Lymphedematous Skin and Subcutis: In Vivo High Resolution Magnetic Resonance Imaging Evaluation

Physico-chemical and morphologic parameters of skin layers and subcutaneous tissue in lymphedematous limb were studied in vivo using magnetic resonance imaging. High resolution images were obtained with a depth resolution of about 70 μm, using a specific surface gradient coil specially designed for skin imaging and connected to a standard whole-body imager at 1.5 T. Twenty-one patients with unilateral lower extremity lymphedema (11 primary and 10 secondary) were examined. Skin thickness, relaxation times, and relative proton density were calculated in lymphedematous limbs and in contralateral extremities. In diseased limbs, the average skin thickness (2.17 mm) was significantly larger (p =1.5 × 10–4) than that of contralateral limb (1.14 mm). Major cutaneous alterations due to lymphedema took place in dermis. In lymphedematous dermis, the significant increase of relaxation time values could be due to a shift in the equilibrium of water inside this tissue in relation to the interactions between macromolecules and water molecules. In lymphedematous epidermis our results showed an increase in the number of free water protons. Information about water and fat distribution in lymphedema was also obtained using chemical shift weighted images. Our results demonstrated a water retention diffusely spread over the entire dermis, and an important fluid retention located in the interlobular spacing and beside the superficial fascia. Inside the subcutis, the mean thickness of the superficial fat lobules was increased more than that of the deep fat lobules. From all the various measurements we could not distinguish primary from secondary lymphedema.