The adoption of multiscale approaches by the biomechanical community has caused a major improvement in quality in the mechanical characterization of soft tissues. The recent developments in elastography techniques are enabling in vivo and non-invasive quantification of tissues’ mechanical properties. Elastic changes in a tissue are associated with a broad spectrum of pathologies, which stems from the tissue microstructure, histology and biochemistry. This knowledge is combined with research evidence to provide a powerful diagnostic range of highly prevalent pathologies, from birth and labor disorders (prematurity, induction failures, etc.), to solid tumors (e.g., prostate, cervix, breast, melanoma) and liver fibrosis, just to name a few. This review aims to elucidate the potential of viscous and nonlinear elastic parameters as conceivable diagnostic mechanical biomarkers. First, by providing an insight into the classic role of soft tissue microstructure in linear elasticity; secondly, by understanding how viscosity and nonlinearity could enhance the current diagnosis in elastography; and finally, by compounding preliminary investigations of those elastography parameters within different technologies. In conclusion, evidence of the diagnostic capability of elastic parameters beyond linear stiffness is gaining momentum as a result of the technological and imaging developments in the field of biomechanics.

Purpose To explore the feasibility of transient elastography (TE) to quantify cervical stiffness changes during normal pregnancy and its spatial variability. Materials and Methods TE was used to quantify the cervical stiffness in four anatomical regions. 42 women between 17 and 43 years of age and at 6 – 41 weeks of gestation were studied. The stiffness was related to gestational age at the time of examination, interval from ultrasound examination to delivery and cervical length to evaluate the potential of TE to assess cervical ripening. In addition, a sensitivity analysis based on Cronbach’s alpha coefficient was carried out to assess the concordance between inter/intra-operator measurements. Results There were significant correlations between cervical stiffness measured in the four regions with gestational age and the remaining time for delivery. Results confirm stiffness variability within the cervix. No significant association was found between cervical length and stiffness in the four ROIs. Associations between gestational age and remaining time for delivery with cervical length present weaker correlations than with cervical stiffness. The external part of the cervix was significantly softer than the internal one, and these stiffness values vary significantly in the anterior compared to the posterior cervix. The measurements taken by the same and by two different observers for different regions in the cervix were reliable and reproducible. Conclusion It is feasible to objectively quantify the decrease of cervical stiffness correlated to gestational age. Transient elastography is a valuable promising tool to provide additional information on the process of cervical effacement to that obtained from digital examination and conventional ultrasound. Further studies are needed to assess the feasibility of the technique in obstetric clinical applications, such as prediction of preterm birth or success in labor induction. Ziel Machbarkeitsprüfung der transienten Elastografie (TE), um räumliche Veränderungen der Zervixsteifkeit (CS) zum Laufe einer Normalschwangerschaft zu erfassen Material und Methoden Die CS wurde mittels TE in 4 Regionen bei 40 Frauen im Alter von 17 bis 43 Jahren in der 6. – 41. Schwangerschaftswoche bestimmt. Die CS wurde mit dem Gestationsalter zum Untersuchungszeitpunkt, dem Intervall zwischen US-Untersuchung und Entbindung und die Zervixlänge korreliert, um das Potenzial der TE hinsichtlich der Zervixreife zu beurteilen. Danach wurde eine Sensitivitätsanalyse (α-Koeffizienten nach Cronbach) durchgeführt, um die Übereinstimmung der Inter-/Intra-Operator-Messungen zu bestimmen. Ergebnisse Die CS korrelierte in 4 Regionen mit dem Gestationsalter und der Zeit bis zur Entbindung signifikant. Die Ergebnisse bestätigen die Variabilität der Steifigkeit innerhalb der Zervix. Kein signifikanter Zusammenhang zwischen Zervixlänge und CS in den 4 ROIs. Gestationsalter und Zeit bis zur Entbindung zeigten eine schwächere Korrelation der Zervixlänge als mit der CS. Der äußere Bereich der Zervix war signifikant weicher als der innere Bereich, und diese CS-Werte variierten signifikant in der vorderen Zervix im Vergleich zur hinteren Zervix. Die Intra und Inter-Observervarianz der Messwerte in den 4 Regionen waren zuverlässig und reproduzierbar. Schlussfolgerung Man kann die sinkende Zervixsteifigkeit im Laufe des Gesationsalters bestimmen. Die TE ist wertvoll und vielversprechend. Sie liefert Zusatzinformationen zur Muttermundöffnung, die über die manuelle Untersuchung und den herkömmlichen US hinaus gehen. Weitere Untersuchungen sind nötig um den Einsatz der TE bei geburtshilflichen Anwendungen, wie Vorhersage von Frühgeburten und erfolgreicher Geburtseinleitung, zu bewerten.

Despite restrictions on their production and use, most of the population is still exposed to Persistent Organic Pollutants (POPs), including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs). These chemicals are thought to contribute to the aetiology of highly prevalent chronic conditions, such as cardiovascular diseases (CVDs), although current evidences are still controversial. To explore the potential contribution of historical POP exposure to 15-year pharmaceutical consumption in relation to CVD. This study is framed within GraMo adult cohort. Participants (n = 387) were recruited in two hospitals in Granada province, Southern Spain (2003-2004). Historical exposure to 5 OCPs and 3 non-dioxine-like PCBs was estimated by analysing adipose tissue concentrations at recruitment. Pharmaceutical consumption from recruitment until year 2017 was quantified by reviewing dispensation databases. Average consumption increase (ACI) in CVD medication was calculated by subtracting average consumption in 2002 to the average yearly consumption during follow-up. ACI was expressed as Defined Daily Dose (DDD)/year units. Data analyses were carried out using a multivariable multinomial logistic regression and weighted quantile sum regression (WQS), with ACI categorized in quartiles (Q) as the dependent variable. Concentrations of most pollutants showed a positive trend with the quartiles of ACI. Particularly, PCB-153 showed increasing and statistically significant odds ratios (ORs) for Q2 (OR: 1.27, 95% confidence interval (CI): 1.07-1.52), Q3 (OR: 1.49, 95 %CI: 1.17-1.88) and Q4 (OR: 1.42, 95 %CI: 1.13-1.78) vs Q1. Similarly, beta-hexachlorocyclohexane (β-HCH) also showed increasing ORs, that reached statistical significance in Q4 (OR: 1.36, 95 %CI: 1.06-1.74) vs Q1. These findings were corroborated by WQS analyses, that revealed a significant mixture effect, predominantly accounted for by PCB-153 and β-HCH. Our results suggest that long-term POP exposure might represent a modifiable risk factor for CVD. These findings are relevant for public health campaigns and management, since pharmaceutical consumption is considered an indicator of both morbidity and health expenditure.

A novel torsional wave sensor designed to characterize mechanical properties of soft tissues is presented in this work. Elastography is a widely used technique since the 1990s to map tissue stiffness. Moreover, quantitative elastography uses the velocity of shear waves to achieve the shear stiffness. This technique exhibits significant limitations caused by the difficulty of the separation between longitudinal and shear waves and the pressure applied while measuring. To overcome these drawbacks, the proposed torsional wave sensor can isolate a pure shear wave, avoiding the possibility of multiple wave interference. It comprises a rotational actuator disk and a piezoceramic receiver ring circumferentially aligned. Both allow the transmission of shear waves that interact with the tissue before being received. Experimental tests are performed using tissue mimicking phantoms and cervical tissues. One contribution is a sensor sensitivity study that has been conducted to evaluate the robustness of the new proposed torsional wave elastography (TWE) technique. The variables object of the study are both the applied pressure and the angle of incidence sensor–phantom. The other contribution consists of a cervical tissue characterization. To this end, three rheological models have fit the experimental data and a static independent testing method has been performed. The proposed methodology permits the reconstruction of the mechanical constants from the propagated shear wave, providing a proof of principle and warranting further studies to confirm the validity of the results.

The objective of this study was to evaluate which hyperelastic model could best describe the non-linear mechanical behavior of the cornea, in order to characterize the capability of the non-linear model parameters to discriminate structural changes in a damaged cornea. Porcine corneas were used, establishing two different groups: control (non-treated) and NaOH-treated (damaged) corneas (n = 8). NaOH causes a chemical burn to the corneal tissue, simulating a disease associated to structural damage of the stromal layer. Quasi-static uniaxial tensile tests were performed in nasal-temporal direction immediately after preparing corneal strips from the two groups. Three non-linear hyperelastic models (i.e. Hamilton-Zabolotskaya model, Ogden model and Mooney-Rivlin model) were fitted to the stress–strain curves obtained in the tensile tests and statistically compared. The corneas from the two groups showed a non-linear mechanical behavior that was best described by the Hamilton-Zabolotskaya model, obtaining the highest coefficient of determination (R² > 0.95). Moreover, Hamilton-Zabolotskaya model showed the highest discriminative capability of the non-linear model parameter (Parameter A) for the tissue structural changes between the two sample groups (p = 0.0005). The present work determines the best hyperelastic model with the highest discriminative capability in description of the non-linear mechanical behavior of the cornea.