title: Optimized radioiodine therapy for Graves' disease: two MIRD-based models for the computation of patient-specific therapeutic 131I activity.
abstract: OBJECTIVE
  (131)I therapy is increasingly used for Graves' hyperthyroidism. Debate remains about the best method for calculating the activity to administer, as well as about the potential benefit of such computed activity. Several arguments plead, nevertheless, in favour of a personalized computation, such as inter-individual variations of thyroid volume and biokinetics.
  
  
  METHODS
  A MIRD-based dosimetric approach, with an additional extension that takes into account the variation of thyroid mass during the treatment, has been developed. This approach includes the benefits of a personalized determination of biokinetics. Results were compared with those of six methods widely used in routine practice. Forty-one patients were enrolled (34 women, seven men; mean age +/-SD: 48.11 +/- 6.4 years). (131)I uptakes were measured at 4, 24 and 96 h (36.2 +/- 14.6%, 42.8 +/- 9.7% and 27.6 +/- 6.8%, respectively), following administration of the tracer. The kinetics of iodine in the thyroid were evaluated using a two-compartment model (effective half-life of 5.1 +/- 1.6 days). Computations of activities to deliver the doses prescribed by the physician were done with the eight formalisms.
  
  
  RESULTS
  There was no statistical difference between results of the two MIRD-based formalisms (227 +/- 148 MBq and 213 +/- 124 MBq), which were also not significantly different from those obtained with the majority of the other methods (from 128 +/- 95 MBq to 275 +/- 223 MBq). However, a large intra-individual difference up to a factor of 2 between two given methods was found.
  
  
  CONCLUSIONS
  The formalism developed appears to be a good compromise between all the common formalisms already used in many institutions. Furthermore, it allows the exposures of target volumes and non-target volumes to be planned individually and practical individual radiation protection recommendations to be implemented.
authors.affiliation: Nuclear Medicine Department, Nantes University Hospital, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Carlier
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Salaun
authors.forename: Marie-Béatrice
authors.initials: MB
authors.lastname: Cavarec
authors.forename: Frédéric
authors.initials: F
authors.lastname: Valette
authors.forename: Alexandre
authors.initials: A
authors.lastname: Turzo
authors.forename: Manuel
authors.initials: M
authors.lastname: Bardiès
authors.forename: Yves
authors.initials: Y
authors.lastname: Bizais
authors.forename: Olivier
authors.initials: O
authors.lastname: Couturier
mesh_terms: D001822:Body Burden; D003198:Computer Simulation; D005260:Female; D005602:France; D006111:Graves Disease / Q000378:metabolism* / Q000532:radiotherapy*; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011785:Quality Assurance, Health Care / Q000379:methods; D011874:Radiometry / Q000379:methods; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D012062:Relative Biological Effectiveness; D016896:Treatment Outcome
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals