ESR Dosimeter Research Articles

ESR dosimeter material properties of phenols compound exposed to radiotherapeutic electron beams

There is a need for a sensitive dosimeter using Electron Spin Resonance spectroscopy for use in medical applications, since non-destructive read-out and dose archival could be achieved with this method. This work reports a systematic ESR investigation of IRGANOX® 1076 exposed to clinical electron beams produced by a LINAC used for radiation therapy treatments. Recently, dosimetric features of this material were investigated for irradiation with 60Co γ-photons and neutrons in both pellet and film shape and have been found promising thanks to their high efficiency of radiation-matter energy transfer and radical stability at room temperature. Here the analysis of the dosimetric features of these ESR dosimeters exposed to clinical electron beams at energies of 7, 10 and 14MeV, is described in terms of dependence on microwave power and modulation amplitude, response on dose, dependence on beam type, detection limits, and signal stability after irradiation. The analysis of the ESR signal as function of absorbed dose highlights that the response of this material is linear in the dose range investigated (1–13Gy) and is independent of the beam energy. The minimum detectable dose is found to be smaller than 1Gy. Comparison of electron stopping power values of these dosimeters with those of water and soft tissue highlights equivalence of the response to electron beams in the energy range considered. The signal intensity was monitored for 40days after irradiation and for all energies considered and it shows negligible variations in the first 500h after irradiation whereas after 1100h the signal decay is only of about 4%. In conclusion, it is found that phenolic compounds possess good dosimetric features which make it useful as a sensitive dosimeter for medical applications.

Spectroscopic investigation of P2O5–CdO–Li2O glass system

A systematic IR, Raman and ESR study of the P2O5–CdO–Li2O glass system—a possible dosimeter material, is reported. The proportion of P2O5 remains constant at 0.5mol% and those of CdO and Li2O are changed from 0 to 0.5mol%. IR and Raman spectra allowed us to identify the structural units which appear in the structural network of these phosphate glasses and also the network modifier role of Cd2+ and Li+ ions. Generally, a local network structure mainly based on Q2 and Q3 tetrahedrons connected by POP linkages is revealed. ESR spectra of gamma irradiated sample with a 60Co gamma source, are characterized by the hyperfine doublet of 31P isotope (I=1/2) and a linear dependence of the ESR signal intensity versus the absorbed doses in the range of 100–3500Gy was obtained. This fact proves that the investigated glass system could be successfully used as ESR dosimeter in medicine and industry.

Synthesis of silver nanoparticles using dl-alanine for ESR dosimetry applications

The potential use of alanine for the production of nanoparticles is presented here for the first time. Silver nanoparticles were synthesized using a simple green method, namely the thermal treatment of silver nitrate aqueous solutions with dl-alanine. The latter compound was employed both as a reducing and a capping agent. Particles with average size equal to 7.5 nm, face-centered cubic crystalline structure, narrow size distribution, and spherical shape were obtained. Interaction between the silver ions present on the surface of the nanoparticles and the amine group of the dl-alanine molecule seems to be responsible for reduction of the silver ions and for the stability of the colloid. The bio-hybrid nano-composite was used as an ESR dosimeter. The amount of silver nanoparticles in the nanocomposite was not sufficient to cause considerable loss of tissue equivalency. Moreover, the samples containing nanoparticles presented increased sensitivity and reduced energetic dependence as compared with pure dl-alanine, contributing to the construction of small-sized dosimeters.

ESR dosimeter based on P2O5–CaO–Na2O glass system

This paper presents the results of a study of thermal properties, solubility and response to 60Co γ-rays by electron spin resonance of the P2O5–CaO–Na2O glass system. The sample compositions were selected by fixing the P2O5mol% content at 50mol%, and varying the CaO mol% at 30 and 40mol%. The spectrum is characterized by hyperfine doublet from 31P isotope (nuclear spin=1/2), and its stability and response to the γ-ray dose were studied to establish the suitability of this glass as a γ-ray dosimeter.

Characterization and application of two kinds of ESR dosimeters

Many previous papers described the use of low-concentration alanine pellets, powder or films for industrial high-dose application, but very few authors presented applications of such dosimeters to the low-dose range used for wastewater, flowers or radiotherapy treatment. The present paper describes the large-scale manufacturing process of high-concentration alanine pellets used for radiotherapy dose control in some French hospitals. The fading process due to sunlight exposure has been evaluated by means of direct UV light irradiation. The major disadvantage of alanine is its strong solubility in water (the pellets are completely dissolved when immersed for 10 min in pure water). The use of barium sulphate, not soluble in water, made it possible to carry out dosimetric measurements even when the dosimeter is completely immersed in water or stored after irradiation in high humidity levels. The paper presents manufacturing process of barium sulphate pellets, their dosimetric characteristics and one application of this dosimeter for the control of the absorbed doses during wastewater treatments.

ESR dosimetry using inorganic materials: a case study of Li 2CO 3 and CaSO 4 : Dy as prospective dosimeters

The CO 2 − radical ion, detected by ESR technique in bones and teeth enamel, was proved to be invaluable in high level and retrospective dosimetry. In these matrices, impurity carbonate (at phosphate sites) was the precursor to CO 2 − With a view to investigate the possibility of using inorganic materials such as lithium carbonate as ESR dosimeters, studies were carried out on gamma-irradiated Li 2CO 3 . The intensity of radiation-induced ESR signals of Li 2CO 3 at g=2.0036 (CO 3 −) and g=2.0006 (CO 2 −) was followed as a function of gamma dose in the low dose range of 1– 1350 Gy. It was observed that the intensity of the ESR signal at g=2.0036 (CO 3 −) was in a linear relation with the radiation dose in the dose range 10– 800 Gy and the signal at g=2.0006 (CO 2 −) showed linear response in the dose range 5– 800 Gy. The lowest dose that could be detected in the present studies using the signal of CO 2 − in Li 2CO 3 powder samples (∼50 mg) is 3.2 Gy. ESR studies were also carried out on the widely used TL dosimetric material CaSO 4 : Dy and in pure CaSO 4 after gamma irradiation. The TL materials were used in powder as well as pellet forms. The linearity of ESR response with dose for powder and pellet forms of CaSO 4 : Dy was also studied using the signals at g=2.0030 (SO 3 −) and at g=2.0139 (SO 4 −). It was observed that the range of linearity of dose response extended between 20 and 1200 Gy, for SO 3 − signals. The results of dosimetric study indicate that the ESR–Li 2CO 3 system could be used in dosimetric applications in radiotherapy. However, for the actual applications further advancement is needed to lower the detection limit. The TL phosphor, CaSO 4 : Dy in powder and pellet forms, could be used as ESR dosimeter in the dose range 20–600 Gy.

Strategy for finding new materials for ESR dosimeters

The right strategy for finding a new ESR dosimetric material sensitive to radiation is to follow the orthodox procedures used in the development of thermoluminescence dosimeters (TLD) and phosphorescence studies. Modern procedures used in materials sciences, such as computer calculation of molecular orbitals (MO), should be employed to estimate the ESR and optical properties of prospective materials. Radiation effects in lithium and magnesium sulfates and metal salts of organic acids, such as lithium and magnesium lactates, have been investigated in search for tissue-equivalent dosimeter with a large G value.

Development of ammonium tartrate as an ESR dosimeter material for clinical purposes

The crystalline substance ammonium tartrate is investigated with respect to its suitability as a clinical dosimetry material. The properties investigated are: the radical stability for absorbed doses relevant for clinical use, the improvement in sensitivity when the crystals are deuterated and the linear electron tranfer (LET)-dependence. After photon irradiation to an absorbed dose of 20 Gy, the signal increases rapidly during the first 6 h. After this period, the changes are more moderate and can be corrected for. The signal-to-noise ratio of irradiated ammonium tartrate is twice the corresponding value of alanine. By deuterating the crystals, the sensitivity can be further improved by a factor of 1.4. As expected, the signal decreases with increasing LET of the radiation, but no changes in the spectrum shape was observed.

Spin Concentration in a Possible ESR Dosimeter: An Electron Spin Echo Study on X-Irradiated Ammonium Tartrate

Several single crystals and powder samples of ammonium tartrate, recently proposed as a possible ESR dosimeter, have been X-irradiated with different doses. The total radical concentration has been determined by quantitative cw ESR, by comparison with a standard. The samples have been studied by electron spin echo spectroscopy. The two-pulse echo decay has been obtained and simulated by a single exponential function for different values of the microwave power of the pulses and for different pulse lengths. The dependence of the phase memory timeTMon the microwave power has been exploited to get information on the contribution of the instantaneous diffusion to spin dephasing. At room temperature in the range of radical concentrations of 1018–1019spins/cm3the instantaneous diffusion is the dominant spin dephasing mechanism. The linear dependence of the instantaneous diffusion on the total concentration of the radicals is in agreement with the theory. From the latter result we conclude that the average radical–radical distance corresponds to a random distribution of the radicals in the matrix. A simple method of measuring the radical concentration by the ESE decays in powder samples of irradiated ammonium tartrate is described.

Ammonium tartrate as an ESR dosimeter material

This study is one step in the search for an ESR dosimeter material with a higher signal intensity than the commonly used l- α-alanine, to be useful in the clinical dose range (approximately 0.1–20 Gy). The substance ammonium tartrate was found and investigated regarding signal intensity, radical stability, dose response and dose resolution. The ESR signal intensity of ammonium tartrate was shown to be more than twice the intensity of the alanine signal. The data indicate that an unstable radiation induced radical contributes to the ESR signal initially; after a couple of hours it has converted to a secondary radical which has a decay slow enough to be considered stable during the first two weeks after irradiation. Ammonium tartrate has a linear dose response in the investigated range of 0.5–4000 Gy and a dose resolution of 0.1 Gy at the 0.5 Gy level where, as a comparison, the corresponding value for alanine is 0.3 Gy. We thus find the substance suitable for clinical dosimetry.

Radical Formation of Lithium Lactate for ESR Dosimetry.

In this letter, preliminary results on ionic organic material, lithium lactate are presented as a possible ESR dosimeter.

A new ESR dosimeter based on Tris(hydroxymethyl)aminomethane

Results are presented on the dosimetric characteristics of a new dosimetry system based on the ESR response of tris(hydroxymethyl)aminomethane. The response to gamma radiation was measured in the absorbed-dose range from 10 to 10 5 Gy and the persistence of signal was monitored along 60 days. There is slight fading when stored at elevated temperatures.

Powder state alanine ⧸ESR dosimeter for measuring the absorbed dose of electron beam

This paper describes the application of powder state alanine/ESR dosimeter for measurement of the absorbed dose of electron beam, for transfer the dose standards and for quality controls of the products processed by electron beam irradiation. The dosimeter is a sealed plastic container containing pre-treated alanine powder. Spectra of the internal standard and the alanine sample are measured simultaneously by using dual - cavity of a ESR spectrometer. The internal standard is a CuCl 2. 2H 2O monocrystal which gives stable ESR signals. A diamond sample is regard as working standard. With these two standards, the measurement accuracy can be improved apparently. The standard dose value is determined with a electron beam calorimeter made in our laboratory for dose calibration purpose. The advantages and the dosimetry characteristics of the application of powder state alanine/ESR dosimeters are discussed. This method is proved accurate and easy to use. In the region of 10-10 4Gy, the dose response show a linear relationship and the precision is better than ± 2%.

The influence of measurement and storage conditions on alanine ESR dosimeters

The influence of measurement and storage conditions on alanine ESR dosimeters