A Hand-Held Indentation System for the Assessment of Mechanical Properties of Soft Tissues In Vivo
ABSTRACT Quantitative assessment of the mechanical properties of soft tissues in vivo is required in both clinical and research fields. This paper introduces a hand-held indentation system that employed an electromagnetic spatial sensor as a displacement transducer. The system was pen-sized, portable, and easy to control. The accuracy and reliability of the system were investigated. The effect of indentation rate on the variation of the values of the measured effective Young's modulus was also studied. A series of elastomers with different Young's modulus (which ranged from 13.08 to 36.19 kPa) were assessed with both the hand-held indentation system and a Hounsfield material testing machine. Intraindividual and interindividual variations of the system were tested by five independent operators. The hand-held indentation system was applied to quantitatively assess the effective Young's modulus of human body parts in vivo . Twenty healthy female subjects aged 21.1 plusmn 1.8 years old were included for the in vivo test. The system was shown to be highly accurate ( R 2 = 0.99) compared with the results obtained by the mechanical testing machine and had good reliability (intraindividual variation = 5.43%, and interindividual variation = 5.99%). The average effective Young's moduli of the region of umbilicus were 11.31 and 12.65 kPa for two different sites, respectively. It is believed that this hand-held indentations system was an accurate reliable tool for rapidly assessing the mechanical properties of human body tissues in vivo .
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ABSTRACT: A series of antibacterial hydrogels were fabricated from an aqueous solution of AgNO3, gelatin and carboxymethyl chitosan (CM-chitosan) by radiation-induced reduction and crosslinking at ambient temperature. The nanosilver particles were in situ synthesized accompanying with the formation of gelatin/CM-chitosan hydrogel. Transmission Electron Microscope and UV–vis analysis have verified the formation and homogeneous distribution of nanosilver particles in the hydrogel matrix. The nanosilver/gelatin/CM-chitosan hydrogels possessed interconnected porous structure, had a compressive modulus of 44 to 56 kPa, and could absorb 62 to 108 times of deionized water to its dry weight. Furthermore, the hydrogels were found to have sound antibacterial effect on Escherichia coli (E. coli), and their antibacterial ability could be significantly enhanced by the increasing of AgNO3 content. The comprehensive results of this study suggest that nanosilver/gelatin/CM-chitosan hydrogels have potential as an antibacterial wound dressing.Radiation Physics and Chemistry 05/2012; 81(5):553–560. DOI:10.1016/j.radphyschem.2012.01.014 · 1.19 Impact Factor
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ABSTRACT: Capsule endoscopy is a frontline medical diagnostic tool for the gastro intestinal tract disorders. During diagnosis, efficient localization techniques are essential to specify a pathological area that may require further diagnosis or treatment. This paper presents the development of a miniature tagging module that relies on a novel concept to label the region of interest and has the potential to integrate with a capsule endoscope. The tagging module is a compact thermo-mechanical actuator loaded with a biocompatible micro tag. A low power microheater attached to the module serves as the thermal igniter for the mechanical actuator. At optimum temperature, the actuator releases the micro tag instantly and penetrates the mucosa layer of a GI tract, region of interest. Ex vivo animal trials are conducted to verify the feasibility of the tagging module concept. X-ray imaging is used to detect the location of the micro tag embedded in the GI tract wall. The method is successful, and radiopaque micro tags can provide valuable pre-operative position information on the infected area to facilitate further clinical procedures.Journal of Micromechanics and Microengineering 03/2011; 21(4):045037. DOI:10.1088/0960-1317/21/4/045037 · 1.73 Impact Factor
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ABSTRACT: Material characterization of soft biological tissues by mixed experimental/numerical (inverse) techniques represents a powerful tool for the analysis of their complex mechanics. However, the uncertainty related to the accuracy and capability of the technique is not yet completely investigated and understood. In this work, a quasi-static indentation procedure is implemented in order to extract the Mooney-Rivlin material parameters and the equivalent Young’s modulus for a hyperelastic rubber-like material. A non-standard approach based on a Finite Element (FE) inverse method is employed. An experimental set-up consisting of a dedicated micro-indentation system has been employed to extract reaction force values as a function of the penetration depth. A cost function, based on the square difference between experimental and numerical data, is optimized trough a modified Nelder-Mead direct search algorithm (MNMA). The accuracy of the identified parameters is discussed using results of a virtual benchmark case study.