the role of synthetic tissue models in evaluating MN functionality. It discusses the underlying rationale for their use, highlights their flexibility and potential in MN application studies, addresses their limitations, and presents their future perspective. Finally, it highlights the need for standardized, scalable artificial tissue platforms to support the translational and commercial advancement of MN technologies. Full article

Substrate-free epidermal antennas promise imperceptible and long-term wearable sensing, yet their electromagnetic performance is fundamentally constrained by the properties of ultrathin conductors. In this work, gold nanomesh is employed for the first time as the radiating conductor of a substrate-free epidermal tattoo antenna operating in the UHF RFID band. Owing to its RF-thin nature, the nanomesh behavior is governed by sheet resistance rather than skin-depth effects, imposing a strict upper bound on achievable radiation efficiency. By combining surface-impedance modeling, full-wave simulations, and on-body experiments, we demonstrate that ohmic losses set a geometry-independent limit on the realized gain of on-skin antennas. An inductively coupled loop architecture is optimized to approach this bound while ensuring mechanical robustness and impedance stability. Measurements on phantoms and human subjects confirm the predicted performance limits within a few decibels, enabling reliable UHF RFID read ranges up to 30–40 cm under standard regulatory constraints. Full article

Background: One method for the radiation therapy of rectal cancer is to set patients supine and treat them with volumetric modulated arc therapy (VMAT). The posterior skin dose is of concern due to undesirable bolusing from mounting surfaces the patient lays upon, namely the carbon fiber couch (CFC). The posterior skin dose may be mitigated by positioning the patient on top of a low-density material that separates the patient from the CFC. Purpose: Our objective was to determine the reduction in the posterior surface dose when a mattress or foam board is used to prop the patient away from the CFC. Materials and Methods: Three clinical rectal cancer patient VMAT plans were selected. A solid water phantom with optically stimulated luminescence dosimeters (OSLDs) placed at the posterior surface was mounted using three setups: directly on the CFC, with a mattress on the CFC, and with a 10 cm thick foam board on the CFC. The three VMAT plans were delivered to this phantom, with OSLDs measuring the posterior surface dose with each setup. In the treatment planning system (TPS), the CFC only, mattress, and foam board setups were simulated on the patient’s anatomy with posterior surface doses reported. Results: The OSLD measurements in the phantom showed that the mattress reduced the posterior surface dose on average by 1.3%, and the foam board reduced the dose by 8.3%. The TPS estimates demonstrated that, on average, the mattress reduced the surface dose by 15.8%, and the foam board reduced the dose by 33.0%. It is likely that the TPS had limitations accurately modeling the surface dose, so OSLD measurements were closer to clinical reality. Conclusions: The mattress does not reduce the posterior skin dose enough to warrant its use as a skin sparing device. The CFC produces a bolusing effect that can be reduced by separating the patient from the CFC with a 10 cm thick foam board. Full article

People suffering from chronic diseases like diabetes, heart disease, and Parkinson’s disease are reliant on their implantable devices to improve their quality of life and to manage their chronic conditions. Despite their advantages, some systems are battery-powered, which can lead to battery failure, resulting in prophylactic surgery. One solution to this issue is an implantable antenna that provides an adequate link margin across various skin sites. In this study, we introduce an implantable antenna design optimized using an open-source PSO algorithm. The antenna is a tunable WMTS-motivated design fabricated on a Rogers 6010.2 substrate and evaluated by simulation and in vitro testing using phantom tissues. Validation measurements are performed to evaluate the effects of implantation depth across various adipose thicknesses. Full article

The field of experimental radiooncology and the quality assessment (QA) aimed at patient safety both profit from the utilisation of biomimetic principles. The work with phantoms based on biological structures of animals or humans, utilising the principles of anatomic mimicry, has a long tradition in radiotherapy research. When phantoms are produced from tissue-equivalent materials, they mimic the radiological properties of tissues and organs, allowing researchers and clinicians to study dose distribution and optimise treatment plans without exposing real patients to radiation. Biomechanical mimicry would take this a step further by creating phantoms that replicate the movement and deformation of organs during physiological movement, such as heartbeat or breathing, enabling a more accurate simulation of dynamic treatment scenarios. Bioinspired sensor technologies, such as artificial skin or integrated detectors, can be used to monitor radiation exposure, organ motion or temperature changes during therapy with high precision. The utility of such a phantom could be further enhanced by creating a realistic tumour microenvironment as an irradiation target, following the principles of microenvironmental biomimicry. Thus, biomimetic strategies can be exploited in the validation of radiotherapy technologies and open new perspectives for adaptive radiotherapy and real-time monitoring. Full article

Background/Objectives: This study investigates the dosimetric impact of a 3D-printed applicator integrating multilayer catheter geometry and high-density shielding, designed for contact interventional radiotherapy (IRT) in non-melanoma skin cancer (NMSC) treatment. The aim is to assess its potential to enhance target coverage and reduce doses in organs at risk (OARs). Methods: A virtual prototype of a multilayer applicator was designed using 3D modeling software and realized through fused deposition modeling. Dosimetric simulations were performed using both TG-43 and TG-186 formalisms on CT scans of a water-equivalent phantom. A five-catheter array was reconstructed, and lead-cadmium-based alloy shielding of varying thicknesses (3–15 mm) was contoured. CTVs of 5 mm and 8 mm thickness were analyzed along with a neighboring OAR. Dosimetric endpoints included V95%, V100%, V150% (CTV), D_2cc (OAR), and therapeutic window (TW). Results: Compared to TG-43, the TG-186 algorithm yielded lower OAR doses while maintaining comparable CTV coverage. Progressive increase in shielding thickness led to improved V95% and V100% values and a notable reduction in OAR dose, with an optimal trade-off observed between 6 and 9 mm of shielding. The TW remained above 7 mm across all configurations, supporting its use in lesions thicker than conventional guidelines recommend. Conclusions: The integration of multilayer catheter geometry with high-density shielding in a customizable 3D-printed applicator enables enhanced dose modulation and OAR sparing in superficial IRT. This approach represents a step toward personalized brachytherapy, aligning with the broader movement in radiation oncology toward patient-specific solutions, adaptive planning, and precision medicine. Future directions should include prototyping and mechanical testing of the applicator, experimental dosimetric validation in phantoms, and pilot clinical feasibility studies to translate these promising in silico results into clinical practice. Full article

Optical brain monitoring techniques, including near-infrared spectroscopy (NIRS), diffuse correlation spectroscopy (DCS), and photoplethysmography (PPG) have gained attention for their non-invasive, affordable, and portable nature. These methods offer real-time insights into cerebral parameters like cerebral blood flow (CBF), intracranial pressure (ICP), and oxygenation. However, confounding factors like extracerebral layers, skin pigmentation, skull thickness, and brain-related pathologies may affect measurement accuracy. This review examines the potential impact of confounders, focusing on in vitro studies that use phantoms to simulate human head properties under controlled conditions. A systematic search identified six studies on extracerebral layers, two on skin pigmentation, two on skull thickness, and four on brain pathologies. While variation in phantom designs and optical devices limits comparability, findings suggest that the extracerebral layer and skull thickness influence measurement accuracy, and skin pigmentation introduces bias. Pathologies like oedema and haematomas affect the optical signal, though their influence on parameter estimation remains inconclusive. This review highlights limitations in current research and identifies areas for future investigation, including the need for improved brain phantoms capable of simulating pulsatile signals to assess the impact of confounders on PPG systems, given the growing interest in PPG-based cerebral monitoring. Addressing these challenges will improve the reliability of optical monitoring technologies. Full article

Non-invasive, in vivo assessment of target substances penetration into the skin remains a significant challenge in dermatology and cosmetology. While various optical methods have been employed for this purpose, each has inherent limitations. Here, we present a novel non-invasive imaging approach using optical coherence elastography (OCE) to simultaneously determine the penetration depth of topically applied osmotically active substances in biological objects and associated water content changes with high sensitivity. Most substances are osmotically active and generate osmotic pressure proportional to their concentration, inducing deformations in biological objects. These osmotic strains can be visualized similarly to mechanical or thermal strains. Using OCE, we evaluated penetration and dehydration depth profiles in polyacrylamide gel phantoms, ex vivo cartilage, and porcine ear skin samples treated with aqueous glycerol solutions of varying concentrations. Additionally, the penetration and effect of jojoba oil were assessed in treated skin samples. The results are consistent with those obtained by other established methods, confirming the reliability and applicability of OCE. This technique offers unique capabilities not achievable with other optical methods, making it a valuable complementary tool for non-invasive studies. It holds significant promise for advancing both research and clinical applications in dermatology and cosmetology, including its potential translation to in vivo assessments. Full article

This work analyzes the radiation shielding effectiveness of biocompatible hydrogel pads containing carbohydrate-based polymer matrices (Alginate, Chitosan, and Cellulose) integrated with the high atomic number (Z) fillers Bismuth Oxide (Bi₂O₃) and Zinc Oxide (ZnO). The Monte Carlo-based toolkit, Geant4, was used to simulate the deposition of the dose throughout a multilayer phantom that mimics the skin (Epidermis, Dermis, Subcutaneous, and Muscle) with a pad on top irradiated with photon and electron beams from 50 keV to 1000 keV. The results indicated that Bi₂O₃ succeeded in causing greater absorption of photons at doses, particularly in deep-layer tissues, from the increase in the filler content as well as the pad thickness. The Cellulose–Bi₂O₃ composites (10 mm thick) not only showed the best deep-shielding property among all investigated combinations but also the Alginate-based pads generally performed better with regard to the surface dose attenuation. The results demonstrate the promising potential of high-Z-doped hydrogels in serving as flexible, light, and biocompatible shielding materials for superficial radiotherapy. Full article

In this study, we present a wearable sensing system for monitoring the physiological status of damaged biological tissues based on a flexible, frequency-coded electromagnetic spiral resonator array. The physiological parameter evaluation is performed in a contactless way, avoiding the placing of electronically active elements directly upon the patient’s skin, thus ensuring safety and comfort. Firstly, we report in detail the physical principles behind the sensing strategy: a passive array is interrogated through an actively fed external single-loop probe that is inductively coupled with the double-layer spiral unit cells. The variation in the physiological parameters influences the array response, thus providing sensing information, due to the different complex dielectric permittivity values related to the tissue status. Moreover, the proposed frequency-coded approach allows for spatial information on the lesion to be retrieved, thus increasing the sensing ability. In order to prove the validity of this general methodology, we created a numerical test case, designing a practical implementation of the wearable sensing system working at a radiofrequency regime (10–100 MHz). In addition, we also fabricated prototypes, exploiting PCB technology, and realized stratified phantoms by incorporating opportune additives to control the dielectric properties. The numerical results and the experimental verification demonstrated the validity of the developed sensing strategy, showing satisfying agreement and, thus, proving the good sensibility and spatial resolution of the frequency-coded array. These results can open the path to a radically novel approach for self-care and monitoring of inflamed status and, more generally, for wearable sensing devices in biomedical applications. Full article