JNMT: Lead barrier cuts rad dose to nuke technologists
A lead barrier can reduce radiation dose to technologists by about two times during nuclear medicine procedures. lowering external radiation doses to technologists within permissible levels, according to a study published in this month’s Journal of Nuclear Medicine Technology.

The study, led by Bircan Sonmez, MD, from the department of nuclear medicine, Karadeniz Technical University, Trabzon, Turkey, used a Geiger-Müller detector to measure dose rates to technologists at various distances from patients behind a lead shield and determined the average time spent by technologists at these distances. Deep-dose equivalents to technologists were obtained.

The nuclear medicine procedures considered by the researchers were thyroid scintigraphy performed using 99mTc pertechnetate, whole-body bone scanning performed using 99mTc-methylene diphosphonate (MDP), myocardial perfusion scanning performed using 99mTc-methoxyisobutyl isonitrile (MIBI), 201Tl (thallous chloride) and renal scanning performed using 99mTc-dimercaptosuccinic acid (DMSA).

The measured deep-dose equivalent to technologists per procedure was within the range of 0.13 to 0.43 uSv using a lead shield and 0.21 to 1.01 uSv without a lead shield. For a total of 95 clinical cases, effective external radiation doses to technologists were found to be within the permissible levels, according to Sonmez and colleagues.

Doses to technologists varied significantly for different diagnostic applications, the researchers found. 99mTc-MIBI myocardial perfusion scans imparted higher doses (1.01 mSv without a lead shield and 0.43 mSv with a lead shield) to technologists than did the other types of scans. Although 201Tl myocardial perfusion scans were applied in the same manner as 99mTc-MIBI, 201Tl yielded lower doses to technologists (0.23 mSv without a lead shield and 0.16 mSv with a lead shield).

The contributions of the patient positioning dose to total dose (without a lead shield) were approximately 18 percent, 31 percent, 14 percent, 13 percent and 9 percent for 99mTc-MDP whole-body bone scans, 99mTc-pertechnetate thyroid scans, 99mTc-DMSA renal scans, 99mTc-MIBI myocardial perfusion scans and 201Tl myocardial perfusion scans, respectively.

The authors noted that even without a rotation of the work force, and even with a major increase in the number of patients, the annual dose to individual technologists would not reach the annual limit (20 mSv) specified by the International Commission on Radiological Protection.

A 2 mm lead barrier reduced the dose to technologists by about two times for the common diagnostic procedures performed in the study.

“This result re-emphasizes that technologists should consider the use of shielding. Furthermore, this study found that external radiation doses to technologists were within permissible levels, regardless of whether a technologist performed only a particular diagnostic procedure,” wrote the authors.

Therefore, rotation of technologists among different tasks is not necessary. Finally, the results of this study could be applied to the scheduling of scanning procedures by pregnant technologists to keep their fetal exposures as low as possible, concluded Sonmez and colleagues.