title: Radioiodine therapy of hyperfunctioning thyroid nodules: usefulness of an implemented dose calculation algorithm allowing reduction of radioiodine amount.
abstract: OBJECTIVE
  Radioiodine is a common option for treatment of hyperfunctioning thyroid nodules. Due to the expected selective radioiodine uptake by adenoma, relatively high "fixed" activities are often used. Alternatively, the activity is individually calculated upon the prescription of a fixed value of target absorbed dose. We evaluated the use of an algorithm for personalized radioiodine activity calculation, which allows as a rule the administration of lower radioiodine activities.
  
  
  METHODS
  Seventy-five patients with single hyperfunctioning thyroid nodule eligible for 131I treatment were studied. The activities of 131I to be administered were estimated by the method described by Traino et al. and developed for Graves'disease, assuming selective and homogeneous 131I uptake by adenoma. The method takes into account 131I uptake and its effective half-life, target (adenoma) volume and its expected volume reduction during treatment. A comparison with the activities calculated by other dosimetric protocols, and the "fixed" activity method was performed. 131I uptake was measured by external counting, thyroid nodule volume by ultrasonography, thyroid hormones and TSH by ELISA.
  
  
  RESULTS
  Remission of hyperthyroidism was observed in all but one patient; volume reduction of adenoma was closely similar to that assumed by our model. Effective half-life was highly variable in different patients, and critically affected dose calculation. The administered activities were clearly lower with respect to "fixed" activities and other protocols' prescription.
  
  
  CONCLUSIONS
  The proposed algorithm proved to be effective also for single hyperfunctioning thyroid nodule treatment and allowed a significant reduction of administered 131I activities, without loss of clinical efficacy.
authors.affiliation: Medical and Radiometabolic Therapy Unit, IRCCS AOU San Martino - IST, Di.M.I., Genoa University, Genoa, Italy - bagnasco@unige.it.
authors.forename: M
authors.initials: M
authors.lastname: Schiavo
authors.forename: M C
authors.initials: MC
authors.lastname: Bagnara
authors.forename: E
authors.initials: E
authors.lastname: Pomposelli
authors.forename: V
authors.initials: V
authors.lastname: Altrinetti
authors.forename: I
authors.initials: I
authors.lastname: Calamia
authors.forename: L
authors.initials: L
authors.lastname: Camerieri
authors.forename: M
authors.initials: M
authors.lastname: Giusti
authors.forename: G
authors.initials: G
authors.lastname: Pesce
authors.forename: C
authors.initials: C
authors.lastname: Reitano
authors.forename: M
authors.initials: M
authors.lastname: Bagnasco
authors.forename: M
authors.initials: M
authors.lastname: Caputo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D011835:Radiation Protection / Q000379:methods*; D019275:Radiopharmaceuticals / Q000008:administration & dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016606:Thyroid Nodule / Q000150:complications / Q000378:metabolism* / Q000532:radiotherapy*
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals