Potential Use of Leg to Arm Tissue Dielectric Constant Ratios as a Lower Extremity Edema Index

Potential use of Leg to Arm Tissue Dielectric Constant Ratios as a Lower Extremity Edema Index Ram Hirpara, OMS-I, Issac Ichoa, OMS-I, Ted Frederic, OMS-I, Harvey Mayrovitz, Ph.D., Kiran C. Patel College of Osteopathic Medicine and College of Medical Sciences Objective: To provide normative tissue dielectric constant (TDC) ratios as reference for assessing lower extremity edema or lymphedema. Background. Assessment of leg edema or lymphedema is useful to determine treatment effectiveness. However, clinical assessment is largely visual and tactile and could be aided by a less subjective approach. Methods. TDC was measured at the foot, calf and forearm and foot/arm and calf/arm ratios were calculated. The logic of using these ratios was that for most lower extremity edematous conditions, there is little or no effect on arm water. Thus, the ratios provide self-contained assessment parameters independent of possible variations in absolute TDC values among patients. These ratios were measured in 44 young and 64 mature persons equally divided by gender to test for age-related differences. Results. Foot/arm ratios of mature vs. young (mean ± SD) were 0.997 ± 0.112 and 1.041 ± 0.184 and did not statistically differ (p =0.157). Calf/Arm ratios were 1.050 ± 0.168 vs. 1.085 ± 0.197 and did not significantly differ (p =0.320). Including both age groups (n = 108) to get combined ratios yielded 1.015 ± 0.146 for foot/arm and 1.013 ± 0.160 for calf/arm. Potential lymphedema threshold ratios, calculated as the mean ratio plus 2SD, were for foot/forearm and calf/forearm 1.307 and 1.333 respectively. Conclusion. Based on the present findings it is proposed that a conservative estimate of lower extremity lymphedema presence could be based on a foot/arm or calf/arm TDC ratio exceeding 1.35. The test of these conclusions requires future research