Tissue Dielectric Constant Measurements Research Articles

Breast Cancer-Related Lymphedema Assessed via Tissue Dielectric Constant Measurements.

This review describes the use of tissue dielectric constant (TDC) measurements mainly in the assessment of breast cancer-related lymphedema (BCRL). PubMed, Web of Science, and EMBASE databases were initially searched using criteria that included the terms "dielectric" and "lymphedema." The initial search yielded a total of 131 titles. After removing studies not focused on upper extremity lymphedema, 56 articles remained. These articles, together withrelevant articles from their bibliographies, formed the basis of the review. The findings show the potential utility and applications of TDC measurements to help detect and track BCRL, whether present in limbs, breasts, or trunks. It is reported as a non-invasive, simple-to-use method, with each measurement requiring less than 10 seconds, suggesting its practicality and useability as an in-office or in-clinic screening and tracking method. Although there are various ways to quantitatively evaluate lymphedema, most, if not all, are restricted to measurements on limbs. Thus, one significant advantage of the TDC approach is that almost any local region of interest can be effectively measured and tracked, which, for BCRL, could include specific regions of arms or hands, breasts, and truncal areas.

Medical Applications of Skin Tissue Dielectric Constant Measurements.

Tissue dielectric constant (TDC) values assess certain skin properties that are dependent on multiple factors but mainly on the relative amount of water content within a locally measured tissue volume. Because of the non-invasive nature of these measurements and their ease of use, the method has been widely used in various medically related applications. The goal of this paper was to review and describe the uses and findings of such TDC measurements, considering and including the wide array of medical applications. The review is in part based on information derived from an analysis of published material obtained via literature searches of four major electronic databases and, in part, based on the author's experience with the TDC measurement methods and their various applications and his professional experiences. The databases searched were PubMed, Web of Science, EMBASE, and CINAHL Complete. Based on the initial search criteria, a total of 1257 titles were identified. After removing duplicates and filtering according to relevancy, 160 remained for detailed further review. In some cases, the bibliography of these retrieved articles provided additional sources. The findings demonstrate multiple research and medical uses and applications of TDC measurements, focusing on detecting and quantifying localized edema and lymphedema in multiple target sites. These include the upper and lower extremities, breasts, and trunk as regions involved in medical conditions causing lymphedema. In addition, the findings suggest that TDC evaluations are a convenient, non-invasive method to study and evaluate other conditions impacting skin, including diabetes mellitus and skin wounds or ulcers. Its ability to detect aspects of tissue changes simply and rapidly at almost any anatomical location makes it a useful tool for investigating multiple dermatological conditions and their treatment as future applications of this method.

Test-Retest Reliability of a Protocol for Assessment of Local Tissue Water in the Head and Neck Area.

Background: Lymphedema measurement is vital to select appropriate treatment and monitor its progress. Quantifying lymphedema in the head and neck area is challenging. The use of tissue dielectric constant (TDC) measurements has shown promising results in other body areas. This study aims to determine the test-retest reliability of a TDC measurement protocol developed for the head and neck area. Methods and Results: A detailed measurement protocol, including eight measurement points per side, was developed. Subsequently, the reliability of the protocol was tested in a sample of healthy participants (n = 50, 28 males). Using the LymphScanner (Delfin, Finland), participants were subjected to two measurement sessions. Each measurement point was measured three times per session. Test-retest reliability for each point was evaluated using intraclass correlation coefficients (ICCs) and standard errors of measurement (SEMs). Using the average of three measurements, reliability was good to excellent for all points (ICCs 0.81-0.95), with small measurement errors (SEMs 1.51-2.86). The reliability of a single measurement was moderate to excellent for all measurement points (ICCs 0.58-0.87), with larger, but still small, measurement errors (SEMs 1.65-3.39). When using single measurements, the lowest ICCs were found for the temporal (left 0.73 and right 0.67) and submandibular (left 0.58 and right 0.77) locations. Conclusion: Measurements with the LymphScanner, taken according to the developed protocol, are reliable in healthy participants. We recommend using the average of three measurements to optimize reliability. The protocol is fit for further testing in patient populations and for determining normal values in a larger scale study with healthy subjects.

A Tissue Dielectric Constant Evaluation of Knee Edema: A Retrospective Intra-rater Reliability and Association Study of Repeated Measures.

This research compared the reliability and association of tissue dielectric constant (TDC) measures of knee edema to circumferential measurements of knee girth recorded as part of a physical therapy examination. Twenty adults having observable unilateral knee edema were enrolled. A single examiner measured edematous knee swelling with a TDC device and a tape measure across two visits. The presence of edema was recorded as a positive number in reporting side-to-side differences and a positive percentage in documenting change over time. Intra-rater reliability of the measures was assessed with an intra-class correlation coefficient (ICC). Percent change in edema was evaluated independently for both methods using a paired t-test, and the association between measures was assessed by a Pearson's statistic. Both measures were reliable (ICC ≥ 0.81), and both detected a significant percentage decrease (p < 0.05) in edema across visits. The TDC measure changed by 8.3%, an amount nearly four times larger compared to knee girth (2.4%). The subsequent follow-up comparison revealed an inverse relationship (p = 0.049; r = -0.44) between the two percent change measurements of edema. The two methods capture different physical attributes of edema. The TDC records the water content of the tissue, while the use of a tape measure records circumferential limb girth. The TDC measurement was reliable and more responsive in detecting a percentage decrease in knee edema in comparison to a circumferential measure of knee girth. The TDC method may have wider use in directly measuring edema in other tissue structures and regions of the body.

Improving the Assessment and Diagnosis of Breast Lymphedema after Treatment for Breast Cancer.

Lymphedema can develop after treatment for breast cancer (BCRL). Lymphedema of the breast is not well studied. Currently, the main techniques used to diagnose and monitor the effectiveness of treatment are subjective clinician assessment and patient reports. Eighty-nine women who had undergone breast cancer treatment were recruited with and without breast lymphedema. Blinded clinical assessment determined the presence or absence of breast lymphedema. Measurement of skin thickness by ultrasound scanning, local tissue water by tissue dielectric constant (TDC) and tissue indentation by tonometry was recorded. Breast cancer treatment and demographic details were documented. Descriptive statistics were undertaken to compare sample characteristics, including the Chi-squared test, Odds Ratio (OR) and Relative Risks (RR) calculated. Increased body mass index (BMI), larger bra size, increased number of positive lymph nodes, axillary surgery, chemotherapy and increased Nottingham Prognostic Index (NPI) were all associated with breast lymphedema (p < 0.05). Ultrasound and TDC measurements were significantly higher in the lymphedema group (p < 0.05). Receiver Operator Characteristic (ROC) curves demonstrated that ultrasound and TDC measurements could distinguish between edematous and non-edematous breasts. Threshold levels were produced, which demonstrated good levels of sensitivity and specificity. These findings have the potential to improve the diagnosis of breast lymphedema.

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.

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.

Tissue Dielectric Constant Measures in Women With and Without Clinical Trunk Lymphedema Following Breast Cancer Surgery: A 78-Week Longitudinal Study.

Following breast cancer surgery with lymph node removal, women are at risk of developing lymphedema in the upper extremity or trunk. Currently, trunk lymphedema diagnosis relies on a clinical assessment because no quantifiable standard method exists. Tissue dielectric constant (TDC) values are quantifiable measures of localized skin tissue water and may be able to detect trunk lymphedema. The goal of this study was to (1) compare parameters derived from TDC measurements with those derived from clinically accepted criteria for trunk lymphedema in women following breast cancer surgery and (2) explore the potential utility of TDC to detect trunk lymphedema early in its progression. This prospective longitudinal study, a secondary analysis from a larger study, observed women with and without clinically determined truncal lymphedema following breast cancer surgery. TDC was measured on the lateral trunk wall at post-surgery weeks 2, 4, 12, and 78 in women who had surgical breast cancer treatment with lymph node removal. Clinical assessment for trunk lymphedema was determined at 78weeks by a lymphedema expert. Comparison of TDC measurements in women with and without clinical trunk lymphedema was analyzed. Clinical assessment identified trunk lymphedema in 15 out of 32 women at 78weeks. These women had TDC ratios statistically higher than women without truncal lymphedema. The overall findings indicate that TDC has the ability to quantify trunk lymphedema and might be valuable in early detection. TDC may be a beneficial tool in the early detection of breast cancer-related trunk lymphedema, which could trigger intervention. A new device may help recognize trunk lymphedema in patients with breast cancer so they could receive appropriate treatment.

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.

Palpation of Increased Skin and Subcutaneous Thickness, Tissue Dielectric Constant, and Water Displacement Method for Diagnosis of Early Mild Arm Lymphedema.

Background: Early diagnosis of mild lymphedema and treatment are important to prevent its progress. The tissue dielectric constant (TDC), measuring local tissue water in the skin and upper subcutis, has neither been related to the water displacement method (WDM) nor been used to diagnose mild arm lymphedema in patients at risk. Our aims were to evaluate TDC and WDM in combination with palpation, examine the association between TDC and WDM measurements, and compare lymphedema-related factors. Methods and Results: Seventy-two women treated for breast cancer were diagnosed with mild arm lymphedema using skin palpation in combination with TDC from fixed measurement sites (threshold ratio for upper arm ≥1.45 and forearm ≥1.3) and/or WDM (lymphedema relative volume [LRV]: ≥5% to ≤8%). Results revealed that 32 (45%) women were diagnosed by TDC only, 19 (26%) by WDM only, and 21 (29%) by both TDC and WDM. TDC ratios exceeding the threshold were most frequently identified on the medial site of the arm, proximal and distal to the antecubital fossa. TDC and WDM were negatively associated; LRV (r = -0.545, p < 0.001). The women diagnosed by TDC only were diagnosed earlier after surgery (p = 0.003) and had a lower LRV (1.3%) than those diagnosed by WDM only (6.3%) or both TDC and WDM (6.2%; p < 0.001). Conclusions: TDC and WDM can be used together for early diagnosis of arm lymphedema, but TDC is the most valid method, determining the diagnosis earlier after surgery and at a lower arm volume than WDM.

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.

Characterizing the tissue dielectric constant of skin basal cell cancer lesions

Measuring tissue dielectric constant (TDC) of cancer tissues to distinguish them from normal or non-cancerous tissues has been an active area of research that has targeted several different cancer types usually using in vitro specimens. The goal of this study was to determine if and to what extent TDC values measured in vivo at 300MHz using a simple hand-held measuring device might differentiate between skin cancer lesions and non-cancerous skin. Triplicate TDC measurements were made in 32 patients who were subsequently diagnosed with skin basal cell carcinoma (BCC) and in 14 patients subsequently diagnosed as having non-cancerous lesions. Lesion TDC values were compared to contralateral unaffected skin and between lesion types. A significantly lower TDC value (mean±SD) of BCC lesions (TDCL ) vs TDC values of contralateral non-affected skin (TDCC ) was found (22.4±16.2 vs 38.1±15.2, P<.00001). A similar pattern was found for non-cancerous lesions with lesion TDC values less than non-affected skin (14.5±9.0 vs 29.1±9.0, P<.0001). However, TDC values were not statistically different between BCC lesions and non-cancerous lesions (22.4±16.2 vs 14.5±9.0, P=.096) and calculated TDCL /TDCC ratios between BCC lesions and non-cancerous lesions also were not significantly different (0.596±0.345 vs 0.501±0.261, P=.364). (1) Main results do not support using TDC measurements to differentiate in vivo skin cancer lesions from non-cancerous lesions. (2) TDC values strongly suggest reduced water content of both cancerous and non-cancerous lesions. (3) Lesion TDC measurements provide reference values for future studies.

Diurnal changes in local skin water assessed via tissue dielectric constant at 300 MHz

Objective. Skin tissue dielectric constant (TDC) measurements are largely dependent on tissue water content. Because TDC measurements and their inter-side ratios are used for a variety of clinical and research purposes we believe that knowledge of potential TDC diurnal variations could be useful. Because of the strong water-dependency of TDC values, our operative hypothesis was that the absolute TDC measured in upper body areas would progressively decrease during the day whereas TDC values in lower extremities would progressively increase during the day. Our goal was to test this hypothesis and determine the degree of inter-side symmetry. Approach. TDC values to a skin depth of 2.0–2.5 mm were self-measured hourly starting at 0800 and ending at 2000 h at four anatomical sites by 12 women who were trained and experienced in the measurement method. Measurements were done bilaterally in triplicate below the eye, mid-cheek, forearm and calf. An assessment of temporal changes in TDC values and inter-side TDC ratios was done via regression and ANOVA. Main results. TDC values from the eye, cheek and forearm progressively decreased (correlation coefficient, R, 0.708 to 0.941). Morning-to-night decreases were 11.2 ± 8.3%, 6.8 ± 5.7% and 5.6 ± 6.0% respectively. TDC values from the calf progressively increased (R = 0.864) with a morning-to-night TDC increase of 9.3 ± 10.7%. In contrast, TDC inter-side ratios (dominant side to nondominant side) were stable over the 13 h monitoring interval with no evidence of significant temporal change. Morning TDC side-averaged values were for the eye, cheek, forearm and calf values averaged 53.8 ± 8.8, 56.7 ± 9.8, 40.6 ± 6.7 and 41.1 ± 4.9 respectively. Significance. Three major outcomes of the present study emerge: (1) the findings demonstrate a previously unestablished gravity dependent skin-water shift via TDC measurement, (2) an estimate of time-of-day TDC differences is provided, and (3) the insensitivity of inter-side TDC ratios to time-of-day is demonstrated, thereby providing confidence in TDC ratios obtained at different times of day.

Experimental and Analytical Comparisons of Tissue Dielectric Constant (TDC) and Bioimpedance Spectroscopy (BIS) in Assessment of Early Arm Lymphedema in Breast Cancer Patients after Axillary Surgery and Radiotherapy.

Early diagnosis of breast cancer treatment-related lymphedema (BCRL) is of great importance for longstanding treatment results. Tissue dielectric constant (TDC) and bioimpedance spectroscopy (BIS) both have a potential for early diagnosis, but have not been compared. One hundred women, treated for breast cancer with breast surgery, axillary dissection, and radiotherapy, were examined within one year after breast cancer treatment, as part of the follow-up procedure. Affected/at-risk and contralateral arms were measured with the TDC technique specific to localized skin water content and the BIS technique assessing arm extracellular fluid (ECF). Thirty-eight patients were clinically diagnosed for lymphedema (38.0%). The sensitivity and specificity for the TDC method were 65.8% and 83.9%, and for BIS method 42.1% and 93.5%, (p < 0.001 and NS), respectively. Of all lymphedema, 18.4% were detected only by TDC and 2.6% by BIS. Affected arm to contralateral arm TDC ratios for upper arm and forearm, 1.56 ± 0.49 and 1.28 ± 0.33, demonstrating the localized feature of the TDC measurements were significantly greater than the BIS arm ratio 1.12 ± 0.12 (both p < 0.001). Discrepancies between TDC and BIS techniques in assessing lymphedema are related to different measurement techniques and assessed tissue water components. Independently of selected technique-specific threshold limit, the TDC technique was more sensitive than the BIS technique in the early assessment of BCRL and demonstrated that nearly 20% of early lymphedema are only superficially localized. The results further supported the complementary role of TDC and arm volume measurements as a highly diagnostic method for early lymphedema.

Young adult gender differences in forearm skin‐to‐fat tissue dielectric constant values measured at 300 MHz

Skin-to-fat tissue dielectric constant (TDC) values depend on measurement depth and gender. Our goal was to assess male-female differences in TDC values associated with differing skin depths. Bilateral forearm TDC measurements were made on young adult male and females with mean ages from 24.7 to 27.3 years. There were four measurement groups distinguished by the TDC measurement depth and include the following numbers of subjects for each gender; 30, 150, 60, and 50 for probe-measurement depths of 0.5, 1.5, 2.5, and 5.0 mm. Data were subsequently compared with values calculated with a simple two-layer model. For females and males, there was a significant difference in TDC values among depths (P < 0.001) with TDC values decreasing with increasing depth. Gender comparisons showed that TDC values of males were significantly (P < 0.001) greater than values for females at each depth. Male-female percentage differences ranged from 14.8% to 22.0%. Model calculations suggest that gender differences might be explained by skin thickness differences. Findings indicate that decisions with regard to skin water content among or between groups based on TDC measurements need to account for gender and are best made when corresponding skin thickness measurements are available. However, changes in TDC values assessed in individual patients and comparisons between corresponding skin areas in affected and non-affected sites are not limited. Thus, assessments of acute treatment effects and assessments of inter-arm or inter-leg TDC differences or ratios within genders are a useful and suitable method to characterize edema and lymphedema features.

Patterns of temporal changes in tissue dielectric constant as indices of localized skin water changes in women treated for breast cancer: a pilot study.

Our goal was to characterize temporal patterns of skin Tissue Dielectric Constant (TDC) as a foundation for possible TDC use to detect and quantify lymphedema. Although limb volumes and bioimpedance analysis (BIA) are used for this purpose, potential TDC-method advantages are that it can be done in about 10 seconds at any body site to depths from 0.5 to 5.0 mm below the epidermis. TDC at forearm, biceps, axilla, and lateral thorax, and BIA values and arm volumes were measured in 80 women with breast cancer prior to surgery and in decreasing numbers at 3, 6, 12, 18, and 24 months post-surgery. Results show that TDC values, reflecting water content in the measurement volume, vary by site and depth but that at-risk/contralateral side ratio (A/C) is relatively independent of site and depth and is the preferred TDC parameter to detect tissue water changes over time in unilateral conditions. Among sites measured, lateral thorax, followed by forearm, appears most useful for TDC measurements with axilla least useful. Pre-surgery TDC inter-side values and A/C ratios showed no significant inter-side differences, suggesting that breast cancer presence per se did not alter tissue water status in this patient population. Sequential changes in TDC A/C ratios detected a greater number of patients who had inter-arm ratio increases exceeding 10% than were detected using BIA ratios. This may indicate a greater sensitivity to localized tissue water changes with the TDC-method. TDC is a technically viable and potentially useful method to track skin water changes in persons treated for breast cancer.