Staff and patient are exposed to un avoidable radiation exposure to a wide range of radionuclides, as 99mTc, 67 Ga and 131I during nuclear medicine procedures. Although the frequency of the nuclear medicine is increasing, few data are available regarding ambient and patient exposure worldwide. The The International Commission on Radiological Protection (ICRP) has lowered the annual dose limit for the eye lens from 150 mSv to 20 mSv (i.e., by a factor of 7.5) for occupational exposures, therefore it is crucial to evaluate its impact in the existing programs on radiation protection and safety. Therefore, measurement of staff doses and ambient doses are important.
The objectives of this study are to measure the ambient radiation and patient dose during whole body bone scintigraphy, thyroid and renal scan procedures. The study was carried out at Alnilain Daignostic Center, Khartoum, Sudan. Staff radiation exposure personnel were calculated as a function of administered dose distance from the patient and at different times after the administration and workload. A calibrated survey meter and thermoluminescent dosimeters (TLDs- GR200A) were used to measure the ambient dose and staff dose, respectively. Prior to measurements, all TLD were calibrated in terms of air kerma free-in-air under reproducible reference condition using 99m Tc with activity 10 mCi (370 MBq). Quality control performed before administration of the radiopharmaceutical and doses are carefully calculated. All scan procedures were performed using MiE single head gamma camera (Orbiter 37 Gamma camera) after administration of 20 mCi, 4 mCi and 5 mCi of 99mTc.
The average ambient dose equivalent rate equal to about 12, 25 and 10 μSv/h was obtained at distance of 1 m, at 1.3 m from patient during bone, renal and thyroid scan respectively. Injection room and hot lab has ambient dose equivalent rates of 1.0 and 30 μSv/h at the same order. The maximum dose were recorded at the reception area equal to 180 μSv/h. Staff may exposed to a dose range from 8.0 to 12.5 mSv annually. Knowledge of ambient dose values is crucial in order to determine exposure personnel who may limit the time spent at high dose areas. The dose values are within the safety limit in the light of the current practice. Although, the ambient dose is high compared to previous studies, the staff exposure was below the annual dose limits in the light of the current workload. Appropriate isolation of the patients, training of staff and a strict compliance with the established radiation safety standards are crucial in order to avoid unnecessary radiation exposure.