Ultrasonic wave attenuation in biological tissues arises from complex interactions between mechanical, structural, and fluidic properties, making it essential to identify dominant mechanisms for accurate simulation and device design. This work introduces a novel integration of experimentally measured tissue parameters into time-explicit nonlinear acoustic wave simulations, in which the equations are directly solved in the time domain using an explicit solver. This approach captures the full transient waveform without relying on frequency-domain simplifications, offering a more realistic representation of ultrasound propagation in heterogeneous media. The study estimates both sound diffusivity and viscous damping parameters (dynamic and bulk viscosity) for a broad range of ex vivo tissues (skin, adipose tissue, skeletal muscle, trabecular/cortical bone, liver, myocardium, kidney, tendon, ligament, cartilage, and gray/white brain matter). Four regression models (power law, linear, exponential, logarithmic) were applied to characterize their frequency dependence between 0.5 and 5 MHz. Results show that attenuation is more strongly driven by bulk viscosity than dynamic viscosity, particularly in fluid-rich tissues such as liver and myocardium, where compressional damping dominates. The power-law model consistently provided the best fit for all attenuation metrics, revealing a scale-invariant frequency relationship. Tissues such as cartilage and brain showed weaker viscous responses, suggesting the need for alternative modeling approaches. These findings not only advance fundamental understanding of attenuation mechanisms but also provide validated parameters and modeling strategies to improve predictive accuracy in therapeutic ultrasound planning and the design of non-invasive, tissue-specific acoustic devices.

The footwear industry significantly impacts the environment, from raw material extraction to waste disposal. Transforming waste into new products is a viable option to mitigate the environmental consequences, reducing the reliance on virgin raw materials. This work aims to develop thermal and acoustic insulation materials using polyester waste from footwear industry. Two nonwoven and two compressed nonwoven structures, comprising 80% polyester waste and 20% commercial recycled polyester (matrix), were produced. The materials were created through needle-punching and compression molding techniques. The study included the production of sandwich and monolayer nonwoven structures, which were evaluated considering area weight, thickness, air permeability, mechanical properties, morphology using field emission scanning electron microscopy, and thermal and acoustic properties. The nonwoven samples presented high tensile strength (893 kPa and 629 kPa) and the highest strain (79.7% and 73.3%) and compressed nonwoven structures showed higher tensile strength (2700 kPa and 1291 kPa) but reduced strain (25.8% and 40.8%). Nonwoven samples showed thermal conductivity of 0.041 W/K.m and 0.037 W/K.m. Compressed nonwoven samples had higher values at 0.060 W/K.m and 0.070 W/K.m. While the sample with the highest conductivity exceeds typical insulation levels, other samples are suitable for thermal insulation. Nonwoven structures exhibited good absorption coefficients (0.640-0.644), suitable for acoustic insulation. Compressed nonwoven structures had lower values (0.291-0.536), unsuitable for this purpose. In summary, this study underscores the potential of 100% recycled polyester structures derived from footwear and textile industry waste, showcasing remarkable acoustic and thermal insulation properties ideal for the construction sector.

Background/Objectives: This review analyzes the effects of invasive and non-invasive methods of knee joint unloading on knee loading, employing a biomechanical model to evaluate their impact. Methods: PubMed, Web of Science, Cochrane, and Scopus were searched up to 15 May 2024 to identify eligible clinical studies evaluating Joint Space Width, Cartilage Thickness, the Western Ontario and McMaster Universities Osteoarthritis Index, the Knee Injury and Osteoarthritis Outcome Score system, Gait velocity, Peak Knee Adduction Moment, time to return to sports and to work, ground reaction force, and the visual analogue scale pain score. A second search was conducted to select a biomechanical model that could be parametrized, including the modifications that each treatment would impose on the knee joint and was capable of estimate joint loading to compare the effectiveness of each method. Results: Analyzing 28 studies (1652 participants), including 16 randomized clinical trials, revealed significant improvements mainly when performing knee joint distraction surgery, increasing Joint Space Width even after removal, and high tibial osteotomy, which realigns the knee but does not reduce loading. Implantable shock absorbers are also an attractive option as they partially unload the knee but require further investigation. Non-invasive methods improve biomechanical indicators of knee joint loading; however, they lack quantitative analysis of cartilage volume or Joint Space Width. Conclusions: Current evidence indicates a clear advantage in knee joint unloading methods, emphasizing the importance of adapted therapy. However, more extensive research, particularly using non-invasive approaches, is required to further understand the underlying knee joint loading mechanisms and advance the state of the art.

Medical phantoms are essential to imaging calibration, clinician training, and the validation of therapeutic procedures. However, most ultrasound phantoms prioritize acoustic realism while neglecting the viscoelastic and anisotropic properties of fibrous soft tissues. This gap limits their effectiveness in modeling realistic biomechanical behavior, especially in wave-based diagnostics and therapeutic ultrasound. Current materials like gelatine and agarose fall short in reproducing the complex interplay between the solid and fluid components found in biological tissues. To address this, we developed a soft, anisotropic composite whose dynamic mechanical properties resemble fibrous biological tissues such as skin and skeletal muscle. This material enables wave propagation and vibration studies in controllably anisotropic media, which are rare and highly valuable. We demonstrate the tunability of damping and stiffness aligned with fiber orientation, providing a versatile platform for modeling soft-tissue dynamics and validating biomechanical simulations. The phantoms achieved Young’s moduli of 7.16–11.04 MPa for skin and 0.494–1.743 MPa for muscles, shear wave speeds of 1.51–5.93 m/s, longitudinal wave speeds of 1086–1127 m/s, and sound absorption coefficients of 0.13–0.76 dB/cm/MHz, with storage, loss, and complex moduli reaching 1.035–6.652 kPa, 0.1831–0.8546 kPa, and 2.138–10.82 kPa. These values reveal anisotropic response patterns analogous to native tissues. This novel natural fibrous composite system affords sustainable, low-cost ultrasound phantoms that support both mechanical fidelity and acoustic realism. Our approach offers a route to next-gen tissue-mimicking phantoms for elastography, wave propagation studies, and dynamic calibration across diverse clinical and research applications.

The objective of this review was to infer how the use of an orthosis affects cartilage in patients with knee osteoarthritis. A search was performed in four different databases (Web of Science, Scopus, EMBASE, and PubMed) up to the 21st of November of 2020 to evaluate how the patient’s condition was monitored. The parameters chosen for this review were medial tibial cartilage volume, x-ray evaluation, Lequesne Index, pain visual analog scale score, Western Ontario and McMaster Universities Arthritis Index pain score, and Knee Injury and Osteoarthritis Outcome Score pain subscale score. The initial search yielded a total of 12,622 documents. After thoroughly screening them, 38 were selected for analysis. Of the resulting data, only two objectively evaluated the cartilage (medial tibial cartilage volume, n = 1; x-ray evaluation, n = 1), with the remainder evaluating subjective symptoms (Lequesne Index, n = 8; pain visual analog scale score, n = 18; Western Ontario and McMaster Universities Arthritis Index pain score, n = 10; Knee Injury and Osteoarthritis Outcome Score pain subscale score, n = 10). The data did not converge toward any general outcome. The articles read demonstrated a great tendency to evaluate qualitative parameters pertinent to the symptoms of this condition or quantitative parameters related to the biomechanics of the knee. However, these parameters are not ideal because they are ambiguous. As such, a shift toward more objective quantitative parameters that directly assess the cartilage volume of the knee should be considered in future clinical trials.

Ultrasound elastography (USE) has gained significant attention in recent years as a non-invasive method for assessing tissue elasticity, offering the potential to improve diagnostic accuracy. With the quick development of this technique, there is a growing demand for calibrated phantoms to validate elastography systems. Therefore, the aim of this review was to provide insights into the current state of elastography research in multiple anatomical structures, which include: liver, breast, prostate, kidneys, blood vessels, heart, eyes, brain, muscles, tendons, and respective phantoms. The PubMed, Scopus, and Web of Science databases were searched from January 2019 to May 2024, using specifically selected keywords, to identify relevant studies. Studies that did not use phantoms were not included in this review. Elastography research uses a wide range of phantoms, mainly for validating innovative approaches and evaluating the performance of existing ones. Phantoms made from gelatin, agar, and poly(vinyl alcohol) cryogel (PVA-C), along with commercially available phantoms, were the most common across the compiled papers. Overall, an effort in the advancement of new elastography approaches is notorious, but the manufacturing of specialized phantoms that more accurately replicate the properties of living tissue remains a field with significant growth potential.