Inter-arm Ratio Research Articles

Interchangeability of Two Electrode Placement Protocols Used by Bioimpedance Spectroscopy Devices in the Detection of Breast Cancer-Related Lymphedema.

Background: Bioimpedance spectroscopy (BIS) devices are routinely used in the assessment of breast cancer-related lymphedema (BCRL). The equipotential electrode placement is a commonly used protocol for the assessment of BCRL. However, the sternal notch electrode placement protocol is also in use. Whether these two protocols are interchangeable is not known. Methods and Results: Ethical approval was received from the institutional ethics committee at Tata Memorial Hospital, India. BIS measurements (whole-body right side and affected and unaffected arms) of 100 women with or at risk of BCRL were measured using equipotential and sternal notch protocols. Resistance at zero frequency (R0) was determined, and agreement of the absolute R0 values and the R0 ratio (unaffected/affected) between protocols was evaluated (Bland-Altman analysis and Passing-Bablok regression analysis). Mean absolute differences between protocols were very small for whole-body right side, affected arm, unaffected arm, and the interarm ratio at 0.23 ohms (95% confidence interval [CI]: -3.8 to 4.3), -5.7 ohms (95% CI: -7.5 to -3.9), -9.09 ohms (95% CI: -11.4 to -6.8), and -0.008 ohms (95% CI: -0.02 to 0.001), respectively. Limits of agreement (two standard deviation) between protocols were narrow for whole-body right side, affected arm, unaffected arm, and interarm ratio without any systematic or proportional differences for whole-body right side and the interarm ratio (5.8% to -5.6%, 3.7% to -7.4%, 3.5% to -8.2%, and 5.8% to -5.6%, respectively). Conclusion: The equipotential and sternal notch protocols could be used interchangeably in BCRL assessment. The Clinical Trial Registration number: CTRI/2017/12/010762.

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.

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.

Reference Values for Assessing Localized Hand Lymphedema Using Interhand Tissue Dielectric Constant Ratios.

Early detection and tracking of breast cancer treatment-related lymphedema have been helped by quantitative assessment methods and parameters, including bioelectrical impedance spectroscopy and tissue dielectric constant (TDC). Such measurements are evaluated with respect to interarm differences or ratios that (when exceeding specified thresholds) are suggestive of lymphedema. Specific threshold ratios depend on the assessment method and have been reported for arms. However, there is far less information available on thresholds to assess lymphedema that manifests in at-risk hands and essentially nothing known about TDC ratios in healthy hands. Such information is essential to establish reference values from which lymphedema threshold TDC values may be estimated. The specific aim of this research was to determine such interhand TDC ratios applicable to both young and mature women. A total of 70 women (35 under 30 years of age, YOUNG, and 35 over 50 years of age, MATURE) participated after signing an approved institutional review board informed consent. TDC values of the hand dorsum web were measured bilaterally in triplicate with participants in a supine resting position. Results showed MATURE TDC values to be about 15% less than YOUNG (p < 0.01) on dominant and nondominant hands, but no statistical difference in dominant/nondominant interarm ratios (1.026 ± 0.100). Based on this data set's overall mean and two standard deviation value, an age-independent interhand TDC threshold ratio of 1.23 emerges as potentially useful for lymphedema detection. This is a good initial start threshold that is usable in future clinical and research assessments.

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.

Molecular Clouds in M51 and in the Galaxy

Studies of molecular clouds in nearby galaxies require high angular resolution. Ten arcseconds corresponds to 0.5 kpc at the distance of M51. Typical gigant molecular clouds (GMC:s) have a size of 5-30 pc (Solomon et al. 1985). However complexes of GMC: s (Superclouds) can be several hundred parsecs (Elmegreen 1985; Rivolo et al. 1985). The higest angular resolution achived in CO(J=1-0) line observations of external galaxies is 7” (Lo et al 1984,1985). The resolution problem can be eased by observing M31 with a distance of only ⋍ 690 kpc (10” corresponds to 34 pc), which has been done by Combes et al. 1977a,b; Boulanger et al. 1984; Ryden and Stark 1985; Stark 1985; Blitz 1985; Ichikawa et al. 1985. In M31 the CO emission is strongly concetrated to the spiral arms with a arm interarm ratio of ≥ 25 (Ryden and Stark 1985; Stark 1985). The emission is caused by many small clouds unresolved with present resolution together with some larger clouds. Streaming is observed to occur across the arms. Extragalatic studies have the advantage of being more easy to interpret in terms of arm interarm contrast, noncircular motion, and galatic structure. They also make possible studies of the mass fraction of gas as a function of radius in different morphological types of galxies. Answers to questions like “Do any relation exist between galaxy type and molecular abundance?” are very important for our understanding of galatic evolution.