Esr dating and dosimetry

Quaternary dating by electron spin resonance (ESR) applied to human tooth enamel

esr dating and dosimetry

ESR dating and dosimetry are based on the fact that ionising radiation produces paramagnetic centres having long lifetimes in a number of materials. ESR dating of shells from Sambaquis (Brazilian shell mounds). In Ikeya, M. & T. Miki (eds.) ESR Dating and Dosimetry. Ionics, Toyko: –Google Scholar. This text concerns new applications of electron spin resonance (ESR) or electron paramagnetic resonance (EPR) to geological and archaeological dating.

Abstract Explosion of the bombs in Hiroshima and Nagasaki corresponds to the only historical moment when atomic bombs were used against civilians. This event triggered countless investigations into the effects and dosimetry of ionizing radiation. The idea was to use the paramagnetism induced in bone after irradiation to measure the radiation dose.

New Applications Of Electron Spin Resonance: Dating, Dosimetry And Microscopy

Technological advances involved in the construction of spectrometers, better knowledge of the paramagnetic center, and improvement in signal processing techniques have allowed us to resume the investigation.

We obtained a reconstructed dose of 9. Introduction Electron Spin Resonance spectroscopy allows the use of constituents of the human body as dosimeter.

It has been widely studied and explored due to its application in retrospective dosimetry in cases of accidental exposure to radiation. This is a subject of great relevance if we consider that advanced medical treatments, like the use of stem cells and transplantation, can be offered to the victims of such exposure depending on the radiation dose they received [ 1 — 3 ].

It is well established that ESR dosimetry of tooth enamel can be applied to assess radiation doses retrospectively. Tooth enamel is a very sensitive material for ESR dosimetry because its high density and high degree of crystallinity remain practically unaltered during life [ 45 ]. Sincethree laboratory inter-comparisons have been made to measure the accuracy of this dosimetry [ 67 ]. Therefore, this technique is useful for the triage of victims, and it can help to define the best possible treatment for such victims [ 910 ].

Although the way of obtaining the dose is not straightforward, in specific cases, ESR dosimetry of bone is also a powerful technique for obtaining data on the received dose.

One example is the case of systemic radiotherapy in which the radiopharmaceutical is directed to the bone region so, in this situation the ESR bone dosimetry is quite useful to evaluate the dose effectively deposited in bone [ 11 — 13 ]. The ESR spectrum of irradiated bone is composed of the radiation-induced signal, due mainly to the CO2- [ 14 ] radical produced in the hydroxyapatite and another, broad signal, due to the other components.

So, methods for isolating the dosimetric signal, in order to obtain a more precise dosimetry are discussed by Wieser [ 15 ] and Breen and Batista [ 16 ] that used physical and chemical methods. More recently, De[ 17 ] used higher frequency Q Band that presents better spectral resolution, allowing better visualization of the components and also the use of a smaller amount of material, with a mass comparable to the one obtained in a biopsy.

Another characteristic of bone dosimetry is the possible influence of bone remodeling that may, over time, destroy the signal induced by ionizing radiation. So, in a situation in which the analysis is performed after a period after irradiation, this factor must be taken into account and the value found by the ESR dosimetry will be the minimum value received by the victim.

Fragments from femur, tibia, phalange were analyzed, showing the estimated distribution of doses received. The doses agreed to visual clinical exams of epidermal damage, but the author draws the attention to the influence of bone metabolism in the dose. This aspect of bone dosimetry was also observed by Kinoshita et al [ 19 ], in another case of accident with a cobalt source, in which the victim had his finger amputated four years after the accident. The comparison with the Fluorescence in situ Hybridization FISH dosimetry shows that the value of the dose received is greater than that directly found in the bone by ESR, due to bone remodeling.

More recently Krefft [ 20 ] analyzed bones extracted from the mandible of radiotherapy patients who, for medical reasons, had to undergo the procedure.

esr dating and dosimetry

They found that 3 and 6 months after the irradiation the doses were consistent with those calculated by treatment planning systems. In these situations, bone dosimetry provides the minimum value of the dose received by the victim.

Electron spin resonance dating - Wikipedia

Another interesting aspect was pointed out by Degteva [ 21 ] and Shishkina [ 22 ]. When there is absorption of radioactive material that is incorporated into hard tissues as bone and tooth, as in the case of downstream settlements residents of Techa River, who were contaminated by 90Sr.

The internal radiation rate of the radioisotope must be considered in the evaluation of the dose received externally. Other papers involving accidents with radioactivity were reported bySchauer[ 23 ] and Clairand [ 24 ]. Schauer[ 23 ] reported an accident with a 3MV accelerator, and additionally, determined that for the same value of absorbed dose, the intensity of radiation induced ESR signal is different for a 0.

And that there is no difference in the intensity between the latter three. Such centres' concentration in a given sample is a measure of the total radiation dose to which a particular sample has been exposed.

This effect can be used to determine the length of time of such exposure and hence, in many cases, a sample's burial time Jonas The aim is to determine the accumulated dose DA to which a sample has been exposed whilst being buried; the exposure time is then determined by comparing DA to the average dose rate over such period: However, no significant difference in the accuracy of dose reconstruction has yet been found using different calibration methods Wieser et al.

Each sample's radiation sensitivity is individually calibrated for dose assessment by the additive dose method; each sample is incrementally irradiated with at least 14 additional doses up to Gy or more avoiding the sample becoming saturated.

A linear regression analysis is applied to the ESR measurements at each dose increment and the original measurement laboratory-un-irradiated sample. The original DA in the sample is obtained from the negative intercept of the regression line with the dose axis; is estimated as being the total radiation provided by all radioactive elements present in a sample and soil and also cosmic radiation Ikeya ; Jonas ; Walker ; Grun Materials and Methods The dentine was initially removed from teeth using a dental drill and water cooling.

The molar enamel powder was divided into nine aliquots. The spectrometer parameters used were: Soil samples were also collected from the Aguazuque site and sent for U, Th and K content analysis by gamma spectrometry.

Radiometric analysis is widely used for determining natural radioisotopes in geological samples by means of spectroscopic methods and, especially, for quantifying the uranium, thorium and potassium present in samples. A linear model was used for fitting ESR signal intensity to dose, as has been done by other authors Baffa et al.

Electron Spin Resonance (ESR) dating of quartz - Freiberg Instruments - Dosimetry and Dating

ROSY software Brennan et al. Soil water content was The software's default values were used for the remaining parameters.

Finding the dose rate to convert DA into an age is a crucial step after DA has been found.

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ROSY software allows age to be calculated from an enamel sample by taking DA due to radioisotopes from adjacent layers into account.

The software computes age based on three uranium absorption models linear, early uptake and a combination of both. Table 1 shows the soil analysis results. The present work did not determine U, Th and K concentration in enamel and dentine as their percentages have been negligible for calculating age in previous work, especially in dates for the Holocene period Kinoshita et al.

Typical soil density, enamel and dentine values were used for calculating age 2. Using these values and the radioisotope concentrations listed in Table 1ROSY software was used for obtaining the alpha, beta and gamma radiation dose rate contribution for each radioisotope in sediment the results are listed in Table 2. These results were the same for any uranium absorption model.

It should be noted that ROSY software calculates these ages using three uranium accumulation models: The way that uranium accumulates in a tooth is established by these models; accumulation increases at the same rate as time in the linear model and accumulation occurs in a short period of time in the early model, relative to a tooth's age and then remains constant after this short period of time. The tooth's age was the same when calculated by these three methods; this result was consistent if taken into account that the accumulation of radioactive elements inside the tooth was negligible.

Conclusions Age determined at many countries' archaeological sites is the result of radiocarbon 14C analysis of particular items found around the burials and not direct dating of individuals found there. The results regarding either physical or geological phenomena may not be chronologically equal, hence the importance of having techniques like ESR which can directly and absolutely determine the age of individuals of interest.

This result agreed with stratigraphic analysis at sites providing soil ages ranging from 2, to 3,y BP for 50 and 80 cm depths Correal, ESR dating accuracy was obtained relatively straightforwardly, using just a few grams of tooth enamel, thereby highlighting some of the advantages and characteristics of the ESR dating method.

esr dating and dosimetry

The results so obtained have contributed towards joining links in the long chain of Colombian and American history where there is still much to do, due to the rich pre-Hispanic and colonial past.

This paper thus represents a pioneering effort aimed at promoting the dating of our ancestors. Rodriguez, for providing facilities and allowing the use of his samples, as well as AM Groot archaeologist for her support during this research. ESR dating of a toxodon tooth from a Brazilian karstic cave.