title: Potential use of iodine-123 metaiodobenzylguanidine radioaerosol as a marker of pulmonary neuroadrenergic function.
abstract: Iodine-123 metaiodobenzylguanidine (123I-MIBG) radioaerosol is of potential use in the investigation of the neuroadrenergic function of the lungs; however, before the method can be successfully employed the following issues need to be clarified: (1) Does the nebulization affect the radiochemical purity of 123I-MIBG? (2) Is the pulmonary distribution of inhaled 123I-MIBG homogeneous in normal subjects? (3) Does the pulmonary clearance of inhaled 123I-MIBG reflect the functional status of the neuroadrenergic system of the lungs? In this study we performed: (1) a chromatographic study of nebulized 123I-MIBG; (2) a quantitative evaluation of the lung distribution of 123I-MIBG radioaerosol in normal subjects as compared with that of technetium-99m diethylene triamine penta-acetic acid (99mTc-DTPA) and (3) an assessment of 123I-MIBG lung clearance both under control conditions and after pharmacologically induced beta-blockade, again compared with 99mTc-DTPA. For these purposes, eight normal subjects were divided randomly into an "MIBG group" and a "DTPA group" (four subjects each) and submitted to three scintigraphic studies each: a baseline study, and studies after the administration of a low (80 mg) and a high (160 mg) dose of propranolol. Radiochemical purity of nebulized 123I-MIBG ranged between 97.18% and 98.70%. The lung distribution of 123I-MIBG, as judged by the aerosol penetration index, was identical to that of 99mTc-DTPA under all study conditions. The 123I-MIBG clearance rate was slower than that of 99mTc-DTPA under baseline conditions (135+/-32 min vs 69+/-27 min, P<0.01) and increased significantly after propranolol administrations, while the 99mTc-DTPA clearance did not change. The following conclusions were drawn: (1) the nebulization does not affect the radiochemical purity of 123I-MIBG; (2) the lung distribution of 123I-MIBG is homogeneous in normal subjects; (3) the pulmonary clearance of 123I-MIBG reflects the functional status of the neuroadrenergic system of the lungs. Thus this scintigraphic method is suitable for research and perhaps for future clinical use.
authors.affiliation: Department of Nuclear Medicine, Catholic University of the Sacred Heart, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Giordano
authors.forename: M L
authors.initials: ML
authors.lastname: Calcagni
authors.forename: B
authors.initials: B
authors.lastname: Rossi
authors.forename: L
authors.initials: L
authors.lastname: Fuso
authors.forename: D
authors.initials: D
authors.lastname: Accardo
authors.forename: S
authors.initials: S
authors.lastname: Valente
authors.forename: R
authors.initials: R
authors.lastname: Pistelli
authors.forename: R
authors.initials: R
authors.lastname: Franceschini
authors.forename: L
authors.initials: L
authors.lastname: Troncone
mesh_terms: D019797:3-Iodobenzylguanidine; D000280:Administration, Inhalation; D000319:Adrenergic beta-Antagonists; D000328:Adult; D000336:Aerosols; D003287:Contrast Media; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D008168:Lung / Q000000981:diagnostic imaging* / Q000294:innervation; D008297:Male; D011433:Propranolol; D011877:Radionuclide Imaging; D013564:Sympathetic Nervous System / Q000000981:diagnostic imaging; D016284:Technetium Tc 99m Pentetate; D014018:Tissue Distribution
chemical_list: D000319:Adrenergic beta-Antagonists; D000336:Aerosols; D003287:Contrast Media; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D019797:3-Iodobenzylguanidine; D011433:Propranolol; D016284:Technetium Tc 99m Pentetate