title: Estimation of effective half life of clearance of radioactive Iodine (I) in patients treated for hyperthyroidism and carcinoma thyroid.
abstract: BACKGROUND
  In medical applications of radioisotopes, for calculations of whole body doses and radiation safety applications, there is a need to estimate radioactive body burden. Local recommendations in Oman stipulate the need for hospitalization of patients treated for radioactive-iodine ((131) I) with activities above 400 MBq. MATERIALS #ENTITYSTARTX00026;
  
  
  METHODS
  A study of body burden estimation from sequentially measured exposure rates from patients treated for carcinoma thyroid and hyperthyroidism was undertaken. A digital auto-ranging beta gamma survey instrument calibrated for measurement of exposure rates is used in this study.
  
  
  RESULTS
  The mean measured exposure rates at 1 m in μSv/h immediately after administration and at 24 h intervals are used for estimation of effective half time of clearance of administered activity. For patients with post-operative thyroid carcinoma, the variation of body burden with time post-administration indicated tri-exponential clearance pattern, with T(½eff) values 14.4 h, 22 h, and 41.3 h. For patients treated for thyrotoxicosis, the body burden showed slow delayed clearance with a T(½eff) - 111.4 h, and exposure rates did not show appreciable fall off after 48 h.
authors.affiliation: Medical Physics Unit, National Oncology Center, Royal Hospital, Muscat-111, Oman.
authors.forename: R
authors.initials: R
authors.lastname: Ravichandran
authors.forename: Jp
authors.initials: J
authors.lastname: Binukumar
authors.forename: Amal Al
authors.initials: AA
authors.lastname: Saadi