EPR在体测量专用调制磁场驱动装置

利用电子顺磁共振（electron paramagnetic resonance,EPR）在体测量人牙齿可以实现无损伤地快速评估人体辐射剂量,具有实际应用价值.本文针对EPR在体测量牙齿剂量的应用特点,研制了专用调制磁场驱动装置,包括功率放大器、调制磁场激励线圈、调制频率设定模块、感应型调制幅度显示模块等.功率放大器采用脉冲功率放大方式取代传统的线性放大方式,用多N-MOSFET管H桥电路,功率容量大、效率高、结构简单,且调制频率设定自如.实验结果表明：（1）此装置可在大于9 cm磁极间距的中心样品位置产生调制幅度为0~0.9 mT的调制磁场,调制频率为10~100 kHz;（2）用该装置与EPR在体测量谱仪配合使用,可以明显观测到1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）样品谱线调制增宽过程以及辐射诱发的整体牙齿中的自由基信号,验证了该装置的高调制效率和实用性.     

Advances towards using finger/toenail dosimetry to triage a large population after potential exposure to ionizing radiation

Rapid and accurate retrospective dosimetry is of critical importance and strategic value for the emergency medical response to a large-scale radiological/nuclear event. One technique that has the potential for rapid and accurate dosimetry measurements is electron paramagnetic resonance (EPR) spectroscopy of relatively stable radiation-induced signals (RIS) in fingernails and toenails. Two approaches are being developed for EPR nail dosimetry. In the approach using ex vivo measurements on nail clippings, accurate estimation of the dose-dependent amplitude of the RIS is complicated by the presence of mechanically-induced signals (MIS) that are generated during the nail clipping. Recent developments in ex vivo nail dosimetry, including a thorough characterization of the MIS and an appreciation of the role of hydration and the development of effective analytic techniques, have led to improvements in the accuracy and precision of this approach. An in vivo nail dosimetry approach is also very promising, as it eliminates the problems of MIS from the clipping and it has the potential to be an effective and efficient approach for field deployment. Two types of EPR resonators are being developed for in vivo measurements of fingernails and toenails.     

A Framework for Comparative Evaluation of Dosimetric Methods to Triage a Large Population Following a Radiological Event

BACKGROUND: To prepare for a possible major radiation disaster involving large numbers of potentially exposed people, it is important to be able to rapidly and accurately triage people for treatment or not, factoring in the likely conditions and available resources. To date, planners have had to create guidelines for triage based on methods for estimating dose that are clinically available and which use evidence extrapolated from unrelated conditions. Current guidelines consequently focus on measuring clinical symptoms (e.g., time-to-vomiting), which may not be subject to the same verification of standard methods and validation processes required for governmental approval processes of new and modified procedures. Biodosimeters under development have not yet been formally approved for this use. Neither set of methods has been tested in settings involving large-scale populations at risk for exposure. OBJECTIVE: To propose a framework for comparative evaluation of methods for such triage and to evaluate biodosimetric methods that are currently recommended and new methods as they are developed. METHODS: We adapt the NIH model of scientific evaluations and sciences needed for effective translational research to apply to biodosimetry for triaging very large populations following a radiation event. We detail criteria for translating basic science about dosimetry into effective multi-stage triage of large populations and illustrate it by analyzing 3 current guidelines and 3 advanced methods for biodosimetry. CONCLUSIONS: This framework for evaluating dosimetry in large populations is a useful technique to compare the strengths and weaknesses of different dosimetry methods. It can help policy-makers and planners not only to compare the methods' strengths and weaknesses for their intended use but also to develop an integrated approach to maximize their effectiveness. It also reveals weaknesses in methods that would benefit from further research and evaluation.     

Limits of retrospective accident dosimetry by EPR and TL with natural materials

The radiation response of natural materials and domestic articles was investigated by EPR and TL to select suitable materials for retrospective dose assessment in accident dosimetry. The thermal stability and the influence of UV-exposure to the radiation-induced EPR centres were investigated. Based on a required precision of ±20% for dosimetry the lower limits of applicability of the materials were determined. The lowest dosimetry limits of 0.5 Gy were found using sugar, boiler scale and egg shells by EPR and 0.3 Gy by using TL with boiler scale. A list of materials found not to be applicable for retrospective radiation accident EPR dosimetry is also given.     

Electron paramagnetic resonance radiation dosimetry in fingernails

There is now an increased need for accident dosimetry due to the increased risk of significant exposure to ionizing radiation from terrorism or accidents. In such scenarios, dose measurements should be made in individuals rapidly and with sufficient accuracy to enable effective triage. Electron paramagnetic resonance (EPR) is a physical method of high potential for meeting this need, providing direct measurements of the radiation-induced radicals, which are unambiguous signatures of exposure to ionizing radiation. For individual retrospective dosimetry, EPR in tooth enamel is a proven and effective technique when isolated teeth can be obtained. There are some promising developments that may make these measurements feasible without the need to remove the teeth, but their field applicability remains to be demonstrated. However, currently it is difficult under emergency conditions to obtain tooth enamel in sufficient amounts for accurate dose measurements. Since fingernails are much easier to sample, they can be used in potentially exposed populations to determine if they were exposed to life-threatening radiation doses. Unfortunately, only a few studies have been carried out on EPR radiation-induced signals in fingernails, and, while there are some promising aspects, the reported results were generally inconclusive. In this present paper, we report the results of a systematic investigation of the potential use of fingernails as retrospective radiation dosimeters.     

Retrospective and emergency dosimetry in response to radiological incidents and nuclear mass-casualty events: A review

This paper reviews recent research on the application of the physical dosimetry techniques of electron paramagnetic resonance (EPR) and luminescence (optically stimulated luminescence, OSL, and thermoluminescence, TL) to determine radiation dose following catastrophic, large-scale radiological events. Such data are used in dose reconstruction to obtain estimates of dose due to the exposure to external sources of radiation, primarily gamma radiation, by individual members of the public and by populations. The EPR and luminescence techniques have been applied to a wide range of radiological studies, including nuclear bomb detonation (e.g., Hiroshima and Nagasaki), nuclear power plant accidents (e.g., Chernobyl), radioactive pollution (e.g., Mayak plutonium facility), and in the future could include terrorist events involving the dispersal of radioactive materials. In this review we examine the application of these techniques in ‘emergency’ and ‘retrospective’ modes of operation that are conducted on two distinct timescales. For emergency dosimetry immediate action to evaluate dose to individuals following radiation exposure is required to assess deterministic biological effects and to enable rapid medical triage. Retrospective dosimetry, on the other hand, contributes to the reconstruction of doses to populations and individuals following external exposure, and contributes to the long-term study of stochastic processes and the consequential epidemiological effects. Although internal exposure, via ingestion of radionuclides for example, can be a potentially significant contributor to dose, this review is confined to those dose components arising from exposure to external radiation, which in most studies is gamma radiation.The nascent emergency dosimetry measurement techniques aim to perform direct dose evaluations for individuals who, as members of the public, are most unlikely to be carrying a dosimeter issued for radiation monitoring purposes in the event of a radiation incident. Hence attention has focused on biological or physical materials they may have in their possession that could be used as surrogate dosimeters. For EPR measurements, in particular, this includes material within the body (such as bone or tooth biopsy) requiring invasive procedures, but also materials collected non-invasively (such as clippings taken from finger- or toenails) and artefacts within their personal belongings (such as electronic devices of which smart phones are the most common). For luminescence measurements, attention has also focused on components within electronic devices, including smartphones, and a wide range of other personal belongings such as paper and other polymer-based materials (including currency, clothing, bank cards, etc.). The paper reviews progress made using both EPR and luminescence techniques, along with their current limitations.For the longer-established approach of retrospective dosimetry, luminescence has been the most extensively applied method and, by employing minerals found in construction materials, it consequently is employed in dosimetry using structures within the environment. Recent developments in its application to large-scale radiation releases are discussed, including the atomic bomb detonations at Hiroshima and Nagasaki, fallout from the Chernobyl reactor and atmospheric nuclear bomb tests within the Semipalatinsk Nuclear Test Site and fluvially transported pollution within the Techa River basin due to releases from the Mayak facility. The developments made in applying OSL and TL techniques are discussed in the context of these applications. EPR measurements with teeth have also provided benchmark values to test the dosimetry models used for Chernobyl liquidators (clean-up workers), residents of Semipalatinsk Nuclear Tests Sites and inhabitants of the Techa River basin.For both emergency and retrospective dosimetry applications, computational techniques employing radiation transport simulations based on Monte Carlo code form an essential component in the application of dose determinations by EPR and OSL to dose reconstruction problems. We include in the review examples where the translation from the physical quantity of cumulative dose determined in the sampled medium to a dose quantity that can be applied in the reconstruction of dose to individuals and/or populations; these take into account the source terms, release patterns and the movements of people in the affected areas. One role for retrospective luminescence dosimetry has been to provide benchmark dose determinations for testing the models employed in dose reconstruction for exposed populations, notably at Hiroshima and Nagasaki. The discussion is framed within the context of the well-known radiation incidents mentioned above.     

BiodosEPR-2006 Meeting: Acute dosimetry consensus committee recommendations on biodosimetry applications in events involving uses of radiation by terrorists and radiation accidents

In the aftermath of a radiological terrorism incident or mass-casualty radiation accident, first responders and receivers require prior guidance and pre-positioned resources for assessment, triage and medical management of affected individuals [NCRP, 2005. Key elements of preparing emergency responders for nuclear and radiological terrorism. NCRP Commentary No. 19, Bethesda, Maryland, USA]. Several recent articles [Dainiak, N., Waselenko, J.K., Armitage, J.O., MacVittie, T.J., Farese, A.M., 2003. The hematologist and radiation casualties. Hematology (Am. Soc. Hematol. Educ. Program) 473–496; Waselenko, J.K., MacVittie, T.J., Blakely, W.F., Pesik, N., Wiley, A.L., Dickerson, W.E., Tsu, H., Confer, D.L., Coleman, C.N., Seed, T., Lowry, P., Armitage, J.O., Dainiak, N., Strategic National Stockpile Radiation Working Group, 2004. Medical management of the acute radiation syndrome: recommendations of the Strategic National Stockpile Radiation Working Group. Ann. Intern. Med. 140(12), 1037–1051; Blakely, W.F., Salter, C.A., Prasanna, P.G., 2005. Early-response biological dosimetry—recommended countermeasure enhancements for mass-casualty radiological incidents and terrorism. Health Phys. 89(5), 494–504; Goans, R.E., Waselenko, J.K., 2005. Medical management of radiation casualties. Health Phys. 89(5), 505–512; Swartz, H.M., Iwasaki, A., Walczak, T., Demidenko, E., Salikhov, I., Lesniewski, P., Starewicz, P., Schauer, D., Romanyukha, A., 2005. Measurements of clinically significant doses of ionizing radiation using non-invasive in vivo EPR spectroscopy of teeth in situ. Appl. Radiat. Isot. 62, 293–299; Weisdorf, D., Chao, N., Waselenko, J.K., Dainiak, N., Armitage, J.O., McNiece, I., Confer, D., 2006. Acute radiation injury: contingency planning for triage, supportive care, and transplantation. Biol. Blood Marrow Transplant. 12(6), 672–682], national [National Council of Radiation Protection and Measurements (NCRP), 1994. Management of persons accidentally contaminated with radionuclides. NCRP Report No. 65, Bethesda, Maryland, USA; NCRP, 2001. Management of terrorist events involving radioactive material. NCRP Report No. 138, Bethesda, Maryland, USA; NCRP, 2005. Key elements of preparing emergency responders for nuclear and radiological terrorism. NCRP Commentary No. 19, Bethesda, Maryland, USA] and international [IAEA, 2005. Generic procedures for medical response during a nuclear or radiological emergency. EPR-Medical 2005, IAEA, Vienna, Austria] agencies have reviewed strategies for acute-phase biodosimetry. Consensus biodosimetric guidelines include: (a) clinical signs and symptoms, including peripheral blood counts, time to onset of nausea and vomiting and presence of impaired cognition and neurological deficits, (b) radioactivity assessment, (c) personal and area dosimetry, (d) cytogenetics, (e) in vivo electron paramagnetic resonance (EPR) and (f) other dosimetry approaches (i.e. blood protein assays, etc.). Emerging biodosimetric technologies may further refine triage and dose assessment strategies. However, guidance is needed regarding which biodosimetry techniques are most useful for different radiological scenarios and consensus protocols must be developed.The Local Organizing Committee for the Second International Conference on Biodosimetry and Seventh International Symposium on EPR Dosimetry and Applications (BiodosEPR-2006 Meeting) convened an Acute Dosimetry Consensus Committee composed of national and international experts to: (a) review the current literature for biodosimetry applications for acute-phase applications in radiological emergencies, (b) describe the strengths and weaknesses of each technique, (c) provide recommendations for the use of biodosimetry assays for selected defined radiation scenarios, and (d) develop protocols to apply these recommended biological dosimetry techniques with currently available supplies and equipment for first responders.The Acute Dosimetry Consensus Committee developed recommendations for use of a prioritized multiple-assay biodosimetric-based strategy, concluding that no single assay is sufficiently robust to address all of the potential radiation scenarios including management of mass casualties and diagnosis for early medical treatment. These recommendations may be used by first responders/first receivers that span time-windows of (i.e. 0–5 days) after the radiological incident for three radiological scenarios including: (a) radiation exposure device (RED), (b) radiological dispersal device (RDD), and (c) an improvised (or otherwise acquired) nuclear device (IND). Consensus protocols for various bioassays (i.e. signs and symptoms recording, bioassay sampling for radioactivity analysis, nail-clipping sampling for EPR analysis and blood collection for hematology, cytogenetics, and blood chemistry analyses) are presented as Appendix materials. As stated in NCRP Commentary No. 19 [NCRP, 2005. Key elements of preparing emergency responders for nuclear and radiological terrorism. NCRP Commentary No. 19, Bethesda, Maryland, USA], multi-parameter triage (i.e. time to vomiting, lymphocyte kinetics, and other biodosimetry indicators) offers the current best strategy for early assessment of absorbed dose.     

Experimental Procedures for Sensitive and Reproducible In Situ EPR Tooth Dosimetry

In vivo electron paramagnetic resonance (EPR) tooth dosimetry provides a means for non-invasive retrospective assessment of personal radiation exposure. While there is a clear need for such capabilities following radiation accidents, the most pressing need for the development of this technology is the heightened likelihood of terrorist events or nuclear conflicts. This technique will enable such measurements to be made at the site of an incident, while the subject is present, to assist emergency personnel as they perform triage for the affected population. At Dartmouth Medical School this development is currently being tested with normal volunteers with irradiated teeth placed in their mouths and with patients who have undergone radiation therapy. Here we describe progress in practical procedures to provide accurate and reproducible in vivo dose estimates.     

Identification and dosimetry of irradiated walnuts (Juglans regia) using EPR

Electron paramagnetic resonance (EPR) is an easy, fast, and reliable tool for identification of irradiated food. Untreated nuts may encounter hazards of carrying several pathogens or microbial contamination; walnuts are of specific importance due to their nutritional and medicinal values, and hence walnut processing via gamma irradiation is a necessary step. EPR was employed for the identification and dosimetry of Cs-137 gamma-irradiated walnuts (shells and kernels). Several important parameters were studied, such as spectral features, microwave power dependence of signal intensities, and short- and long-term time dependences. Responses of walnut shells and kernels to different radiation doses in the range 0–10 kGy were investigated. Results confirmed that EPR is a suitable tool for the identification and dosimetry of irradiated walnuts using either their shells or only kernels.     

EPR of gamma irradiated solid sucrose and UV spectra of its solution. An attempt for calibration of solid state/EPR dosimetry

A simple new approach for independent calibration of solid state/EPR (SS/EPR) dosimetry system is reported. It is based on the fact that: (i) gamma-irradiation of solid sucrose (sugar) induces stable EPR detectable free radicals accompanied by UV detectable brown colour stable in the solid state and in solution; (ii) both the EPR intensity of gamma-irradiated solid sucrose and its solution UV absorbance linearly depend on the absorbed dose high energy radiation and may be independently used for dosimetric purpose; (iii) UV spectrometers are calibrated. The correlation between EPR response and absorbed dose radiation of solid sucrose and UV absorption of its solutions is used in the present communication for calibration purpose. The procedure of sucrose extraction from sucrose-paraffin dosimeters is described. The calibration procedure may be applied to any other (alanine, self-calibrated, etc.) SS/EPR dosimeters, simultaneously irradiated with sucrose.     

在体EPR专用磁场装置性能的改进

为测试在体EPR牙齿辐射剂量测量专用磁场装置,开展了初步性能试验. 针对扫描磁场非线性造成谱线的畸变情况,对在体EPR专用磁场装置性能进行了改进,给出了一种校正扫描磁场非线性的实现方法,通过对扫描磁场驱动电流进行反向刻度校正,可有效改善EPR谱线的畸变情况. 初步试验进一步证明了水平磁场在体测量方案的可行性,磁场装置性能的改进为实现X波段EPR辐射剂量在体测量向实际应用奠定基础.     

Egyptian limestone for gamma dosimetry: an electron paramagnetic resonance study

The electron paramagnetic resonance (EPR) properties of limestone from a certain Egyptian site were investigated in order to propose an efficient and low-cost gamma dosimeter. Radiation-induced free radicals were of one type which was produced in the limestone samples at g=2.0066 after exposure to gamma radiation (⁶⁰Co). EPR spectrum was recorded and analyzed. The microwave power saturation curve and the effect of changing modulation amplitude on peak-to- peak signal height were investigated. The response of limestone to different radiation doses (0.5–20 kGy) was studied. Except for the decrease in signal intensities during the first five hours following irradiation, over the period of two months fair stabilities of signal intensities were noticed. From the current results, it is possible to conclude that natural limestone may be a suitable material for radiation dosimetry in the range of irradiation processing.     

Radiation dose reconstruction from L-band in vivo EPR spectroscopy of intact teeth: Comparison of methods

In vivo EPR tooth dosimetry is a more challenging problem than in vitro EPR dosimetry because of several potential additional sources of variation associated with measurements that are made in the mouth of a living subject. For in vivo measurement a lower RF frequency is used and, unlike in the in vitro studies, the tooth cannot be processed to optimize the amount and configuration of the enamel that is measured. Additional factors involved with in vivo measurements include the reproducibility of positioning the resonator on the surface of the tooth in the mouth, irregular tooth geometry, and the possible influence of environmental noise. Consequently, in addition to using the theoretical and empirical models developed for analyzing data from measurements of teeth in vitro, other unconventional and more robust methods of dose reconstruction may be needed. The experimental parameter of interest is the peak-to-peak amplitude of the spectrum, which is correlated to the radiation dose through a calibration curve to derive the reconstructed dose. In this study we describe and compare the results from seven types of computations to measure the peak-to-peak amplitude for estimation of the radiation induced signal. The data utilized were from three sets of in vivo measurements of irradiated teeth. Six different teeth with different doses were placed in the mouth of a volunteer in situ and measurements of each tooth were carried out on three different days. The standard error of dose prediction (SEP) is used as a figure of merit for quantifying precision of the reconstruction. We found that many of the methods gave fairly similar results, with the best error of prediction resulting from a computation based on a Lorentzian line model whose center field corresponds to the known parameter of the radiation-induced EPR spectra of teeth, with corrections from a standard sample that was measured as part of the data acquisition scheme. When the results from the three days of measurement were pooled, the SEP decreased dramatically, which suggests that one of the principal sources of variation in the data is the ability to precisely standardize the measurements conditions within the mouth. There are very plausible ways to accomplish improvements in the existing procedures.     

Clinical applications of in vivo EPR: Rationale and initial results

In vivo electron paramagnetic resonance (EPR) has been very useful for studies in animals, and these results suggest that there are some very attractive potential applications in human subjects. In this article, we describe our rationale for the clinical application of in vivo EPR, some of the principal technical challenges, the initial results in human subjects, and our evaluation of the areas where in vivo EPR is likely to play an important clinical role in the near future. The most obvious area of very high potential for clinical applications is tissue oximetry, where in vivo EPR can provide repeated and accurate measurements of tissue pO₂, a type of measurement that cannot be obtained by other techniques. Oximetry is capable of providing clinicians with information that can impact directly on diagnosis and therapy, especially for peripheral vascular disease, oncology, and wound healing. The other area of great immediate importance is the ability of in vivo EPR to measure clinically significant exposures to ionizing radiation after the fact, which may occur due to accidents, terrorist activity, or nuclear war. The results obtained already from human subjects demonstrate the feasibility of the use of in vivo EPR for measurements in human subjects. We anticipate that in vivo EPR will play a vital role in the clinical management of various pathologies in the years to come.     

Gafchromic® film dosimetry for low energy X radiation

Recent developments have produced low energy X ray systems capable of providing a radiation dose to adequate volumes suitable for sterile inset programmes. To support the adoption of these new systems, the performance of the Gafchromic^® HD-810 dosimetry system previously used for gamma irradiation needed to be better understood at the lower photon energies. For low energy photons, the optical density of the irradiated Gafchromic HD-810 film dosimeters significantly depends on the material surrounding them. For example, if paper, Mylar^® or PVC is used to house the dosimeter during irradiation, the optical density can vary by as much as a factor of three or more for the same dose. This paper is an attempt to elucidate the performance of the Gafchromic HD-810 film dosimeters for such low energy X radiation (∼150 keV). Our data show that this behaviour can be explained by the fact that these materials have significantly different photon mass attenuation coefficient. This conclusion was reinforced with mathematical simulation using Monte Carlo modelling. We also show that with the different structure of another Gafchromic film dosimeter (MD-V2-55) this effect is virtually non-existent. An understanding of the behaviour of thin film dosimeters like Gafchromic HD-810 under radiation is crucial for reliable dosimetry. We hope that this work can also provide guidance in the use of other thin film dosimeters at similar low photon energies.     

Protocol for emergency EPR dosimetry in fingernails

There is an increased need for after-the-fact dosimetry because of the high risk of radiation exposures due to terrorism or accidents. In case of such an event, a method is needed to make measurements of dose in a large number of individuals rapidly and with sufficient accuracy to facilitate effective medical triage. Dosimetry based on EPR measurements of fingernails potentially could be an effective tool for this purpose. This paper presents the first operational protocols for EPR fingernail dosimetry, including guidelines for collection and storage of samples, parameters for EPR measurements, and the method of dose assessment. In a blinded test of this protocol application was carried out on nails freshly sampled and irradiated to 4 and 20 Gy; this protocol gave dose estimates with an error of less than 30%.     

Radiation Dosimetry Using Alanine and Electron Paramagnetic Resonance (EPR) Spectroscopy: A New Look at an Old Topic

The detection and quantification by electron paramagnetic resonance (EPR) spectroscopy of stable radicals formed in alanine by exposure to γ-radiation is used as a secondary standard for radiation dosimetry measurements, even though the EPR signal is actually derived from >1 radical with different spectral properties. For high radiation doses, microwave power saturation and spectral linewidths are both dependent on the received dose, and result in non-linear calibration curves. Furthermore, using a high-sensitivity microwave cavity, the power at which EPR signal saturation commences is ~0.3–0.4 mW for samples with irradiation doses ≤10 kGy; these values are an order of magnitude lower than those normally used in alanine dosimetry. In addition, the central peak of the first derivative spectrum, the height of which is commonly used in dosimetry measurements, is the most susceptible to microwave power saturation. Therefore, for high-level dosimetry we now recommend that analyses be performed under non-saturating conditions, and that the spectral acquisition parameters should be determined with a standard irradiated to ≤10 kGy to eliminate any intensity problems associated with variable saturation characteristics. At low radiation doses, variations in spectral saturation characteristics are negligible, and partially saturating conditions along with modulation amplitudes much higher than those normally used can reliably produce improved signal-to-noise ratios and allow extension of the methodology to practical working limits of ~0.1–0.2 Gy.     

Importance of volume limitation for tissue redox status measurements using nitroxyl contrast agents: a comparison of X-band EPR bile flow monitoring (BFM) method and 300 MHz in vivo EPR measurement

Methods proposed for in vivo redox status estimation, X-band (9.4 GHz) electron paramagnetic resonance (EPR) bile flow monitoring (BFM) and 300 MHz in vivo EPR measurement, were compared. The spin probe 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (carbamoyl-PROXYL) was utilized for both methods, due to its suitable lipophilicity. EPR signal decay of a nitroxyl spin probe in the bile flow and in the liver region (upper abdomen) of several rat groups with different selenium status were measured by both the BFM and the in vivo EPR method, respectively. The nitroxyl radical clearance measured with in vivo EPR method may be affected not only by the redox status in the liver but also by information from other tissues in the measured region of the rat. On the other hand, the time course of nitroxyl radical level in the bile flow of rats was found to be a reliable index of redox status. Measurement site and/or volume limitation, which was achieved by the BFM method in this paper, is quite important in estimating reasonable EPR signal decay information as an index of tissue/organ redox status.     

Feasibility of Q-Band EPR Dosimetry in Biopsy Samples of Dental Enamel, Dentine and Bone

Electron paramagnetic resonance (EPR) dosimetry of tooth enamel in X-band has been established as a suitable method for individual reconstruction of doses 0.1 Gy and higher. The objective was to demonstrate the feasibility of using Q-band EPR in small biopsy tooth enamel samples to provide accurate measurements of radiation doses. Q-band spectra of small (<10 mg) irradiated samples of dentine and bone were studied to investigate the possibility of using Q-band EPR for dose measurements in those materials if there are limited amounts of enamel available, and there is no time for the chemical sample preparation required for accurate X-band measurements in dental enamel. Our results have shown that Q-band provides accurate measurements of radiation doses higher than 0.5 Gy in tooth enamel biopsy samples as small as 2 mg. Q-band EPR spectra in powdered dentine and bone demonstrated significantly higher resolution and sensitivity than in conventional X-band measurements.