Mathematical Analysis of Multi-Frequency Bioimpedance for Body-Composition Assessment

Physicians and Dieticians usually rely on a body-composition (BC) assessment for diagnosing and treating their patients. Measuring BC provides a quantitative estimation of the amount and distribution of fat, muscle, bone, and water compartments in the body. There is no single measurement and/or error-free method in existence that allows for the measurement of all tissues. The Bioelectrical Impedance Analysis (BIA) instruments are preferred in medicine because of their precision and reliability for measuring BC. BIA measures the opposition to the flow of a weak electric AC at single or multiple frequencies through electrodes attached to the hands and feet of a subject. In the following, we will give a detailed analysis of the mathematical description of the BIA technique, with emphasis on frequency dispersion analysis by circular arc plots in the complex plane and equivalent circuit modeling for validating BC data of various compartments.