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MICROWAVES
In the electromagnetic spectrum, microwaves lie between infrared light and radio waves. Microwaves can heat substances via a process called dielectric heating. The latter occurs when energy causes a rotation of dipole molecules. Because it is an ion, water has a high dipole moment whereas fat has a low dipole moment. As a result, there is less absorption in the subcutaneous layer and selectivity for the dermis. Furthermore, application of concurrent cooling protects the upper dermis and selecยญ tively heats the deeper dermis.
Dielectric heating by microwaves was found to induce both eccrine and apocrine sweat gland thermolysis with relative selectivity. This discovery led to the first commercially available therapeutic microwave device โ miraDryยฎ (Miramar Labs). Studies have shown that 90% of patients had at least a 50% reduction in sweating, and ~80% maintained this reduction at 12 months. All subjects experienced transient swelling, discomfort, and/or numbness within the treatment area, with a few patients noting longer-lasting side effects including altered sensation in or around the treatment site, papulonodules in the axillae, and hair loss.
Fig. 137.18 Nanopulse stimulation (NPS). Cellular apoptotic death. A Abdominal skin, untreated. B Abdominal skin, 1 day after NPS treatment. C Abdominal skin, 5 days post NPS treatment. From Kaufman D, Martinez M, Jauregui L, et al. A dose-response study of a novel method of selective tissue modification of cellular structures in the skin with nanosecond pulsed electric fields. Lasers Surg Med 2020;52:315โ22.