Assessment of dose and DNA damages in individuals exposed to low dose and low dose rate ionizing radiations during computed tomography imaging

Abstract

PurposeComputed tomography (CT) is a frequently used imaging modality that contributes to a tenfold increase in radiation exposure to the public when compared to other medical imaging modalities. The use of radiation for therapeutic need is always rationalized on the basis of risk versus benefit thereby increasing concerns on the dose received by patients undergoing CT imaging. Therefore, it was of interest to us to investigate the effects of low dose and low dose-rate X-irradiation in patients who underwent CT imaging by recording the doses received by the eye, forehead and thyroid, and to study the levels of damages in the lymphocytes in vivo. Materials and methodsLithium manganese borate doped with terbium (LMB:Tb) thermo luminescence dosimeters (TLD) were used to record the doses in the patient’s (n=27) eye, forehead, and thyroid and compared with the dose length product (DLP) values. The in vivo DNA damages measured were compared before and after CT imaging using chromosomal aberration (CA) and micronucleus (MN) assays. ResultsThe overall measured organ dose ranged between 2±0.29 and 520±41.63mGy for the eye, 0.84±0.29 and 210±20.50mGy for the forehead, and 1.79±0.43 and 185±0.70mGy for the thyroid. The in vivo damages measured from the blood lymphocytes of the subjects showed an extremely significant (p<0.0001) increase in CA frequency and significant (p<0.001) increase in MN frequency after exposure, compared to before exposure. ConclusionThe results suggest that CT imaging delivers a considerable amount of radiation dose to the eye, forehead, and thyroid, and the observed increase in the CA and MN frequencies show low dose radiation effects calling for protective regulatory measures to increase patient’s safety. This study is the first attempt to indicate the trend of doses received by the patient’s eye, forehead and thyroid and measured directly in contrast to earlier values obtained by extrapolation from phantoms, and to assess the in vivo low dose effects in an Indian patient population undergoing CT procedures.