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Background: Severity of liver cirrhosis plays an important role in determining the safe extents of hepatectomy in patients with hepatocellular carcinoma (HCC). The aim of this study was to investigate whether direct liver stiffness measurement can help surgeons to evaluate the severity of liver cirrhosis in HCC patients., Methods: Overall, 119 HCC patients who underwent open hepatectomy were retrospectively studied. The severity of liver cirrhosis was histologically staged using the Laennec staging system. Direct liver stiffness measurement was performed during operation using a sclerometer device named LX-C Shaw hardmeter, and its efficacy in assessing the severity of liver cirrhosis was compared with that of transient elastography (TE) and cirrhotic severity scoring (CSS) previously proposed by our team., Results: Liver stiffness measured by LX-C Shaw hardmeter was significantly correlated with the severity of liver cirrhosis. Spearman correlation coefficients for the correlation between the severity of liver cirrhosis and direct liver stiffness measurement, TE, and CSS were 0.751, 0.454, and 0.705, respectively (all P < 0.001). The areas under the receiver operating characteristic curves (AUCs) of direct liver stiffness measurement were 0.891 for moderate cirrhosis and 0.944 for severe cirrhosis and superior to those of TE (0.735 and 0.776, respectively) and CSS (0.888 and 0.905, respectively)., Conclusions: Direct liver stiffness measurement is a useful method in evaluating the severity of liver cirrhosis in HCC patients.

Postpartum haemorrhage (PPH) is a potentially life-threatening condition. Women undergoing caesarean section (CS) are at particular risk, and improvements in the management of PPH during CS are required. We investigated the use of a tissue hardness metre to quantify uterine contractions during CS with a view to its application for obstetric bleeding management. Fifty pregnant women at term who underwent elective CS were recruited. Using a tissue hardness metre, we measured uterine hardness twice during CS: after placental removal and before peritoneum closure. Each measurement was conducted at two standardised points: fundus and corpus uteri. Concurrently, obstetricians subjectively graded uterine contractions as weak, medium, or strong. The hardness metre accurately quantified the degree of uterine contraction assessed by the obstetricians, and could be an effective clinical tool for early recognition of intra-operative massive bleeding. IMPACT STATEMENT What is already known on this subject? Maintaining adequate uterine contraction leads to prevention of excessive blood loss, which decreases the incidence and severity of PPH. However, the assessment of uterine contraction is currently judged by obstetricians, who manually and subjectively evaluate uterine contraction according to uterine hardness. Therefore, uterine atony remains a clinical diagnosis without a universal definition. What do the results of this study add? The present study investigated the use of a tissue hardness metre to quantify uterine contractions during CS with a view to its application for obstetric bleeding management. The hardness metre was able to quantify the degree of uterine contraction perceived by obstetricians. Quantifying uterine hardness during CS correlates with the amount of intra-operative bleeding and is useful for early recognition of massive haemorrhage. What are the implications of these findings for clinical practice and/or further research? To improve the management of atonic PPH and avoid serious complications, the tissue hardness metre should be considered as a potential clinical tool during CS.

This study proposes a skin analysis device using a truncate hollow cone (THC) probe for measuring both transepidermal water loss (TEWL) and skin hardness. Because skin health is closely related to the epidermal barrier function and skin mechanical property, it is important to measure their biophysical indicators at the same time, to understand skin conditions and diagnose skin disorders such as atopic dermatitis and systemic sclerosis. Previous skin analyzers, however, required different probes with different protocols for each biophysical indicators, which makes the measurement inconvenient and increases the measurement uncertainty. The present device consists of a THC probe equipped with humidity and force sensors, and an actuator that simultaneously measure both TEWL and skin hardness which indicate the integrity of the epidermal barrier function and the skin mechanical property, respectively. Using artificial reference skins, the prototype device showed the TEWL with a sensitivity and linearity of 0.011 (%/s)/(g/m 2 /h) and 99.5%, and the hardness with 0.075 N/(Shore 00) and 97.6%, respectively, which are within the appropriate range for the properties of human skin. The on-body measurement of five subjects showed that the proposed device could measure both the TEWL and skin hardness without any crosstalk from each other. The proposed device has great potential for in-depth analysis of the health status of the skin which could indicate various skin diseases.

Introduction: For developing a hardness multipoint measurement system for understanding hardness distribution on biological body surfaces, we investigated the spring strength of the contact portion main axis of a biological tissue hardness meter (product name: PEK)., Methods: We measured the hardness of three-layered sheets of six types of gel sheets (90 mm × 60 mm × 6 mm) constituting the acupuncture practice pads, with PEK measurements of 1.96 N, 2.94 N, 3.92 N, 4.90 N, 5.88 N, 6.86 N, 7.84 N, 8.82 N, and 9.81 N of the main axis spring strength. We obtained measurements 10 times for the gel sheets and simultaneously measured the load using a digital scale. We measured the hardness distribution of induration embedded and breast cancer palpation models, with a main axis with 1.96 N, 4.90 N, and 9.81 N spring strengths, to create a two-dimensional Contour Fill Chart., Results: Using 4.90 N spring strength, we could obtain measurement loads of ≤3.0 N, and the mean hardness was 5.14 mm. This was close to the median of the total measurement range 0.0-10.0 mm, making the measurement range the largest for this spring strength. We could image the induration of the induration-embedded model regardless of the spring strength., Conclusion: Overall, 4.90 N spring strength was best suited for imaging cancer in the breast cancer palpation model., (Copyright © 2017. Published by Elsevier B.V.)

Background: A new electro-mechanical device for measuring the lateral stiffness of the skin is now available. It basically allows to recording the forces that the skin opposes to a lateral displacement (1-2 mm) of a pinching type movement. Preliminary assays of this device to various skin sites and an artificial substrate aimed at defining its major characteristics (sensitivity, reproducibility, variations according to skin site)., Methods: The calibration of the device (Khelometer ® ) and assessment of its reproducibility were carried out through the use of elastometer substrates of various stiffness's. The device was then used, in vivo, at different skin sites (scalp, inner and outer forearms, cheeks) of 213 healthy Japanese women of various ages. The short-time effect of a hydrating regimen (7% glycerol) was recorded on the outer forearm., Results: This new device offers an appreciable reproducibility in vitro and in vivo (coefficient of variation of 2-4% and 5-14%, respectively). Unlike other biophysical methods, the Khelometer ® can be easily applied onto the human scalp that shows a higher stiffness than the two other skin sites, increasing with age and presence of alopecia. In all the three studied skin sites, the impact of age leads to significantly higher lateral skin stiffness (LSS, expressed as N/mm) values. The latter were found significantly different between the two sides of the forearms where the outer (sun-exposed) side showed statistically slightly higher LSS, than the unexposed inner side. LSS values found on cheeks (≈0.5 N/mm) were about four times lower than those of the scalp (≈2 N/mm) and about half those of forearms (≈1 N/mm). The effect of a 7% glycerol based formula was recorded 20 min post application onto the forearm, leading to a slight drop in LSS (approx. 15%) as compared to a vehicle-applied skin site., Conclusion: These preliminary studies clearly indicate that this new device, applicable to any skin site, offers appreciable assets such as sensitivity and reproducibility. Accordingly, it appears as a new approach in the non-invasive biophysical measurements of the skin surface, in both advanced and applied research investigations., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Noninvasive measurement of tissue viscoelastic properties is gaining more attention for screening and diagnostic purposes. Recently, measuring dynamic response of tissue under a constant force has been studied for estimation of tissue viscoelastic properties in terms of retardation times. The essential part of such a test is an instrument that is capable of creating a controlled axial force and is suitable for clinical applications. Such a device should be lightweight, portable, and easy to use for patient studies to capture tissue dynamics under external stress. In this paper, we present the design of an automated compression device for studying the creep response of materials with tissue-like behaviors. The device can be used to apply a ramp-and-hold force excitation for a predetermined duration of time and it houses an ultrasound probe for monitoring the creep response of the underlying tissue. To validate the performance of the device, several creep tests were performed on tissue-mimicking phantoms, and the results were compared against those from a commercial mechanical testing instrument. Using a second-order Kelvin-Voigt model and surface measurement of the forces and displacements, retardation times T 1 and T 2 were estimated from each test. These tests showed strong agreement between our automated compression device and the commercial mechanical testing system, with an average relative error of 2.9% and 12.4%, for T 1 and T 2 , respectively. Also, we present the application of compression device to measure local retardation times for four different phantoms with different size and stiffness.

Background: One of the key strategies for anti-ageing in the cosmetics industry today is to target the structural changes responsible for ptosis of the skin, given its impact on age perception. Several objective and non-invasive methods are available to characterise the biomechanical properties of the skin, which are operator-dependent, involving skin contact and providing single-dimensional numerical descriptions of skin behaviour. The research introduces the DynaSKIN, a device using non-contact mechanical pressure in combination with fringe projection to quantify and visualise the skin response in 3-dimensions. We examine the age correlation of the measurements, how they compare with the Cutometer ® , and measure skin dynamics following application of a skincare regimen containing established anti-ageing ingredients., Methods: DynaSKIN and Cutometer ® measurements were made on the cheek of 80 Caucasian women (18-64 years). DynaSKIN volume, mean depth and maximum depth parameters were correlated with age and 15 Cutometer ® parameters. Subsequently, the firming efficacy of a skincare regimen featuring acetyl aspartic acid (AAA) and a peptide complex was examined in a cohort of 41 volunteers., Results: DynaSKIN volume, mean depth and maximum depth parameters correlate with age and the Cutometer ® parameters that are associated with the skin relaxation phase (R1, R2, R4, R5, R7 and F3). Furthermore, the DynaSKIN captured significant improvements in skin firmness delivered by the skincare regimen., Conclusion: The DynaSKIN is a novel device capable of capturing skin biomechanics at a high level of specificity and successfully detected the firming properties of a skincare regimen. Its independent measuring principle, consumer relevance and skin firmness 3D visualisation capabilities bring objectivity and novelty to product efficacy substantiation evaluation., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Biomechanical tissue properties have been hypothesized to play a critical role in the quantification of prosthetic socket production for individuals with limb amputation. In this investigation, a novel indenter platform is presented and its performance evaluated for the purposes of residual-limb tissue characterization. The indenter comprised 14 position- and force-controllable actuators that circumferentially surround a biological residuum to form an actuator ring. Each indenter actuator was individually controllable in position ( [Formula: see text] accuracy) and force (330 mN accuracy) at a PC controller feedback rate of 500 Hz, allowing for a range of measurement across a residual stump. Data were collected from 162 sensors over an EtherCAT fieldbus to characterize the mechanical hyperviscoelastic tissue response of two transtibial residual-limbs from a study participant with bilateral amputations. At five distinct anatomical locations across the residual-limb, force versus deflection data-including hyperviscoelastic tissue properties-are presented, demonstrating the accuracy and versatility of the multi-indenter platform for residual-limb tissue characterization.

Tablet hardness, a measure of the breaking force of a tablet, is based on numerous factors. These include the shape of the tablet and the mode of the application of force. For instance, when a pentagonal-shaped tablet was tested with a traditional hardness tester with flat platens, there was a large variation in hardness measurements. This was due to the propensity of vertices of the tablet to crush, referred to as an "improper break". This article describes a novel approach to measure the hardness of pentagonal-shaped tablets using modified platens. The modified platens have more uniform loading than flat platens. This is because they reduce loading on the vertex of the pentagon and apply forces on tablet edges to generate reproducible tablet fracture. The robustness of modified platens was assessed using a series of studies, which included feasibility and Gauge Repeatability & Reproducibility (R&R) studies. A key finding was that improper breaks, generated frequently with a traditional hardness tester using flat platens, were eliminated. The Gauge R&R study revealed that the tablets tested with novel platens generated consistent values in hardness measurements, independent of batch, hardness level, and day of testing, operator and tablet dosage strength.

A triaxial force-sensitive microrobot was developed to dynamically perturb skin in multiple deformation modes, in vivo. Wiener static nonlinear identification was used to extract the linear dynamics and static nonlinearity of the force-displacement behavior of skin. Stochastic input forces were applied to the volar forearm and thenar eminence of the hand, producing probe tip perturbations in indentation and tangential extension. Wiener static nonlinear approaches reproduced the resulting displacements with variances accounted for (VAF) ranging 94-97%, indicating a good fit to the data. These approaches provided VAF improvements of 0.1-3.4% over linear models. Thenar eminence stiffness measures were approximately twice those measured on the forearm. Damping was shown to be significantly higher on the palm, whereas the perturbed mass typically was lower. Coefficients of variation (CVs) for nonlinear parameters were assessed within and across individuals. Individual CVs ranged from 2% to 11% for indentation and from 2% to 19% for extension. Stochastic perturbations with incrementally increasing mean amplitudes were applied to the same test areas. Differences between full-scale and incremental reduced-scale perturbations were investigated. Different incremental preloading schemes were investigated. However, no significant difference in parameters was found between different incremental preloading schemes. Incremental schemes provided depth-dependent estimates of stiffness and damping, ranging from 300 N/m and 2 Ns/m, respectively, at the surface to 5 kN/m and 50 Ns/m at greater depths. The device and techniques used in this research have potential applications in areas, such as evaluating skincare products, assessing skin hydration, or analyzing wound healing.

The goals of this study were to compare neck and shoulder stiffness values determined by shear wave ultrasound elastography with those obtained with a muscle hardness meter and to verify the correspondence between objective and subjective stiffness in the neck and shoulder. Twenty-four young men and women participated in the study. Their neck and shoulder stiffness was determined at six sites. Before the start of the measurements, patients rated their present subjective symptoms of neck and shoulder stiffness on a 6-point verbal scale. At all measurement sites, the correlation coefficients between the values of muscle hardness indices determined by the muscle hardness meter and shear wave ultrasound elastography were not significant. Furthermore, individuals' subjective neck and shoulder stiffness did not correspond to their objective symptoms. These results suggest that the use of shear wave ultrasound elastography is essential to more precisely assess neck and shoulder stiffness., (Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

Background: We aimed to test whether testis rigidity (hardness) measured using a newly-designed device we previously introduced would offer more reliable assessment of histologic damage in undescended testes than conventional methods (consistency feel at palpation, volume measurement)., Materials and Methods: Forty-five 18-d-old Lewis rats underwent surgical inhibition of descent of left testes and were followed to 40 (n = 16), 63 (n = 14), or 90 days (n = 15). Another 45 18-d-old Lewis rats were sham operated (left side) and followed likewise (n = 14, n = 15, and n = 16). At the designated time points, testes were exposed bilaterally, rigidity was measured, and consistency at palpation was scored; testes were removed and subjected to length, width, weight measurements, volume calculation, and histomorphometry (mean Johnsen score [MJS], mean tubular diameter [MTD], and mean capsule width [MCW]). Testes of experimental group were compared with ipsilateral testes of sham-operated rats., Results: At all time points, undescended testes had decreased rigidity, MJS, and MTD, increased MCW, decreased volume and weight; contralateral testes remained unaffected. Rigidity was associated only with MJS and MTD, and most strongly with MJS (multiple stepwise linear regression, F = 694.44, P < 0.0005). MJS could be precisely predicted from rigidity: MJS = 0.699 × testis rigidity (F = 1358.82, P < 0.0005). This model showed good fit between predicted and actual MJS values (R(2) = 0.94), low error, nonsignificant bias, sensitivity 75% and specificity 90%. Model validation showed low prediction error and nonsignificant bias, indicating generalizability. Testis volume and palpation proved imprecise MJS predictors., Conclusions: Testis rigidity is an effective predictor of histologic damage in rat undescended testes, with diagnostic value superior to testis palpation scoring and volume measurement., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: Long-term exposure to sunlight changes skin features like amount of facial wrinkling and skin elasticity, which is useful in estimating skin health and age-related changes. Skin elasticity is evaluated by quantitative methods such as the noninvasive suction device Cutometer(®) , which is widely used to evaluate regional body-elasticity differences and correlate these findings with the results of other instrumental data. Few field studies have been done with the Ballistometer(®) device, another noninvasive method for measuring skin elasticity., Method: In this study, we measured the skin elasticity of each subject's forehead, cheek, and volar forearm using two devices with different means of obtaining quantitative measurements - Ballistometer(®) (Diastron Ltd.) and Cutometer(®) (CK electronics)., Results: The results from testing with the Ballistometer(®) and Cutometer(®) devices showed that the degree of skin elasticity of the volar forearm is greater than those found on the cheek and forehead. The parameters measured by the Ballistometer(®) showed high correlation patterns. On the cheek skin, the correlation coefficient between Ballisto-parameters and R parameters (R0, R3, R8) was higher than other skin sites., Conclusion: Taken together, R parameters measured by the Cutometer(®) device have been widely distributed in the evaluation of skin elasticity in research and cosmetics. Although the methodologies are different, the Ballistometer(®) device is also a useful tool to evaluate skin elasticity., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

We demonstrate an interferometric fiber-optic bending/nano-displacement sensor based on a plastic dual-core fiber. The light coupled into the two fiber cores is first guided along the fiber, and then reflected by the mirror coated at the fiber end. Reflected light coming out of the fiber produces interference that shifts as the fiber bends. The interference shift is interrogated using a slit and a photodetector. The resolution of our sensor is ∼3×10(-4) m(-1) for sensing the bending curvature, and ∼70 nm for sensing the displacement.

Background: Indentation techniques haves been applied to measure stiffness of human soft tissues. Tissue properties and geometry of the indentation instrument control the measured response., Methods: Mechanical roles of different soft tissues were characterized to understand the performance of the indentation instrument. An optimal instrument design was investigated. Experimental indentations in forearm of human subjects (N = 11) were conducted. Based on peripheral quantitative computed tomography imaging, a finite element (FE) model for indentation was created. The model response was matched with the experimental data., Results: Optimized values for the elastic modulus of skin and adipose tissue were 130.2 and 2.5 kPa, respectively. The simulated indentation response was 3.9 ± 1.2 (mean ± SD) and 4.9 ± 2.0 times more sensitive to changes in the elastic modulus of the skin than to changes in the elastic modulus of adipose tissue and muscle, respectively. Skin thickness affected sensitivity of the instrument to detect changes in stiffness of the underlying tissues., Conclusion: Finite element modeling provides a feasible method to quantitatively evaluate the geometrical aspects and the sensitivity of an indentation measurement device. Systematically, the skin predominantly controlled the indentation response regardless of the indenter geometry or variations in the volume of different soft tissues., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Preservation of structural integrity inside cells and at cell-extracellular matrix (ECM) interfaces is a key challenge during freezing of biomaterials. Since the post-thaw functionality of cells depends on the extent of change in the cytoskeletal structure caused by complex cell-ECM adhesion, spatiotemporal deformation inside the cell was measured using a newly developed microbead-mediated particle tracking deformetry (PTD) technique using fibroblast-seeded dermal equivalents as a model tissue. Fibronectin-coated 500 nm diameter microbeads were internalized in cells, and the microbead-labeled cells were used to prepare engineered tissue with type I collagen matrices. After a 24 h incubation the engineered tissues were directionally frozen, and the cells were imaged during the process. The microbeads were tracked, and spatiotemporal deformation inside the cells was computed from the tracking data using the PTD method. Effects of particle size on the deformation measurement method were tested, and it was found that microbeads represent cell deformation to acceptable accuracy. The results showed complex spatiotemporal deformation patterns in the cells. Large deformation in the cells and detachments of cells from the ECM were observed. At the cellular scale, variable directionality of the deformation was found in contrast to the one-dimensional deformation pattern observed at the tissue scale, as found from earlier studies. In summary, this method can quantify the spatiotemporal deformation in cells and can be correlated to the freezing-induced change in the structure of cytosplasm and of the cell-ECM interface. As a broader application, this method may be used to compute deformation of cells in the ECM environment for physiological processes, namely cell migration, stem cell differentiation, vasculogenesis, and cancer metastasis, which have relevance to quantify mechanotransduction.

Background: The invasive measuring techniques are of great help in the evaluation of skin physiological functions and topical formulation. The reproducibility and accuracy of the instrument are crucial., Aims: The aim of this study is to reveal the differences and correlations in measuring skin hydration, pH, sebum, elasticity and melanin on the forearm or faces between two commercially available series of instruments., Materials & Methods: 20 subjects were enrolled to be measured by the two series of instruments. The measurements by each series were performed on the left/right side of the body randomly. The pH, sebum, elasticity and melanin measurements were performed on the faces in different areas, while the hydration measurements were operated on the forearms before and after wet dressing, respectively., Results: Positive correlations were found in the values of skin SC hydration, pH, sebum and melanin detected by the two series. The values related to skin elasticity measured by the two instruments were statistically negative correlated. The Soft Plus series has higher variation in detecting skin hydration, pH, and melanin than the instruments from Courage & Khazaka., Discussion: The differences of the two series must be instrument related. The difference in level of measurement can be due either to differences in the design of the probe, to differences in time for measurement, to differences in left/right part of the body or a combination of these three., Conclusion: The two series have significant correlations. The instruments from CK are more reproducible., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The number of tablets marketed with a score line to aid divisibility is increasing. The subdivision of scored tablets in order to ensure dose flexibility may be an easier and cheaper solution from the aspect of production. However, to ensure the appropriate mechanical properties and divisibility of tablets so as to guarantee consequent dosing is a difficult problem, which is influenced by many properties of the applied materials, such as the physicochemical behaviour, the plasticity, the degree of elasticity, the mechanism of compression, etc. These exert a significant influence on the postcompressional properties of tablets, and hence on the subdivision of tablets. Despite the considerable difficulties, the increasing importance in paediatrics and the ever stricter requirements of the drug authorities, the subdivision of scored tablets is a poorly studied field. This paper deals with the influence of physico-chemical properties of materials on the postcompressional parameters of tablets, and especially on the subdivision of tablets. For measurement of the force required to break tablets into halves, a laboratory-constructed hardness tester was utilized.

The initiating explosive devices are prohibited in rock breaking near the goaf of the highly gassy mine. It is effective and applicable to cracking the hard roof with static cracking agent. By testing the static cracking of cubic limestone (size: 200 × 200 × 200 mm) with true triaxial rock mechanics testing machine under the effect of bidirectional stress and by monitoring the evolution process of the cracks generated during the acoustic emission experiment of static cracking, we conclude the following: the experiment results of the acoustic emission show that the cracks start from the lower part of the hole wall until they spread all over the sample. The crack growth rate follows a trend of "from rapidness to slowness." The expansion time is different for the two bunches of cracks. The growth rates can be divided into the rapid increasing period and the rapid declining period, of which the growth rate in declining period is less than that in the increasing period. Also, the growth rate along the vertical direction is greater than that of the horizontal direction. Then the extended model for the static cracking is built according to the theories of elastic mechanics and fracture mechanics. Thus the relation formula between the applied forces of cracks and crack expansion radius is obtained. By comparison with the test results, the model proves to be applicable. In accordance with the actual geological situation of Yangquan No. 3 Mine, the basic parameters of manpower manipulated caving breaking with static crushing are settled, which reaps bumper industrial effects.

Tactile sensing is commonly carried out by humans using their fingers or hands to estimate the physical properties of an object. A large body of literature covers a range of applications of these methods in clinical situations. The objective of this work is to show the breadth of application areas explored and the achievements that have been made in the measurement of physical variables of interest to physicians using tactile force and resonance sensors. Although a broad spectrum of applications has been considered, of particular interest is the application of these methods to determine tissue properties in vivo. Progress in this direction has been made by various groups particularly with respect to piezoelectric and capacitance sensors. Also described are the findings of a preliminary study of a tactile system designed to examine the abdomen of the clinically super-obese patient.

The soft tissue aspiration experiment has been further developed for application during laparoscopic surgery. The new setup has been tested and validated under lab-conditions and came then to in vivo operation. It is to our knowledge the first time ever a mechanical experiment has been performed under laparoscopic conditions on the human, which enables determining corresponding constitutive model equations. As most important results, the feasibility of laparoscopic tissue aspiration has been demonstrated and, based on an ad hoc parameter for the tissue stiffness, the liver and the stomach gave significantly different responses. Furthermore, the determined constitutive behavior for one healthy human liver was in line with results obtained from tissue aspiration during open surgery. Eventually, laparoscopic tissue aspiration might qualify as minimally invasive testing method for tactile feedback systems. The presented results are preliminary and more research is required., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Aim: Implant survival and success rates are strictly related to the density of the bone they are placed in. Bone density, in fact, affects both implant primary stability and implant micromovements after implant positioning. Current bone density classifications rely on subjective, scarcely reproducible evaluations. A novel implant micro motor featuring a bone density measurement probe has been recently introduced. The objective of this study was to test such bone density measurement system for its capability of distinguishing different bone density areas in the upper and in the lower jaw., Methods: 1254 implant placement sites had their bone density measured during standard implant placement at a single clinical facility. After data collection bone density distribution was statistically analyzed in order to test the hypothesis of a non-homogeneous distribution in four different predefined anatomical maxillary zones, namely pre-antral (between teeth from 14 to 24) and sub-antral (more distally) in the upper maxilla and interforaminal (between and including teeth from 34 to 44) and retroforaminal (more distally) zone., Results: Measured bone density values, organized according the named four anatomical zones, produced a statistically significant inhomogeneous pattern (P<0.001). Density distribution was consistent with data from literature, but not always corresponding with the one achieved by applying the well known Misch classification., Conclusion: The measuring system we tested allowed to distinguish different and clinically significant anatomical zones according to their different bone density, and can represent a fundamental diagnostic tool to plan the proper implant placement steps.

Liver fibrosis is a kind of chronic damage of the liver and can lead to cirrhosis, one of the top 10 causes of death in the Western world. However, there is still a lack of noninvasive methods for diagnosing liver fibrosis. Fibroscan (Echosens, Paris, France), a device based on A-mode transient elastography, has shown promising results. In this study, a transient elastography system with real-time B-mode imaging for non-invasive liver fibrosis assessment, named Liverscan, was developed; its performance was tested and compared with that of the Fibroscan. A specific measurement probe was designed and fabricated with a B-mode ultrasound transducer fixed along the axis of a mechanical vibrator. It was integrated with the Liverscan to measure liver stiffness based on the shear wave propagation in liver tissues. The system was validated by mechanical indentation test using custom-made agar-gelatin phantoms with different stiffness. To further test its feasibility, in vivo measurements were conducted in 67 volunteers (age, 34 ± 3 years; body mass index, 21.3 ± 2.8 kg/m(2); Mean ± SD., 34 male and 33 female), including 20 patients with various liver diseases, and 28 (19 male and 9 female) being tested by both Liverscan and Fibroscan. A significant linear correlation between the stiffness measured by the mechanical indentation test and that by the Liverscan (r = 0.973; p < 0.001) was obtained. The in vivo liver stiffness measured by Liverscan was also correlated with that by Fibroscan significantly (r = 0.886; p < 0.001). There was a significant difference in liver stiffness between the 20 patients and the other healthy subjects (14.1 ± 3.4 kPa vs. 10.5 ± 2.1 kPa; p = 0.001). The intra- and inter-observer tests indicated that the measurements were repeatable with intra-class correlation coefficients being 0.987 (p < 0.001) and 0.988 (p < 0.001), respectively. This study demonstrated that Liverscan with a specifically designed probe was able to measure and differentiate liver of different stiffness using the established measurement protocol under the guidance of real-time B-mode ultrasound imaging., (Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

A new method with a simple algorithm was developed to accurately measure Poisson's ratio of soft materials such as polyvinyl alcohol hydrogel (PVA-H) with a custom experimental apparatus consisting of a tension device, a micro X-Y stage, an optical microscope, and a charge-coupled device camera. In the proposed method, the initial positions of the four vertices of an arbitrarily selected quadrilateral from the sample surface were first measured to generate a 2D 1st-order 4-node quadrilateral element for finite element numerical analysis. Next, minimum and maximum principal strains were calculated from differences between the initial and deformed shapes of the quadrilateral under tension. Finally, Poisson's ratio of PVA-H was determined by the ratio of minimum principal strain to maximum principal strain. This novel method has an advantage in the accurate evaluation of Poisson's ratio despite misalignment between specimens and experimental devices. In this study, Poisson's ratio of PVA-H was 0.44 ± 0.025 (n = 6) for 2.6-47.0% elongations with a tendency to decrease with increasing elongation. The current evaluation method of Poisson's ratio with a simple measurement system can be employed to a real-time automated vision-tracking system which is used to accurately evaluate the material properties of various soft materials.

Hydrogels have gained wide usage in a range of biomedical applications because of their biocompatibility and the ability to finely tune their properties, including viscoelasticity. The use of hydrogels on the microscale is increasingly important for the development of drug delivery techniques and cellular microenvironments, though the ability to accurately characterize their micromechanical properties is limited. Here we demonstrate the use of microelectromechanical systems (MEMS) resonant sensors to estimate the properties of poly(ethylene glycol) diacrylate (PEGDA) microstructures over a range of concentrations. These microstructures are integrated on the sensors by deposition using electrohydrodynamic jet printing. Estimated properties agree well with independent measurements made using indentation with atomic force microscopy.

Purpose: Compression is necessary in mammography to improve image quality and reduce radiation burden. Maximizing the amount of breast in contact with the image receptor (IR) is important. To achieve this, for the craniocaudal projection, there is no consensus within the literature regarding how the IR should be positioned relative to the inframammary fold (IMF). No information exists within the literature to describe how pressure balancing between IR and paddle, and IR breast footprint, might be optimized. This paper describes a novel method for measuring the respective pressures applied to the breast from the IR and the paddle and a method to simultaneously measure the breast footprints on the IR and the paddle., Methods: Using a deformable breast phantom and electronic pressure-sensitive mat, area and pressure readings were gathered from two mammography machines and four paddles at 60, 80, and 100 N with the IR positioned at -2, -1, 0, +1, and +2 cm relative to the IMF (60 combinations in total)., Results: Paddle and IR footprints were calculated along with a uniformity index (UI). For all four paddle/machine/pressure combinations the greatest IR footprint was achieved at IMF +2 cm. The UI indicates that the best pressure/footprint balance is achieved at IMF +1 cm., Conclusions: The authors' method appears to be suited to measuring breast footprints and pressures on IR and paddle and a human female study is planned.

The deformability of human fingers is central to addressing the real-life hazard of finger jamming between the window and seal entry of a power-operated motor vehicle side door window. The index and little fingers of the left hand of 109 participants and of 20 cadaver specimens were placed in a measurement setup. Participants progressively jammed their fingers at five different dorsal-palmar jam positions up to the maximum tolerable pain threshold, whereas the cadaver specimens were jammed up to the maximum possible deflection. Force-deflection curves were calculated corresponding to increasing deflection of the compressed tissue layers of the fingers. The average maximum force applied by the participants was 42 N to the index finger and 35 N to the little finger. In the cadaver fingers, the average of the maximum force applied was 1886 N for the index finger and 1833 N for the little finger. In 200 jam positions, 25 fractures were observed on radiographs; fractures occurred at an average force of 1485 N. These data assisted the development of a prototype of a bionic test device for more realistic validation of power-operated motor vehicle windows.

We report on an optical noncontact method for the detection of soft-tissue tumors based on the measurement of their elasticity. A focused air-puff system is used to excite surface waves (SWs) on soft tissues with transient static pressure. A high-speed phase-sensitive optical coherence tomography system is used to measure the SWs as they propagate from the point of excitation. To evaluate the stiffness of soft tissues, the Young's modulus is quantified based on the group velocity of SWs. Pilot experiments were performed on ex vivo human myxoma and normal fat. Results demonstrate the feasibility of the proposed method to measure elasticity and differentiate soft-tissue tumors from normal tissues.

The purpose of this work is to study the elastoplastic properties of novel intermetallic coatings grown by hot dipping on medical steel 316 LVM and their correlation with the scratch resistance by means of instrumented ultramicroindentation techniques. Elastoplastic properties are defined by the plasticity index (PI), which correlates the hardness and the Young's modulus, and the yield strength that delimits the elastic-plastic transition. To avoid overestimations of the PI due to the so-called indentation size effect, macroscopic hardness values were determined. The PI of the coating increases from 0.6 to 0.8 with increasing immersion time. These values are always lower than those of the bare substrate (0.9) but higher than those found for ceramics (∼0.5). The increase of the PI is accompanied by a decrease in the yield strength from 0.73 to 0.34 GPa, which highlights the relevance of the compressive residual stresses and their relaxation with increasing immersion time. The higher plasticity is shown by higher apparent friction coefficients (0.159), which are always lower than those of the bare steel (0.264). Therefore, these intermetallic coatings could be considered "hard but tough" coatings, suitable for enhancing the wear resistance of the medical steel, especially when using short periods of immersion. The study provides evidence that the load-depth curve of indentation contains abundant information and that its analysis can be used to determine various mechanical properties of coatings that could be important for load bearing components., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: The objective of our study was to develop a novel capacitive force sensor that enables simultaneous measurements of yaw torque around the pressure axis and normal force and shear forces at a single point for the purpose of elucidating pressure ulcer pathogenesis and establishing criteria for selection of cushions and mattresses., Methods: Two newly developed sensors (approximately 10 mm × 10 mm × 5 mm (10) and 20 mm × 20 mm × 5 mm (20)) were constructed from silicone gel and four upper and lower electrodes. The upper and lower electrodes had sixteen combinations that had the function as capacitors of parallel plate type. The full scale (FS) ranges of force/torque were defined as 0-1.5 N, -0.5-0.5 N and -1.5-1.5 N mm (10) and 0-8.7 N, -2.9-2.9 N and -16.8-16.8 N mm (20) in normal force, shear forces and yaw torque, respectively. The capacitances of sixteen capacitors were measured by an LCR meter (AC1V, 100 kHz) when displacements corresponding to four degrees of freedom (DOF) forces within FS ranges were applied to the sensor. The measurement was repeated three times in each displacement condition (10 only). Force/torque were calculated by corrected capacitance and were evaluated by comparison to theoretical values and standard normal force measured by an universal tester., Results: In measurements of capacitance, the coefficient of variation was 3.23% (10). The Maximum FS errors of estimated force/torque were less than or equal to 10.1 (10) and 16.4% (20), respectively. The standard normal forces were approximately 1.5 (10) and 9.4 N (20) when pressure displacements were 3 (10) and 2 mm (20), respectively. The estimated normal forces were approximately 1.5 (10) and 8.6 N (10) in the same condition., Conclusions: In this study, we developed a new four DOF force sensor for measurement of force/torque that occur between the skin and a mattress. In measurement of capacitance, the repeatability was good and it was confirmed that the sensor had characteristics that enabled the correction by linear approximation for adjustment of gain and offset. In estimation of forces/torque, we considered accuracy to be within an acceptable range.

The aim of this study is to evaluate the performance of a motion capture system and discuss the application potential of the proposed system in in vivo bone-segment deformation measurements. In this study, the effects of the calibration procedure, camera distance and marker size on the accuracy and precision of the motion capture system have been investigated by comparing the captured movement of the markers with reference movement. The results indicated that the system resolution is at least 20 microm in a capture volume of 400 X 300 X 300 mm3, which mostly covers the range of motion of the tibia during the stance phase of one gait cycle. Within this volume, the system accuracy and precision decreased following the increase of camera distance along the optical axis of the cameras. With the best configuration, the absolute error and precision for the range of 20 microm displacement were 1.2-1.8 microm and 1.5-2.5 microm, respectively. Small markers (Ø3-8 mm) yielded better accuracy and repeatability than the larger marker (Ø10.5 mm). We conclude that the proposed system is capable of recording minor displacements in a relative large volume.

In a wide range of biomechanical modeling of aorta from traumatic injury to stent grafts, the arterial wall has been considered as a single homogeneous layer vessel, ignoring the fact that arteries are composed of distinct anatomical layers with different mechanical characteristics. In this study, using a custom-made nanoindentation technique, changes in the mechanical properties of porcine thoracic aorta wall in the radial direction were characterized using a quasi-linear viscoelastic model. Two layers of equal thickness were mechanically distinguishable in descending aorta based on the radial variations in the instantaneous Young's modulus E and reduced relaxation function G(t). Overall, comparison of E and G(∞) of the outer half (70.27±2.47 kPa and 0.35±0.01) versus the inner half (60.32±1.65 kPa and 0.33±0.01) revealed that the outer half was stiffer and showed less relaxation. The results were used to explain local mechanisms of deformation, force transmission, tear propagation and failure in arteries., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Replicating bacterial chromosomes continuously demix from each other and segregate within a compact volume inside the cell called the nucleoid. Although many proteins involved in this process have been identified, the nature of the global forces that shape and segregate the chromosomes has remained unclear because of limited knowledge of the micromechanical properties of the chromosome. In this work, we demonstrate experimentally the fundamentally soft nature of the bacterial chromosome and the entropic forces that can compact it in a crowded intracellular environment. We developed a unique "micropiston" and measured the force-compression behavior of single Escherichia coli chromosomes in confinement. Our data show that forces on the order of 100 pN and free energies on the order of 10(5) k(B)T are sufficient to compress the chromosome to its in vivo size. For comparison, the pressure required to hold the chromosome at this size is a thousand-fold smaller than the surrounding turgor pressure inside the cell. Furthermore, by manipulation of molecular crowding conditions (entropic forces), we were able to observe in real time fast (approximately 10 s), abrupt, reversible, and repeatable compaction-decompaction cycles of individual chromosomes in confinement. In contrast, we observed much slower dissociation kinetics of a histone-like protein HU from the whole chromosome during its in vivo to in vitro transition. These results for the first time provide quantitative, experimental support for a physical model in which the bacterial chromosome behaves as a loaded entropic spring in vivo.

Surface microscopy of individual biological cells is essential for determining the patterns of cell migration to study the tumor formation or metastasis. This paper presents a correlated and effective theoretical and experimental technique to automatically address the biophysical and mechanical properties and acquire live images of biological cells which are of interest in studying cancer. In the theoretical part, a distributed-parameters model as the comprehensive representation of the microcantilever is presented along with a model of the contact force as a function of the indentation depth and mechanical properties of the biological sample. Analysis of the transfer function of the whole system in the frequency domain is carried out to characterize the stiffness and damping coefficients of the sample. In the experimental section, unlike the conventional atomic force microscope techniques basically using the laser for determining the deflection of microcantilever's tip, a piezoresistive microcantilever serving as a force sensor is implemented to produce the appropriate voltage and measure the deflection of the microcantilever. A micromanipulator robotic system is integrated with the MATLAB(®) and programmed in such a way to automatically control the microcantilever mounted on the tip of the micromanipulator to achieve the topography of biological samples including the human corneal cells. For this purpose, the human primary corneal fibroblasts are extracted and adhered on a sterilized culture dish and prepared to attain their topographical image. The proposed methodology herein allows an approach to obtain 2D quality images of cells being comparatively cost effective and extendable to obtain 3D images of individual cells. The characterized mechanical properties of the human corneal cell are furthermore established by comparing and validating the phase shift of the theoretical and experimental results of the frequency response.

Palpation is an intuitive examination procedure in which the kinesthetic and tactile sensations of the physician are used. Although it has been widely used to detect and localize diseased tissues in many clinical fields, the procedure is subjective and dependent on the experience of the individual physician. Palpation results and biomechanics-based mechanical property characterization are possible solutions that can enable the acquisition of objective and quantitative information on abnormal tissue localization during diagnosis and surgery. This paper presents an integrated approach for robotic palpation combined with biomechanical soft tissue characterization. In particular, we propose a new palpation method that is inspired by the actual finger motions that occur during palpation procedures. To validate the proposed method, robotic palpation experiments on silicone soft tissue phantoms with embedded hard inclusions were performed and the force responses of the phantoms were measured using a robotic palpation system. Furthermore, we carried out a numerical analysis, simulating the experiments and estimating the objective and quantitative properties of the tissues. The results indicate that the proposed approach can differentiate diseased tissue from normal tissue and can characterize the mechanical information of diseased tissue, which means that this method can be applied as a means of abnormality localization to diagnose prostate cancers.

During conventional surgical tasks, surgeons use their tactile perception in their finger tips to sense the degree of softness of biological tissues to identify tissue types and to feel for any abnormalities. However, in robotic-assisted surgical systems, surgeons are unable to sense this information because only surgical tools interact with tissues. In order to provide surgeons with such useful tactile perception, therefore, a tactile sensor is required that is capable of simultaneously measuring contact force and resulting tissue deformation. Accordingly, this paper discusses the design, prototyping, testing, and validation of an innovative tactile sensor that is capable of measuring the degree of softness of soft objects such as tissues under both static and dynamic loading conditions and which is also magnetic resonance compatible and electrically passive. These unique characteristics of the proposed sensor would also make it a practical choice for use in robotic-assisted surgical platforms. The prototype version of this sensor was developed by using optical micro-systems technology and, thus far, experimental test results performed on the prototyped sensor have validated its ability to measure the relative softness of artificial tissues.

In this study the saliency of hardness and softness were investigated in an active haptic search task. Two experiments were performed to explore these properties in different contexts. In Experiment 1, blindfolded participants had to grasp a bundle of spheres and determine the presence of a hard target among soft distractors or vice versa. If the difference in compliance between target and distractors was small, reaction times increased with the number of items for both features; a serial strategy was found to be used. When the difference in compliance was large, the reaction times were independent of the number of items, indicating a parallel strategy. In Experiment 2, blindfolded participants pressed their hand on a display filled with hard and soft items. In the search for a soft target, increasing reaction times with the number of items were found, but the location of target and distractors appeared to have a large influence on the search difficulty. In the search for a hard target, reaction times did not depend on the number of items. In sum, this showed that both hardness and softness are salient features.

A hand held stiffness meter can be used to measure indentation stiffness of human soft tissues, sensitively altered, e.g., by pathological tissue swelling. Under indentation load, the relative contribution of each soft tissue component (i.e., skin, adipose tissue and muscle) to the biomechanical response is not known. In the present study, we evaluated the biomechanical role of different soft tissues in relaxed, physically stressed and oedemic human forearm. Soft tissue stiffness of the forearms of nine healthy human subjects was measured under four different test protocols: (1) forearm at rest, (2) forearm under isometric flexor loading, (3) forearm under isometric extensor loading, and (4) forearm under venous occlusion. In (2) and (3) the loading forces were monitored using a dynamometer, and in (4) the soft tissue swelling was induced by venous occlusion using a pressure cuff. At the site of indentation, thickness of different tissue layers (skin, adipose tissue and muscle) was measured using B-mode ultrasound imaging. Layered, hyperelastic finite element (FE) model of the indentation measurement was created and the model response was matched with that of the stiffness meter to determine the elastic modulus for each tissue in the model. Optimized values of the elastic modulus for skin and adipose tissue at rest were 210 kPa and 1.9 kPa, respectively. Further, significance of the variations in stiffness of different tissues on the indentation response was tested. Experimentally, indentation stiffness of the forearm increased during isometric extensor and flexor loads as well as under venous occlusion by 53, 91 and 15%, respectively. The FE model could reproduce the experimental responses primarily by the increased modulus of skin; 112% (446 kPa), 210% (651 kPa) and 21% (254 kPa) under flexor and extensor loading as well as during venous occlusion, respectively. The indentation response was 9-16 times more sensitive to changes in the mechanical properties of skin than those of adipose tissue and muscle. In conclusion, the present stiffness meter may be used to quantify in vivo mechanical properties of soft tissues in the forearm, sensitively modulated by soft tissue swelling and muscle loading., (Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.)

Background: Currently, most of mitral valve annuloplasty surgeries are performed by using open heart surgery. However, if such operation would be performed by using minimally invasive surgery via catheter-based techniques (CBT), it offers various advantages for both surgeons and patients., Methods: Two piezoresistive force sensors are used in the structure of the tactile sensor, which can easily be miniaturized and integrated into surgical catheters. The tactile sensor was fabricated and tested to characterize different elastomers, as the phantom of cardiac tissues. Based on a developed finite element analysis (FEA) of the elastomers, the interaction between the sensor and those materials were modelled to validate the output of the sensor., Results: The results of the mechanical and psychophysical tests confirm the capability of the proposed sensor to measure the relative hardness/softness of different soft tissues., Conclusions: The proposed tactile sensor will help surgeons to characterize different types of cardiac tissues and would facilitate the use of CBT to perform mitral valve annuloplasty., (Copyright © 2011 John Wiley & Sons, Ltd.)

Researchers have increasingly recognized the need to quantify the material properties of primate food items, particularly hardness (H) and stiffness (E), which is measured as elastic modulus. Assessing E in the field is particularly difficult because the typical equipment needed to perform the requisite analyses is expensive and cumbersome. Alternatively, researchers can use hand-held, relatively inexpensive, portable durometers that measure H on Shore scales. Shore-D durometers show a reliable ability to characterize H in harder-stiffer materials, and Shore-D measures in these materials can be reliably converted to E. Shore-A durometers-employed in past field studies of food properties-do not accurately characterize the properties of harder-stiffer materials, which are likely to be those materials exerting the greatest mechanical demands on primate masticatory morphology. We offer recommendations for Shore-D durometer usage in the field., (2011 Wiley Periodicals, Inc.)

The fast neutron irradiation facility of the Portuguese Research Reactor was characterized after the reduction in uranium enrichment and rearrangement of the core configuration. In this work we report on the determination of the hardness parameter and the 1MeV equivalent neutron flux along the facility, in the new irradiation conditions, following ASTM E722 standard., (2010 Elsevier Ltd. All rights reserved.)

Background: The mechanical characterization of prostate tissue has not received much attention and is often disconnected from the clinic, where samples are readily attained., Methods: We developed a spherical indenter for the clinic to generate force-displacement data from ex vivo prostate tissue. Indentation velocity, depth, and sphere diameter, and four means of estimating elastic modulus (EM) were validated. EM was then estimated for 26 prostate specimens obtained via prostatectomy and 6 samples obtained from autopsy. Prostatectomy prostates were evaluated clinically upon digital rectal exam and pathologically post-extirpation., Findings: Whole-mount measurements yielded median EM of 43.2 kPa (SD=59.8 kPa). Once sliced into cross-sections, median EM for stage T2 and T3 glands were 30.9 and 71.0 kPa, respectively, but not significantly different. Furthermore, we compared within-organ EM difference for prostates with (median=46.5 kPa, SD=22.2 kPa) and without (median=31.0 kPa, SD=63.1 kPa) palpable abnormalities., Interpretation: This work finds that diseased prostate tissue is stiffer than normal tissue, stiffness increases with disease severity, and large variability exists between samples, even though disease differences within a prostate are detectable. A further study of late-stage cancers would help to strengthen the findings presented in this work., (Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.)

This paper describes an elasticity sensing system for left ventricle of small laboratory animal. We first show the basic concept of the proposed method, where a ring shaped specimen is dilated by a balloon type probe using a pressure based control, and the elasticity of the specimen is estimated by using the stress and strain information. We introduce a dual cylinder model for approximating the strengths of the specimen's material and the balloon. Based on this model, we can derive Young's modulus of the specimen. After explaining the developed experimental system, we show a couple of experimental results using rats and mice, where HFPEF (Heart Failure Preserved Ejection Fraction) group can be distinguished from a normal group.

Young's Modulus was measured on the trachea and first three generations of pig airways by compression. A simple and low-cost system for measuring the elastic properties of small bio-materials is presented. The force-displacement measurements have been undertaken on dissected cartilage and trachea mucosa from pig trachea and bronchial segments. Young's Modulus of trachea wall, 1.78 ± 0.51 MPa, is found to be dominated by the trachea cartilage of value 1.74 ± 0.85 MPa while the modulus for trachea mucosa was 0.15 ± 0.03 MPa. The Young's Modulus of the airway wall from the first three generations of bronchi decreases from 1.35 ± 0.17 to 0.35 ± 0.10 MPa which is also found to be dominated by the airway cartilage. Airway mucosa is found to have similar Young's modulus of 0.036 ± 0.005 MPa for the first three generations of bronchial airways.

Although the market for replacement of diseased metacarpophalangeal (MCP) joints is dominated by single-piece silicone prostheses, several two-piece designs have been implanted. One such is the Digital Joint Operative Arthroplasty (DJOA) which consists of a part-spherical stainless steel metacarpal component which articulates within a matching concave phalangeal component made of ultra high molecular weight polyethylene (UHMWPE). A DJOA MCP prosthesis was tested using a clinically-validated finger simulator while a second DJOA prosthesis acted as a statically-loaded soak-control. Testing ran to 7.1 million cycles of flexion-extension. It was found that the UHMWPE components, both test and control, gained in weight by a similar amount. Therefore apparently there was no wear of the test components. However, the initial and final surface finish values of the test stainless steel metacarpal head were relatively high. Calculations based on this roughness data, plus recent dynamically-loaded soak data, may explain the apparent lack of wear.

Scaffold design remains a main challenge in tissue engineering due to the large number of requirements that need to be met in order to create functional tissues in vivo. Computer simulations of tissue differentiation within scaffolds could serve as a powerful tool in elucidating the design requirements for scaffolds in tissue engineering. In this study, a lattice-based model of a 3D porous scaffold construct derived from micro CT and a mechano-biological simulation of a bone chamber experiment were combined to investigate the effect of scaffold stiffness on tissue differentiation inside the chamber. The results indicate that higher scaffold stiffness, holding pore structure constant, enhances bone formation. This study demonstrates that a lattice approach is very suitable for modelling scaffolds in mechano-biological simulations, since it can accurately represent the micro-porous geometries of scaffolds in a 3D environment and reduce computational costs at the same time.

Purpose: Tactile sensing techniques may distinguish tumor from healthy tissue and have potential for intraoperative brain tumor diagnosis. The aim of this study is to develop a biocompatible real-time sensing system to measure tactile information such as softness and smoothness, and its application to brain tumor diagnosis., Methods: An active tactile sensor is developed using balloon expansion. This compact system provides instantaneous tactile information and has potential for brain tumor diagnosis. Measurements are obtained on soft samples with different stiffness and surface condition with testing of boundary condition influence on thickness and area of the object. Then, measurements on white matter and gray matter of porcine ex vivo brain are done as the first step for brain tumor diagnosis., Results: The sensor can discriminate samples with different stiffness and surface condition subject to influence by boundary conditions. The sensor can evaluate an object relatively under the same boundary conditions but requires enough thickness and area to evaluate absolutely. Measurements on brain show that the sensor can discriminate between white matter and gray matter., Conclusions: Although the sensor has problems on absolute evaluation, results show that the sensor can evaluate tactile information, and it has potential for brain tumor diagnosis.

Osteoporosis-related vertebral fractures represent a major public health problem. Anatomy-specific CT-based finite element (FE) simulations could help in identifying which vertebrae have the highest risk of fracture and thus help to decide upon the need for vertebroplasty or other surgical intervention. Continuum level FE simulations require effective macroscopic material properties of the vertebra. Micro finite element (microFE) models can be used to circumvent the difficult experiments that are necessary to determine these effective properties. From a quantitative point of view, these microFE models depend critically on the chosen trabecular tissue properties. The question remains whether linear elastic microFE models of vertebral trabecular bone with and without specimen-specific tissue properties yield similar results as non-destructive macroscopic experiments under moist conditions. microFE models were set up from microCT scans with specimen-specific or average tissue moduli measured by nanoindentation under dry and wet testing conditions. Non-destructive macroscopic mechanical compression, tension and torsion tests were performed. Experimentally obtained and simulated apparent stiffnesses were compared. No significant difference was found when comparing microFE simulations with wet tissue properties and experiments for tension, compression and torsion (p>0.05). Concordance correlation coefficients were high for tension and compression (r(c)(wet)>or=0.96,p<0.05) but moderate for torsion (r(c)(wet)=0.81,p<0.05). The agreement between simulation and experiment was confirmed by Bland-Altman plots which showed mean differences

Objective: In order to quantitatively evaluate testicular consistency, we designed a device for measurement of testis rigidity, which reflects the resistance caused by testicular pressure and elasticity. The device was tested in experimental models of cryptorchidism and torsion., Materials and Methods: The Testis Rigidity Tester (TRT) prototype consists of a system of weights and levers. It measures the force needed for a known deformation of the testis, defined as rigidity. We inhibited testis descent in 10 18-day-old Lewis rats; another 10 age-matched rats underwent sham operation. At the age of 40 days we measured testicular rigidity using the TRT. Additionally, left testes of eight adult Lewis rats underwent 720 degrees torsion; rigidity was measured by the TRT before and 1h after torsion. To investigate repeatability of TRT measurements, the rigidity of five twisted testes was measured 10 times by three researchers., Results: The TRT revealed a significant decrease of rigidity in undescended testes and an increase in twisted testes. Measurements were repeatable, independent of the observer., Conclusion: The TRT is a safe, reliable and objective device that successfully measured the altered rigidity in experimental models of testicular disease., (Copyright (c) 2010 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.)