Enrichment and vertical profiles of 210Po and 210Pb in monazite areas of coastal Karnataka

A study on radiation level and radionuclide distribution in the environment of coastal Karnataka has revealed the presence of low-level monazite deposit in the Ullal beach area. The paper presents systematic studies on the distribution, enrichment and vertical profiles of ²¹⁰Po and ²¹⁰Pb, important daughter products of ²³⁸U, in Ombattu Kere, Summer Sand and the Bhagavathi Temple region of the Ullal beach area of coastal Karnataka. Sand samples collected at different depths from these locations were analyzed for ²¹⁰Po and ²¹⁰Pb activities to understand the distribution, enrichment and vertical profiles of these radionuclides in monazite area. The activity of ²¹⁰Po in the Ullal region is found to vary from 1.7 to 43.2 Bq kg^?1 with a mean value of 11.2 Bq kg^?1 and that of ²¹⁰Pb varies from 1.0 to 66.7 Bq kg^?1 with a mean value of 19.1 Bq kg^?1. The mean ²¹⁰Po/²¹⁰Pb ratio was observed to be 0.6. The absorbed gamma dose rate in the region varies in the range 39–460 nGy h^?1 with a mean value of 193 nGy h^?1.     

Activity size distributions for long-lived radon decay products in aerosols collected in Barcelona (Spain)

The activity median aerodynamic diameters (AMADs) of long-lived radon decay product (²¹⁰Pb, ²¹⁰Po) in aerosols collected in the Barcelona area (Northeast Spain) during the period from April 2006 to February 2008 are presented. The ²¹⁰Po mean AMAD was 420 nm, while the ²¹⁰Pb mean AMAD was 500 nm. The temporal evolution of ²¹⁰Pb and ²¹⁰Po AMADs shows maxima in autumn and winter and minima in spring and summer. ²¹⁰Pb AMAD are being used to estimate the mean-residence time of atmospheric aerosols.     

A 238Pu irradiator for exposure of cultured cells with alpha-radiation: Construction,calibration and dosimetry

An alpha-particle irradiator that can facilitate investigations of alpha-radiation effects on human cells in radiation protection, carcinogenesis and radioimmunotherapy was constructed. The irradiator was based on a 1.3 GBq ²³⁸Pu source, housed in a stainless steel tube flushed with helium. Radiation provided by ²³⁸Pu consists mainly of alpha-particles with energy of 5.5 MeV. The alpha-particle fluence and energy spectra were measured with a silicon semiconductor detector. Monte Carlo simulations were used to estimate the mean number of alpha-particles and the mean absorbed alpha-particle dose to cells for various irradiation times and distances between cells and source. There was a linear dependence between exposure time and alpha-particle fluence for exposure times above 1 s. The alpha-particle activity concentration varied with a factor 2.7 over the source area, while the variation in energy peak position was <4%. At the cell nucleus position and with a distance of 45 mm between the source and the mylar dish surface, the α-fluence was 4.6×10⁴ counts/(mm² s), the average incident α-particle energy was 2.5 MeV and the average linear energy transfer was 167 keV/μm. The average dose rate to the cells, with 5 μm diameter nucleus, was 1.2 Gy/s. The ²³⁸Pu α-particle irradiator is feasible for irradiation of cells and it can be used for studies of both direct effects and bystander effects of alpha-radiation.     

Activity standardization and decay data of 64Cu

The activity of a solution of ⁶⁴Cu was measured by 4πβ(PC)-γ coincidence counting and liquid scintillation counting using the CIEMAT/NIST method. In addition, 4π ionization chambers were used to establish and preserve calibration factors for secondary standardizations and for a determination of the half-life, for which a value of 12.704(5) h was measured. The photon emission probabilities were determined using gamma-ray spectrometry, finding values of p(511 keV)=0.3512(22) and p(1346 keV)=0.00474(5).The results were checked for consistency, and an ampoule was submitted to the BIPM to have the activity result entered into the database of the International Reference System (SIR), yielding the first entry for this radionuclide.     

Influence of 210Pb on the continuous background of gamma-ray spectrometers

The contribution of the ²¹⁰Pb activity in gamma-ray spectrometer's lead shields to the spectrometer background was determined on the basis of the time dependence of the count rate in the background continuum. The time dependence, reflecting the decay of ²¹⁰Pb, was measured over a time interval of about 10 years. It is shown that the maximum contribution to the spectrometer background due to ²¹⁰Pb is around 200 keV, and that the largest fractional contribution to the total background is in the energy interval from 100 to 300 keV.     

Experimental characterization of the dosimetric properties of a newly designed I-Seed model AgX100 (125)I interstitial brachytherapy source

PurposeTo measure the dosimetric properties of the Model AgX100 ¹²⁵I source for interstitial brachytherapy.Methods and MaterialsThe photon energy spectrum emitted by the AgX100 source was measured using a high-resolution germanium spectrometer customized for low-energy brachytherapy source spectrometry. The dose distribution around the source was measured using the 1 × 1 × 1 mm³ lithium fluoride thermoluminescent dosimeters in water-equivalent solid phantoms. The dosimetric parameters needed for dose calculation using the American Association of Physicists in Medicine Task Group No. 43 (TG-43) formalism were determined and compared with the results of a Monte Carlo simulation by an independent research group and with the TG-43 consensus values of the well-established model 6711 source.ResultsIt was found that (1) the photon energy spectrum emitted by the AgX100 source was nearly identical to that emitted by the model 6711, (2) the dose-rate constant determined by the photon spectrometry technique (0.957 ± 0.037 cGy·h^?1·U^?1) and by the thermoluminescent dosimeter technique (0.995 ± 0.066 cGy·h^?1·U^?1) was within 1.5% of the corresponding values determined for the model 6711 source, and (3) the radial dose function and the anisotropy function of the AgX100 source were also found to be similar to the consensus data established for the model 6711 source in the TG-43 update report.ConclusionsA comprehensive dosimetric characterization has been carried out for the model AgX100 ¹²⁵I source. The American Association of Physicists in Medicine TG-43 dosimetry parameters for this source has been determined from the experimental data.     

Temporal variations of 7Be, 210Pb and 137Cs in moss samples over 14 month period

Concentrations of ²¹⁰Pb, ⁷Be and ¹³⁷Cs in moss samples were continuously measured, using low-background HPGe spectrometer at Novi Sad, Serbia (45°14′45″N, 19°51′35″E). Weekly data collected over 14 month period from January 2007 to March 2008 are presented and discussed. Measured values of ⁷Be activity concentrations in dry moss samples are ranged from 201 to 920 Bq/kg showing prominent increase in summer and autumn season. Data for ²¹⁰Pb, ranged from 347 to 885 Bq/kg do not show such trend. The average concentration of ¹³⁷Cs is 8.9 Bq/kg. It is shown that yield of ⁷Be can be estimated using average values of activity concentrations. Precipitation amount and duration of precipitation are measured and their possible influence on activity concentrations measured in moss samples was considered.     

Evaluation of uncertainty and detection limits in Pb and Po measurement in water by alpha spectrometry using Po spontaneous deposition onto a silver disk

An easy and accurate method for the determination of ²¹⁰Pb and ²¹⁰Po in water using ²¹⁰Po spontaneous deposition onto a silver disk is proposed and assessed for its detection capabilities according to the ISO Guide for the expression of uncertainty in measurement (GUM) and ISO Standard 11929-7 concerning the evaluation of the characteristic limits for ionizing radiation measurements. The method makes no assumption on the initial values of the activity concentrations of ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po in the sample to be analyzed, and is based on the alpha spectrometric measurement of ²¹⁰Po in two different aliquots: the first one measured five weeks after the sampling date to ensure radioactive equilibrium between ²¹⁰Pb and ²¹⁰Bi and the second after a sufficient time for the ingrowth of ²¹⁰Po from ²¹⁰Pb to be significant. As shown, for a recommended time interval of seven months between ²¹⁰Po measurements, the applicability of the proposed method is limited to water samples with a ²²⁶Ra to ²¹⁰Pb activity ratio C_Ra/C_Pb≤4, as usual in natural waters. Using sample and background counting times of 24 h and 240 h, respectively, the detection limit of the activity concentration of each radionuclide at the sampling time for a 1 L sample typically varies between 0.7 and 16 mBq L⁻¹ for ²¹⁰Pb in water samples with an initial activity of ²¹⁰Po in the range 0-200 mBq L⁻¹, and between 0.6 and 8.5 mBq L⁻¹ for ²¹⁰Po in water samples with an initial activity of ²¹⁰Pb in the same range.     

Evaluation of the chromium contamination at Ribeirão dos Bagres,Franca (SP), Brazil,by the 210Pb method

This paper presents a chronological study focusing the use of ²¹⁰Pb in four sediment cores collected at Ribeirão dos Bagres in the region of Franca, São Paulo State, Brazil. When evaluating the sedimentation rate by using the ²¹⁰Pb method, it was possible to monitor historical changes occurring in the concentrations of chromium present in the sediments. In order to do so, several specific parameters were determined in sediments, as chromium concentration, major oxides, organic matter, grain size, and chemical and physical–chemical parameters of waters. The sediments possessed a Cr concentration range of 0.83–26.25 mg/kg that is below the world's average of shales. The sedimentation rates obtained from the ²¹⁰Pb analysis were between 0.07 and 0.77 g cm⁻² year⁻¹, while the linear sedimentation rate was from 0.6 to 3.2 cm/year. The adoption of the CIC (Constant Initial Concentration) ²¹⁰Pb model allowed characterize older sediments, aged 177 years, and younger sediments, aged 4 years. The organic matter in the sediments was more abundant in the first few centimeters of practically all profiles, and the analysis of oxides showed that silica is the major constituent of the sediments, in which there is predominance of sand and silt. In addition, the analysis of the physical and chemical parameters of waters indicated that they are suitable for navigation and natural harmony landscape.     

The 222Rn standard system established at IFIN-HH,Romania

The paper presents the ²²²Rn Standard System realized at the Radionuclide Metrology Laboratory from IFIN-HH, Romania. It contains a Pylon solid ²²⁶Ra source, and a glass circuit for circulation and recovery of ²²²Rn in glass ampoules, at the 77 K temperature. The radon can be recovered both in ampoules with liquid scintillator (LS), for absolute standardization of ²²²Rn by liquid scintillation counting (LSC) (Cassette et al., 2006), and in evacuated ampoules as gas, simultaneously or by the transfer of radon from gas into LS ampoules, in order to establish the traceability chain. The absolute standardization consists in the registration of the double coincidence counting rate in LS, due to the whole sequence of short life components of the ²²²Rn chain, in equilibrium conditions. The main correction applied to the measurement results is due to the decay of ²¹⁴Po during the extendable dead time of the system. The following procedure was applied to take it into account. The value of the base duration of the dead time was precisely measured and used for the data corrections. The measurements of each source were repeated during a period of several days, and the decay curve parameters were calculated. If the dead time value and the correction formulae, presented throughout the paper, were adequate, then the re-determination of the ²²²Rn half life, T_1/2=(3.8232±0.0008) d, using the decay curve of the corrected counting rates should be correct. On the other hand, the effective dead time values obtained by parallel calculations were compared. The paper presents the results obtained in the standardization of several sources, by LSC, and the evaluation of the uncertainties associated to the method.     

9Be(d,n)10B-based neutron sources for BNCT

In the frame of accelerator-based BNCT, the ⁹Be(d,n)¹⁰B reaction was investigated as a possible source of epithermal neutrons. In order to determine the configuration in terms of bombarding energy, target thickness and Beam Shaping Assembly (BSA) design that results in the best possible beam quality, a systematic optimization study was carried out. From this study, the optimal configuration resulted in tumor doses ≥40 Gy-Eq, with a maximum value of 51 Gy-Eq at a depth of about 2.7 cm, in a 60 min treatment.The optimal configuration was considered for the treatment planning assessment of a real Glioblastoma Multiforme case. From this, the resulted dose performances were comparable to those obtained with an optimized ⁷Li(p,n)-based neutron source, under identical conditions and subjected to the same clinical protocol.     

Desferrioxamine as an appropriate chelator for 90Nb: Comparison of its complexation properties for M-Df-Octreotide (M = Nb,Fe, Ga,Zr)

The niobium-90 radioisotope (90Nb) holds considerable promise for use in immuno-PET, due to its decay parameters (t½ = 14.6 h, positron yield = 53%, Eß+mean = 0.35 MeV and Eß+max = 1.5 MeV). In particular, 90Nb appears well suited to detect in vivo the pharmacokinetics of large targeting vectors (50–150 kDa). In order to be useful for immuno-PET chelators are required to both stabilize the radionuclide in terms of coordination chemistry and to facilitate the covalent attachment to the targeting vector. Different chelators were evaluated for this purpose in terms of radiolabelling efficiency and stability of the radiolabelled Nb(V) complex and in order to determine the most suitable candidate for conjugation to a biologically relevant targeting vector. For the purpose of studying the complexation properties the niobium radioisotope 95Nb was used as an analogue of 90Nb, by virtue of its longer half-life (35 days) and lower cost (reactor-based production). Acyclic and cyclic chelators were investigated, with desferroxamine [Df: (N'-{5-[acetyl(hydroxy)amino]pentyl}-N-[5-({4-[(5-aminopentyl) (hydroxy)amino]-4-oxobutanoyl} amino)pentyl]-N-hydroxysuccinamide)] emerging as the best candidate. Greater than 99% radiolabelling was achieved at room temperature over a wide pH range. The 95Nb-Df complex is sufficiently stable for immuno-PET (< 7% degradation over 7 days in vitro). As a proof-of-principle, a Df conjugate featuring a well-established targeting vector, (D)-Phe1-octreotide, was evaluated. The fast labelling kinetics of the unconjugated chelator (Df) were retained for Df-succinyl-(D)Phe1-octreotide (Df-OC), with > 90% labelling after 1 h at room temperature over the pH range 5–7. Stability studies, performed in vitro in serum at physiological temperature (37 °C), revealed that 87 ± 2% of the radiolabelled molecule remained intact after 7 days. Competition studies with relevant metal ions (zirconium(IV), gallium(III) and iron(III)) have been performed with Df-OC to gain insight to the relative stability [Nb-Df]-OC complex to transmetallation. At equimolar metal ion concentrations the [Nb-Df]-OC complex showed the greatest overall stability. The favourable radiolabelling characteristics of Df-OC and its stability indicate that Df is a potentially very useful chelator for the development of radiopharmaceuticals for 90Nb-PET.     

Measurement of the half-life of 68Ga

The half-life of the positron-emitter ⁶⁸Ga has been measured by following the decay rate with two systems based on ionization chamber and Ge detectors. The decay rate was measured for periods of time up to 10 half-lives. The combination of the 6 results obtained with both systems gives a value of T_1/2=67.845(18) min, in good agreement with recommended data and with an uncertainty lower than any other previously reported value.     

Half-life measurements of lutetium-176 using underground HPGe-detectors

The half-life of ¹⁷⁶Lu was determined by measuring the ¹⁷⁶Lu activity in metallic lutetium foils. Three different HPGe-detectors located 225 m underground were employed for the study. Measurements using the sum-peak method were performed and resulted in an average massic activity of (52.61±0.36) Bq g⁻¹. The foils were of natural isotopic abundance so using the massic activity and the value of the natural isotopic abundance of (2.59±0.01)%, a half-life of (3.722±0.029)×10¹⁰a could be calculated.     

Excitation function of the 64Ni(α,p)67Cu reaction for production of 67Cu

The excitation function of the ⁶⁴Ni(α,p)⁶⁷Cu reaction was measured from threshold up to 24 MeV in order to investigate the possibility of production of the β⁻-emitting therapeutic radioisotope ⁶⁷Cu (T_1/2=61.9 h). Two stacks of thin metallic self-supporting foils of ⁶⁴Ni (enrichment 77.8%) prepared by electrolytic deposition were irradiated by α-particle beams. The radioactivity was determined via HPGe detector γ-ray spectrometry. Some ⁶⁷Ga activity (which emits the same γ-rays as ⁶⁷Cu), formed via the ^natCu(α,x)⁶⁷Ga process on trace copper impurity in the Ni foils, was also observed. Corrections were done for ⁶⁷Ga activity contribution and for the ⁶⁷Cu activity escape fraction from the thin Ni-foil. The maximum cross section of the ⁶⁴Ni(α,p)⁶⁷Cu reaction amounts to 34 mb at 22 MeV. The experimental results were compared with theoretical predictions. The integral yield of ⁶⁷Cu at 24 MeV α-particle energy, calculated from the excitation function, amounts to 544 KBq/μAh (48.5 MBq/μA at saturation). It is thus a low-yield reaction.     

Dose characterization of the rad sourceTM 2400 X-ray irradiator for oyster pasteurization

The RS 2400's cylindrical X-ray source yields dose rates high enough to allow the irradiator to replace widely used gamma irradiators. Except for the leftmost 5 cm, beam uniformity is within 10% at the tube surface. At maximum operating parameters, the beam has HVL₁=13.66 mm aluminum, HC=0.47, and hν_eq=88.5 keV. Maximum dose rates to tissue are 65 Gy min⁻¹±3.1% at tube surface, 37 Gy min⁻¹±3.1% at center of canisters, 14.1 Gy min⁻¹±6.5% for thin-shelled oysters, and 12.3 Gy min⁻¹±6.2% for thick-shelled oysters.     

The effect of uranium migration on radionuclide distributions for soil samples at the El-Gor area,Sinai, Egypt

The concentrations and distributions of the activity of natural radionuclides in soil samples were investigated in fifteen soil samples at El-Gor area representing two profiles (A and B) using a HP–Ge detector and alpha counting by SSNTD (CR-39), respectively. The average concentrations of the radionuclides ²³⁸U, ²²⁶Ra, ²³⁵U, ²³²Th and ⁴⁰K are 203.4, 177.23, 9.77, 43.33 and 386.22 Bq kg⁻¹ (dry weight), respectively, and profile A and ²³⁸U, ²²⁶Ra, ²³⁵U, ²³²Th and ⁴⁰K have average concentrations of 232.58, 246, 11.7, 31.7, and 277.07 Bq kg⁻¹ for profile B, respectively. The eTh and eU were estimated to detect the migration process of uranium into or out of an area or uranium to or from the studied profiles. The results indicate a migration of uranium by 29% for profile A and 65.37% for profile B. The activity ratio (²³⁸U/²²⁶Ra) was found to be 0.9 in profile A and 1.15 in profile B. These ratios coincide with the uranium migration processes. The responsible mass corresponding to the measured ²²⁶Ra activity was also calculated. The radon activity concentrations for the two profiles are nearly 300 Bq m⁻³. The emanation coefficient (η) was calculated from the ratio of the expected radon activity to the measured radon for the studied soil samples. The value of η was found to depend only on the radium activity regardless to soil formation.     

Ex Vivo and In Vivo Evaluation of the Norepinephrine Transporter Ligand [(11)C]MRB for Brown Adipose Tissue Imaging

IntroductionIt has been suggested that brown adipose tissue (BAT) in humans may play a role in energy balance and obesity. We conducted ex vivo and in vivo evaluation using [¹¹C]MRB, a highly selective NET (norepinephrine transporter) ligand for BAT imaging at room temperature, which is not achievable with [¹⁸F]FDG.MethodsPET images of male Sprague–Dawley rats with [¹⁸F]FDG and [¹¹C]MRB were compared. Relative [¹⁸F]FDG or [¹¹C]MRB retention at 20, 40 and 60 min post-injection was quantified on awake rats after exposing to cold (4 °C for 4 h) or remaining at room temperature. Rats pretreated with unlabeled MRB or nisoxetine 30 min before [¹¹C]MRB injection were also assessed. The [¹¹C]MRB metabolite profile in BAT was evaluated.ResultsPET imaging demonstrated intense [¹¹C]MRB uptake (SUV of 2.9 to 3.3) in the interscapular BAT of both room temperature and cold-exposed rats and this uptake was significantly diminished by pretreatment with unlabeled MRB; in contrast, [¹⁸F]FDG in BAT was only detected in rats treated with cold. Ex vivo results were concordant with the imaging findings; i.e. the uptake of [¹¹C]MRB in BAT was 3 times higher than that of [¹⁸F]FDG at room temperature (P = 0.009), and the significant cold-stimulated uptake in BAT with [¹⁸F]FDG (10-fold, P = 0.001) was not observed with [¹¹C]MRB (P = 0.082). HPLC analysis revealed 94%–99% of total radioactivity in BAT represented unchanged [¹¹C]MRB.ConclusionsOur study demonstrates that BAT could be specifically labeled with [¹¹C]MRB at room temperature and under cold conditions, supporting a NET-PET strategy for imaging BAT in humans under basal conditions.     

Radiation surveillance using an unmanned aerial vehicle

Radiation surveillance equipment was mounted in a small unmanned aerial vehicle. The equipment consists of a commercial CsI detector for count rate measurement and a specially designed sampling unit for airborne radioactive particles. Field and flight tests were performed for the CsI detector in the area where ¹³⁷Cs fallout from the Chernobyl accident is 23–45 kBq m⁻². A 3-GBq ¹³⁷Cs point source could be detected at the altitude of 50 m using a flight speed of 70 km h⁻¹ and data acquisition interval of 1 s. Respective response for ¹⁹²Ir point source is 1 GBq. During the flight, the detector reacts fast to ambient external dose rate rise of 0.1 μSv h⁻¹, which gives for the activity concentration of ¹³¹I less than 1 kBq m⁻³. Operation of the sampler equipped with different type of filters was investigated using wind-tunnel experiments and field tests with the aid of radon progeny. Air flow rate through the sampler is 0.2–0.7 m³ h⁻¹ at a flight speed of 70 km h⁻¹ depending on the filter type in question. The tests showed that the sampler is able to collect airborne radioactive particles. Minimum detectable concentration for transuranium nuclides, such as ²³⁹Pu, is of the order of 0.2 Bq m⁻³ or less when alpha spectrometry with no radiochemical sample processing is used for activity determination immediately after the flight. When a gamma-ray spectrometer is used, minimum detectable concentrations for several fission products such as ¹³⁷Cs and ¹³¹I are of the order of 1 Bq m⁻³.