To assess nasal and paranasal sinus masses by diffusion-weighted echoplanar magnetic resonance imaging (MRI).

This prospective study included 55 consecutive patients (34 males, 21 females; aged 14–64 years, mean 39 years) with nasal and paranasal sinus masses. All underwent diffusion-weighted MRI using single-shot echoplanar imaging (EPI) with a b factor of 0.500 and 1000s/mm². Apparent diffusion coefficient (ADC) maps were constructed, allowing ADC values of the mass to be calculated and correlated with histopathological findings.

The mean ADC value of nasal and paranasal sinus malignant lesions (1.10±0.25×10⁻³mm²/s) was significantly different (P=0.001) from that of benign lesions (1.78±0.41×10⁻³mm²/s). Also, there was a significant ADC difference between carcinoma and sarcoma (P=0.01) as well as between well differentiated and poorly differentiated malignancies (P=0.005). Using an ADC value of 1.53×10⁻³mm²/s as the threshold value for differentiating malignant from benign lesions, the best result obtained had an accuracy of 93%, sensitivity of 94%, specificity of 92%, a positive predictive value of 92% and negative predictive value of 94%. However, the use of 0.97×10⁻³mm²/s and 1.16×10⁻³mm²/s as threshold values to differentiate carcinomas from sarcomas and poorly differentiated malignancy, respectively, gave the best results.

The ADC value is a non-invasive imaging parameter that can be used to assess nasal and paranasal sinus masses, as it can help in the differentiation of malignant tumors from benign lesions, and in the characterization and grading of malignancies.