Comparative evaluation of orbital lesions by ultrasonography and computed tomography

Introduction: Ultrasonography has proved its accuracy in orbital imaging by virtue of its high frequency probes and b mode imaging. The CT extends privilege of perfect anatomical images and better delineation using intravenous contrast. The current study evaluated clinical and radiological presentation of various orbital lesions; and compared diagnostic accuracy of USG and CT. Material and methods: A prospective observational study was planned at a tertiary teaching institute on 100 patients referred to radiology department for ultrasonography and computed tomography of orbit. Patients with lesions arising primarily from orbit or spread from adjacent structures were included in the study. Observations: Majority of patients were pediatric; common etiology being retinoblastoma and infection. The central orbital space was most predisposed in inflammatory and vascular lesions: and, peripheral orbital space in neoplastic, trauma, congenital, lacrimal gland and fossa lesions. The diagnostic sensitivity of USG in evaluation of orbital lesions was found to be 93.6 % as against 100% with CT. Diagnostic specificity of CT was higher than USG when single specific diagnosis was given (93% vs 68% respectively), as well as when final diagnosis was given as second differential (96% vs 78.7% respectively). Conclusion: Orbital vascular lesions and Retinoblastoma can be diagnosed easily on both USG and CT. Both USG and CT failed to differentiate between aspergillosis, mucormycosis and sino-nasal malignancies extending to orbit. CT is more sensitive and specific than USG and should be the preferred modality for suspected orbital lesions.