Introduction: Currently there is no ideal imaging technique which could estimate the degree of inflammation in thyroid eye disease.
Aim: A new, rapid and cost-effective method, using 99mTc-labelled DTPA and 4-headed SPECT, was developed which is able to diagnose inflammatory activity in patients with endocrine orbitopathy (EOP).
Methods: The MRI T2 relaxation time was used as reference. Comparative orbital SPECT with the more specific 99mTc-Neospect (depreotide) was also performed in the same patients.
Results: Visual evaluation of orbital SPECT frames of patients suffering from active EOP could be easily distinguished from inactive EOP patients'. Despite the supposedly different characteristics of the two tested radiopharmaceuticals, there was essentially no difference between their accumulation in the orbit and the information obtained. The MRI activity scores correlated well with 99mTc-DTPA activity uptake (AU). The mean AU value in patients with inactive EOP was 6.26 +/- 1.6 10(-6) ID/cm3, while in active EOP 10.78 +/- 0.61 10(-6) ID/cm3, significantly higher. The 99mTc-DTPA accumulation in the orbital region in active disease was similar to that of depreotide. There was a good correlation (r = 0.91, P < 0.0001) between the two methods.
Conclusion: The authors concluded that 99mTc-DTPA orbital SPECT is a potentially useful method, which--after initial clinical and MRI staging--gives useful quantitative estimation of disease activity in endocrine orbitopathy. It may provide important visual and quantitative information during the follow up of patients.