Calculation of effective dose to family members of patients with thyroid diseases
Abstract
Radioactive iodine 131I has been used for many years to treat benign thyroid disease. Treatment of thyroid cancer with 131I NaI is the most common application of radionuclide therapy in nuclear medicine and has been in use for many decades. At the Institute of pathophysiology and nuclear medicine at Skopje this kind of radiotherapy is performed since 1956y. Approximately 50 thyroid cancer patients and the same number hyperthyroid patients have been treated with radioactive iodine 131I every year. The patients, treated with radioactive iodine 131I present a radiation hazard to other individuals such as hospital staff, the patient’s family and members of the public with whom a treated patient may come in close contact. This situation can be overcome by imposing restriction on the behavior of the patient, to minimize the dose to close relatives and other individuals. In 1991, the International Commission of Radiological Protection (ICRP)has recommended a radiation constraint of 1 mSv/year to the general population. According to Basic Safety Standards Directive, the dose limits to the general public are not valid for “exposure of individuals, who are knowingly and willingly helping, other than as a part of their occupation, in the support and comfort of in-patient or out-patients undergoing medical diagnosis or treatment”. Proposed dose constraint from the BSS is: 0.3 mSv per episode for the public, 1 mSv for children, for the adults up to sixty years the dose constraint is 3 mSv and for adults more than 60 years old it is 15 mSv. The implementation of this guideline differs among various countries. In the Republic of Macedonia about fifty thyroid cancer patients are treated on in-patient basis and approximately fifty hyperthyroid patients is treated ambulatory on out-patient basis. According to the local hospital rule and old guidelines the maximum given activity to hyperthyroid patients, treated on out-patient basis, is 1110 MBq. The new, not yet established guidelines, proposed to reduce the maximum given activity to hyperthyroid patients, treated on out-patient basis, from 1110 – 555 MBq. This group of patient’s present great radiation hazard to their family members. Upon discharge from hospital, the patients as well as their family members were given brief radiation instructions. The aim is to minimize the transfer of radioactive material to person coming in close contact with patient. There are several papers in the literature concerning the subject of doses received by family members of thyroid cancer and hyperthyroid patients. Most of the published studies agree that doses to the family members are bellow the proposed dose constraint of 1 mSv. There are also several papers that present cases where children or other persons have received higher radiation doses than proposed dose limit and usually it is case with hyperthyroid patients and their close relatives. This study was undertaken to measure the effective doses to family members of patients treated with radioactive iodine 131I for thyroid diseases at nuclear medicine department in Skopje.
The main purpose of this study was to estimate the radiation exposure to family members of hyperthyroid and thyroid cancer patients treated with radioactive iodine 131I and to calculate the effective dose according given activity using Radiation Dose Assessment Resource (RADAR) software.
Keywords
Effective dose, iodine, thyroid.
