Sara Matteoli

Investigation on the load-displacement curves of a human healthy heel pad: In vivo compression data compared to numerical results

The aims of the present work were to build a 3D subject-specific heel pad model based on the anatomy revealed by MR imaging of a subjects heel pad, and to compare the load-displacement responses obtained from this model with those obtained from a compression device used on the subjects heel pad. A 30 year-old European healthy female (mass=54kg, height=165cm) was enrolled in this study. Her left foot underwent both MRI and compression tests. A numerical model of the heel region was developed based on a 3D CAD solid model obtained by MR images. The calcaneal fat pad tissue was described with a visco-hyperelastic model, while a fiber-reinforced hyperelastic model was formulated for the skin. Numerical analyses were performed to interpret the mechanical response of heel tissues. Different loading conditions were assumed according to experimental tests. The heel tissues showed a non-linear visco-elastic behavior and the load-displacement curves followed a characteristic hysteresis form. The energy dissipation ratios measured by experimental tests (0.25±0.02 at low strain rate and 0.26±0.03 at high strain rate) were comparable with those evaluated by finite element analyses (0.23±0.01 at low strain rate and 0.25±0.01 at high strain rate). The validity and efficacy of the investigation performed was confirmed by the interpretation of the mechanical response of the heel tissues under different strain rates. The mean absolute percentage error between experimental data and model results was 0.39% at low strain rate and 0.28% at high strain rate.

In vivo thermographic analysis of the corneal surface in keratoconic patients undergoing riboflavin-UV-A accelerated cross-linking.

Purpose: To assess corneal thermal profile during combined riboflavin and accelerated UV corneal collagen cross-linking (A-CXL) using in vivo surface thermographic analysis. Methods: In this open-label, nonrandomized, prospective pilot study, 28 eyes of 28 patients were included. The study was conduced at the Department of Surgery and Translational Medicine, University of Florence, Italy, in collaboration with the Ophthalmic Operative Unit of Siena University, Italy. All patients underwent high-fluence A-CXL in pulsed light and continuous light UV-A exposure at 30 and 18 mW/cm2. Patients were divided into 4 groups: 7 for continuous light A-CXL, 7 for pulsed light A-CXL at 30 mW/cm2 with 7.2 J energy, 7 for continuous light A-CXL, and 7 for pulsed light A-CXL at 18 mW/cm2 with 5.4 J energy. Corneal surface temperature measurements were recorded using an infrared FLIR thermocamera (FLIR 320A; FLIR Systems). Corneal temperature values were detected in the surface area exposed to UV-A light irradiation, selecting it in the acquired thermographic image. The maximum temperature value detected in the area studied was recorded and considered for comparative analysis. Results: Infrared thermocamera measurements of the corneal surface during A-CXL treatments showed an average temperature of 31.5°C during the entire procedure in all groups and UV-A powers (30 mW/cm2 at 7.2 J/cm2 and 18 mW/cm2 at 5.4 J/cm2) and light exposure modality remained under the threshold of collagen thermal injury. Conclusions: Accelerated corneal collagen cross-linking did not cause thermal rise over the threshold of thermal injury to the corneal surface, demonstrating a safe thermal profile both at 30 mW/cm2 with 7.2 J and 18 mW/cm2 with 5.4 J energy dose.

Relationship between ocular surface temperature and peripheral vasoconstriction in healthy subjects: A thermographic study

An impairment of ocular blood flow regulation is commonly considered one of the main pathogenetic mechanisms involved in the development of several eye diseases, like glaucoma. The aim of this study was to investigate whether an alteration of ocular blood supply induced by peripheral vasoconstriction might be detected by measuring the ocular surface temperature. The ocular surface temperature was evaluated in a group of 38 healthy young subjects (28 males and 10 females; mean age: 25.4 ± 4.1 years) by infrared thermography. For each subject, the experimental procedure consisted of two thermographic acquisitions both lasting 10 s, recorded before and during the immersion of both hands in a mixture of ice and water (1.6 °C ± 0.4 °C). Specifically, the second acquisition began 20 s after the hand immersion. Analysis of variance was used to compare the ocular surface temperature of the two profiles. The analysis of infrared images was carried out every 2 s: at the eye opening (t0) until 10 s (t5), for both profiles. Data showed that ocular surface temperature increased significantly (p-value < 0.05), especially near the sources of ocular blood supply, that is, temporal and nasal areas (mean increasing temperature at t0 for P1 = 0.12 °C ± 0.13 °C). Therefore, these results suggest a response of the ocular hemodynamic to the peripheral vasoconstriction. The ocular surface temperature may represent a cheap, non-invasive and non-time-consuming test to evaluate ocular vaso-regulation.

Ocular Surface Temperature in Age-Related Macular Degeneration

Background. The aim of this study is to investigate the ocular thermographic profiles in age-related macular degeneration (AMD) eyes and age-matched controls to detect possible hemodynamic abnormalities, which could be involved in the pathogenesis of the disease. Methods. 32 eyes with early AMD, 37 eyes with atrophic AMD, 30 eyes affected by untreated neovascular AMD, and 43 eyes with fibrotic AMD were included. The control group consisted of 44 healthy eyes. Exclusion criteria were represented by any other ocular diseases other than AMD, tear film abnormalities, systemic cardiovascular abnormalities, diabetes mellitus, and a body temperature higher than 37.5°C. A total of 186 eyes without pupil dilation were investigated by infrared thermography (FLIR A320). The ocular surface temperature (OST) of three ocular points was calculated by means of an image processing technique from the infrared images. Two-sample t-test and one-way analysis of variance (ANOVA) test were used for statistical analyses. Results. ANOVA analyses showed no significant differences among AMD groups (P value >0.272). OST in AMD patients was significantly lower than in controls (P > 0.05). Conclusions. Considering the possible relationship between ocular blood flow and OST, these findings might support the central role of ischemia in the pathogenesis of AMD.

Diagnostic accuracy of heel pad palpation - a phantom study.

UNLABELLED Falanga torture involves repetitive blunt trauma to the soles of the feet and typically leaves few detectable changes. Reduced elasticity in the heel pads has been reported as characteristic sequelae and palpatory testing of heel pad elasticity is therefore part of medicolegal assessment of alleged torture victims. The goal was to test the accuracy of two experienced investigators in determining whether a heel pad model was soft, medium or hard. The skin-to-bone distance in the models varied within the human range. METHOD Two blinded investigators independently palpated nine different heel pad models with three different elasticities combined with three different skin-to-bone distances in five consecutive trials and categorized the models as soft, medium or hard. RESULTS Two experienced investigators were able to identify three known elasticities correctly in approximately two thirds of the cases. The skin-to-bone distance affected the accuracy. CONCLUSION The use of clinical examination in documenting alleged exposure to torture warrants a high diagnostic accuracy of the applied tests. The study implies that palpatory testing of the human heel pad may not meet this demand. It is therefore recommended that a device able to perform an accurate measurement of the viscous-elastic properties of the heel pad be developed.

Ocular surface temperature in patients with evaporative and aqueous-deficient dry eyes: a thermographic approach

OBJECTIVE In recent decades infrared thermography (IRT) has facilitated accurate quantitative measurements of the ocular surface temperature (OST), applying a non-invasive procedure. The objective of this work was to develop a procedure based on IRT, which allows characterizing of the cooling of the ocular surface of patients suffering from dry eye syndrome, and distinguishing among patients suffering from aqueous deficient dry eye (ADDE) and evaporative dry eyes (EDE). APPROACH All patients examined (34 females and 4 males, 23-84 years) were divided into two groups according to their Schirmer I result (⩽ 7 mm for ADDE and  >  7 mm for EDE), and the OST was recorded for 7 s at 30 Hz. For each acquisition, the temperatures of the central cornea (CC) as well as those of both temporal and nasal canthi were investigated. MAIN RESULTS Findings showed that the maximum temperature variation (up to 0.75  ±  0.29 °C) was at the CC for both groups. Furthermore, patients suffering from EDE tended to have a higher initial OST than those with ADDE, explained by the greater quantity of the tear film, evenly distributed over the entire ocular surface, keeping the OST higher initially. Results also showed that EDE patients had an average cooling rate higher than those suffering from ADDE, confirming the excessive evaporation of the tear film. SIGNIFICANCE Ocular thermography paves the way to become an effective tool for differentiating between the two different etiologies of dry eye syndrome.

Investigations on the viscoelastic behaviour of a human healthy heel pad: In vivo compression tests and numerical analysis

The aim of this study was to investigate the viscoelastic behaviour of the human heel pad by comparing the stress–relaxation curves obtained from a compression device used on an in vivo heel pad with those obtained from a three-dimensional computer-based subject-specific heel pad model subjected to external compression. The three-dimensional model was based on the anatomy revealed by magnetic resonance imaging of a 31-year-old healthy female. The calcaneal fat pad tissue was described with a viscohyperelastic model, while a fibre-reinforced hyperelastic model was formulated for the skin. All numerical analyses were performed to interpret the mechanical response of heel tissues, with loading conditions and displacement rate in agreement with experimental tests. The heel tissues showed a non-linear, viscoelastic behaviour described by characteristic hysteretic curves, stress–relaxation and viscous recovery phenomena. The reliability of the investigations was validated by the interpretation of the mechanical response of heel tissues under the application of three pistons with diameter of 15, 20 and 40 mm, at the same displacement rate of about 1.7 mm/s. The maximum and minimum relative errors were found to be less than 0.95 and 0.064, respectively.

Analysis and comparison of clutch techniques of two dental implants.

From the clinical point of view, primary implant stability is a fundamental requirement. The aim of the present work was to investigate the primary stability of two types of dental implants, with truncated cone (TC) and cylindrical (CL) geometry, by evaluating their performance by means of pull-out tests. Moreover, several samples were tested by varying surgical preparation method as well as the material where the implant was housed in order to assess whether primary stability could be affected by these factors. A critical load which corresponds to a displacement of 0.2mm in pull-out test was chosen as indicator of the implant primary stability. CL implants had the advantage of requiring lower torques during the installation phase, and thus, applying less local stresses on the bone. Among the housing preparation methods investigated in the present study, the housings realized by using two mill cutters of different diameters for different depths implied higher primary stability for TC implant.

Investigation into the elastic properties of ex vivo porcine corneas subjected to inflation test after cross-linking treatment

Background The aim of this work was to evaluate the effect of cross-linking (CXL) on ex vivo porcine corneal elastic properties, using an inflation procedure. Methods Twelve corneas were subjected to standard CXL (370 nm, 3 mW/cm2, 30 minutes), while 12 were used as controls. Corneal thickness was measured by Visante optical coherence tomography, before and immediately after treatment, and before inflation test. Both intraocular pressure and radial apical cornea displacement were measured during inflation. Stress-strain curves were obtained by applying the linear shell theory. The elastic modulus was evaluated by calculating the slope of the stress-strain curves. Results Results showed a statistically significant increase in elastic modulus (p<0.0001), with a mean of 3,868 ± 502 kPa for cross-linked corneas and 2,727 ± 238 kPa for untreated corneas, when subjected to high pressure (40-60 kPa). CXL significantly increased porcine cornea stiffness by about 42%. Findings did not show any significant difference within the physiological range of pressure (2-4 kPa). Conclusions The inflation test has been proven to be a valuable tool for the investigation of corneal biomechanics, maintaining both integrity and geometry of corneal tissue.

A novel image processing procedure for thermographic image analysis

AbstractThe imaging procedure shown in this paper has been developed for processing thermographic images, measuring the ocular surface temperature (OST) and visualizing the ocular thermal maps in a fast, reliable, and reproducible way. The strength of this new method is that the measured OSTs do not depend on the ocular geometry; hence, it is possible to compare the ocular profiles belonging to the same subject (right and left eye) as well as to different populations. In this paper, the developed procedure is applied on two subjects’ eyes: a healthy case and another affected by an ocular malignant lesion. However, the method has already been tested on a bigger group of subjects for clinical purpose. For demonstrating the potentiality of this method, both intra- and inter-examiner repeatability were investigated in terms of coefficients of repeatability (COR). All OST indices showed repeatability with small intra-examiner (%COR 0.06–0.80) and inter-examiner variability (%COR 0.03–0.94). Measured OSTs and thermal maps clearly showed the clinical condition of the eyes investigated. The subject with no ocular pathology had no significant difference (P value = 0.25) between the OSTs of the right and left eye. On the contrary, the eye affected by a malignant lesion was significantly warmer (P value < 0.0001) than the contralateral, where the lesion was located. This new procedure demonstrated its reliability; it is featured by simplicity, immediacy, modularity, and genericity. The latter point is extremely precious as thermography has been used, in the last decades, in different clinical applications. Graphical abstractOcular thermography and normalization process