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Abstract
Low dose radiation has been defined as doses in the range under 100 mSv of low linear energy transfer (low-LET) radiation. There are two sources of ionizing radiation: natural and artificial radiation. Medical radiation exposure is the most common artificial radiation exposure. The frequency and volume of medical radiation exposure has markedly increased because of recent developments in medical technology. Radiation protection is now a concern due to the increasing use of computed tomography (CT) scans and diagnostic X-rays. This article introduced several models and hypotheses regarding the possible carcinogenic risks associated with low-LET radiation. Although opinions vary on the health effects of low level radiation exposure, current studies of medical radiation rely on exposure information collected prospectively, including cohort studies such as atomic bomb survivor studies. Although there are differences in perspective, the majority of studies have supported 'linear-no-threshold model without threshold' between low-LET radiation and the incidence of cancer risk. There is a need for further studies on medical radiation exposure including CT and positron emission tomography in order to understand the health effects of low-LET radiation, including the cancer incidence.
Figures and Tables
Figure 1
A hypothetical extrapolated dose response model for cancer risk estimation in low-dose radiation exposure. (A) Linear-no-threshold model, (B) linear quadratic model, (C) linear model with a threshold, (D) hormesis.
Figure 2
Risk of cancer attributable to diagnostic X-ray exposures versus annual X-ray frequency (From Berrington de Gonzalez A, et al. Lancet 2004;363:345-351, with permission from Elsevier) [20]. a)Taken from worldwide survey.
Table 1
Different positions of various societies about cancer risk of linear no-threshold (LNT) model at <100 mSv radiation exposure
From Einstein AJ, et al. JAMA 2007;298:317-323, with permission from AMA-ASSN [10].
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