Recent developments in Graves' ophthalmopathy imaging.

Abstract

Orbital ultrasound, computed tomography, and magnetic resonance are commonly used as imaging techniques to demonstrate pathological changes in ocular adnexa of patients with Graves' ophthalmopathy. Low cost, short time of investigation, and lack of radiation characterize ultrasound. Nevertheless, a clear differentiation regarding disease activity is not possible, nor is the evaluation of orbital tissue precise enough. Short investigation time, precise imaging of the orbital apex and moderate costs are advantages of tomography. This method delivers a significant radiation dose to the lens, which if repeated constitutes a risk for cataract development. For this reason, magnetic resonance imaging is preferable, particularly if repeated scans are required to assess response to treatment. Precise tissue differentiation and lack of ionizing radiation uniquely suit magnetic resonance for eye studies. Although sensitive in demonstrating interstitial edema within the rectos muscles in active disease, as well as providing a good predictive value with respect to immunosuppressive therapy, quantitative magnetic resonance imaging is an expensive method and is non-specific for the orbital changes in ophthalmopathy. Because of a favorable target to background ratio, octreoscan carries a high sensitivity and may be regarded as a semi-objective tool in the evaluation of patients with Graves' ophthalmopathy, both at initial stages as well as during treatment. A positive orbital octreoscan indicates a clinically active disease in which immunosuppressive treatment might be of therapeutic benefit. However, it is an expensive method with a non-negligible radiation burden. Also, it is neither specific nor does it offer detailed orbital imaging. In summary, in unclear cases of proptosis or recently developed diplopia, prior to orbital decompression surgery, or if imaging is needed in subjects with ophthalmopathy, magnetic resonance actually is the imaging method of choice.