Detecting Lymphedema: Bioimpedance Spectroscopy and the Tissue Dielectric Constant

The current issue of Lymphatic Research and Biology gives us the opportunity to visit, and re-visit, some of the various methodologies that are in current clinical use for the detection and diagnostic validation of lymphedema.

In recent years, the detection of latent and early lymphedema has been greatly facilitated by the advent of bioimpedance spectroscopy (BIS).^1–4 Increasingly widespread use of this technique has facilitated the implementation of early therapeutic interventions in the at-risk population, with an associated optimization of outcomes. ⁵

In this issue of the Journal, Lahtinen and colleagues have undertaken a comparative assessment of a more recently developed technique for the detection of edema. ⁶ The authors have compared bioimpedance spectroscopy to quantitation of the tissue dielectric constant (TDC). The TDC method uses an open-ended coaxial probe to quantitate the dielectric properties of the examined tissues. The dielectric properties correlate to tissue water content. Prior studies have suggested the utility of this technique in the detection of early lymphedema.^7,8 The current investigation focuses upon a study population of breast cancer survivors at risk for the development of secondary lymphedema. In the investigators hands, the comparison between BIS and TDC suggested greater sensitivity for TDC with equivalent specificity. The authors attribute the greater sensitivity of TDC to its capacity to detect early, superficial accumulation of tissue water. Further studies are warranted to determine whether these differences can be substantiated, and to determine the future complementarity of these diagnostic approaches in the management of at-risk patient populations.