Estimation of Radiation Burden to Relatives of Patients Treated withRadioiodine for Cancer Therapy

摘要

Patients treated with radioiodine present a radiation hazard and precautions are necessaryto limit the radiation dose to family members, nursing staff and members of the public. The precautionsadvised are usually based on the instantaneous dose rates or iodine retention and do not take into accountthe time spent in close proximity with a patient. The purpose of this study was to draw guidelines based onthe actual measurements and to confirm whether the present guidelines in our country for discharge ofpatients treated for thyroid disorder with radioiodine (131I) are adequate or not. External exposure rateswere measured on patients treated for cancer therapy using a calibrated ionization survey meter at the timeof discharge from the hospital. The limit of discharge of patients in our country is either the retainedactivity of 555 MBq in the body or an exposure rate of 2.5 mR/hr at one metre. The patient forthrotoxicosis is treated as an outpatient basis I.e. the patient does not require hospitalization. The patientand their relatives were given lockets embedded with CaSO4:Dy dosimeters at the time of discharge fromthe hospital. These lockets were given with a chain to be worn in the neck for 15 days. These lockets werecollected after a fortnight and read out in a conventional TLD reader. These dose estimates can be used tocalculate the limits for the patient movements so as to limit doses received to less than 1 mSv for thefamily members. This study dealt only with the external exposure; the problem of internal contaminationwas not considered. In our study the doses to the patient were also measured. In most of these cases, thedose received by the relatives of the patients were more than 1 mSv, which was more than the limitprescribed by the International Commission of Radiological Protection (ICRP) for the general public andin few cases these values were more than 5 mSv, the limit prescribed by ICRP for the comforter. It is clearthat measurement of retained activity, without reference to patient behavior patterns is insufficient toformulate adequate advice on restriction.