Pre- and Post-Treatment Diffusion-Weighted Imaging Characteristics of Sinonasal Adenoid Cystic Carcinoma.

Sinonasal adenoid cystic carcinoma (ACC) is a rare, aggressive malignancy that commonly involves the nasal cavity and paranasal sinuses, with a propensity for perineural invasion and distant spread. Diffusion-weighted imaging (DWI) is a useful tool for evaluating tumor characteristics and monitoring treatment response. This case series aims to review the pre- and post-treatment diffusion characteristics of sinonasal ACC, focusing on the apparent diffusion coefficient (ADC) values. A series of 8 cases of sinonasal ACC that underwent pre- and post-treatment magnetic resonance imaging with DWI were retrospectively analyzed. Circular regions of interest were drawn on representative ADC images of the lesions. Pre-treatment mean ADC values ranged from 651 to 1156 × 10-6 mm2/second, while the post-treatment average ADC values ranged from 1351 to 1879 × 10-6 mm2/second. Post-treatment changes in ADC values were observed in all cases, demonstrating an increase in ADC, indicative of positive treatment response. This case series suggests that DWI could serve as a non-invasive imaging tool for evaluating post-treatment response of sinonasal ADC. Post-treatment changes in ADC potentially correlate with treatment response and disease progression. Hence, DWI could play a supplemental role in monitoring therapy, highlighting its potential in guiding clinical management decisions for patients with sinonasal ACC.