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 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vivo</i> 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 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vivo</i> . Twenty healthy female subjects aged 21.1 plusmn 1.8 years old were included for the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vivo</i> test. The system was shown to be highly accurate ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 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 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vivo</i> .