Electron paramagnetic resonance (EPR) in medical dosimetry

This paper describes the fundamentals of electron paramagnetic resonance (EPR) and its application to retrospective measurements of clinically significant doses of ionizing radiation. X-band is the most widely used in EPR dosimetry because it represents a good compromise between sensitivity, sample size and water content in the sample. Higher frequency bands (e.g., W and Q) provide higher sensitivity, but they are also greatly influenced by water content. L and S bands can be used for EPR measurements in samples with high water content but they are less sensitive than X-band. Quality control for therapeutic radiation facilities using X-band EPR spectrometry of alanine is also presented

BiodosEPR-2006 consensus committee report on biodosimetric methods to evaluate radiation doses at long times after exposure

The requirements for biodosimetric techniques used at long times after exposure, i.e., 6 months to more than 50 years, are unique compared to the requirements for methods used for immediate dose estimation. In addition to the fundamental requirement that the assay measures a physical or biologic change that is proportional to the energy absorbed, the signal must be highly stable over time to enable reasonably precise determinations of the absorbed dose decades later. The primary uses of these biodosimetric methods have been to support long-term health risk (epidemiologic) studies or to support compensation (damage) claims. For these reasons, the methods must be capable of estimating individual doses, rather than group mean doses. Even when individual dose estimates can be obtained, inter-individual variability remains as one of the most difficult problems in using biodosimetry measurements to rigorously quantify individual exposures. Other important criteria for biodosimetry methods include obtaining samples with minimal invasiveness, low detection limits, and high precision. Cost and other practical limitations generally prohibit biodosimetry measurements on a large enough sample to replace analytical dose reconstruction in epidemiologic investigations. However, these measurements can be extremely valuable as a means to corroborate analytical or model-based dose estimates, to help reduce uncertainty in individual doses estimated by other methods and techniques, and to assess bias in dose reconstruction models. There has been extensive use of three biodosimetric techniques in irradiated populations: EPR (using tooth enamel), FISH (using blood lymphocytes), and GPA (also using blood); these methods have been supplemented with luminescent methods applied to building materials and artifacts. A large number of investigations have used biodosimetric methods many years after external and, to a lesser extent, internal exposure to reconstruct doses received from accidents, from occupational exposures, from environmental releases of radioactive materials, and from medical exposures. In most applications, the intent has been to either identify highly exposed persons or confirmed suspected exposures. Improvements in methodology, however, have led many investigators to attempt quantification of whole-body doses received, or in a few instances, to estimate organ doses. There will be a continued need for new and improved biodosimetric techniques not only to assist in future epidemiologic investigations but to help evaluate the long-term consequences following nuclear accidents or events of radiologic terrorism

EPR dosimetry intercomparison using smart phone touch screen glass

This paper presents the results of an interlaboratory comparison of retrospective dosimetry using the electron paramagnetic resonance method. The test material used in this exercise was glass coming from the touch screens of smart phones that might be used as fortuitous dosimeters in a large-scale radiological incident. There were 13 participants to whom samples were dispatched, and 11 laboratories reported results. The participants received five calibration samples (0, 0.8, 2, 4, and 10 Gy) and four blindly irradiated samples (0, 0.9, 1.3, and 3.3 Gy). Participants were divided into two groups: for group A (formed by three participants), samples came from a homogeneous batch of glass and were stored in similar setting; for group B (formed by eight participants), samples came from different smart phones and stored in different settings of light and temperature. The calibration curves determined by the participants of group A had a small error and a critical level in the 0.37-0.40-Gy dose range, whereas the curves determined by the participants of group B were more scattered and led to a critical level in the 1.3-3.2-Gy dose range for six participants out of eight. Group A were able to assess the dose within 20 % for the lowest doses (<1.5 Gy) and within 5 % for the highest doses. For group B, only the highest blind dose could be evaluated in a reliable way because of the high critical values involved. The results from group A are encouraging, whereas the results from group B suggest that the influence of environmental conditions and the intervariability of samples coming from different smart phones need to be further investigated. An alongside conclusion is that the protocol was easily transferred to participants making a network of laboratories in case of a mass casualty event potentially feasible