Tissue Dielectric Constant Values Research Articles

DIAGNOSTIC COMPARABILITY OF RATIO OF TISSUE DIELECTRIC CONSTANT (TDC) BETWEEN PATIENTS WITH LIPEDEMA AND THOSE WITH LOWER LIMB LYMPHEDEMA (LLL): A PROSPECTIVE OBSERVATIONAL STUDY

Lipedema is usually thought of as a disease of women. Potentially diagnostic comparative data is needed between patients with lipedema and those with lower limb lymphedema (LLL). Since there is no gold standard to diagnose lipedema, some promising modalities such as Tissue Dielectric Constant (TDC) need to be investigated among patients with lipedema and lymphedema. This study was completed with a total of 26 patients (14 lipedema, 12 LLL). Local tissue water was assessed with Moisture MeterD compact (DelfinTech, Kuopio, Finland) according to the TDC method at 300 MHz within a 2.5 mm tissue penetration depth via the following reference points: Thigh, calf (20 cm upper and lower point of knee level, respectively), and malleoli (5 cm upper point of medial malleolus). Patients with LLL showed significantly higher TDC values and interlimb TDC ratios in all affected points and unaffected malleolus points compared to patients with lipedema. No significant difference was achieved between genders with LLL in all reference points. The area under the curve (AUC) for thigh, calf, and malleolus reference points were found as 0.851 (95%CI .678-1.00), 0.801 (95%CI 0.612-0.989) and 0.786 (95%CI 0.596- 0.976), respectively. Patients with LLL showed significantly higher TDC values compared to patients with lipedema, these differences should be carefully interpreted in patients with bilateral LLL and those with lipo-lymphedema.

Intra-day variations in volar forearm skin hydration.

Skin hydration (SKH) measurements are used for multiple purposes: to study skin physiology, to clinically investigate dermatological issues, and to assess localized skin water in pathologies like diabetes and lymphedema. Often the volar forearm is measured at various times of day (TOD). This report aims to characterize intra-day variations in volar forearm SKH to provide guidance on expected TOD dependence. Forty medical students (20 male) self-measured tissue dielectric constant (TDC) on their non-dominant forearm in triplicate as an index of local skin tissue water every 2 h starting at 0800 and ending at 2400h. All were trained and pre-certified in the procedure and had whole-body fat (FAT%) and water (H2O%) measured. Day average TDC (TDCAVG) was determined as the average of all time points expressed as mean±SD. Males versus females had similar ages (25.1±2.2 yearsvs. 25.1±1.5 years), higher H2O% (56.6±5.0vs. 51.8±5.7, p=0.002), and higher TDCAVG (32.7±4.1vs. 28.5±5.1, p=0.008). TDC values were not significantly impacted by H2O% or FAT%. Female TDC exhibited a significant decreasing trend from morning to night (p=0.004); male TDC showed no trend. Skin water assessed by TDC shows some intra-day variations for females and males but with quite different temporal patterns. Clinical relevance relates to the confidence level associated with skin hydration estimates when measured at different times of day during normal clinic hours which, based on the present data, is expected to be around 5% for both males and females.

Chronic Venous Insufficiency With Emphasis on the Geriatric Population.

The underpinning of Chronic Venous Insufficiency (CVI) is valvular dysfunction, which manifests on a spectrum depending on the severity of insufficiency and duration of the disease. The mainstay of treatment relies on compression therapy of a proper type and intensity. In older adults, special consideration must be taken during the patient encounter to account for age-related factors. This review discusses the clinical presentation, diagnosis, and mimicking of CVI, focusing mainly on older adults. The epidemiology, risk factors, disease burden, and grave complications -- such as thrombosis and ulceration, are reviewed. The physiological impacts of CVI are described, providing the background for treatment strategies, including non-invasive, medical, and surgical therapies. The findings show advanced age to be an important risk factor contributing to CVI and that other age-related factors add to the risk of severe complications. Clinical assessments combined with objective measurements that assess localized skin water using tissue dielectric constant values or whole limb assessments may aid in the differential diagnosis. Furthermore, understanding the mechanism of action of compression therapy, the mainstay of CVI treatment, and its physiological impacts, allows for its informed use in geriatric patients with increased risks of potential compression-related side effects.

Tissue Dielectric Constant and Skin Stiffness Relationships in Lower Extremity Lymphedema.

Background: Lower extremity lymphedema or edema (LELE) may progressively transition from a state of excess tissue fluid to increased fat accumulation and collagen deposition, with tissue fibrosis and hardening. Such changes may lead to altered tissue water holding and thereby impact tissue dielectric constant (TDC). This study seeks to evaluate the relationship between TDC and tissue indentation force (TIF) in patients with LELE and assess the utility of the leg/arm TDC ratio (LAR) as an indicator of LELE. Methods and Results: Thirty females (49-91 years) with previously diagnosed LELE were evaluated during a scheduled session. TDC and TIF were measured 8 cm proximal to the medial malleolus on the medial and lateral aspects of both legs and on one forearm 8 cm distal to the antecubital fossa. The TDC-TIC relationship and the LAR were subsequently determined. Main results showed an absence of a significant correlation between TDC and TIF on medial or lateral leg sites but a positive correlation on the normal forearm site. Further, LAR values exceeded the published proposed threshold of 1.35 for 29/30 patients when using medial-side TDC values and 28/30 patients when using lateral-side TDC values. Conclusions: Findings suggest that for patients with LELE, TDC values are significantly elevated on medial and lateral standardized sites. The LAR determined using either medial or lateral sites that are similar to each other and have values consistent with a lymphedema threshold of 1.35. In edematous legs of the type evaluated herein, there is no apparent relationship between TDC values and indentation force.

Circumferential and Depth Variations in Tissue Dielectric Constant Values as Indices of Lower Leg Localized Skin Water.

The primary goal of this study was to quantify circumferential (medial, anterior, lateral) and measurement depth variations (0.5 mm, 1.5 mm, 2.5 mm) in tissue dielectric constant (TDC) values as an aid to their use to assess the presence and progression of lower extremity edema and lymphedema. Measurements were done in 30 healthy non-edematous women to provide reference data to estimate expected values and thresholds when evaluating clinical edematous or lymphedematous conditions. A second goal was to determine the extent to which TDC values evaluated at lower leg sites depend on body mass index (BMI). The study protocol (#12180901) was approved by the university’s institutional review board and subjects were evaluated after signing an approved informed consent. The study group had an age range of 19-54 years with a mean age and SD of 30.6 ± 10.1 years and had a BMI between 18.1-44.1 Kg/m2 with a mean BMI and SD of 24.5 ± 5.4 Kg/m2. The main findings show that at the three circumferential sites (medial, anterior, and lateral) located eight cm from the mid-malleolus, there are small but statistically significant differences in TDC values at every measurement depth (0.5 mm, 1.5 mm and 2.5 mm). For each depth, the maximum difference occurs between the medial and lateral locations with lateral locations having a greater TDC value at all depths. Despite the wide range of BMI values of the subjects evaluated, no significant relationship between TDC value and BMI was detected. It is concluded that TDC measurements in the lower leg reveal statistically significant differences among circumferential sites and measurement depths that should be considered when evaluating or tracking lower extremity tissue water changes associated with edema, lymphedema or other conditions related to skin water. The absolute values of these non-edematous TDC values herein determined may provide a basis for calculating TDC thresholds applicable to edematous or lymphedematous lower leg conditions.

Tissue Dielectric Constant of the Lower Leg as an Index of Skin Water: Temporal Variations.

Tissue dielectric constant (TDC) measurements are a convenient, reliable, and accurate way to noninvasively access local tissue water content and its change with time or treatment. The method has been widely used for upper extremity lymphedema assessments but less so for lower extremities. For lower extremity assessments, it would be useful to have an estimate of the expected inter-leg TDC differentials of normal non-affected legs to help interpret measured inter-leg differentials when such measurements are done in patients with lower extremity edema or lymphedema. The goals of this study were to determine normal inter-leg TDC differences, quantify TDC temporal changes during 60 minutes of supine lying in a group of 10 middle-aged women (42-57 years), and evaluate the change in TDC values as measured throughout the day from 0800 to 2000 hours in a group of 10 younger women (23-28 years). The overall findings indicate that TDC measurements, as an assessment parameter of lower extremity localized skin-to-fat tissue water, are only minimally dependent on potential confounding factors such as 60-minute supine lying or the time of day at which the measurements are made. If the small sample size of the present study is reflective of the larger population, an inter-leg TDC ratio exceeding a value of 1.2 is suggested as a threshold for judging unilateral lower extremity edema or lymphedema. This possibility needs assessment in women with these conditions.

Tissue Dielectric Constant Differentials between Malignant and Benign Breast Tumors

IntroductionThis study's purpose was to characterize tissue dielectric constant (TDC) values of malignant and benign breast tumors and assess the potential utility of TDC differentials to help distinguish between malignant and benign tumors. MethodsPrior to their diagnostic biopsy, TDC was measured at 300 MHz in 59 women with previously detected breast tumors. TDC measurements were made by touching skin directly over the tumor and on the non-affected breast with a hand-held 22 mm diameter probe. Each measurement took less than 10 seconds. An inter-breast TDC ratio (RATIO) was calculated as the ratio of the tumor breast TDC value divided by the non-affected breast TDC value measured on the contralateral breast at a corresponding anatomical site. Absolute TDC values and RATIOS were compared for malignant and benign tumors based on post-measurement biopsy determinations. ResultsBiopsy findings indicated tumors were malignant in 29 patients and benign in 30. Compared to the non-affected breast, malignant tumor TDC values were greater (P = .0002) whereas for benign tumors, there was no inter-breast difference (P = .256). No patient with a benign tumor exceeded a RATIO of 1.15 whereas 12 of the 29 patients with malignant tumors exceeded this threshold and tended to have larger volume tumors. ConclusionA tentative threshold RATIO of 1.15 may be discriminatory between malignant and benign tumors if the tumor is sufficiently large. Further research using a probe with a greater penetration depth is warranted to potentially increase discrimination.

FOREARM AND BICEPS CIRCUMFERENTIAL VARIATIONS IN SKIN TISSUE DIELECTRIC CONSTANT AND FIRMNESS

Tissue dielectric constant (TDC) and skin firmness assessed via indentation force (FORCE) help quantify lymphedema and track changes. We sought to determine potential differences in these parameters dependent on arm circumferential locations. Thus, TDC and FORCE were measured in 40 healthy women at medial, anterior and lateral locations on forearm and biceps. In five other women with unilateral lymphedema (68.6±7.6 years), TDC was measured at corresponding circumferential forearm positions. Measurements were done in triplicate using compact noninvasive devices. Results for healthy women (23.8±2.7 years) showed forearm medial TDC values (26.7±2.2) were less than anterior (28.0±2.4) or lateral (28.0±2.5) positions (p<0.001). Lymphedema patients had elevated values but similar medialanterior- lateral patterns (33.7±8.0, 39.8±10.2 and 42.9±10.0). Biceps medial TDC values (24.1±2.2) were also less than either anterior (27.0±2.1) or lateral (28.2±3.3). Contrastingly, medial FORCE values at forearm and biceps were less than at anterior and lateral locations (p<0.001) and increased in the order of medialanterior- lateral on forearm (p<0.001). The present findings provide reference values for both TDC and FORCE of commonly measured arm sites with specificity as to circumferential variations. This observed variation indicates the need for care in locating measurement positions for tracking patients with lymphedema.

Breast Tissue Dielectric Constant as a Potential Breast Edema Assessment Parameter.

Background: Many methods can quantitatively assess limb lymphedema, but methods to assess breast edema/lymphedema are quite limited. Thus, there is a need for a convenient and accurate way to quantify and track changes in this condition. Herein, breast tissue dielectric constant (TDC) values that depend on tissue water were used to obtain reference TDC values and interbreast TDC ratios. Methods and Results: TDC was measured in both breasts of 61 women who were about to undergo an ultrasound-guided diagnostic biopsy of a single mass (tumor) in 1 breast. Patient age and body mass index were (mean ± SD) 65.1 ± 11.6 (41-87 years) and 28.9 ± 5.1 (19.1-43.7 kg/m2). TDC was measured at a standardized site (12 o'clock position) with the TDC probe placed with its outer edge at the periphery of the subareolar region. TDC values of healthy breasts versus tumor breasts showed tumor breasts 3% greater (30.4 ± 4.6 vs. 29.5 ± 4.6, p = 0.02). Patients with benign tumors (N = 33) showed no difference between breasts (30.5 ± 4.4 vs. 30.8 ± 4.6 p = 0.434) and had an interbreast TDC ratio (tumor breast/healthy breast) of 1.013 ± 0.077. Patients with malignant tumors (N = 28) had tumor breast values 5% greater (29.8 ± 4.8 vs. 28.4 ± 4.6, p = 0.018) and an interbreast ratio of 1.056 ± 0.117. The overall interbreast ratio (N = 61) was 1.033 ± 0.099. Conclusion: Breast TDC values from nonedematous breasts provide the basis for calculating potential edematous/lymphedematous threshold values based on the measured means +2.5 standard deviation (SD). Accordingly, a TDC threshold value of 41 and an interbreast ratio of 1.28 were determined. These parameters have potential applicability for early detection in at-risk patients and those suspected of having breast edema/lymphedema.

Tissue Dielectric Constant Combined With Arm Volume Measurement as Complementary Methods in Detection and Assessment of Breast Cancer-Related Lymphedema.

Background: To investigate the role of tissue dielectric constant (TDC) in the detection and assessment of breast cancer-related lymphedema (BCRL) and to determine whether the TDC could potentially be used as a complementary method for arm volume measurement. Methods: Sixty-nine patients with BCRL were enrolled in this study. Local tissue water was assessed bilaterally by using the TDC method in four sites: upper arm, forearm, hand, and lateral thorax. Arm circumferences were measured at the 4-cm interval, starting from the shoulder to the wrist by using a tape measure. The arm volume was calculated by a standard formula. Patients' demographic information and clinical characteristics were also recorded. Results: Fifty-one of the 69 patients were diagnosed with clinical lymphedema. Using a TDC ratio of 1.2 or a diagnostic reference standard of ≥2 cm arm circumference, the sensitivity of these two methods was found to be identical at 73.9%. The TDC values in four sites on the affected side were significantly higher (p < 0.05) relative to the unaffected side. The inter-side TDC ratio of upper arm and forearm was substantially higher than that of lateral thorax and hand (p < 0.05). The TDC ratio of upper arm, forearm, and hand, especially of the upper arm and forearm, was positively correlated with inter-limb volume difference and stage of lymphedema. Conclusion: The TDC method elucidated a meaningful clinical correlation to the arm volume measurement. Applying those two methods together showed promise in the detection and assessment of BCRL. The forearm and upper arm were reliable examination sites for TDC measurements in the clinic.

An Approach Toward Assessing Head-and-Neck Lymphedema Using Tissue Dielectric Constant Ratios: Method and Normal Reference Values.

Background: There are multiple methods to quantitatively assess limb lymphedema, but quantitative methods to assess external lymphedema in persons with head-and-neck lymphedema are quite limited. Quantification in this difficult condition currently uses multiple time-consuming head, face, and neck metric measurements, the accuracy of which is unclear. Thus, there is an important need for a new approach that is sufficiently convenient yet accurate to quantify head-and-neck lymphedema. The approach adopted was to use tissue dielectric constant (TDC) measurements that depend on tissue water, at neck and a submental area, and normalize these to TDC values at the forearm as a way to develop subject-independent indices. Methods and Results: TDC was measured in 60 self-reported healthy nonlymphedematous adults (34 female, 18-81 years, 18.5-45.7 Kg/m2) at two neck sites and one arm site bilaterally and at a submental area. Neck-to-arm-index (NAI) and submental-to-arm-index (SAI) ratios were calculated. TDC values (mean ± standard deviation [SD]) for neck, submental, and arm were, respectively, 37.4 ± 6.9, 35.9 ± 7.7, and 30.1 ± 4.6. Mean NAI and SAI values were 1.253 ± 0.222 and 1.214 ± 0.296 respectively. Head-and-neck lymphedema thresholds calculated as mean + 2.5 SD were for NAI and SAI 1.80 and 1.95, respectively. Conclusions: An approach to help quantify and track head-and-neck lymphedema using TDC neck and/or submental values normalized to a person's forearm TDC values indicates threshold values between 1.80 and 1.95. These ratios, denoted as NAI and SAI, are suggested for use to detect and track changes in lymphedema status based on a patient's changing indices associated with lymphedema treatment.

Effects of local forearm skin heating on skin properties

This study investigated impacts of local skin heating on skin properties and tested whether skin changes depended on heat-induced hyperaemia. It was reasoned that heat-induced vasodilation impacts accompanying interstitial fluid changes. Forearm skin was locally heated from a baseline of 35°C to 40-42°C in 30 young adults (15 females, 15 males, 24.9±2.1years) and non-heated in 10 others (5 females, 5 males, 25.2±1.3years. Skin blood flow (SBF) was continuously measured using a laser Doppler method and skin tissue dielectric constant (TDC), stratum corneum capacitance (SCC) and transepidermal water loss (TEWL) were measured before and after maintained heat for 12min. TDC values were determined to effective measurement depths of 1.5mm (TDC15) and 2.5mm (TDC25). Results showed a large heat-induced hyperaemia, with SBF increasing on average 8.8-fold from its baseline of 35°C. Heating also caused significant increases in TDC, SCC and TEWL that, compared to preheating, increased approximately 1.1-fold, 3.1-fold and 4.5-fold. None of these skin changes correlated with the magnitude of the SBF hyperaemic response. Absence of this correlation may indicate that in young healthy adults, increased capillary filtration due to heat-induced arteriolar vasodilation is rapidly accommodated by postcapillary reabsorption, enhanced lymphatic activity and TEWL processes. An alternate explanation is that heating caused increased red cell oscillations that were detected as part of the laser Doppler increase without representing increased capillary flux. The major determinant of the Increases in TDC, SCC and TEWL is likely a consequence of heat-induced eccrine gland activation. Studies of older persons or those with depressed function are warranted.

Heat-related changes in skin tissue dielectric constant (TDC).

The impact of 20min of whole-body heating (WBH) on the tissue dielectric constant (TDC) of forearm and hand skin was evaluated in 24 young adults. TDC was measured in triplicate at 300MHz using an open-ended transmission line method in which the effective measurement depth was about 2mm. TDC measurements are an effective way to assess and track localized oedema and lymphoedema. The underlying hypothesis was that heat-induced eccrine gland activation would increase TDC values via an increase in fluid within the TDC measurement volume. The goal was to test this concept and to determine the magnitude of the change when environmental temperatures were elevated to near 42°C and to estimate TDC recovery time. The practical aspect of this research is motivated by the fact that patients in whom such measurements are made may arrive at the clinic in various states of sweat gland activation. Thus, knowledge of the effect of such activation on measured TDC values permits better understanding of possible relationships between such activation and TDC values. Results showed that increasing environmental temperature from 23·3±1·6 to 41·5±1·3°C increased forearm and thenar eminence skin temperatures to 37·8±0·5 and 37·9±0·4°C, respectively. These changes were associated with increases in TDC at arm from 30·7±4·6 to 36·3±5·7 (18·2%) and at hand from 34·7±4·9 to 45·1±5·5 (30%). Based on calculated TDC recovery rates, it is concluded that temperature-related TDC variability can be minimized using a wait time of at least 15min after bandage removal prior to TDC measurements in affected limbs.

Test-Retest Reliability of Volume and Local Tissue Water Measurements in Lower Limbs of Healthy Women and Men.

Background: Measurements of lower limb (LL) volume and local tissue water by tissue dielectric constant (TDC) are common in lymphedema management. Knowledge of normal variability in health subjects is important and can serve as a base for early lymphedema diagnosis but is currently lacking. The aim of this study was to evaluate test-retest reliability of LL volume and TDC values in healthy women and men. Methods and Results: Thirty-three women and 28 men were measured twice, 2 weeks apart. Volume was calculated from circumferential measurements every 4 cm and TDC in 14 points. Test-retest reliability was evaluated using intraclass correlation coefficient (ICC), changes in the mean, standard error of measurement in percentage (SEM%), and smallest real difference in percentage (SRD%). For volume, reliability was high (ICC 0.99) and measurement errors were low in both women and men (SEM%: 1.1%-1.3%; SRD%: 3.1%-3.6%). For TDC, reliability was fair to excellent in women (ICC 0.63-0.93) and poor to excellent in men (ICC 0.21-0.89). Measurement errors were acceptable in all points in women (SEM%: 3.9%-10.2%; SRD% 10.8%-28.2%), but only in 11 points in men (SEM%: 3.9%-14.5%; SRD%: 10.9%-40.1%). The points close to bone and tendons in men had lower reliability and higher measurement errors. Conclusion: Measurements of LL volume and TDC are reliable in healthy women and men; both methods can be recommended. However, TDC points close to bone and tendons in men should be used with caution.

FACTORS AFFECTING INTERPRETATION OF TISSUE DIELECTRIC CONSTANT (TDC) IN ASSESSING BREAST CANCER TREATMENT RELATED LYMPHEDEMA (BCRL)

Tissue dielectric constant (TDC) measurements are increasingly used as quantitative adjunctive tools to detect and assess lymphedema. Various factors affect measured TDC values that may impact clinical interpretations. Our goal was to investigate possible impacts of: 1) anterior vs. medial arm measures, 2) total body water (TBW%) and arm fat percentages (AF%), 3) measurement depth, and 4) skin firmness. In 40 healthy women (24.5±2.5 years), TDC was measured bilaterally on anterior forearm to 0.5, 1.5, 2.5, and 5.0 mm depths using a multiprobe device and on anterior and medial aspects using a compact device. TBW% and AF% were measured at 50KHz and skin firmness measured by skin indentation force (SIF). Results showed: 1) No statistically significant difference in TDC values between anterior and medial arm, 2) a moderate direct correlation between TDC and TBW% (r=0.512, p=0.001), 3) an inverse correlation between TDC and AF% (r= -0.494, p<0.001) with correlations greatest at the deepest depth, and 4) a slight but statistically significant inverse correlation between TDC and SIF (r= -0.354, p=0.001). TDC values with compact vs. multiprobe were within 6% of each other with interarm (dominant/nondominant) ratios not significantly different. The findings provide a framework to help interpret TDC values among divergent conditions.

Skin tissue dielectric constant in women with high body fat content.

Skin tissue dielectric constant (TDC) measurements at a frequency of 300MHz are used to assess skin properties in many conditions. Impacts of patient obesity on these values are unknown, and its quantitative assessment was the goal of this research. Women in a weight loss program (N=32) had TDC measured on forearm, biceps, neck, jowl, and submental regions along with measurements of total body fat (TBF), water (TBW), intracellular water (ICW), and extracellular water (ECW) via multi-frequency bioimpedance. Group age (mean±SD) was 40.0±11.6years (20-70years) with body mass index (BMI) of 31.8±6.7Kg/m2 (23.0-49.9Kg/m2 ). For analysis, subjects were divided into those with BMI<30Kg/m2 (subgroup A, n=16) vs ≥30Kg/m2 (subgroup B, n=16). Tissue dielectric constant at forearm and biceps decreased significantly (P<.001) with increasing depth from 0.5 to 1.5 to 2.5mm but TDC values and their inter-side ratios did not differ between subgroups A and B at any measured site. Although correlations between TBW, ECW, and ICW were significant (P<.001), there was no dependence of TDC values on any of these parameters. Previously unknown TDC values for obese persons are provided and based on subgroup analyses suggest that skin TDC values in overweight and obese persons are not confounded by variables such as TBW and TBF. Further, since inter-side ratios and their SD's yielded thresholds for forearm and biceps similar to those established for women with normal BMI, use of these clinical inter-arm TDC ratios now is extended to include a wider BMI range.

IMPACT OF BODY FAT AND OBESITY ON TISSUE DIELECTRIC CONSTANT (TDC) AS A METHOD TO ASSESS BREAST CANCER TREATMENT-RELATED LYMPHEDEMA (BCRL)

Obesity is linked to the risk of breast cancer and treatment-related lymphedema (BCRL). Thus, knowledge of how obesity, or more specifically total body fat percentage (TBF) and body mass index (BMI), affect measurements that are used to detect or track lymphedema is clinically important. Tissue dielectric constant (TDC) is one measure used to help characterize lymphedema features, detect its presence, and assess treatment-related changes. The goal of this research was to determine the extent to which TDC values depend on TBF and BMI. TDC was measured on both forearms (2.5mm depth) in 250 women (18-72 years) along with TBF (impedance, 50KHz). TBF was 12.2%- 54.4% (median=29.3%) and BMI was 14.7Kg/m2-44.3 Kg/m2 (median=22.6 Kg/m2). TDC values and interarm ratios were compared between subgroups that had TBF and BMI values in lower vs. upper quartiles. Subjects in the upper quartile had slightly lower TDC values (1.3 TDC units, p <0.01) that was at most a 5% differential. Contrastingly, TDC interarm ratios were not dependent on TBF or BMI levels. These findings suggest that when tracking lymphedema changes using the TDC method, treatment-related or temporal changes in a woman's TBF or BMI are unlikely to significantly impact TDC values or their interarm ratios.

Minimum Detectable Changes Associated with Tissue Dielectric Constant Measurements as Applicable to Assessing Lymphedema Status

Background: Tissue dielectric constant (TDC) measurements are increasingly being used as a tool to help characterize lymphedema features, detect its presence, and assess treatment related changes. Although the underlying physics of this technology has been well described in the literature, there has been little systematic study of in vivo reliability aspects. A central unanswered question is the minimal detectable change (MDC) that, with a given level of confidence, may be ascribed to this technology. Our goal was to address this issue using test-retest measurements from which intraclass correlations coefficients (ICC) and MDC could be estimated. Methods and Results: Forty volunteers (20 females) aged 19-61 years with body mass indices of 14.7-47 kg/m2 and body fat percentages of 12.0%-48.9% were evaluated. Two measurers (M1 and M2) used two different TDC measuring devices (multiprobe and compact) to measure TDC in triplicate sequentially and bilaterally at three locations; anterior forearm, hand palmar mid-thenar eminence, and dorsum mid-web. These measurements were made by each measurer twice constituting test-retest values (T1 and T2). From these measurements ICC2,1 and MDC at 95% confidence were determined for each site and probe for absolute TDC values and for inter-side ratios. MDC values for absolute TDC ranged from 2 to 9 TDC units, and for inter-side ratios ranged from 5.3% to 8.0% depending on site and probe. ICC2,1 values ranged from 0.765 to 0.982. Conclusions: The MDC values herein documented may be used to provide guidance to aid interpretation of measured TDC changes or differences in a clinical environment.

Spatial and Temporal Variability of Upper Extremity Edema Measures After Breast Cancer Surgery.

Background: Tissue dielectric constant (TDC), as an index of local tissue water, and girth measurements are quantitative methods to measure and characterize lymphedema. Objective: To describe the spatial and temporal variability in arm girth and TDC values in women surgically treated for breast cancer and to describe the relationship between these measures. Methods and Results: This was a prospective longitudinal study that observed 36 women for 78 weeks after breast cancer surgery with lymph node removal. Arm circumferences and TDC values, as indices of local tissue water, were measured on both arms at multiple sites at postsurgery weeks 2, 4, 12, and 78 in women undergoing surgical breast cancer treatment with one or more axillary lymph nodes removed. TDC and girth values remained relatively uniform from visit-to-visit for both at-risk and contralateral control arms with no overall statistically significant difference in values (p > 0.05). There was a strong inverse correlation between arm girth and the TDC value in both the at-risk and control arms (p < 0.001). Overall, there was no statistically significant difference in TDC interarm ratios among visits or anatomical sites. TDC values for at-risk and control arms tended to significantly decrease with increasing distance from the wrist (p < 0.001). Conclusion: TDC arm values and girth measures remained relatively uniform in women after breast cancer surgery. The fact that TDC values are higher distally than proximally provides new information from which TDC measurements may be interpreted and also provides a better understanding of arm spatial variability in relation to girth measures.

Assessing Upper and Lower Extremities Via Tissue Dielectric Constant: Suitability of Single Versus Multiple Measurements Averaged.

Background: Tissue dielectric constant (TDC) measurements as an index of local tissue water are useful in a range of applications most notably to characterize and assess lymphedema. Once a measuring device is applied to skin and a result is obtained in less than 10 seconds, but multiple sites may be required and use of the standard triplicate measurements may be time prohibitive. Thus, this study's goal was to provide data from which informed judgments could be made as to the impact of making a single measurement to reduce expended clinic time. Methods and Results: Sixty subjects (30 female) were recruited with an average age (mean ± standard deviation) of 30.6 ± 13.4 years. TDC was measured in triplicate bilaterally at forearm, hand palm, lateral calf, medial calf, and foot dorsum. The agreement in absolute TDC values and interside ratios was evaluated for assessments made using only the first TDC measurement, the average of duplicates and the standard triplicate. Results showed that differences between single and multiple measurement averages were anatomical site dependent with the smallest coefficient of variation (2.19%) at the forearm and the largest at the lateral calf (4.59%). Conclusions: Results suggest that when clinical time is of major concern, useful TDC data may be obtained in upper limbs using single TDC measurements per anatomical site whereas lower extremity skin assessments should be done using at least duplicate and preferably triplicate measurements. However, as with all such time reliability considerations, clinical judgment should be exercised and aided by the various findings of this study.