Comparing the Values of Tissue Fluid Accumulation Using Tissue Dielectric Constant and Bioimpedance Analysis in...

To quantitatively assess short-term, intervention-associated changes in tissue water distribution using tissue dielectric constant (TDC) and bioimpedance analysis (BIA) in healthy volunteers, and to explore correlations between the two modalities.

Thirty-one healthy participants underwent a lymphedema-related intervention on their dominant arm, which included pumping and clearing of the terminus, manual lymphatic drainage, and low-level laser therapy. TDC and BIA were measured before and after the intervention. TDC-derived percentage of water content (PWC) was obtained at nine anatomical sites using a Lymphscanner, while BIA was performed using an InBody S10. Pre- and post-intervention differences were analyzed, and correlations between ΔTDC and ΔBIA parameters were evaluated using Spearman's correlation coefficients.

TDC showed small, site-dependent superficial water changes, with significant decreases in PWC at the trunk and breast, and a mild increase at the shoulder on the intervention side. BIA revealed significant increases in R0 and impedance at several frequencies, while extracellular water to total body water ratio and reactance remained unchanged. Correlation analyses identified a few site-specific significant associations between ΔTDC and ΔBIA parameters; however, these correlations were weak-to-moderate and exhibited no consistent pattern across sites or frequencies.

Although TDC and BIA both detected small intervention-associated changes in healthy volunteers, the limited correlations between the two modalities suggest that they are not interchangeable. TDC reflects localized superficial tissue water, whereas BIA assesses broader segmental fluid distribution. Therefore, their combined use may provide complementary information by evaluating distinct aspects of tissue water distribution. Further studies involving patients with lymphedema are warranted.