title: 1-23I-MIBG thyroid uptake: Implications for MIBG imaging of the heart.
abstract: 123I-MIBG has been widely used in patients with heart failure and neurological disorders. The patients are pre-treated with Lugol's oral solution or potassium perchlorate to prevent thyroid uptake of unlabeled 123I to limit the thyroid radiation exposure. However, despite the inhibition of the iodide pump, the thyroid is frequently visualized. The aim of this study was to study the pattern of thyroid uptake.
  
  
  
  We reviewed the 123I-MIBG images of 57 patients studied in three different centers in Italy for cardiac (n = 42) or neurological (n = 15) indications. They were imaged at 15 minutes and 4 hours after injection and in all patients, the thyroid was included in the imaging field of view. In 2 of the 3 centers, the patients were pre-treated with Lugol's oral solution and/or potassium perchlorate (group 1) but in the third center, they were not (group 2). The following imaging parameters were evaluated: heart-to-mediastinum ratio (H/M), thyroid-to-mediastinum ratio (T/M) at 4 hours, and tracer wash out from the heart (HWO) and from the thyroid (TWO).
  
  
  
  In the cardiac patients, the HWO was 22.98 ± 7.16% and TWO was 11.4 ± 11.86% (P < .0001). The TWO was 12.2 ± 13.1% in group 1 and 10.05 ± 8.97% in group 2 (P = NS). In the neurological patients the HWO was 26 ± 8.1% and the TWO was 20.32 ± 6.41 (P < .05). The difference in TWO was statistically significant (P < .01) between cardiac and neurological patients, whereas the HWO was not. The 4-hour H/M was 1.49 ± 0.23 in cardiac patients vs 1.4 ± 0.39 in neurological patients (P = NS). The 4-hour T/M was 1.33 ± 0.3 in cardiac patients vs 1.15 ± 0.13 in neurological patients (P < 0.05).
  
  
  
  The thyroid visualization in MIBG imaging is likely an expression of thyroid sympathetic innervation. The differences in TWO and T/M ratio in cardiac and neurological patients probably express differences in thyroid dopaminergic receptors. Thus, pre-treatment with potassium perchlorate or Lugol's solution may not be justified in patients undergoing 123I-MIBG imaging in whom the risk of side effects due to pre-treatment could be higher than the risk due to thyroid radiation exposure.
authors.affiliation: Chair of Nuclear Medicine and Nuclear Medicine Unit, Department of Medical Imaging, University and Spedali Civili, Piazza Spedali Civili, 1, Brescia, Italy. giubbini@med.unibs.it.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Giubbini
authors.affiliation: Nuclear Medicine Unit, San Giacomo Apostolo Hospital, Castelfranco Veneto, TV, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Milan
authors.affiliation: Cardiology Department, Fondazione Maugeri Centro Medico, Veruno, NO, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Marcassa
authors.affiliation: Chair of Nuclear Medicine and Nuclear Medicine Unit, Department of Medical Imaging, University and Spedali Civili, Piazza Spedali Civili, 1, Brescia, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Paghera
authors.affiliation: Chair of Nuclear Medicine and Nuclear Medicine Unit, Department of Medical Imaging, University and Spedali Civili, Piazza Spedali Civili, 1, Brescia, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Fracassi
authors.affiliation: Chair of Nuclear Medicine and Nuclear Medicine Unit, Department of Medical Imaging, University and Spedali Civili, Piazza Spedali Civili, 1, Brescia, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Camoni
authors.affiliation: Health Physics Department, Spedali Civili, Brescia, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Rodella
authors.affiliation: Chair of Nuclear Medicine and Nuclear Medicine Unit, Department of Medical Imaging, University and Spedali Civili, Piazza Spedali Civili, 1, Brescia, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bertagna
authors.affiliation: Chair of Nuclear Medicine and Nuclear Medicine Unit, Department of Medical Imaging, University and Spedali Civili, Piazza Spedali Civili, 1, Brescia, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Motta
authors.affiliation: Chair of Nuclear Medicine and Nuclear Medicine Unit, Department of Medical Imaging, University and Spedali Civili, Piazza Spedali Civili, 1, Brescia, Italy.
authors.forename: Mattia
authors.initials: M
authors.lastname: Bertoli
authors.affiliation: Nuclear Medicine Unit, Fondazione Maugeri Centro Medico, Veruno, NO, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Campini
mesh_terms: D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics*; D000368:Aged; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006333:Heart Failure / Q000000981:diagnostic imaging* / Q000378:metabolism*; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D009206:Myocardium / Q000378:metabolism; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000378:metabolism*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine
keywords: 123I-MIBG; congestive heart failure; radiation exposure; thyroid scintigraphy