A Non-Invasive Technique with Ultrasound Surface Wave Elastography for Evaluation of Limb Lymphedema: A Pilot Study
Tony CT Huang, MBBS, Samyd S. Bustos, MD, Juntao Shao, MBBS, Boran Zhou, PhD, Xiaoming Zhang, PhD, Oscar J. Manrique, MD.
Mayo Clinic, Rochester, MN, USA.
Background:Ultrasound surface wave elastography (USWE) has been used to study the viscoelasticity of the skin in patients with systemic sclerosis and the fibrosis extent in lungs of patients with interstitial lung diseases.One advantage of USWE is its capability to measure subcutaneous tissue up to 45 mm. USWE may be used to assess skin, subcutaneous connective tissue and muscle. Herein, we conducted a study to determine if USWE produces different recording patterns in healthy and lymphedematous limb, which could potentiate its use as a non-invasive diagnostic tool. Methods: Prospective study in adults with limb lymphedema between March and April 2019. We used three anatomic landmarks for measurement: 10 cm above ankle/wrist, and 10 cm above and below knee/elbow. Both normal and affected limbs were measured. A 0.1-s harmonic vibration was generated by the indenter of the handheld shaker on the limb. The vibration was generated at 3 frequencies: 100, 150 and 200 Hz. Ultrasound probe was positioned adjacent to yet not in touch with the indenter and used for detecting the tissue motion. Particle velocity in the axial direction was measured using autocorrelation technique. Shear wave speed (SWS) of the tissue was measured using 2D processing window technique.A region of interest was selected to measure superficial and deep tissues. Results:Eleven patients with secondary lymphedema (6 upper and 5 lower limb lymphedema) were included. Based on the International Society of Lymphology staging system, 3 were stage I, whereas 8 had stage II-III. Mean time with symptoms of lymphedema was 70.7 months (range, 3 - 362). The magnitudes of the wave speeds of the superficial fat tissue at 100, 150 and 200 Hz at lymphedema sites (3.97 ± 0.06, 4.89 ± 0.82, 5.95 ± 0.49 m/s) were statistically higher than those of the control sites (2.35 ± 0.32, 2.81 ± 0.46, 3.12 ± 0.61 m/s), respectively. The magnitudes of the wave speeds of the deep fat tissue at 100, 150 and 200 Hz at lymphedema sites (4.24 ± 0.43, 5.12 ± 0.76, 6.06 ± 0.66 m/s) were statistically higher than those of the control sites (2.55 ± 0.07, 2.94 ± 0.43, 3.24 ± 0.4 m/s), respectively. Conclusion:Based on this pilot prospective study, we believe that USWE may be a promising tool to objectively evaluate patients with limb lymphedema. In addition, this none-invasive, dynamic method can potentially assess and compare the surgical outcomes before and after functional lymphatic surgery.
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