Study On Near Infrared Measurement Of Human Subcutaneous Fat Thickness

A self-serviced, portable and simple body composition testing apparatus is highly valued as obesity becomes more and more common in our modern society. The conventional methods have some disadvantages for home use, such as expensive, time-consuming, and uncomfortable. 2/3 of human fat are stored on subcutaneous layer, and we attempt to achieve the near infrared (NIR) measurement of body subcutaneous fat thickness which is a key parameter of body fat content. The method has the advantages such as simple, fast and visual. The works of the dissertation concentrated on study of the measurement principles, computer simulation, fundamental experiment design and potable apparatus design. Firstly, the fundamental principles of measurement are described. Epidermis, subcutaneous fat and muscle constitute human skin. The epidermis features good NIR penetration, while subcutaneous fat is characteristic of low absorption and high backward scattering. In contrast, the muscle, the lower layer of fat, demonstrates high absorption and high forward scattering properties, enabling only a small number of scattered photons to reach the detector. Therefore, we can detect subcutaneous fat thickness by NIR backward scattering light. Then, the Monte-Carlo simulation is applied to study the theoretic feasibility and related properties. Simulation result shows that the maximum depth of average photon transmission is in linear relationship with the light-source separation. The thicker fat is, the more intense the backward emergence light is; the farther the detector is from the light source, the more correlated the emergence intensity and fat thickness are . Thereafter, the basic experiments are designed. The near infrared spectrum measurement by NIR spectrometer verified the feasibility of NIR method. And measurement by using a probe with 9 rings of fibers is conducted to discuss the measuring conditions. The result gives two hints as follows. 1) The contact method should be used. 2) The farther the detector is from light source, the thicker the fat can be measured. Consequently we should try to enlarge the source-detector distance. Finally, a portable apparatus is designed. The pork fat thickness measurement proves that if the thickness is less than 7mm, the measurement error can be controlled less than 0.5mm. And the measurement of human subcutaneous fat thickness indicates that the apparatus can be used to predict the thickness tendency.