title: The impact of 99mTc-DTPA orbital SPECT in patient selection for external radiation therapy in Graves' ophthalmopathy.
abstract: OBJECTIVE
  In Graves' ophthalmopathy (GO), there is a demand to differentiate the immunologically active disease state, when immunosuppressive therapy is necessary, from the inactive state, when the patient would not benefit from it. We measured the inflammatory activity in the retrobulbar region using Tc-diethylene triamine pentaacetic acid (DTPA) SPECT before and after external radiation to determine whether this method is suitable for predicting the effectiveness of this therapy.
  
  
  METHODS
  Thirty-two patients with suspected active GO were involved in this retrospective study. The initial image, DTPA uptake value (UV) and its change after therapy were assessed to monitor the effect of the therapy and investigate whether a pretreatment scan is capable of predicting the outcome.
  
  
  RESULTS
  Depending on the change in DTPA UV after radiotherapy, three patient groups were formed: decreased, increased or minimally changed (less than 1×10 injected dose (ID)/ml). The initial DTPA UVs of these groups were significantly different (P<0.001). Improvement was observed mainly in patients with higher initial values. When comparing the groups with low (<12×10 ID/ml) versus high (≥12×10 ID/ml) initial uptake, an unexpected increase was observed in the first group after therapy (mean: +2.89±2.66×10 ID/ml), whereas the average change in the DTPA UV was negative in the latter group as anticipated (-2.24±4.47×10 ID/ml, P<0.00001).
  
  
  CONCLUSIONS
  We found that in GO patients a high DTPA UV may predict the response to orbital radiation therapy. DTPA orbital SPECT may be a suitable technique for the selection of GO patients for radiation therapy.
authors.affiliation: Department of Nuclear Medicine, Medical and Health Science Center, University of Debrecen, Nagyerdei krt. 98., Debrecen H-4032, Hungary.
authors.forename: Lajos
authors.initials: L
authors.lastname: Szabados
authors.forename: Endre V
authors.initials: EV
authors.lastname: Nagy
authors.forename: Bernadett
authors.initials: B
authors.lastname: Ujhelyi
authors.forename: Hilda
authors.initials: H
authors.lastname: Urbancsek
authors.forename: József
authors.initials: J
authors.lastname: Varga
authors.forename: Edit
authors.initials: E
authors.lastname: Nagy
authors.forename: László
authors.initials: L
authors.lastname: Galuska
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D049970:Graves Ophthalmopathy / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009915:Orbit / Q000000981:diagnostic imaging* / Q000528:radiation effects; D018579:Patient Selection; D012189:Retrospective Studies; D016284:Technetium Tc 99m Pentetate; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon; D016896:Treatment Outcome
chemical_list: D016284:Technetium Tc 99m Pentetate