99mTc(V)-DMSA SPECT for the assessment of disease activity in Graves' ophthalmopathy

The aim of this study was to evaluate the use of 99mTc(V)-dimercaptosuccinic acid (99mTc(V)-DMSA) scintigraphy for the assessment of disease activity in patients with Graves' ophthalmopathy (GO) and compare their clinical parameters.

The study involved 20 patients who were clinically inactive and eight patients who were clinically active, a total 28 GO patients (18 female, 10 male; mean age: 39.2+/-13.4 years) and 12 control subjects (six female, six male; mean age: 57.12+/-12 years). Planar and SPECT orbital images were obtained 4 h after the intravenous injection of 555-740 MBq 99mTc(V)-DMSA, using low-energy, high-resolution, parallel-hole collimators with dual-head detectors. All SPECT data were reconstructed on conventional axial, sagittal and coronal projections using an iterative reconstruction. Semi-quantitative evaluation was performed comparing the orbital activity with nasal activity based on four grades. GO was classified according to the NOSPECS classification of the American Thyroid Association. Disease was considered clinically active if symptoms and signs deteriorated over 3 months.

No significant correlation was detected between clinical activity and classification (P=0.192). However, clinical activity and 99mTc(V)-DMSA uptake were significantly correlated (P=0.0001). There was no correlation between the clinical classification and scintigraphic grading. Bilateral orbital index of the active group was significantly higher than that of the inactive group (P=0.0001).

99mTc(V)-DMSA imaging discriminates the active from inactive GO as well as showing an ongoing subclinical inflammation in the orbits of the patients with GO, regardless of the disease activity clinically. Our results revealed that 99mTc(V)-DMSA is a promising agent for the diagnosis of active Graves' ophthalmopathy.