Comparison of ultrasound, CT and MRI in the assessment of parotid masses

In order to compare the advantages and failings of the current imaging procedures used for the staging of parotid masses, 121 patients were investigated: 30 with ultrasound (US) and CT, 55 with US and MRI, and 36 with US, CT and MRI. The accuracy of the three imaging modalities was evaluated in detecting parotid lesions; in assessing their location (intra- or extraglandular) and nature (benign or malignant); and in defining their intraglandular extent (superficial or deep lobe) as well as their relationship with surrounding structures. The imaging findings were related to the cytohistological data from US-guided biopsy or from surgical resection. In the 36 patients studied with all three modalities the diagnostic accuracy (excluding double errors in the same patient) was 77.7% for US, 86.1% for CT and 94.4% for MRI. US was thus shown to be less accurate than CT or MRI, and MRI not significantly superior to CT. US with fine-needle aspiration cytology should be the first-line imaging technique; CT and MRI have to be- considered for lesions more than 3 cm in diameter or for masses arising in the deep lobe of the gland. The results of this series show that MRI provides better results than CT in displaying the relationship of the mass with contiguous structures. © 1994 Springer-Verlag.