Quantitative Evaluation of Shear Wave Elastography on Radiation-Induced Neck Fibrosis in Patients With Nasopharyngeal Carcinoma.

The value of shear wave elastography (SWE) for quantitatively assessing neck fibrosis induced by radiotherapy (RT) in patients with nasopharyngeal carcinoma was evaluated over time. We prospectively observed 56 patients with nasopharyngeal carcinoma before and after therapeutic neck irradiation. The elasticity parameters including Emax and Emean were used to measure the stiffness of the bilateral sternocleidomastoid muscles. Twenty-seven patients completed a 1.5-year follow-up, with examinations beginning at 3, 6, 12, and 18 months after RT. Forty controls were recruited for reliability tests (along with the patients) and measurement comparisons. The consistency of SWE measurements with the Late Effects Normal Tissue Task Force-Subjective, Objective, Management and Analytic (LENT-SOMA) scale was tested. The intraclass correlation coefficients of elasticity indices for both patients and controls were higher than 0.75. The Emax and Emean of bilateral sternocleidomastoid muscles in the pre-RT patient group were comparable with those of the controls, and increased with increasing postirradiation duration (r = 0.514-0.555; P < 0.01). Significant increases in the Emax and Emean were observed 18 months after RT. The SWE correlated well with the LENT-SOMA score when assessing radiation-induced neck fibrosis 1.5 years after RT (r = 0.557-0.649; P < 0.01). Furthermore, both the Emax and Emean in the LENT-SOMA grade 0 subtype were higher 18 months after RT than before RT (P < 0.01). Because of its high reliability and good consistency with the LENT-SOMA score and better stiffness reflection at grade 0, SWE may be used to objectively and quantitatively evaluate the variation trend of radiation-induced neck fibrosis.