TISSUE DIELECTRIC CONSTANT (TDC) AS AN INDEX OF LOCALIZED ARM SKIN WATER: DIFFERENCES BETWEEN MEASURING PROBES AND GENDERS

Abstract

An easily measured, non-invasive,quantitative estimate of local skin tissue wateris useful to assess local lymphedema and itschange. One method uses skin tissue dielectricconstant (TDC) values that at 300 MHzTDC depend on free and bound water withinthe measurement volume. In practice suchmeasurements have been done with a researchtypemulti-probe, but recently a hand-heldcompact-probe has become available that maybe more clinically convenient. Because mostavailable published data is based on multiprobemeasurements it is important to characterizepossible differences between devicesthat unless known might lead to ambiguousquantitative comparisons between TDCvalues. Thus, our purpose was to evaluatepotential differences in measured TDC valuesbetween multi-probe and compact-probedevices with respect to probe effectivesampling depth, anatomical site, and genderand also to compare compact-probe TDCvalues measured on women with and withoutbreast cancer (BC). TDC was measuredbilaterally on forearms and biceps of 32 maleand 32 female volunteers and on 12 femalepatients awaiting surgery for breast cancer.Results show that 1) TDC values at 2.5 mmdepth were significantly less than at 1.5 mm;2) Female TDC values were significantly lessthan male values; 3) TDC values were notdifferent between females with and withoutBC; and 4) dominant/non-dominant armTDC ratios were not significantly differentfor any probe among genders or armanatomical site. These findings indicate thatprobe type differences in absolute TDC valuesare present and should be taken into accountwhen TDC values are compared. However,comparisons based on inter-arm TDC ratiosare not statistically different among probeswith respect to gender or anatomical location.