Acoustic Radiation Force Impulse quantitative elastography: a new noninvasive technique for the evaluation of parotid glands. A preliminary study in controls and in patients with irradiated nasopharyngeal carcinoma.

Abstract

Aim: We aim to define the values of the shear wave velocity (SWV) in the normal parotid glands (PG) and to identify the modifications of tissue stiffness in patients with irradiated nasopharyngeal carcinoma. Material and methods: Sixty normal parotid glands pertaining to 30 healthy volunteers and 40 pathological parotid glands pertaining to 20 patients who had had underwent radiation therapy for nasopharyngeal carcinoma were included in this study. The patients underwent a B mode ultrasonography examination and the volume of the parotid gland was determined. A subsequent Acoustic Radiation Forde Impulse Imaging (ARFI) examination was performed and the SWV were determined for the central and the periphery of the glandular parenchyma. Results: The mean volume of the gland in the volunteers’ group (12.02±0.6 ml) was significantly higher than in the group of patients who underwent radiation therapy (10.3±0.74 ml) (p<0.0001).  The SWV values in the normal group were lower compared to the patients group (1.54±0.6 m/s vs. 1.76±0.73 m/s, p<0.0001). Conclusion: Elastography using the ARFI technique constitutes an objective method used for the evaluation of glandular stiffness in both normal and post radiotherapy glands. The SWV values determined in patients who underwent head and neck radiotherapy are increased, indicating a greater tissue stiffness thereby implying a structural transformation of the glandular parenchyma.