title: Exhalation of ¹³¹I after radioiodine therapy: measurements in exhaled air.
abstract: OBJECTIVE
  A considerable amount of radioiodine is exhaled after radioiodine therapy leading to unwanted radiation exposure through inhalation. This study focused on the concentration of radioactivity exhaled and its chemical nature.
  
  
  METHODS
  Air exhaled by 47 patients receiving (131)I-iodine for different thyroid diseases (toxic goitre n = 26, Graves' disease n = 13, thyroid cancer n = 8) was investigated with a portable constant air-flow sampler. Different chemical iodine species were collected separately (organic, elemental and aerosolic) up to 26 h after administration of the radioiodine capsule. The data approximated to a monoexponential time-activity curve when integrated over 100 h. The radioactivity in the filters was measured with a well counter at defined time points after administration.
  
  
  RESULTS
  The radioactivity of (131)I in the exhaled air 1 h after administration ranged from 1 to 100 kBq/m(3). Two parameters (half-life of radioiodine exhalation and time-integrated activity over 100 h) were substantially higher in patients with cancer after near-total thyroidectomy (11.8 ± 2.1 h and 535 ± 140 kBq / m(3), respectively) than in patients with hyperfunctioning thyroid tissue due to toxic adenoma (7.6 ± 2.5 h and 115 ± 27 kBq / m(3), respectively) or Graves' disease (6.4 ± 3.6 h and 113 ± 38 kBq / m(3), respectively). The percentage of radioiodine in the exhaled air in relation to radioiodine administered to the patient was between 80 ppm and 150 ppm. The fraction of organically bound radioiodine (mean value) for all time points after administration was 94-99.9%. This percentage did not depend on the type of thyroid disease.
  
  
  CONCLUSIONS
  The amount of exhaled radioiodine is small but by no means negligible on the first day after administration. This is the first study to provide experimental evidence on a systematic basis that radioiodine becomes exhalable in vivo, i.e. in the patient. The mechanism of organification of orally administered radioiodine remains to be investigated.
authors.affiliation: Clinic of Nuclear Medicine, University of Cologne, Kerpener Straße 62, 50937 Cologne, Germany. klaus.schomaecker@uni-koeln.de
authors.forename: Klaus
authors.initials: K
authors.lastname: Schomäcker
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Sudbrock
authors.forename: Thomas
authors.initials: T
authors.lastname: Fischer
authors.forename: Markus
authors.initials: M
authors.lastname: Dietlein
authors.forename: Carsten
authors.initials: C
authors.lastname: Kobe
authors.forename: Mark
authors.initials: M
authors.lastname: Gaidouk
authors.forename: Harald
authors.initials: H
authors.lastname: Schicha
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000388:Air / Q000032:analysis; D001944:Breath Tests / Q000379:methods; D005260:Female; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis; D007457:Iodine Radioisotopes / Q000032:analysis* / Q000493:pharmacokinetics* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals / Q000032:analysis* / Q000493:pharmacokinetics / Q000627:therapeutic use; D013959:Thyroid Diseases / Q000378:metabolism* / Q000532:radiotherapy
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals