New imaging procedures in thyroid-associated ophthalmopathy

Abstract

Lymphocytic and other mononuclear cell infiltrations of the retrobulbar space are observed in thyroid-associated ophthalmopathy (TAO). The identification of somatostatin receptors on lymphocytes has provided a rationale for receptor-imaging with the radiolabeled somatostatin analog Octreotide in TAO. Furthermore, previous investigations have shown that quantitative magnetic resonance imaging (MRI) allows non-invasive detection of acute inflammatory changes in extraocular muscles. Therefore, in patients with TAO and controls, scans of the orbits were obtained at 4h and 24h after i.v. injection of the radionuclide and orbital MRI was performed. Compared to controls, patients with TAO showed a three-fold increased uptake (p = 0.0032). When considering patients with active disease only, an even higher uptake was observed (vs controls p = 0.0006). MRI revealed markedly increased values of T2 relaxation time in extraocular muscles of untreated patients with active disease as well as a positive correlation between T2 of the eye muscles and orbital uptake of Octreotide (p < 0.001). Somatostatin receptor scintigraphy may be useful as a diagnostic tool for measuring acuity of inflammation in patients with thyroid eye disease. Through this method, as in quantitative MRI, there may be the possibility of selecting those patients who might benefit from treatment with immunosuppressive agents and/or Octreotide.

Key Words:

• Octreotide scan
• magnetic resonance imaging
• thyroid-associated ophthalmopathy