Applications of Ultrasonic Technology in Biomedical Sciences

1. Introduction

Ultrasonic sensing and imaging technologies play a pivotal role in contemporary biomedical science due to their non-invasive nature, real-time capability, and compatibility with a wide range of biological tissues. Ultrasound consists of mechanical waves propagating at frequencies above the audible range, whose interaction with soft tissues and biological structures provides valuable information on their mechanical, structural, and functional properties. These features have positioned diagnostic ultrasound as one of the most widely used imaging modalities in clinical practice, with established applications in cardiology, neurology, oncology, musculoskeletal assessment, and veterinary medicine [1,2].

From a physical standpoint, ultrasonic wave propagation in biological media is governed by acoustic and elastic wave phenomena, including frequency-dependent attenuation, scattering, and dispersion, which are strongly influenced by tissue microstructure. In this context, quantitative ultrasound techniques have emerged to move beyond qualitative B-mode interpretation by estimating intrinsic tissue parameters such as attenuation coefficients, backscatter statistics, or scatterer distributions. These approaches enable objective and reproducible tissue characterization and have demonstrated particular potential for detecting subtle pathological alterations that may remain undetected using conventional imaging alone [3,4].

Significant advances in ultrasound acquisition and image formation have been reported in recent years. Ultrafast imaging based on plane wave transmission and advanced beamforming strategies has enabled high-temporal-resolution imaging while preserving spatial quality [5]. Alongside this, the development of large-scale and sparse array architectures has improved spatial resolution and near-field performance while mitigating hardware and channel-count limitations, which is especially relevant in biomedical and preclinical imaging scenarios [6,7].

Beyond imaging, ultrasound has become an essential tool for functional and physiological assessment. Doppler-based methods and related ultrasound biomarkers are widely used to evaluate blood flow dynamics, vascular compliance, and hemodynamic responses under different physiological or pharmacological conditions [8]. Likewise, neuromuscular and peripheral nerve ultrasound has gained increasing clinical relevance as a complementary diagnostic modality, providing detailed anatomical information that enhances the accuracy of neuromuscular disorder assessment [9].

Ultrasound is also playing an expanding role in experimental and preclinical research, particularly in oncology and therapeutic applications. Focused Ultrasound (FUS) enables localized energy delivery through thermal or mechanical mechanisms while preserving surrounding tissues, and its use in neuro-oncology, including pediatric brain tumors, is an active area of investigation [10,11]. Furthermore, advances in acoustic field manipulation have fostered renewed interest in acoustic lenses for biomedical applications. Planar Fresnel-type acoustic lenses, including MRI-compatible designs, have demonstrated the ability to achieve spatial focusing and beam shaping without complex electronic control, offering promising solutions for image enhancement, therapeutic targeting, and hybrid imaging environments [12].

Altogether, the continued convergence of acoustic physics, quantitative imaging methodologies, advanced hardware design, and clinically driven applications reflects the dynamic evolution of ultrasonic technologies in biomedicine. The contributions collected in this Special Issue exemplify this multidisciplinary trend, spanning methodological innovation, experimental validation, and applied clinical research, and point toward future ultrasound systems that are increasingly quantitative, adaptive, and application-specific.

2. An Overview of Published Articles

This Special Issue brings together nine high-quality contributions addressing recent advances in ultrasonic sensing and imaging, with a particular emphasis on biomedical and clinical applications. Throughout this section, the numbers in parentheses (e.g., (1), (2), etc.) refer to the individual articles included in this issue, as listed in the Section “List of Contributions”. The collection comprises eight original research articles and one comprehensive review paper. For clarity, the contributions are discussed within thematic categories reflecting their main methodological and application domains, while preserving the order in which they appear in the list of contributions.

2.1. Clinical and Functional Diagnostic Ultrasound

Choi et al. (1) investigated the effects of varying caffeine dosages and consumption timings on cerebral vascular and cognitive functions in healthy adults using diagnostic ultrasound. By monitoring carotid artery blood flow, blood pressure, and oxygen saturation, the authors demonstrated that a moderate caffeine intake induces measurable hemodynamic changes. In particular, a dose of 200 mg produced more pronounced increases in systolic blood pressure and oxygenation compared to 100 mg, while moderate caffeine consumption was associated with reduced cognitive response times. The study highlights the sensitivity of ultrasound to functional physiological variations and underscores its potential for non-invasive cerebral assessment, while also emphasizing the importance of defining safe consumption guidelines to maximize stimulatory benefits without compromising vascular health.

Jožef and Podnar (3) examined the role of peripheral nerve ultrasonography as a complementary diagnostic tool in patients with different forms of polyneuropathy. In this retrospective study, ultrasound imaging provided non-invasive anatomical information that complemented conventional electrophysiological testing, particularly by revealing nerve enlargement patterns in demyelinating conditions such as chronic inflammatory demyelinating polyradiculoneuropathy. The results showed that nerve ultrasound yielded clinically relevant additional information in approximately half of the analyzed cases, either by supporting initial diagnostic hypotheses or by identifying focal neuropathies not detected through standard methods. These findings reinforce the role of ultrasonography as a sensitive and practical technique that improves diagnostic accuracy and aids in distinguishing between hereditary and acquired neuropathies.

Esterellas-Sánchez et al. (4) reported a prospective study evaluating the impact of left ventricular ejection fraction on the multimodal assessment of congestion in patients with acute heart failure. By integrating clinical examination, biochemical biomarkers such as NT-proBNP and CA125, and the Venous Excess Ultrasound Score (VExUS), the authors compared different heart failure phenotypes. Although patients with reduced ejection fraction presented higher biomarker levels and greater fluid accumulation, venous congestion grades assessed using the VExUS protocol were comparable across all groups. The findings demonstrate that VExUS constitutes an objective and reproducible ultrasound-based metric for quantifying venous congestion independently of systolic function, supporting its use in standardized diagnostic workflows and in guiding personalized decongestive therapy in hospital settings.

2.2. Ultrasound-Based Experimental and Preclinical Studies

Ricci et al. (2) investigated the effects of Low-Intensity Continuous Ultrasound (LICU) on three-dimensional PANC-1 pancreatic cancer spheroids as a preclinical model to assess ultrasound-induced viability and structural changes. Using artificial vision tools and confocal microscopy, the authors demonstrated that an excitation frequency of 3.5 MHz was particularly effective in inducing cellular death and reducing spheroid volume. A key finding of the study is that LICU treatment minimized spheroid disaggregation, a critical factor in reducing the risk of metastasis during therapeutic intervention. By proposing a precise methodological framework to optimize ultrasound parameters, this work highlights the potential of non-invasive, non-thermal ultrasonic stimulation as an alternative or complementary strategy to conventional oncological treatments and validates the relevance of three-dimensional tumor models for investigating mechanically induced cellular responses.

Pérez-Marín and Quevedo-Sánchez (8) conducted a comparative study of testicular echotexture and scrotal thermography in beef bulls before and after electroejaculation to optimize reproductive assessment protocols. The results showed a significant increase in testicular echogenicity following semen collection, accompanied by a reduction in scrotal surface temperature of approximately 3 °C, reflecting functional tissue responses to the procedure. The authors also provide methodological guidelines for ultrasound analysis, demonstrating that the evaluation of multiple small regions of interest within the testicular parenchyma yields more accurate and reproducible information than global assessments of the entire testis. Although no direct correlation was found between imaging-derived parameters and semen quality, the study emphasizes the complementary diagnostic value of ultrasonography and thermography for detecting subclinical abnormalities and testicular asymmetries, supporting their role in comprehensive veterinary reproductive evaluation.

2.3. Quantitative Ultrasound, Advanced Imaging, and Anatomical Assessments

Elvira et al. (5) proposed an advanced quantitative ultrasound framework aimed at improving biological tissue characterization beyond conventional B-scan imaging. The methodology integrates envelope statistics, modeled through the homodyned K-distribution, with spectral analysis to enable the simultaneous estimation of attenuation coefficients and scatterer clustering parameters. Validation was carried out using polyvinyl alcohol phantoms loaded with different particle concentrations designed to mimic the acoustic properties of real biological tissues. The results demonstrate that biparametric imaging significantly enhances the identification of tissue structures and pathological features compared to traditional single-parameter approaches, allowing a more detailed representation of tissue physical properties. This quantitative strategy represents a promising avenue for improving objective diagnosis and for supporting data-driven and artificial intelligence–assisted medical imaging workflows.

Martínez-Graullera et al. (6) investigated the optimization of volumetric ultrasound imaging using large-scale two-dimensional sparse arrays, with a particular focus on preclinical cerebrovascular studies in small-animal models. The authors addressed key technical challenges associated with conventional large 2D arrays, including tissue attenuation and beam steering limitations imposed by element size. To overcome these constraints, they proposed an aperture diversity–based strategy combined with nonlinear processing techniques, replacing conventional beam tilting with sparse aperture configurations. Through numerical simulations and tailored apodization schemes, the proposed approach achieved enhanced spatial resolution and image contrast while preserving high acquisition speed. The methodology effectively mitigated imaging artifacts and optimized the use of electronic channels, demonstrating its suitability for high-fidelity three-dimensional reconstructions in complex biological environments.

Miguel-Pérez et al. (7) conducted an extensive anatomical, ultrasound, and histological investigation of the palmaris longus muscle, a forearm structure characterized by high anatomical variability and clinical relevance in reconstructive surgery. The coordinated use of ultrasonography, anatomical dissections, and histological analysis across 72 human upper limbs allowed for a precise assessment of muscle presence, dimensions, and morphological variants. The results confirmed that ultrasound provides high accuracy in identifying anatomical variations or the absence of the muscle, which is critical for preoperative planning of tendon graft procedures. Additionally, the study detailed the spatial relationship between the palmaris longus tendon and the median nerve, helping to minimize surgical complications. Overall, the findings underscore the reliability of ultrasound as a non-invasive diagnostic tool and its value in optimizing surgical decision-making without compromising neurological function.

2.4. Review and Emerging Therapeutic Applications

Kleinknecht et al. (9) present a comprehensive review on focused ultrasound (FUS) and its emerging therapeutic applications in pediatric brain tumors, with particular emphasis on Low-Intensity Focused Ultrasound (LIFU) as a non-invasive treatment strategy. The article analyzes the potential of LIFU to address diffuse midline gliomas, a group of pediatric brain tumors historically associated with poor prognosis and limited therapeutic options. One of the key challenges highlighted is the presence of the blood–brain barrier (BBB), which restricts the delivery of most pharmacological agents to the central nervous system. In this context, LIFU emerges as a promising technique capable of transiently and locally disrupting this barrier, thereby enhancing drug penetration into tumor tissue.

The review summarizes preclinical evidence demonstrating that LIFU can significantly increase the efficacy of chemotherapy, immunotherapy, and radiotherapy by improving the delivery of therapeutic agents. Furthermore, the authors discuss ongoing early-phase clinical trials that assess the safety and feasibility of these approaches in pediatric patients, often employing advanced magnetic resonance imaging–guided systems. While preliminary results are encouraging, the review also identifies key technical and clinical challenges, including the complexity of pediatric skull anatomy and the need for standardized treatment protocols. Overall, this contribution establishes a critical reference framework that highlights the transformative potential of focused ultrasound technologies for improving the prognosis of children with aggressive brain tumors and outlines future directions for research and clinical translation in pediatric neuro-oncology.

3. Conclusions

This Special Issue, focused on advances in ultrasonic sensing and imaging for biomedical and clinical applications, provides a comprehensive and up-to-date snapshot of current research trends in the field. The nine contributions included in this collection reflect both methodological innovation and applied relevance, highlighting the continued evolution of diagnostic ultrasound as a key non-invasive tool in modern medicine. Collectively, the published articles report significant progress in areas such as advanced imaging strategies, including plane wave imaging and large-scale sparse arrays, quantitative ultrasound techniques for tissue characterization, and multimodal approaches combining envelope statistics, spectral analysis, and complementary diagnostic information. In addition, several contributions address clinically oriented studies, demonstrating the applicability of ultrasound in neuromuscular, cardiovascular, oncological, and neurological assessments, as well as its role in experimental and preclinical contexts. The thematic diversity of this Special Issue is consistent with the scope outlined in the “Overview of Published Articles” section and underscores the versatility of ultrasonic methods in different biomedical scenarios. From fundamental methodological developments to clinically driven investigations, these contributions collectively illustrate the growing maturity of ultrasonic sensing technologies and their capacity to provide reliable, quantitative, and clinically meaningful information.

In general, this Special Issue highlights the ongoing convergence of technological innovation, signal and image processing advances, and clinical application in the field of ultrasound. We believe that the nine contributions presented here offer valuable information for researchers, clinicians, and engineers working in ultrasonic sensing and imaging. Looking forward, the next great frontier in biomedical ultrasound will involve standardizing complex therapeutic protocols, overcoming anatomical barriers, and simultaneously leveraging quantitative multiparametric data to integrate artificial intelligence into personalized clinical workflows.

The Guest Editors would like to thank all authors for their high-quality contributions and their commitment throughout the review and revision process, which has been essential to the success of this Special Issue.