Abstract: PURPOSE: To explore the sonographic appearance of leukoplakia in non-masticatory oral mucosa, classifying mucosal leukoplakia according to the characteristics of sonogram, and providing reference for clinical diagnosis and treatment. METHODS: Eighteen patients (24 lesions) were diagnosed as oral leukoplakia at the Department of Oral Mucosal Diseases, Shanghai Ninth People's Hospital. The lesions were located in the tongue, floor of mouth, buccal mucosa and libial mucosa. Before the biopsy was taken, intra-oral path ultrasound was performed at the Department of Ultrasound to observe the lesion's extent, continuity, presence or absence of keratinization, the thickness of each layer in the epithelium, and color doppler flow imaging of the lesions. Quantitative analysis software 'Qontraxt' was used to randomly measure the relative echo intensity of the mucosal surface in leukoplakia areas, and summarize the keratinization type. SPSS 25.0 software package was used for statistical analysis of the data, and paired t test was used for inter-group comparison of the data. RESULTS: Oral leukoplakia sonograms showed that the epithelial layer appeared keratinization, the epithelial was thickened, and the echo was enhanced. The stratum intermedium showed a low echo thickening band, and the echo of partial lesions' surface decreased or the blood flow signal in oral mucosa increased. The hyperechoic band in the leukoplakia area was significantly thickened (P<0.001), and the echo was enhanced, with the tongue and buccal mucosa being the most significant. The hypoechoic band was significantly thicker (P<0.001), with the buccal mucosa and labial mucosa being the most significant. The surface and stratum corneum echo intensity values were determined by Qontraxt quantitative analysis software to determine whether there were keratinization and the keratinization types. The echo intensity values was 43.28±9.33 in non-OLK area, 92.88±3.12 in OLK with orthokeratosis, and 84.75±5.76 in OLK with parakeratosis. CONCLUSIONS: Ultrasound imaging can effectively define mucosal leukoplakia and measure the thickness of each layer in the epithelium. In addition, special adjoint changes such as ulcers, infections and cancerous changes can be detected. Intraoral ultrasonic imaging can provide imaging evidence for clinical diagnosis, treatment planning and post-treatment follow-up and contribute to avoid unnecessary mucosal iatrogenic injury or recurrence of disease after treatment.

Key words: Oral mucosal leukoplakia, Intraoral ultrasound, Quantitative analysis