Low Levels Of Radioactivity Research Articles

Significance of Sentinel Lymph Nodes with Low Gamma Counts in Breast Cancer Patients via Radioisotopic Sentinel Lymph Node Biopsy

Objective: Sentinel lymph node biopsy (SLNB), a standard diagnostic procedure worldwide, uses blue dye and/or radioisotopic methods to detect clinically node-negative breast cancer. With the latter method, we often experience axillary lymph nodes with extremely low levels of radioactivity, compared with the maximum radioactive nodes. Here, we investigated the significance and possibility of metastasis in low radioactive SLNs in patients with and without metastasis in maximum radioactive SLNs. Patients and methods: Between 2003 and 2011, we subjected a total of 453 breasts in 443 patients with earlystage invasive ductal carcinoma to SLNB using a combination of blue dye and radioisotopic methods. All lymph nodes detected via gamma -probe were considered SLNs and resected. Results: SLNs were identified in 452 (99.8%) of 453 cases; of these, SLN metastasis was pathologically diagnosed in 118 cases (26.1%). Two or more SLNs were detected in 232 (51.2%) of 453 cases; of these, 46 cases (19.8%) had SLNs with gamma counts < 10% of the maximum detected values. Metastasis was detected in these low-gamma-count SLNs in 4 of 453 cases (0.9%), even though no metastasis had been detected in SLNs with maximum radioactivity levels. Macrometastasis was pathologically demonstrated in 3 of 4 cases. Conclusion: We identified several cases of metastatic SLNs with very low radioactivity, despite a lack of metastasis in SLNs with maximum radioactivity. These findings indicate that the evaluation of SLNs with gamma counts < 10% of the patient maximum would provide more precise information about the axillary status and help to maintain a low SLNB false-negative rate.

Using Natural Tracers to Track the Groundwater Flow in a Mining Area

Natural tracers, including 222Rn, 226Ra, δ18O, and δ2H are frequently used in hydrological studies to determine the origin, dynamics and mixing of waters. In order to assess the seasonal variation of groundwater flow in Rosia Montana mining area, water samples have been collected from ten points for nine months, on a monthly basis. The 222Rn and 226Ra concentrations reflect a low level of radioactivity in the area, the values being below the national and international thresholds for drinking water. Significant differences in the trends of the isotopic composition have been noticed, both for the mining affected and non-affected sampling sites, suggesting different pathways, residence times and geochemical processes that may occur. A Local Meteoric Water Line needs to be built in order to compare the measured isotopic ratios. The groundwater recharge in the system of galleries comes from atmospheric precipitations, being submitted to a longer or shorter path, and very likely, to different degrees of interaction with the rock. The performed preliminary investigations have revealed the good potential to a more complete image on the underground water circulation and related processes by using a combination of isotopic and classic chemical analyses.

Clarification of the calculation of minimum detectable activity in low-level radioactivity measurements

We discuss a new method to determine the value of minimum detectable activity (MDA) in low-level measurements. The method is based on the Feldman–Cousins unified approach which effectively combines the construction of confidence intervals with the determination of the decision threshold and MDA. The new method requires a single probability to be pre-specified for the determination of MDA as well as decision threshold and confidence interval, in contrast with the ISO 11929 method requiring three probabilities.

Abundance and distribution of radioelements in lunar terranes: Results of Chang’E-1 gamma ray spectrometer data

The gamma ray spectrometer (GRS) onboard Chang’E-1 has acquired valuable datasets recording the gamma ray intensities from radioelements (Potassium (K), Thorium (Th) and Uranium (U), etc.) on lunar surface. We extracted the elemental concentrations from the GRS data with spectral fitting techniques and mapped the global absolute abundance of radioelements in terms of the ground truths from lunar samples and meteorites. The obtained global concentration maps of these radioelements indicate heterogeneous distribution among three major lunar crustal terranes (i.e., Procellarum KREEP Terrane (PKT), Feldspathic Highlands Terrane (FHT), and South Pole Aitken Terrane (SPAT)) in relation with their origin and distinct geologic history. The majority of radioelements are restricted in PKT, approving the scenario of KREEP (Potassium (K), rare earth elements (REE), Phosphorus (P)) residua concentrating under the Procellarum region. Moreover, we found the consistency of distribution for radioelements and basalts, concluding that the subsequent volcanism might be associated with local concentrations of radioelements in western Oceanus Procellarum and northwestern South Pole Aitken Basin. The prominent and asymmetric radioactive signatures were confirmed in SPAT comparing to FHT dominated by low level radioactivity, while the magnitudes are much lower than that of PKT, indicating a primary geochemical heterogeneity for the Moon.

The metabolism and disposition of GSK2140944 in healthy human subjects

1. GSK2140944 is a novel bacterial topoisomerase inhibitor in development for the treatment of bacterial infections. The metabolism and disposition in healthy human subjects was investigated.2. Six male subjects received [14C] GSK2140944 orally (2000 mg) and as a single 2-hour i.v. infusion (1000 mg). Urinary elimination (59%) was major by the i.v. route, whereas fecal elimination (53%) pre-dominated via the oral route. Accelerator mass spectrometry (AMS) was used for the analysis of plasma and bile samples due to the low level of radioactivity in samples (low specific activity of the doses). Unchanged GSK2140944 was the predominant circulating component (>60% DRM), with the main circulating metabolite M4 formed by oxidation of the triazaacenaphthylene moiety representing 10.8% (considered major) and 8.6% drug-related material by the oral and i.v. route, respectively. Approximately 50% of the oral dose was absorbed and eliminated mainly as unchanged GSK2140944 in urine (∼20% of dose). Elimination via metabolism (∼13% of dose) was relatively minor. The facile oxidation of GSK2140944 to metabolite M4 was believed to be a result of activation by adjacent electron withdrawing groups.3. This study demonstrates the use of AMS to overcome radioprofiling challenges presented by low specific activity resulted from high doses administration.

Comparisons organized by Ionizing Radiation Metrology Laboratory of FTMC, Lithuania

The newly established Ionizing Radiation Metrology Laboratory of the National Metrology Institute (FTMC) in Lithuania organized four comparisons in the field of low-level radioactivity measurements in water. For gamma-ray emitters, the activity concentration in the samples was in the range 1–25Bq/kg, while for tritium it was around 2Bq/g. The assigned values of all comparisons were traceable to the primary standards of the Czech Metrology Institute (CMI).

Determination of the natural and artificial radioactivity of a selection of traditional Mexican medicinal herbs by gamma spectrometry

This work presents the results of a gamma spectrometry analysis of 30 traditional Mexican medicinal herbs. The analysis was carried out using low level background shielding, a hyper-pure germanium detector, and a multichannel analyzer system. Natural and artificial radiactivity concentration from 226Ra (through 214Pb and 214Bi), 228Th (through 208Tl), 228Ra (through 228Ac), 40K, and 137Cs were determined in this analysis. The results show low concentration levels of natural radioactivity and no artificial radionuclides, and different contents of natural 40K, in the studied medicinal herbs. These low concentration levels of natural radionuclides, cannot be consider a health risk for common consumers.

Radionuclide, scintillation cocktail and chemical/color quench influence on discriminator setting in gross alpha/beta measurements by LSC

Gross alpha/beta measurements in drinking waters enable radiochemical composition analysis in environmental studies providing efficient screening method that can indicate whether water contains elevated levels of any radionuclide. Routine gross alpha/beta activity monitoring in drinking waters has been carried out for a few years in laboratory for low-level radioactivity measurements in Novi Sad according to ASTM method, performing measurements on liquid scintillation counter Quantulus 1220 which can simultaneously generate alpha/beta spectra of samples by Pulse Shape Analysis (PSA circuit). In this paper, PSA discriminator impact was investigated to ensure obtaining of accurate and reliable alpha/beta activities. One novelty of presented work is PSA parameter setup with two combinations of radionuclides (241Am, 226Ra and 90Sr/90Y) with varying activity concentrations. Performed experiments also make contribution to investigations on the manner in which chemical and color quench affect optimal PSA parameter setting and further on, their altogether influence on gross alpha/beta activity measurements. Nitromethane, 15.8 M nitric acid and water, as well as yellow and yellow-orange dye, were used as quenching agents in order to test PSA/interference factor behavior in the presence of quenchers with different quenching strengths. Variation of PSA setting in quenched samples with two different commercially available cocktails (Ultima Gold LLT and OptiPhase HiSafe 3) was also tested. Lastly, application i.e. assessment of obtained PSA-SQP(E) correlation on the obtained results of activity concentrations of few artesian well water samples and colored spiked samples, based on the measured SQP(E) value of samples, has been demonstrated.

Development of a protocol to measure iron-55 in solid matrices in the environment

The development of metrology of iron-55 in low-level radioactivity in environmental solid matrices was realised for conducting radioecological studies.A protocol was developed based on the adaptation of existing methods for the purification of iron-55 with selective chromatographic resin, which was then measured with liquid scintillation. The loss attached treatment chemical steps were quantified with elemental iron by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The tests were used to define the iron retention capacity of selective chromatographic resin, a key element in chemical treatment, and test sample size needed to reach the detection limit of 30 Bq kg−1 dry.The solid samples were analysed with the developed protocol. The activities obtained from iron-55 were below the detection limit of 30 Bq kg−1 dry.

Manufacture and Utilization of a Low-level Radioactive 68Ge/68Ga Generator in a Radiochemistry Laboratory Course

The low-level radioactivity of a (68)Ge/(68)Ga generator is a suitable tool for measuring radioactive growth and decay after (68)Ga milking due to their desirable nuclear decay properties, such as the EC decay of (68)Ge with no γ-ray emission andthe β(+) decay of (68)Ga with a weak γ-ray emission. To experience andund erstandrad ioactive equilibrium during a university laboratory course, we surveyedandtestedthe production of a small amount of (68)Ge and set up educational programs to manufacture a (68)Ge/(68)Ga generator for measuring the growth andd ecay of (68)Ga. The irradiation of natGa with 25 μA of a 30 MeV proton beam from a cyclotron for 4 h yields ca. 111 MBq of (68)Ge, which was sufficient to supply to several universities. For use as the adsorbent of the generator column, particles of hydrated tin (VI) oxide were prepared from precipitated tin hydroxide gel. Repeated elution of (68)Ga from the handmade (68)Ge/(68)Ga generator gave constant amounts of (68)Ga with acceptable breakthrough of (68)Ge. The feedback from the student's experience with the (68)Ge/(68)Ga generator was evaluatedby annual questionnaire surveys, which were given to all students taking the course every year from 2012 to 2014. It has been made clear that more than half of the students were interested in the (68)Ge/(68)Ga generator program, andthis interest increasedfrom 54.9%in 2012 to 78.6%in 2014. A low-level radioactive (68)Ge/(68)Ga generator is thus expectedto be a suitable experimental tool for demonstrating the phenomenon of radioactivity to students in an intriguing way.

(67/68)Ga-labeling agent that liberates (67/68)Ga-NOTA-methionine by lysosomal proteolysis of parental low molecular weight polypeptides to reduce renal radioactivity levels.

The renal localization of gallium-67 or gallium-68 ((67/68)Ga)-labeled low molecular weight (LMW) probes such as peptides and antibody fragments constitutes a problem in targeted imaging. Wu et al. previously showed that (67)Ga-labeled S-2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (SCN-Bz-NOTA)-conjugated methionine ((67)Ga-NOTA-Met) was rapidly excreted from the kidney in urine following lysosomal proteolysis of the parental (67)Ga-NOTA-Bz-SCN-disulfide-stabilized Fv fragment (Bioconjugate Chem., (1997) 8, 365-369). In the present study, a new (67/68)Ga-labeling reagent for LMW probes that liberates (67/68)Ga-NOTA-Met was designed, synthesized, and evaluated using longer-lived (67)Ga in order to reduce renal radioactivity levels. We employed a methionine-isoleucine (MI) dipeptide bond as the cleavable linkage. The amine residue of MI was coupled with SCN-Bz-NOTA for (67)Ga-labeling, while the carboxylic acid residue of MI was derivatized to maleimide for antibody conjugation in order to synthesize NOTA-MI-Mal. A Fab fragment of the anti-Her2 antibody was thiolated with iminothiolane, and NOTA-MI-Mal was conjugated with the antibody fragment by maleimide-thiol chemistry. The Fab fragment was also conjugated with SCN-Bz-NOTA (NOTA-Fab) for comparison. (67)Ga-NOTA-MI-Fab was obtained at radiochemical yields of over 95% and was stable in murine serum for 24 h. In the biodistribution study using normal mice, (67)Ga-NOTA-MI-Fab registered significantly lower renal radioactivity levels from 1 to 6 h postinjection than those of (67)Ga-NOTA-Fab. An analysis of urine samples obtained 6 h after the injection of (67)Ga-NOTA-MI-Fab showed that the majority of radioactivity was excreted as (67)Ga-NOTA-Met. In the biodistribution study using tumor-bearing mice, the tumor to kidney ratios of (67)Ga-NOTA-MI-Fab were 4 times higher (6 h postinjection) than those of (67)Ga-NOTA-Fab. Although further studies including the structure of radiometabolites and/or cleavable linkages are required, the results of the present study indicate that the current chemical design is applicable to the development of (67)Ga-labeled Fabs for low renal radioactivity levels.

32P measurement of urine samples and internal dose assessment for radiation workers in life science laboratories

32P measurements of urine samples and internal dose assessments were conducted for workers in life science laboratories. A procedure for sample pre-treatment was established and validation was performed to exclude interference and to detect 32P levels accurately. The detection conditions for Cherenkov radiation were evaluated and the accuracy of Cherenkov radiation measurements validated. The analytical and measurement procedures were applied to urine samples collected from 11 workers from life sciences laboratories. The results of the measurements generally indicated very low background radiation levels, but daily urine samples from two workers were above the minimum detectable activity. The 32P concentrations for two of the workers were 29.3 ± 10.4 Bq•d−1 and 24.1 ± 11.8 Bq•d−1, respectively, at intake levels of 4.12 kBq and 2.61 kBq. The effective doses for these two workers were 4.6 μSv and 2.9 μSv. Overall, the results indicate very low levels of radioactivity, except for cases related to specific working conditions.

Measurement uncertainties in whole body counting and radon progeny.

Measurement uncertainty is an important quality index in gamma spectrometry related to the level of bias and precision involved in the measuring procedure. Quality control measurements during the commissioning of a 16-input whole body counter showed substantial deviations between the experimentally determined precision and the theoretical estimation, indicating either equipment malfunction or lack of reproducibility of the experimental setup. In this study, the role of the magnitude and variability of airborne background radiation present in the counting room and the human body in the deterioration of the precision of counters employing NaI(Tl) detectors was investigated. Correction methods and actions based on case-specific background features were developed and applied. The experimental observations were benchmarked using a mathematical model of the counter. The efficacy of the developed methods was tested by measurements, and updated precision values were obtained. Quasi-equilibrium between the gamma-emitters Bi and Pb in the counting room and the human body is a prerequisite for accurate direct low-level radioactivity measurements in the human body.

Final results of Borexino Phase-I on low-energy solar neutrino spectroscopy

Borexino has been running since May 2007 at the LNGS with the primary goal of detecting solar neutrinos. The detector, a large, unsegmented liquid scintillator calorimeter characterized by unprecedented low levels of intrinsic radioactivity, is optimized for the study of the lower energy part of the spectrum. During the Phase-I (2007-2010) Borexino first detected and then precisely measured the flux of the 7Be solar neutrinos, ruled out any significant day-night asymmetry of their interaction rate, made the first direct observation of the pep neutrinos, and set the tightest upper limit on the flux of CNO neutrinos. In this paper we discuss the signal signature and provide a comprehensive description of the backgrounds, quantify their event rates, describe the methods for their identification, selection or subtraction, and describe data analysis. Key features are an extensive in situ calibration program using radioactive sources, the detailed modeling of the detector response, the ability to define an innermost fiducial volume with extremely low background via software cuts, and the excellent pulse-shape discrimination capability of the scintillator that allows particle identification. We report a measurement of the annual modulation of the 7 Be neutrino interaction rate. The period, the amplitude, and the phase of the observed modulation are consistent with the solar origin of these events, and the absence of their annual modulation is rejected with higher than 99% C.L. The physics implications of phase-I results in the context of the neutrino oscillation physics and solar models are presented.

The filling strategy of the Borexino experiment

The detection of solar neutrinos by means of a liquid scintillator requires very low levels of radioactivity throughout the whole active volume. The selection of clean detector materials and the purification of the scintillator are necessary, but not sufficient conditions. It is also crucial that during the filling operations the scintillator is not contaminated, either by air or by getting in contact with dirty surfaces. This paper describes the procedures which we adopted to minimize these risks and achieve very good levels of radio-purity which we finally got in Borexino.

Insulinoma imaging with glucagon-like peptide-1 receptor targeting probe 18F-FBEM–Cys39-exendin-4

Glucagon-like peptide-1 receptor (GLP-1R) is a specific target for insulinomas imaging since it is overexpressed in the tumor. Exendin-4 exhibits high affinity for the GLP-1R. In this study, a novel (18)F-labeled exendin-4 analog, (18)F-FBEM-Cys(39)-exendin-4, was synthesized and its potentials for GLP-1R imaging were also evaluated. (18)F-FBEM was synthesized by coupling (18)F-fluorobenzoic acid ((18)F-FBA) with N-(2-aminoethyl) maleimide, and the reaction conditions were optimized. Cys(39)-exendin-4 was then conjugated with (18)F-FBEM to obtain (18)F-FBEM-Cys(39)-exendin-4. The GLP-1R targeting potential and pharmacokinetic profile of the tracer were analyzed in INS-1 insulinoma and MDA-MB-435 breast tumor model, respectively. Under the optimal conditions, the yield of radiolabeled (18)F-FBEM was 49.1±2.0% (based on (18)F-FBA, non-decay corrected). The yield of (18)F-FBEM-Cys(39)-exendin-4 was 35.1±2.6% (based on the starting (18)F-FBEM, non-decay corrected). The radiochemical purity of (18)F-FBEM-Cys(39)-exendin-4 is >95%, and the specific activity was at least 35GBq/μmol. The GLP-1R-positive INS-1 insulinoma xenograft was clearly visible with good contrast to background, whereas GLP-1R-negative MDA-MB435 breast tumor was barely visible. Low levels of radioactivity were also detected at pancreas and lungs due to few GLP-1R expressions. GLP-1R binding specificity was demonstrated by reduced INS-1 tumor uptake of the tracer after coinjection with an excess of unlabeled Cys(39)-exendin-4 at 1h postinjection. The thiol-reactive reagent, (18)F-FBEM, was prepared with high yield and successfully conjugated to Cys(39)-exendin-4. Favorable preclinical data showing specific and effective tumor targeting by (18)F-FBEM-Cys(39)-exendin-4 suggest that the tracer may be a potential probe for insulinomas imaging.

A compact and high efficiency GAGG well counter for radiocesium concentration measurements

After the Fukushima nuclear disaster, social concern about radiocesium (137Cs and 134Cs) contamination in food increased. However, highly efficient instruments that can measure low level radioactivity are quite expensive and heavy. A compact, lightweight, and reliable radiation detector that can inexpensively monitor low level radiocesium is highly desired. We developed a compact and highly efficient radiocesium detector to detect ~32keV X-rays from radiocesium instead of high energy gamma photons. A 1-mm thick GAGG scintillator was selected to effectively detect ~32keV X-rays from 137Cs to reduce the influence of ambient radiation. Four sets of 25mm×25mm×1mm GAGG plates, each of which was optically coupled to a triangular-shaped light guide, were optically coupled to a photomultiplier tube (PMT) to form a square-shaped well counter. Another GAGG plate was directly optically coupled to the PMT to form its bottom detector. The energy resolution of the GAGG well counter was 22.3% FWHM for 122keV gamma rays and 32% FWHM for ~32keV X-rays. The counting efficiency for the X-rays from radiocesium (mixture of 137Cs and 134Cs) was 4.5%. In measurements of the low level radiocesium mixture, a photo-peak of ~32keV X-rays can clearly be distinguished from the background. The minimum detectable activity (MDA) was estimated to be ~100Bq/kg for 1000s measurement. The results show that our developed GAGG well counter is promising for the detection of radiocesium in food.

Automation Highlights from the Literature

Automation Highlights from the Literature

Design, synthesis and biological evaluation of negatively charged 111In-DTPA-octreotide derivatives

Our previous studies indicated that 111In-diethylenetriaminepentaacetic acid (111In-DTPA)-octreotide derivatives with an additional negative charge by replacing N-terminal d-phenylalanine (d-Phe) with an acidic amino acid such as l-aspartic acid (Asp) or its derivative exhibited low renal radioactivity levels when compared with 111In-DTPA-d-Phe1-octreotide. On the basis of the findings, we designed, synthesized and evaluated two Asp-modified 111In-DTPA-conjugated octreotide derivatives, 111In-DTPA-Asp1-octreotide and 111In-DTPA-Asp0-d-Phe1-octreotide. While 111In-DTPA-Asp1-octreotide showed negligible AR42J cell uptake, 111In-DTPA-Asp0-d-Phe1-octreotide exhibited AR42J cell uptake similar to that of 111In-DTPA-d-Phe1-octreotide. When administered to AR42J tumor-bearing mice, 111In-DTPA-Asp0-d-Phe1-octreotide exhibited renal radioactivity levels significantly lower than did 111In-DTPA-d-Phe1-octreotide at 1 and 3h post-injection. No significant differences were observed in tumor accumulation between 111In-DTPA-Asp0-d-Phe1-octreotide and 111In-DTPA-d-Phe1-octreotide after 1 and 3h injection. The findings in this study suggested that an interposition of an Asp at an appropriate position in 111In-DTPA-d-Phe1-octreotide would constitute a useful strategy to develop 111In-DTPA-d-Phe1-octreotide derivatives of low renal radioactivity levels while preserving tumor accumulation.

Conditional clearance of radioactive demolition waste in motorway scenario

The paper describes the model application of conditional clearance radioactive demolition waste arising from decommissioning of nuclear power plants and the calculation of individual effective dose absorbed during construction and operation stage of motorway. Large quantities of materials with very low level radioactivity may occur during the decommissioning of NPPs after the end of its lifetime or after a nuclear accident. Part of the decommissioning waste consists of the contaminated demolition waste, which is necessary to be processed and stored on a designated storage sites or disposed. The construction of such stores or repositories requires significant financial and material resources. Possible solving of this issue is conditional clearance of very low level radioactive waste and its reuse in construction of roads, where they are incorporated for 50 to 100 years. This period is necessary for natural radioactive decay of radionuclides to the levels applicable for unconditional clearance. The foundation of a road represents a significant potential for recycling of concrete rubble from the decommissioning. Calculation of external exposure was performed by means of VISIPLAN 3D ALARA, internal exposure due to inhalation was calculated by AMBER 5.4. The outputs of calculations are the individual effective dose absorbed during working activities from all relevant exposure pathways. Final results include clearance levels specific mass activities of demolition waste designated for clearance.