Mechanical Index Research Articles

We aimed to assess the prognostic performance of different indexes of oxygenation, respiratory mechanics and ventilation intensity in predicting 90-day mortality, and to estimate their independent associations, in a "real world" observational cohort of acute respiratory distress syndrome (ARDS) patients on ICU mortality. This is a secondary analysis of the "Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure" (LUNG SAFE), an international prospective cohort study of patients with severe respiratory failure involving 459 Intensive Care Units (ICUs) from 50 countries. We evaluated prognostic performance of oxygenation (PaO2/FiO2), respiratory mechanics (normalized elastance) and ventilation intensity (plateau pressure, driving pressure (DP); 4DP+RR and mechanical power (MP)) measured on day 1 of controlled mechanical ventilation in ARDS patients, with respect to ICU mortality within 90 days of admission. For each parameter, associations with mortality were assessed using logistic regression models, estimating effect sizes (odds ratios, OR with 95% confidence interval, CI), model discrimination (area under the ROC curve), calibration, and overall predictive accuracy. Among 2813 early ARDS patients, 516 (18.3%) met inclusion criteria: mean age 60 years (±16), 61% male. Normalized elastance, plateau, DP and 4DP+RR were significantly associated with mortality, with adjusted ORs ranging from 1.02 (95%CI 1.01-1.03) for 4DP+RR to 1.48 (95%CI 1.15-1.95) for normalized elastance. These parameters showed higher predictive accuracy for mortality compared to PaO2/FiO2 and MP. MP showed a U-shaped relationship with mortality abut it was not significantly associated with it. Its predictive accuracy decreased after accounting for positive end-expiratory pressure (PEEP) and dynamic resistance, with PEEP also demonstrating a U-shaped association with mortality. Normalized elastance, DP and 4DP+RR-measured at day1 of ARDS-were best predictors of ICU mortality, and outperformed oxygenation and MP. DP showed the best balance between predictive accuracy and clinical simplicity. These results reinforce the importance of focusing on DP and 4DP+RR as key metrics to guide lung-protective strategies and ARDS severity classification.

Background: Stackable metallic or magnetic multi-template systems translate a prosthetically (facially) driven plan into each surgical phase of full-arch rehabilitation. Our objective was to map and critically describe the clinical applications, accuracy, and short-term outcomes of stackable/sequential guides and to illustrate the operational steps with a standardized magnet-retained case. Methods: Following a prospectively registered protocol (OSF, June 2025), we performed a scoping review in accordance with and PRISMA guidance. PubMed, Scopus and Embase were searched to 26 June 2025 for primary human studies using stackable or sequential static guides to place ≥4 implants per arch with immediate (≤72 h) loading. Duplicate-independent screening and data-charting captured guide design, planning platform, surgical accuracy, implant survival, prosthetic outcomes and patient-reported measures. A single non-analytic clinical vignette was included solely to illustrate the facially driven stackable workflow. Results: Eight studies (five countries, 2021–2025) encompassing 351 implants and one additional clinical case met the inclusion criteria. Mechanical indexing predominated (7/9 protocols); only two papers, including our case, used magnetic retention. Mean coronal and angular deviations, reported in two cohorts, were 0.95 mm/2.8° and 0.87 mm/2.67°, respectively—well within accepted thresholds for full-arch guided surgery. Immediate loading was achieved in 100% of arches; cumulative implant survival was 97.1% after 3–12 months. Patient-reported satisfaction exceeded 90 mm on VAS scales when measured. Our case demonstrated 0.90 mm/2.95° accuracy, 100% implant stability ≥ 35 N cm and uneventful provisionalisation at 12 weeks. Conclusions: Early clinical reports show clinically acceptable accuracy and high short-term survival with streamlined workflow. However, evidence remains heterogeneous and short-term; prospective multi-centre studies with standardized accuracy metrics, ≥3-year follow-up, validated PROMs, and cost-effectiveness analyses are still needed.

Introduction: The pathophysiological mechanisms of left ventricular diastolic dysfunction (LVDD) involve impaired relaxation and restricted filling of the left ventricle (LV). Both mechanical and metabolic impairments are expected to occur in the myocardium in LVDD. The mechano-metabolic interplay underlying LVDD-related remodeling remains understudied. Understanding this interplay is especially important for identifying sex-specific susceptibilities to LVDD. In this study, we present an approach to assess key biomechanical and energetic differences through ex-vivo benchtop assays of cardiac mechanoenergetics. Methods: M ale (n=8) and f emale (n=8) 8-10-week-old wild-type mice were used. The LV free wall (LVFW) was harvested from the mice and immediately placed in PBS at 1°C. Mechanical testing was performed to measure passive stiffness and viscoelastic relaxation time (M and F; n = 4 each). The ex-vivo tissue was subjected to equibiaxial stretch at 1% per second and allowed to relax for a period of 10 minutes. Energetics were quantified by homogenizing 10 mg of LVFW tissue using buffer A and analyzing the supernatant ATP concentration (M and F; n = 4 each). Results: Sex differences were evident in both passive mechanical and metabolic indices of LVFW tissues. Stress-strain analysis revealed significantly higher total stress in male mice compared to females at various stages of equibiaxial stretching (Fig. 1A). However, a very similar viscoelastic relaxation behavior was observed between male and female (Fig. 1B). Despite the presence of increased LVFW stiffness in the male mice (Fig. 1C), consistent relaxation time constants were maintained between all mice, evidenced via similar standard deviation (Fig. 1D). Energetic analysis showed a significant difference between male and female mice (M vs. F: 1.75 ± 0.58 vs. 0.48 ± 0.15 nmol) (Fig. 1E). Conclusion: This study provided ex vivo insights into sex-specific mechano-metabolic markers of the myocardial tissue in mice. Our findings demonstrate that male mice possess stiffer myocardial tissue and higher basal ATP concentrations compared to females, despite similar stress relaxation kinetics. Future work using this approach will investigate the mechano-metabolic remodeling in LVDD that accounts for sex-based physiological differences in myocardial stiffening and metabolic impairments.

The left atrium (LA) undergoes significant structural and functional alterations in patients with mitral stenosis (MS) due to increased afterload and pressure overload. percutaneous transvenous mitral commissurotomy (PTMC) is the preferred treatment for severe MS, yet its long-term impact on LA mechanical function remains poorly understood. This study evaluates the intermediate and long-term effects of PTMC on LA function in patients with severe MS and normal sinus rhythm. This prospective, non-randomized, observational study included 53 patients (mean age: 33.3 ± 6.44 years) with severe symptomatic MS who underwent successful PTMC. LA volumes and mechanical function indices, including LA stroke volume (VS), LA ejection fraction (LAEF), LA expansion index (LAEI), LA passive emptying fraction (LAPEF), and LA active emptying fraction (LAAEF), were assessed using two-dimensional echocardiography at baseline, immediately post-PTMC, and at 1, 3, and 5 years. Generalized estimating equations (GEE) were used to analyse temporal trends in LA function. LA reservoir (LAEF, LAEI) and conduit function (LAPEF) showed significant improvement up to 1year post-PTMC, followed by a plateau at 3 and 5 years. LA pump function (LAAEF) demonstrated a delayed but sustained improvement up to 3 years, with no further changes thereafter. Phasic LA volumes (Vmax, Vmin, Vp) decreased significantly up to 1 year, stabilizing over the long term. PTMC leads to significant improvement in LA functional indices, particularly within the first year, followed by stabilization in the long term. These findings suggest that while PTMC induces favourable LA remodeling, certain structural changes may be irreversible. Further research is needed to assess the impact of these functional improvements on long-term clinical outcomes, including AF and mortality.

This study investigates low-intensity ultrasound (LIUS) as a noninvasive method for stimulating and regenerating hair follicles in androgenetic alopecia (AGA), with a focus on optimizing parameters for both safety and efficacy. Finite element method (FEM) simulations in COMSOL Multiphysics® modeled acoustic pressure fields and calculated the mechanical index (MI) in a multilayer skin-follicle structure. Simulations were conducted at frequencies from 20 kHz to 1 MHz with a constant intensity of 0.1 W/cm2. MI profiles helped identify parameters for stable and inertial cavitation. In vivo experiments were conducted using C57BL/6 male mice with DHT-induced alopecia, which were subjected to ultrasound sonication at 150 kHz and 1 MHz at various intensities. Skin temperature was monitored during treatment, and hair regrowth was assessed. Simulations revealed frequency-dependent beam narrowing and pressure changes, with peak pressures increasing from 81 kPa at 20 kHz to 145 kPa at 1 MHz. The 150 kHz frequency showed intrafollicular RMS pressures nearing cavitation thresholds. Dermal MI profiles at 150 kHz peaked at ∼0.95 at a depth of ∼0.3 cm, while at 1 MHz, MI increased significantly with increasing intensity. In vivo treatments under optimized conditions yielded safe temperature increases and enhanced hair regrowth compared to controls. Selecting appropriate frequency and intensity can optimize MI for beneficial mechanical effects while preventing unsafe cavitation. Future studies will follow up on in vivo results and conduct clinical trials to confirm therapeutic efficacy and safety.

The mechanical strength and integrity of bone are greatly influenced by age, sex, and underlying pathological conditions. Common methods, such as 3-point and 4-point bending tests in murine models, have been used to assess whole-bone strength. This work follows up on our recent systematic review, which highlights significant variability in reported mechanical indices for point-bending. This study used finite element analysis (FEA) simulations on a mouse femur to reveal that angular malalignment in point-bending setups can lead to up to 72% differences in modulus values. To address these inconsistencies, we developed a contactless bending mechanical testing system, which induces bending without direct-contact pins on the bone, eliminating variability associated with traditional bending tests. Validated through digital image correlation (DIC), the contactless system achieved mechanical properties comparable to the point-bending literature, with significantly reduced coefficients of variance by 32% for failure load, 40% for modulus, and 47% for failure stress. Our results indicate that the contactless bending system enhances precision and reproducibility, offering a robust alternative to current point-bend methods for reliable bone mechanical testing in musculoskeletal research. Further validation will help establish this approach as a new testing option in the field.

BackgroundCarotid body (CB) ablation can reduce sympathetic activity and blood pressure but impair the body's ability to regulate hypoxia. This study explores the efficacy and safety of using microbubble contrast agents combined with high mechanical index diagnostic ultrasound irradiation (HMIUI) to modulate CB activity in treatment of hypertension in rabbits.MethodsObese hypertensive rabbits were randomly divided into three groups: unilateral intervention group (UIG, n = 6), bilateral intervention group (BIG, n = 10), and control group (CG, n = 7). Rabbits received intravenous injection of sulfur hexafluoride microbubbles for 15 min, and irradiation at the carotid bifurcation by continuous diagnostic ultrasound FLASH mode simultaneously. Blood pressure (BP), hypoxic ventilatory response (HVR), peripheral chemoreceptor sensitivity (PCS), and baroreceptor sensitivity (BRS) were measured, and values were compared with before the intervention and 1 month after. In addition, pathology and electron microscopy were used to observe the histological and ultrastructural changes of CB.ResultsIn both UIG and BIG groups, systolic and diastolic blood pressure significantly decreased compared to pre-intervention (p < 0.05). Compared to the control group, the BIG group showed a decrease of 10 mmHg exceeding in systolic and diastolic blood pressures. HVR and PCS decreased by nearly 50% from pre-intervention. Changes in CB injury and fibrous tissue proliferation were found by Histological. TUNEL assay showed varying degrees of apoptosis in the treated CB, and immunofluorescence confirmed the reducing expression of type I and II cells.ConclusionsUltrasound microbubbles combined with HMIUI effectively modulate CB function and reduce blood pressure in an obese hypertensive rabbit model in the short term.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12938-025-01451-z.

Compact programmable transmit scheme for contrast imaging using nonlinear difference-frequency ultrasound signals.

Ultrasound is widely regarded as a safe imaging modality; however, emerging ultrasound-based techniques-such as shear wave elastography and contrast-enhanced ultrasound-operate with varying acoustic output parameters that may approach or exceed traditional diagnostic limits. As these technologies are increasingly integrated into human research studies, Institutional Review Boards (IRBs) face the challenge of assessing their safety profiles. This article provides a comprehensive, organ-, and modality-specific review of current guidelines for ultrasound exposure parameters, including the mechanical index (MI), thermal index (TI), and acoustic intensity. Special emphasis is placed on less conventional applications, such as elastography in the eye and fetal applications, and on understanding the thermal and mechanical bioeffects associated with emerging techniques. We clarify distinctions in safety oversight and provide practical guidance to IRB members tasked with evaluating diagnostic ultrasound research protocols. Our aim is to facilitate informed decision-making and ensure patient safety while enabling innovation in ultrasound-based clinical research.

Establishment of gluten structural observation methods and constitutive mechanical property index systems for two types of cooked white-salted udon noodles

Experimental Investigation of Physical, Mechanical and Wear Index in Polymer Matrix Composites for Potential Structural Applications

Abstract Welding procedures in high-hardenability steels often lead to adverse microstructural changes, resulting in a sharp decline in mechanical properties within the weld metal zone and the heat-affected zone. Due to the limited tensile strength Rm of commercially available welding consumables, which in many cases do not exceed 1000 MPa, the reduction in mechanical properties can reach up to 60% in steels with hardness levels of 600 HBW. Martensitic boron steels are among the materials with the highest mechanical strength indices and are used both in components exposed to abrasive wear and in ballistic protection. Consequently, welding techniques often produce joint zones with functional properties (e.g., ballistic resistance or resistance to abrasive wear) that fail to meet the required performance of the base material. Only through advanced welding techniques, the use of high-quality fillers, and subsequent heat treatment can the highest mechanical strength indices be achieved in the weld zone. This article presents the results of tests on the resistance of 450 HBW grade steel welded joints to dynamic loads. The research demonstrated that, when subjected to firing using intermediate 7.62 × 39 mm ammunition (43 model, PS bullet) from a distance of 10 m, a minimum plate thickness of 5 mm ensures material continuity across all characteristic zones of the welded joint.

ITRUSST consensus on biophysical safety for transcranial ultrasound stimulation.

To investigate the effects of irrational irrigation on tomato yield and quality, and the effects of different irrigation regimes on tomato biotexture mechanics, irrigation experiments were carried out in greenhouses, focusing on the two factors of irrigation frequency and irrigation quantity. Results showed that when the irrigation regime was A1 (150% ETc, 1 time/interval 1 day) or E3 (50% ETc, 1 time/interval 13 days), the fruit cracking rate was up to 69.53%; when the irrigation regime was C3 (50% ETc, 1 time/interval 5 days), the cracking rate was as low as 8.75%. Irrigation regime also had significant effects on the mechanical indicators. Meanwhile, the irrigation regime significantly affected the content and status of pectin in the cell wall but had no significant effect on hemicellulose and cellulose. With a short irrigation cycle and large irrigation amount, WSP (Water-soluble Fraction) increased, CSP (CDTA-soluble Fraction) and NSP (Na2CO3-soluble Fraction) decreased, and the fruit was easy to crack. The crystallinity, supporting power, and cracking resistance of pectin polysaccharides in C were strong, while those in A, B, D, and E were opposite. Research showed that the cracking of tomato induced by irrigation was due to the change of the composition and structure of the polysaccharide in the cell wall. This study can provide a reasonable irrigation regime such as C3 treatment for fruit farmers, which has the effect of both saving water and improving quality. The screened mechanical phenotypic indexes are conducive to reverse localization of crack control genes and enhancing tomato crack resistance breeding level.

Abstract Background: Patients with advanced pancreatic ductal adenocarcinoma (PDAC) have limited therapeutic treatment options, largely due to the tumor’s dense stromal microenvironment, which hinders drug penetration and significantly reduces the effectiveness of systemic chemotherapy (Kane et al., 2020). Acoustic cluster therapy (ACT) is an investigational ultrasound-mediated drug delivery platform that combines a proprietary intravenous formulation (PS101) with focused ultrasound to enhance chemotherapeutic delivery. In ACT, PS101—comprised of microclusters of perfluorobutane microbubbles and perfluoromethylcyclopentane microdroplets —is injected intravenously and insonated over the tumor site using diagnostic-frequency ultrasound (∼2 MHz). Upon reaching the tumor vasculature, ultrasound activation triggers microcluster expansion into transient ACT bubbles (∼22 μm average diameter), which deposit in &amp;lt;2% of the local microvasculature. A subsequent enhancement ultrasound pulse (0.5 MHz, low mechanical index) applied for 5 minutes induces oscillations of these ACT bubbles, increasing vascular permeability and promoting transvascular and stromal penetration of co-administered chemotherapy. In vivo non-clinical evaluation of ACT has shown a marked synergistic anti-cancer effect with a range of chemotherapy agents and tumor xenograft models including pancreatic cancer. In many of these models, the differential effect levels observed using ACT with chemotherapy versus chemotherapy alone have been substantial (Ng, 2022). Han et al. (2024) recently demonstrated the value of sonochemotherapy in patients with advanced PDAC. Methods: This is a phase 2, multicenter, open-label, single-arm clinical trial (NCT06850623) employing a Simon’s two-stage design (n=25) to evaluate the safety and efficacy of ACT in combination with standard-of-care mFOLFIRINOX chemotherapy in treatment-naïve patients with borderline resectable or unresectable locally advanced pancreatic cancer (LAPC). The primary objective is to evaluate the efficacy of ACT with mFOLFIRINOX, as assessed by overall response rate according to Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1. Secondary objectives include the evaluation of safety and tolerability; anti-tumor activity; the proportion of participants who become eligible for tumor resection following treatment; and overall survival. Key eligibility include 1) histologically or cytologically proven diagnosis of PDAC not deemed suitable for primary curative surgery and have radiographic and pathological disease consistent with inoperable LAPC or borderline resectable pancreatic cancer 2) no previous anti-cancer treatment for pancreatic cancer, 3) tumor localizable with ultrasound without contrast with a maximum distance of 14 cm between the furthest tumor margin and the probe as measured by ultrasound and 4) suitable to receive treatment with mFOLFIRINOX. Enrollment began in June 2025. Citation Format: Erin Pierce, Matt Siegel, Katie Morgan, S. Danielle. Legrand, Ragnar Bendiksen, Nicola Little, Amir Snapir, Erkut Borazanci. A phase 2 study to investigate the efficacy and safety of acoustic cluster therapy with modified FOLFIRINOX in patients with locally advanced pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research—Emerging Science Driving Transformative Solutions; Boston, MA; 2025 Sep 28-Oct 1; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl_3):Abstract nr A068.

Mechanical solid stress plays a pivotal role in tumor progression and therapeutic response. Elevated solid stress compresses intratumoral blood vessels, leading to hypoperfusion, and hypoxia, which impair oxygen and drug delivery. These conditions hinder the efficacy of drugs and promote tumor progression and treatment resistance compromising therapeutic outcomes. To enhance treatment efficacy, mechanotherapeutics and ultrasound sonopermeation have been developed to improve tumor perfusion and drug delivery. Mechanotherapy aims to reduce tumor stiffness and mechanical stress within tumors to normal levels leading to decompression of vessels while simultaneously improving perfusion. On the other hand, ultrasound sonopermeation strategy focuses on increasing non-invasively and transiently tumor vessel wall permeability to boost perfusion and thus, improve drug delivery. Within this framework and aiming to replicate published experimental data in silico, we developed a mathematical model designed to derive optimal conditions for the combined use of mechanotherapeutics and sonopermeation, with the goal of optimizing efficacy of nano-immunotherapy. The model incorporates complex interactions among diverse components that are crucial in the multifaceted process of tumor progression. These components encompass a variety of cell populations in tumor, such as tumor cells and immune cells, as well as components of the tumor vasculature including endothelial cells, angiopoietins, and the vascular endothelial growth factor. Seeking initial model verification, we carried out validation of model predictions with published experimental data, wherein a strong correlation was observed between the model predictions and the actual experimental measurements of critical parameters, which are essential to reinforce the overall accuracy of the mathematical framework employed. In addition, a parametric analysis was performed with primary objective to investigate the impact of various critical parameters that influence sonopermeation. Model predictions showed maximal drug delivery and tumor volume reduction at an acoustic pressure range of 0.24–0.27 MPa and mechanical index of 0.17, consistent with values used in clinical trials following sonopermeation treatment. The analysis provided optimal guidelines for the use of sonopermeation in conjunction with mechanotherapy, that contribute to identify optimal conditions for sonopermeation.

In metabolic syndrome, cardiomyocyte changes induced by metabolic and proinflammatory factors impair repolarization and exacerbate the heterogeneity of the transmural dispersion of repolarization, and this is proarrhythmogenic. Limited data in the literature on the capabilities of speckle tracking echocardiography for assessing proarrhythmogenicity in metabolic syndrome exists. 71 patients with newly diagnosed metabolic syndrome, aged 35–55 years, were studied. Ischemic heart disease was excluded in all patients with stress test cycle ergometry, CT-angiography or selective coronary angiography. All patients underwent a 48-h Holter ECG recording. Based on the latter, they were divided into two groups: 38 patients (53.5%) with a high arrhythmogenic load (supraventricular or ventricular tachycardia, atrial fibrillation/flutter, ventricular extrasystoles over 10%, frequent supraventricular extrasystoles > 500/24 h are included); and 33 patients (46.5%) with low arrhythmogenic load (no significant rhythm disturbances are included). Echocardiography was performed with a GE Vivid T9 emphasizing global longitudinal strain, mechanical dispersion index and left atrium strains. Statistically significant differences in the global longitudinal strain, mechanical dispersion index, and left atrium strain were found between the group with low arrhythmogenicity and the group with high arrhythmogenicity (p < 0.0001). The index of mechanical dispersion has the most optimal sensitivity and specificity of all investigated echocardiographic markers. These results support the mechanical dispersion index as an additional tool for assessing proarrhythmogenicity in metabolic syndrome.

Influence of Microbubble Properties and Carrier Frequency on Ultrasound Cavitation-Induced Flow Augmentation.

Expansive soils, characterised by significant hydrophilicity and water swelling properties, frequently cause foundation expansion, cracking, and reduced bearing capacity and strength. This study used microbially induced calcium carbonate precipitation (MICP) technology to improve expansive soils’ swelling and strength characteristics. The expansive soil was treated by adjusting the cementing solution concentration (0.5–1.5 mol/l). The physical and mechanical indices and fracture development of soil samples before and after improvement were compared with evaluate the improvement effect. Meanwhile, the action mechanism of MICP technology was explored from a microscopic point of view. It was found that 1 mol/l cementing solution concentration had the most significant effect on the swelling inhibition of expansive soil. Under this condition, the soil samples’ unconfined compressive strength, shear strength, and calcium carbonate (CaCO3) generation reached the highest values. Moreover, its fracture development was also significantly improved. Microanalysis showed that calcium carbonate crystals generated by the MICP technique formed attachments on the surface of soil particles, effectively filling the soil pores and cementing the soil particles. The large pores were filled into small pores, improving the expanded soil microstructure. This study provides an effective solution for improving expansive soils with important engineering application value significance.

The mechanical properties of cells are crucial for elucidating various physiological and pathological processes. Cells are found to exhibit a universal power-law rheological behavior at low frequencies. Although, they behave in a different manner at high-frequency regimes, which leaves the transition region largely unexplored. Here, we investigate single-cell rheological behaviors across different cell types (primary hematopoietic stem cells, the hippocampal neuronal cell line, and human dental pulp stem cells) by atomic force microscopy-microrheology method, uncovering a universal two-stage power-law rheological behavior. Cells behave fluid-like at shorter timescales and solid-like at longer scales. To characterize the transition region between these stages, we introduce a timescale parameter, termed "transition time." Notably, for all the cell types under study, we find that the transition time decreases with increasing elastic moduli and increases for larger power-law exponent. Furthermore, based on our previous self-similar hierarchical model, we propose a theoretical method to determine the upper and lower bounds of the transition time range. Our experimental results exhibit an excellent agreement, consistently falling within the predicted theoretical limits. Furthermore, we present six crucial mechanical indices that depict both the dynamic and static mechanical properties of single cells. These parameters can effectively differentiate cell types and provide a comprehensive perspective on the mechanical states of cells. Our study may offer new insights into the viscoelastic transformation of cells from fluid-like to solid-like behaviors and highlights the mechanisms underlying various timescales during biomechanical processes.