Lymphedema Assessment Tools Compared: A Clinician’s Guide to BIS and TDC. Discover Why TDC Outperforms BIS in Lymphedema Detection and monitoring.
- Emma Danciu
- Jun 27
- 9 min read
Updated: 6 days ago
While lymphedema has been known for millennia, its recognition as a distinct, measurable, and treatable condition is relatively recent. Its systematic classification and clinical importance as a condition requiring measurement, assessment, and long-term monitoring developed gradually, only gaining significant attention in the 20th century and accelerating in the 21st.
It wasn’t until post-WWII and the rise of cancer treatments, especially radical mastectomies, that secondary lymphedema became a significant health issue. Swelling in the arm after breast cancer surgery prompted both patients and clinicians to push for preventive strategies, objective assessment tools and treatment protocols.
By the 1980s–1990s, lymphedema clinics began emerging, especially in Europe and North America.
From the 1990s onward, driven by research in oncology, dermatology, and rehabilitation, lymphedema was formally recognized as a chronic medical condition requiring early diagnosis and lifelong management. There was a push to develop objective, quantifiable methods for measuring swelling and fluid accumulation, and technologies began to evolve:
Tape measurements and water displacement were early tools.
Perometry and bioimpedance spectroscopy (BIS) were introduced for limb volume and fluid analysis.
More recently, the Tissue Dielectric Constant (TDC), a cutting-edge patented technology emerged, enabling localized, repeatable, accurate, and non-invasive assessment of tissue water.
Advances in cancer survivorship care, along with advancements in rehabilitation medicine and medical device technology, has shifted lymphedema from being an overlooked symptom to a monitorable medical challenge. Clinicians today are more prepared than ever to address this issue.
Monitoring lymphedema is no longer optional—it is central to evidence-based treatment, clinicians, and quality of life preservation for patients.
When it comes to effectively identifying and managing lymphedema, especially in dynamic clinical settings, the LymphScanner™ emerges as the more flexible, accurate, practical and cost-efficient solution compared to the SOZO device from ImpediMed.
BEHIND THE TECHNOLOGY
SOZO uses bioimpedance spectroscopy (BIS) to assess fluid levels by passing a low-level electrical current through the entire arm and leg. The technology then calculates the total extracellular fluid volume in the limb based on the resistance the current encounters.
The problem is that the fluid is not distributed equally throughout the limb. In cases of lymphedema or post-treatment swelling, fluid often accumulates in specific, localized regions like near the wrist or elbow (after breast cancer surgery), around the ankle or thigh, or in one quadrant of a limb.
Since SOZO measures the entire limb as a single unit, it can’t detect where the fluid is accumulating, has to calculate an average fluid level across the whole limb, and may miss subtle, localized swelling, especially in early-stage or regionally restricted lymphedema. The clinical consequence of this averaging effect means that localized edema can be “diluted” in the overall measurement. Clinicians don’t know exactly where fluid is building up, and the treatment decisions may lack site-specific precision.
For example, if a patient has swelling only in the upper arm, but the forearm is unaffected, SOZO’s result may show a normal or borderline reading, despite meaningful fluid buildup in one area.
Because SOZO only gives an averaged fluid value for the whole limb, it cannot accurately localize swelling, making it less reliable for precise diagnosis and monitoring—especially when fluid is unevenly distributed.
Practically, SOZO, requires patients to take off jewelry, shoes, socks, and in some cases gloves, stand still and place limbs in fixed positions. Because the metal in jewelry conducts electricity, the results obtained will be skewed. Also, if patients have metal plates in their body due to surgery, the results will not be objective. In order to carry out the measurement, the patients’ hands and feet have to be in direct contact with the device.
Due to its larger, console-style design with a fixed base unit and attached cables, the device lacks portability and is confined to designated examination rooms—making it particularly challenging for patients with Stage 3 or 4 lower-limb lymphedema, who may struggle to walk to the machine.
While SOZO may appear to be a self-contained unit, it’s actually not a standalone solution for lymphedema assessment and clinical data management. The hardware requires integration with an external software platform to operate effectively and to access the full range of its features.
The collected data is not analyzed or displayed on the device itself. Instead, it is uploaded to ImpediMed’s proprietary cloud-based software platform, where the algorithms process the readings to produce L-Dex scores (lymphedema index values), patient trends and historical comparisons, as well as reports and visualizations.
Clinicians must log in to ImpediMed’s software platform to view, interpret, and manage patient data. This means that internet access is required, clinical data is not stored locally on the device, and workflow depends on access to their cloud platform.
Without a valid software subscription, users lose access to the processed data and patient records—even if the device is physically available.
COST-EFFECTIVENESS
The SOZO business Model is subscription-based. It requires annual software licensing fees.
Clinicians don’t fully own the system; access to its features depends on continued payment. These recurring costs accumulate quickly and can become a financial burden over time—especially for smaller clinics.
The device is priced at $5,000, with additional annual fees of $15,000 for the cloud-based software.
SOZO locks users into a recurring-cost model, requiring not only an initial investment for the device itself, but also ongoing annual software licensing fees, and platform access costs. These recurring expenses create a dependency on the manufacturer’s infrastructure and limit long-term cost control. Clinics and hospitals must continue paying year after year just to retain access to core features—making budgeting less predictable and overall ownership significantly more expensive over time.
Instead of empowering users with full ownership, this pricing strategy creates dependence on the manufacturer’s terms—reducing cost transparency and flexibility.
FROM WHOLE-LIMB AVERAGES TO LOCAL PRECISION: HERE IS THE LYMPHSCANNER™
If you are looking for a solution that offers unparalleled flexibility, localized precision, affordable ownership, and freedom from complex licensing, the LymphScanner™ is the clear choice. It adapts to your patient—not the other way around—and empowers professionals in clinical settings to measure, monitor, and manage lymphedema with unmatched confidence and efficiency.
The LymphScanner™ uses the patented Tissue Dielectric Constant (TDC) technology to measure Percentage of Water Content (PWC) at any anatomical sites with high repeatability, making it invaluable in lymphedema early detection, including cases affecting legs, breast, post-operative lymphedema cases and unique in head and neck applications.
The TDC refers to how well the tissue stores and responds to an electrical field. Since water has a very high dielectric constant, and most other tissue components do not, measuring the dielectric properties of the skin gives its water content.
A safe, low-level electromagnetic signal (300 MHz) is emitted into the skin through the LymphScanner™’s probe, the signal penetrates to a defined depth of 2.5 mm, the device detects how much of that signal is stored and reflected back.
The result is a TDC value, which correlates directly with the local water content of the tissue and the higher the TDC, the more fluid is present.
Because the TDC measures the skin’s water content and the result is a number that doesn’t have any physical unit attached to it—like grams, centimeters, or volts, it is converted into PWC (Percent Water Content) values to make the data easier to interpret clinically.
TDC-to-PWC measurement is reproducible and numerical—ideal for clinical documentation.
Whether assessing baseline, early-stage lymphedema or tracking localized treatment response, the LymphScanner™ delivers standardized, site-specific data you can trust.
Why TDC Matters
Localized
Measures precisely where fluid is accumulating—unlike whole-limb bioimpedance tools.
Reproducible
Delfin's design ensures consistent probe pressure and depth, which are critical for reliable readings. It guarantees exceptional reproducibility and accuracy.
Non-invasive & quick
TDC measurements take only a few seconds and require no needles, electrodes, or prep.
Depth-selective
Allows assessment at 2.5 mm.
Ideal for over time monitoring
Perfect for tracking subtle changes in specific anatomical regions.
The TDC technology is a cornerstone of precision skin measurement. It allows clinicians to detect, quantify, and monitor edema or water content with high spatial resolution and reproducibility, setting the LymphScanner™ apart in clinical applications.
Practically, the LymphScanner™ offers true flexibility in measurement. It is designed to work in any patient posture, including sitting, standing or lying down. This is particularly critical for patients who cannot maintain a static posture, such as post-surgical, bedridden, or head and neck lymphedema patients.
Its undeniable advantage lies in its clinical applicability in various settings, without needing standardized positioning, removal of clothing or jewelry, or restrictions related to in-body metallic plates.
Designed for specialists, built for versatility, the LymphScanner™’s ergonomic, user-focused design allows it to be used by anyone from surgeons to oncology nurses and Certified Lymphedema Therapists (CLT), without special infrastructure. Handheld, cordless and lightweight, Its design supports rapid and on-the-spot measurements anywhere – at bedside, in the field, or across multiple clinic locations.
It is not only medically effective but scientifically reliable for clinical monitoring. Working as a stand-alone device, the LymphScanner™ does not require any complex preparation, calibration each session, or cloud logins. The interface is intuitive, and the learning curve is minimal. It has been designed to be flexible, enabling the clinician to collect data directly from the LymphScanner™ and transfer them to any preferred software.
What Definitely Sets the LymphScanner™ apart
The LymphScanner™, based on Tissue Dielectric Constant (TDC) technology, is scientifically validated through a growing body of peer-reviewed publications and clinical studies. Its precision, reproducibility, and sensitivity to localized fluid changes have made it a trusted tool in both research and clinical practice for the early detection and monitoring of lymphedema.
One pivotal clinical study(*) directly compared TDC measurements with Bioimpedance Spectroscopy (BIS). The results were striking:
TDC detects lymphedema with 97.4% accuracy,
while BIS detects it in only 42.1% of cases.
These findings underscore the clinical superiority of TDC for identifying early- and late-stage lymphedema—especially in cases where fluid accumulation is subtle or regionally localized.
COST-EFFECTIVENESS
The LymphScanner™ is a one-time purchase with no mandatory software subscription, dramatically lowering the total cost of ownership. Being FDA cleared, and as per their requirement, it has to be calibrated every year to ensure the LymphScanner™ continues to deliver accurate, effective, and safe measurements throughout its lifetime.
Calibration is a standard part of routine device maintenance, required to meet the FDA regulatory standards and ensure ongoing clinical reliability.
The device is priced at $4,950, with $0 annual fees. Calibration annual cost is $1,095.
Over 5 years, SOZO “ownership” typically costs $80,000 due to recurring annual software license fees, while the LymphScanner™ will cost $9,330.
The LymphScanner™ offers clinicians a transparent, affordable, and predictable solution without hidden fees or unexpected changes.
In the evolving field of lymphedema detection, monitoring, and management, precision and practicality must go hand in hand. Yet many clinicians continue to rely on bulky, expensive, and often limited devices like SOZO by ImpediMed—despite the availability of more advanced, user-friendly technologies.
It’s time to re-evaluate.
The LymphScanner™, powered by Delfin’s patented TDC (Tissue Dielectric Constant) technology, is rapidly gaining ground as the new standard in lymphedema assessment.
So, Join the Shift Toward Precision, Practicality and Cost-Effectiveness!
Comparative Overview: SOZO vs. LymphScanner™
FEATURE | SOZO | LYMPHSCANNER™ |
|---|---|---|
Technology | Bioimpedance Spectroscopy (BIS) | Tissue Dielectric Constant (TDC) |
Measurement Type | Segmental (Whole Limb) | Localized (Specific Site) |
Clinical Use | Full-limb fluid analysis | Localized lymphedema measurement on any part of the body |
Head & Neck Capability | ❌ No, Not possible | ✅ Yes, validated for HNL |
Position Required | ⚠️ Standing ONLY | ✅ ANY POSITION |
Targeted Monitoring | ❌ No | ✅ Yes |
Time Per Measurement | ~30–60 seconds | ~5 seconds |
Training Required | Moderate | Minimal |
Portability | ⚠️ Very Limited (console-based) | ✅ Handheld, lightweight |
Software | ⚠️ Proprietary Cloud system WITH ANNUAL FEES | ✅ Local PC Software NO RECURRING FEES |
Software Integration/Cloud | ⚠️ Required for L-DEX tracking & compliance | ✅ No software necessary. NO CLOUD DEPENDENCY |
Device Cost | ⚠️ $5,000 + $15,000/year subscription fees | $4,950 + $0 subscription fees |
Cost Model | ⚠️ Device + ongoing software subscription | ✅ One-time cost, Calibration once a year (FDA Compliance) |
Ownership Model | Subscription-based model | Purchase-based model |
Reimbursement | ✅ Covered under CPT 93702 | ✅ Covered under CPT 93702 |
PUBLICATIONS
LYMPHATIC RESEARCH AND BIOLOGY
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.
RESEARCH SQUARE
Assessing non-invasive imaging devices to detect temperature differentiation and lymphatic/venous flow to the head and neck during head down tilt, supine and sitting positions The NIID Study (non-invasive imaging device).
WILEY
A prospective observational cohort study examining the development of head and neck lymphedema from the time of diagnosis.
LYMPHATIC RESEARCH & BIOLOGY
Tissue Dielectric Constant Combined With Arm Volume Measurement as Complementary Methods in Detection and Assessment of Breast Cancer-Related Lymphedema.
NSU FLORIDA
Noninvasive Assessment of Leg Lymphedema by Tissue Dielectric Constant Ratios.
(*):LYMPHATIC RESEARCH AND BIOLOGY - Volume 13, Number 3, 2015 - ©Mary Ann Liebert, Inc. - DOI: 10.1089/lrb.2015.0019
"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".
Tapani Lahtinen, PhD,1 Jan Seppa¨ la¨ , PhD,1 Tuomas Viren, PhD,1 and Karin Johansson, PhD2
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