Real-Time Elastography In Assessing Fibrosis Of Irradiated Salivary Glands Of Nasopharyngeal Carcinoma

Objective To evaluate the intensity of fibrosis of salivary glands in patients with nasopharyngeal carcinoma (NPC) post-radiotherapy (post-RT), compared to the normal, and analyze correlation between fibrosis of glands and the extent of xerostomia.Methods 50 post-RT patients and 40 healthy volunteers were enrolled into the study. Elasticity index (EI) of gland parenchyma was measured by real-time elastography (RTE). The extent of xerostomia was classified referring to late radiation reaction of RTOG/EORTC. Not only longitudinal dimension, thickness dimension of parotid and submandibular glands but also boundary, echogenicity and homogeneity were gauged and evaluated gradually by gray-scale ultrasound.Results EI values of parotid gland (parotid) and submandibular gland (subman) in post-RT patients were significantly higher than those in healthy volunteers (1.3±0.6 vs 1.0±0.3,1.9±0.8 vs 1.3±0.4, P< 0.01). No correlation was observed between El of irradiated gland and xerostomia (ys=-0.145, γh=-0.120, P> 0.05). Longitudinal and thickness dimension of post-RT salivary glands were significantly smaller than those of healthy group (P< 0.01). Normal parotid and subman were hyperechoic on sonography, which appeared higher than adjacent muscle and adipose tissue, however irradiated glands tended to be hypoechoic and isoechoic compared with the former (P< 0.01). There was significant difference in homogeneity of glands between the two groups that homogeneous in normal glands but heterogeneous in post-RT glands (P< 0.01). The boundary in normal subman was well-defined and ill-defined in normal parotid, which was exactly opposite with that in post-RT parotid and subman. Difference in boundaries between parotid and subman were both significant (P< 0.05).Conclusion Ultrasonic Elastography (UE) is an available means for assessing fibrosis of irradiated salivary gland in NPC patients. Salivary glands of post-RT have become stiffer, smaller, hypoechoic, heterogenous, ill-defined of most subman but well-defined of most parotid.