Radiation Dosimetry in Thyroid Cancer Patients

Radioactive iodine is utilized commonly for ablation of remnant thyroid tissue after thyroidectomy and treatment of persistent disease and metastases in differentiated thyroid cancer patients. As it involves ionizing radiation, it is important to ensure that the patients receive optimum amount of radiation to destruct the target tissue while keeping the radiation-related side effects to minimum. In clinical practice, standard activity doses are preferred for thyroid cancer patients, assuming that biokinetics are similar in all patients. Lately, many clinicians offered to individualise the radioactive iodine therapy by calculating the optimal amount of radioactivity using patient dosimetry. Radiation dosimetry is used to calculate the minimum effective and maximum tolerated absorbed dose for a successful radioactive iodine therapy. This approach enables to administer increased amount of therapeutic activity while minimizing the related side effects. This chapter presents some of the basic principles of patient dosimetry and radioiodine biokinetics following radioactive iodine admin‐ istration in differentiated thyroid cancer patients. Following radioactive iodine therapy, radiation protection measures are necessary to protect the public from ionizing radiation after discharge of the patient from hospital. Radiation exposure to patients, family members and caregivers and attempts to decrease the exposure during therapy are also going to be discussed.