Abstract
Aims: Therapeutic use of unsealed radioisotopes with an objective of providing radiation dose to the target or affected tissue has been in clinical practice for more than 70 years. Oral administration of radioiodine is an established therapy for the treatment of differentiated thyroid cancers. To avoid unacceptably high radiation exposures to patients' family members and other related people by applying ALARA (as low as reasonable achievable) principle, patients who administered the therapeutic dosage of ¹³¹I are required to be hospitalized for some period until the retained radioactivity in the body or the exposure rate at one meter falls to acceptable levels according to national and international limits. The main aim of this study was to investigate the exposure rate patterns of inpatients administered with therapeutic radioiodine and discuss the associated radiation safety issues.

Methods: This work presents the exposure rate patterns in patients treated with ¹³¹I at our institute from 2004 to 2011. A total of 83 patients with thyroid cancer treated with different activities of ¹³¹I ranging from 50 to 150 mCi were included in this study. 76% of the patients were females and 24% male with an age range of 17 to 70 years.

Results: The majority of patients (77.11%) were discharged at the exposure rate of less than 02 mR/hr (milliRoentgen/ hour), whereas only 22.89% patients were discharged at the exposure rate between 02 mR/hr and 05 mR/hr. Only 1.2% of total patients discharged after first 24 hours following ¹³¹I administration whereas 33.73%, 25.3% and 21.67% patients were discharged after 48, 72 and 96 hours after the dose administration. Only 1.2% of the patients stayed the longest duration in isolation (264 hours or 11 days) at the hospital.

Conclusion: With proper radiation safety measurements and pursuance of instructions, reduction in exposure to family members of patients and public can be suitably achieved.