Comparison Between Dose Estimated Through Calculation Based On A Mathematical Model And Dose Reconstructed By EPR Dosimetry With Tooth Enamel For Medical Diagnostic X-ray Workers

Many people work on medical diagnostic X-ray work Which has a long history in China. In order to judge the effect of X-ray on heath and take better measures for intervention, reliable relationship between exposure and health effect relationship is necessary. In the research of the relationship, effects assessment is according to dose. Therefore, the reliability and accuracy of dose are required. Individual dose information on an X-ray worker is often absent in China before 1985. Therefore, retrospective dosimetry for X-ray workers is very important to analyse their radiation hazards.In order to perform dosimetry for X-ray workers, a numerical method named NWM (normalized workload method) was developed and has been widely applied domestically. Doses for 10,599 X-ray workers were calculated by NWM. For 91.9% of the X-ray workers, dose is within 0.2Gy. Main effects related to radiation dose is the distinct increase of peripheral blood lymphocyte aberration rate and micronucleus rate and the significant increase of the leukemia incidence and mortality rates.The present paper tried to use EPR (electron paramagnetic resonance) with tooth enamel for retrospective dose assessment to validate NWM. EPR dosimetry is a physical method for the assessment of absorbed dose from ionizing radiation. It is based on the measurement of stable radiation induced radicals in human calcified tissues (primarily in tooth enamel). EPR dosimetry with teeth is now firmly established in retrospective dosimetry. It is a powerful method for providing information on exposure to ionizing radiation many years after the event, since the 'signal' is 'stored' in the tooth. This technique is of particular relevance to relative low dose exposures or when the results of conventional dosimetry are not available.The availability of tooth sample from X-ray workers is a premise of the research. In the past the sample size in relevant research is small. 25 teeth donated by 18 X-ray workers were collected with the occupational record of the donators. The sample size included is large in low-dose radiation epidemiology research with EPR dosimetry. And this is the first time to validate NWM using experimental method with large sample size. What's more, there are six teeth collected from the same X-ray worker, which will help the accumulation of important information for the effect of tooth position on the reconstructed dose caused by low-energy photon radiation.The present paper adopted Visual Basic 6.0 programming language to establish a computer system for dose estimates of NWM. A series of experiments were designed for EPR dosimetry methodology, the improved experimental method was applied to reconstruct dose for X-ray worker with tooth enamel. Finally, the results were obtained by the two methods and trend analysis was performed.