Role of Octreoscan and Correlation with MR Imaging in Graves' Ophthalmopathy

Abstract

Since the identification of somatostatin receptors on lymphocytes, orbital infiltration with mononuclear cells in Graves' ophthalmopathy has provided a rationale for receptor imaging with the radiolabeled somatostatin analog Octreotide. In 40 patients with Graves' ophthalmopathy and 10 controls, 110 MBq indium-Octreotide were administered i.v., and scans were performed at 4 and 24 h after injection. An uptake ratio between the orbits and the brain was determined. In 20 ophthalmophathy patients, magnetic resonance imaging (MRI) of the orbits was performed and the T2 relaxation time was measured within the rectus muscles. Compared to controls (4 h Octreotide uptake: median 6.0 counts/pixel/MBq, orbit/brain ratio 5.6), ophthalmopathy patients showed a 2- to 3-fold increased uptake (15.8 counts/pixel/MBq vs controls p = 0.0032; ratio 12.6, vs controls p = 0.003). When considering patients with active disease only, a higher uptake was registered (16.8 counts/pixel/MBq vs controls p 0.0048, ratio 15.6 vs controls p = 0.0006). Untreated patients showed a markedly higher uptake (23 counts/pixel/MBq) compared to patients receiving steroid therapy (12.6, p = 0.001). MRI of the orbit revealed a correlation between T2 relaxation time of the eye muscles and orbital uptake of Octreotide (p < 0.001).

Somatostatin receptor gene expression and inhibitory effects of octreotide on primary cultures of orbital fibroblasts from Graves' ophthalmopathy

“…We also show that retroorbital fibroblasts specifically bind SST-14, and respond in vitro to the SST analogue octreotide by inhibition of cAMP production and cell growth. The presence of functional ssts on retroorbital tissues of patients with GO was suggested by the uptake of 111 In-DTPA--Phe 1 -octreotide into the orbits during the  2. sst subtype mRNA expression in primary fibroblast cultures from retroorbital tissues GO1 GO2 GO3 GO4 GO5 GO6 GO7 GO8 GO9 GO10 C1 C2 C3 C4 C5 active phase of the disease (Chang et al 1991, Postena & Krenning 1994, Kahaly et al 1995, Krassas et al 1995, Colao et al 1998 (Reisine & Bell 1995, Patel 1997. Octreotide, at physiological concentrations, inhibited cAMP accumulation in vitro, demonstrating that, as in other cell systems (Patel 1997), ssts in retroorbital fibroblasts are negatively coupled to adenyl-cyclase activity.…”

“…Accumulation of radiolabelled SST analogue in retroorbital tissue has been demonstrated in vivo by 111 In-DTPA--Phe 1 -octreotide (Octreoscan) scintigraphy (Chang et al 1991, Postena & Krenning 1994, Kahaly et al 1995, Krassas et al 1995, Colao et al 1998, suggesting the presence of specific binding sites for octreotide on the orbit components. It is not clear whether octreotide binds to retroorbital fibroblasts or to infiltrating immune cells.…”

Novel Approaches to the Management of Graves` Ophthalmopathy

“…Octreoscan positivity is higher in Graves' patients with than in those without ophthalmopathy 11 ; in patients with active than in those with inactive GO [11][12][13] ; in patients with recent-onset than in those with longstanding eye disease 12 . Octreoscan positivity correlates with other indicators of activity of the ophthalmopathy, such as high CAS 10 or T2-relaxation time of the extraocular muscles at magnetic resonance imaging 14 . Thus, a positive octreoscan is an indicator of GO activity 15 and may predict a subsequent favorable response not only to SMSa therapy but also to high-dose glucocorticoids and/or orbital radiotherapy 11,[16][17][18] .…”

Immunosuppressive therapy in patients with thyroid eye disease: an overview of current concepts

“…Identification of patients with TED is based primarily on clinical signs and symptoms affecting one or both eyes (4). Additional information can be obtained from newer imaging methods such as magnetic resonance imaging (MRI) or computed tomography (CT), which identify gross changes in the retrobulbar space such as muscle swelling, edema, and sometimes fibrosis (2,5,6).…”