title: Dosimetry in differentiated thyroid carcinoma (12-1402R).
abstract: OBJECTIVE
  The aim of this study has been to perform a dosimetric study in the treatments of differentiated thyroid cancer (DTC) performed in our center in order to find a dose-effect correlation.
  
  
  METHODS
  Thirty patients treated for DTC with 3700 MBq of (131)I have been included in this study. For reasons of radiological protection all of them spent two nights as inpatients. Dose rate at 1 m from all patients was measured approximately 20 and 44 h after the administration of the radioiodine and a whole body scan in the gamma camera was performed approximately 1 week later. With those measurements and by using a model of two compartments the activities in thyroid bed remnants and in the whole body were calculated as a function of time. The integration of both activities yields the corresponding cumulated activities. Absorbed doses to thyroid bed remnants and to the whole body can be calculated following the MIRDOSE method-that is, by multiplying the corresponding cumulated activities by the corresponding S factors.
  
  
  RESULTS
  The absorbed doses to thyroid bed remnants calculated in this study fall into a very wide range (13-1161 Gy) and showed the highest correlation factors with the following parameters: the absorbed dose rate to thyroid bed remnants, the cumulated activity in thyroid bed remnants, and the maximum radioiodine uptake in thyroid bed remnants. The absorbed doses to the whole body range from 0.12 to 0.23 Gy. The ablation was successful in all patients, and in spite of the wide range of absorbed doses to thyroid bed remnants obtained, no dose-effect correlation could be obtained.
  
  
  CONCLUSIONS
  Facing DTC treatments from a dosimetric viewpoint in which a predosimetry to calculate the activity of (131)I to be administered is performed is a subject difficult to handle. This statement is based on the fact that although a very wide range of absorbed doses to thyroid bed remnants was obtained (including several absorbed doses well below some dose thresholds previously published to achieve ablation of thyroid bed remnants), ablation of thyroid bed remnants was successful for all patients and therefore no dose-effect correlation could be determined.
authors.affiliation: Department of Medical Physics, Gurutzeta-Cruces Hospital, Gurutzeta plaza, Barakaldo, Spain. pablo.minguezgabina@osakidetza.net
authors.forename: Pablo
authors.initials: P
authors.lastname: Minguez
authors.forename: Jose
authors.initials: J
authors.lastname: Genolla
authors.forename: Jose Javier
authors.initials: JJ
authors.lastname: Celeiro
authors.forename: Jose Cruz
authors.initials: JC
authors.lastname: Fombellida
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006207:Half-Life; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D011874:Radiometry; D011879:Radiotherapy Dosage; D013954:Thyroglobulin / Q000097:blood; D013964:Thyroid Neoplasms / Q000097:blood / Q000188:drug therapy / Q000532:radiotherapy*; D013972:Thyrotropin / Q000097:blood / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes; D013972:Thyrotropin; D013954:Thyroglobulin