MR imaging of nasal masses.

Magnetic resonance (MR) imaging is useful in evaluating the wide spectrum of diseases that cause nasal masses. MR imaging is most helpful in (a) defining tumor margins and possible intracranial extension and (b) differentiating tumor (which has intermediate, heterogeneous signal intensity on T2-weighted images) from concurrent postobstructive sinusitis and other infectious or inflammatory masses (which have high, homogeneous signal intensity on T2-weighted images if the secretions are well hydrated). The analysis becomes more complicated in cases with desiccated and mixed composition secretions. MR imaging also allows characterization of very vascular tumors, which show flow voids or marked enhancement. Low signal intensity on T1-weighted images and marked low signal intensity on T2-weighted images are characteristic of fungal sinusitis, and fat within a nasal mass indicates a dermoid or epidermoid cyst. Idiopathic midline granuloma, Wegener granulomatosis, and "cocaine nose" manifest as predominantly destructive midline masses. Despite the advantages of MR imaging, computed tomography remains the preferred imaging modality for evaluating nasal masses that contain calcification or originate from bone or cartilage.