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Understanding the TDC
What is the Tissue Dielectric Constant (TDC)?
The Tissue Dielectric Constant (TDC) technology is based on low power microwaves that only shake water molecules. It provides a convenient, reliable, and accurate way to assess local tissue water content, instantly and non-invasively. (1)
Delfin Technologies developed and patented this measurement technology to be used in instruments such as the LymphScanner and the MoistureMeterD 4 probes.
LymphScanner
MoistureMeter D 4 Probes
The devices generate a high frequency, low power electromagnetic wave of 300MHz, send it through a probe and in the subcutaneous tissues. The reflected electromagnetic wave is analyzed, and the calculated value obtained between 1 and 78.5 is the Tissue Dielectric Constant. It is then converted in Percentage Water Content (PWC), between 0 and 100%.
The TDC is a dimensionless physical quantity. It is known that tissue water has a higher dielectric constant value, while fat and tissue macromolecules, especially proteins, have a very low dielectric constant. So based on the Tissue Dielectric Constant, we can determine the percentage of water content.
The TDC technology has been widely used for the evaluation of patients who are at risk or have already developed edema/lymphedema. A TDC ratio can be used to compare the healthy limb versus the affected one for early detection.
There are Published Clinical Studies written by Dr. Harvey Mayrovitz, PhD, Researcher at Nova University Florida, in which he determined TDC ratio thresholds for the early detection of lower limb edema/lymphedema. For instance, “an inter-leg TDC ratio exceeding a value of 1.2 is suggested as a threshold for judging unilateral lower extremity edema or lymphedema.(2)
Dr. Mayrovitz also proposed that a “calf/forearm TDC ratio that exceeds 1.35 is suggestive of lower extremity lymphedema and that the calf/forearm ratio could be used to track temporal changes and therapy-related improvements.”(3)
The TDC technology is very valuable as it measures the Percentage Water Content (PWC) locally and in any position. The result appears instantly. It is also non-sensitive to metals or bones. The TDC is essential for patients’ early diagnosis. It provides an objective follow-up of patients’ edema or lymphedema, after interventions and treatments. Measurements made with the TDC technology are very convenient as the patients do not need to get undressed, remove their shoes, or jewelry. This technology is very accurate, with a 2% detection variance, and combined with the water displacement method, it is twice as sensitive as any other technology.
As a first country, Sweden has included the TDC technology in their national cancer rehabilitation guidelines for diagnosis of breast cancer related lymphedema. The measurement of extracellular fluid for lymphedema assessment is CPT coded (93702).
Medical Applications
Primary Lymphedema
Inherited condition caused by developmental issues in the lymphatic system. It can occur due to: Congenital malformations (Lymphatic vessels or nodes may be absent, underdeveloped, or not functioning properly from birth), or genetic factors (It often runs in families and can be present at birth or develop later in life - during adolescence or adulthood).
Secondary Lymphedema
It is more common and results from damage to the lymphatic system due to external factors, such as: Surgery (especially when lymph nodes are removed, like in cancer surgeries (mastectomy for example)), radiation therapy (Radiation can damage lymph nodes or vessels), infection or injury (severe infections or trauma can block or damage lymphatic pathways, or cancer (tumors may block lymphatic drainage).
Venous Edema
Also known as venous insufficiency edema, it is a type of swelling that occurs when the veins in the legs are unable to efficiently return blood back to the heart. This condition is primarily caused by chronic venous insufficiency (CVI), where the valves in the veins become damaged or weakened, leading to poor blood flow and the pooling of blood in the lower limbs.
The main cause of venous edema is the failure of venous valves, leading to blood pooling in the veins of the legs. This increased pressure forces fluid out of the blood vessels and into the surrounding tissues, causing swelling.
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It primarily affects the lower legs and ankles. The edema is usually more noticeable at the end of the day or after prolonged standing or sitting, and it typically reduces overnight when the legs are elevated.
Venous edema is generally a sign of underlying venous insufficiency and requires proper management to prevent complications like skin changes or ulcers.
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There are 6 stages of venous insufficiency, from C1 to C6, and the LymphScanner is the perfect instrument to assess venous edema from stage C3 to C6.
C1
Spider Veins
C2
Varicose Veins
C3
Edema (swelling)
C4
Skin Discoloration
C5 & C6
Venous Ulcer
Lipedema (different from Lymphedema)
Lipedema is a chronic condition primarily involving an abnormal accumulation of fat cells, typically in the lower body (hips, thighs, buttocks, and sometimes arms). It is often hormone-related and can be triggered by puberty, pregnancy, or menopause.
Lymphedema is caused by a dysfunction or damage in the lymphatic system, leading to the accumulation of lymph fluid in tissues.
Lymphedema is due to lymphatic fluid buildup, affecting a wider range of tissues, including hands and feet, tending to be less painful, while lipedema involves abnormal fat accumulation with minimal fluid retention and is often painful.
Early detection of Lymphedema, surgery related
LymphScanner
Regional assessment of Lymphedema
the LymphScanner and the MoistureMeterD 4 probes can instantly assess lymphedema locally, on any part of the body, and in any position. They assess lymphedema stages, from undetectable subclinical to advanced.
There are 4 Lymphedema stages:
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Subclinical Stage: Abnormal flow in the lymphatic system. No signs or symptoms detectable by conventional methods.
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Mild Stage: Accumulation of fluid with swelling. Swelling resolves with elevation. Pressing on the area may leave a dent (pitting edema).
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Moderate Stage: Permanent swelling that does not resolve with elevation. Pressing on the area no longer leaves a dent. Changes in the skin with scarring and thickening.
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Severe Stage: Elephantiasis (large, deformed limb), skin thickening with “wart-like” growth and extensive scarring.
Lymphedema therapy follow-up
By measuring regularly the difference between the healthy limb and the affected one, the doctor can do a therapy follow up to treat, reduce and heal lymphedema. With the MoistureMeterD 4 probes comes the DMC software stocking all the data.
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It allows users to set up individual projects, store and view measurement data and plot the results or export them to other programs for editing.
References
(1) Harvey N. Mayrovitz, PhD, Assessing Free and Bound Water in Skin at 300MHz Using Tissue Dielectric Constant Measurements with the MoistureMeterD.
(2) Harvey N. Mayrovitz, PhD, Tissue Dielectric Constant of the Lower Leg as an Index of Skin Water: Temporal Variations. (Cureus, 2022).