Low-level activity measurement of 131Xem, 133Xem, 135Xe and 133Xe in atmospheric air samples using high-resolution dual X-gamma spectrometry.

High-resolution dual X and gamma spectrometry has been optimized to improve the sensitivity in analyzing radioxenon from environmental samples, especially for the metastable isotopes (131Xem and 133Xem). The full-energy peak (FEP) efficiency curve in the 20-700 keV range has been established with a global uncertainty better than +/-3% using a Monte Carlo simulation. The minimum detectable activity concentrations (MDC) achievable at the laboratory for 131Xem, 133Xem, 133Xe and 135Xe are presented and the influence of 133Xe activity on the metastable radioxenon MDCs is evaluated.     

238U, 235U, 137Cs and 133Xe in soils from two campuses in University of Douala—Cameroon

An evaluation of ²³⁸U, ²³⁵U, ¹³⁷Cs and ¹³³Xe in soils from two campuses in University of Douala—Cameroon using gamma spectroscopy based Broad Energy Germanium Detector (BEGe6530) has been performed. The mean activities in soils from Campuse 1 were 40.16±8.98 Bq/kg for ²³⁸U, 3.39±0.33 Bq/kg for ²³⁵U, 0.46±0.33 Bq/kg for ¹³⁷Cs and 0.14±0.16 Bq/kg for ¹³³Xe. In Campus 2, the mean activities in soils were 31.45±12.24 Bq/kg, 3.02±1.00 Bq/kg, 0.30±0.26 Bq/kg and 0.35±0.24 Bq/kg for ²³⁸U, ²³⁵U, ¹³⁷Cs and ¹³³Xe, respectively. Using the in situ survey meter, the mean values of the absorbed dose rate measured was 71.43 nGy/h for Campus 1 and 62.72 nGy/h for Campus 2. The evaluated average outdoor effective dose for Campus 1 and 2 were 87.60 µSv/yr and 76.93 µSv/yr, respectively. The overall results obtained in this work were generally low compared to that of UNSCEAR.     

Comparison of 99mTc-TRODAT-1 SPECT and 18 F-AV-133 PET imaging in healthy controls and Parkinson’s disease patients

^99mTc-TRODAT-1 is the first clinical routine ^99mTc radiopharmaceutical to evaluate dopamine neurons loss in Parkinson's disease (PD). ¹⁸ F-AV-133 is a novel PET radiotracer targeting the vesicular monoamine transporter type 2 (VMAT2) to detect monoaminergic terminal reduction in PD patients. The aim of this study is to compare both images in the same health control (HC) and PD subjects.MethodsEighteen subjects (8 HC and 10 PD) were recruited for ^99mTc-TRODAT-1 SPECT, ¹⁸ F-AV-133 PET and MRI scans within two weeks. The SPECT images were performed at 4-h post-injection for 45 min, and the PET images were performed at 90 min post-injection for 10 min. Each PET and SPECT image was normalized into Montreal Neurological Institute template aided from individual MRI for comparison. For regional analysis, volume of interest (VOIs) of bilateral caudate nuclei, anterior, posterior putamen and occipital cortex (as reference region) were delineated from the normalized MRI. The specific uptake ratio (SUR) was calculated as (regional mean counts/reference mean counts − 1). The nonparametric Mann–Whitney U test was used to evaluate the power of differentiating control from PD subjects for both image modalities. The correlations of the SURs to the clinical parameters were examined. For voxelwise analysis, two-sample t-test for group comparison between HC and PD was computed in both image modalities.ResultsThe SURs of caudate nucleus and putamen correlated well between two image modalities (r = 0.81, p < 0.001), and showed significant different between HC and PD subjects. Of note, the ¹⁸ F-AV-133 SUR displayed a better correlation to PD clinical laterality index as compared to ^99mTc-TRODAT-1 (r = 0.73 vs. r = 0.33). Voxelwise analysis showed more lesions for PD subjects from ¹⁸ F-AV-133 image as compared to ^99mTc-TRODAT-1 especially at the substantia nigra region.Conclusion¹⁸ F-AV-133 PET demonstrated similar performance in differentiation PD from control, and a better correlation to clinical characteristics than that of ^99mTc-TRODAT-1 SPECT. ¹⁸ F-AV-133 PET also showed additional information in substantia nigra integrity in PD subjects by voxelwise analysis. Collectively, ¹⁸ F-AV-133 could be a promising and better tracer for clinical use to detect monoaminergic terminal reduction in PD patients.     

MCNP HPGe detector benchmark with previously validated Cyltran model

An exact copy of the detector model generated for Cyltran was reproduced as an MCNP input file and the detection efficiency was calculated similarly with the methodology used in previous experimental measurements and simulation of a 280 cm³ HPGe detector. Below 1000 keV the MCNP data correlated to the Cyltran results within 0.5% while above this energy the difference between MCNP and Cyltran increased to about 6% at 4800 keV, depending on the electron cut-off energy.     

Ultra-high resolution mass separator—Application to detection of nuclear weapons tests

A Penning trap-based purification process having a resolution of about 1 ppm is reported. In this context, we present for the first time a production method for the most complicated and crucially important nuclear weapons test signature, ^133mXe. These pure xenon samples are required by the Comprehensive Nuclear-Test-Ban Treaty Organization to standardize and calibrate the worldwide network of xenon detectors.     

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.     

A magnet system for the suppression of conversion electrons in alpha spectrometry

A new magnet system has been designed and constructed to reduce coincidence effects between alpha particles and conversion electrons in high-resolution alpha-particle spectrometry. By means of a magnetic field, the conversion electrons are deflected away from the PIPS^® detector. Compared to existing magnet systems, the new system is not restricted to point sources and can accommodate source diameters up to about 30 mm. Two yokes were built, allowing for configurations with 20 mm or 36 mm distance between the magnets. The effectiveness of both configurations is demonstrated by measuring the conversion electron spectrum of a ²³⁷Np source. The magnet system effectively rejects 93 (7)% of electrons up to 85 keV (36 mm) and 90 (9)% of electrons up to 320 keV (20 mm). It has been successfully applied in the alpha-particle spectrometry of the long-lived nuclides ²³⁶U and ²³⁸U, resulting in significant improvement of the accuracy of alpha emission probabilities.     

Re-induction of cell differentiation and 131I uptake in dedifferentiated FTC-133 cell line by TSHR gene transfection

IntroductionRadioiodine therapy is commonly used to treat differentiated thyroid cancer (DTC), but a major challenge is dedifferentiation of DTC with the loss of radioiodine uptake. TSHR is a key molecule regulating thyrocyte proliferation and function. This study aimed to test the therapeutic potential of TSHR in dedifferentiated DTC by gene transfection in order to restore cell differentiation and radioiodine uptake.MethodsDedifferentiated FTC-133 (dFTC-133) cells were obtained by monoclonal culture of FTC-133 cell line after ¹³¹I radiation. Recombinant plasmid pcDNA3.1-hTSHR was transfected into dFTC-133 cells by using Lipofectamine 2000 reagent. Immunofluorescence analysis was carried out to confirm TSHR expression and its location. Radioiodine uptake assay was thereafter investigated. mRNAs and proteins of TSHR and other thyroid differentiated markers were detected by real-time PCR and western blot respectively.ResultsAmong the thyroid specific genes in dFTC-133 cells with stable low radioiodine uptake, TSHR was down-regulated most significantly compared with FTC-133. Then, after TSHR gene transfection, augmented expression of TSHR was observed in dFTC-133 cell surface and cytoplasm by immunofluorescence analysis. It was found that ¹²⁵I uptake was 2.9 times higher (t = 28.63, P < .01) in cells with TSHR transfection than control. The mRNAs of TSHR, NIS, TPO and Tg were also significantly increased by 1.7 times (t = 13.8, P < .05), 4 times (t = 28.52, P < .05), 1.5 times (t = 14.43, P < .05) and 2.2 times (t = 19.83, P < .05) respectively compared with control group.ConclusionDecreased TSHR expression correlated with FTC-133 ongoing dedifferentiation. TSHR transfection contributed to the re-differentiation of dedifferentiated thyroid follicular carcinoma cells.     

New measurements and evaluation of excitation functions for (p,xn), (p,pxn) and (p,2pxn) reactions on 133Cs up to 70 MeV proton energy

Cross sections for production of the therapeutic radioisotope ¹³¹Cs via the ¹³³Cs(p,3n)¹³¹Ba→¹³¹Cs route were investigated at cyclotrons. Excitation functions of the ¹³³Cs(p,x)^{133m,133mg,131mg,129g,129m,128}Ba, ^{132,129cum,127cum}Cs and ^{129m(ind),127cum,125cum}Xe nuclear reactions were measured up to 70 MeV proton energy. The experimental data were compared to the results of model calculations performed by means of ALICE-IPPE, EMPIRE-II and TALYS computer codes. Good overall agreement was observed. On the basis of the measured excitation functions integral yields were deduced. Charged particle production routes of ¹³¹Cs are discussed.     

33S as a cooperative capturer for BNCT

³³S is a stable isotope of sulfur for which the emission of an α-particle is the dominant exit channel for neutron-induced reactions. In this work the enhancement of both the absorbed and the equivalent biologically weighted dose in a BNCT treatment with 13.5 keV neutrons, due to the presence of ³³S, has been tested by means of Monte Carlo simulations. The kerma-fluence factors for the ICRU-4 tissue have been calculated using standard weighting factors. The simulations depend crucially on the scarce ³³S(n,α)³⁰Si cross-section data. The presence of a high resonance at 13.5 keV was established by previous authors providing discrepant resonance parameters. No experimental data below 10 keV are available. All of this has motivated a proposal of experiment at the n_TOF facility at CERN. A setup was designed and tested in 2011. Some results of the successful test will be shown. The experiment is scheduled for the period November to December 2012.     

Effect of co-ligands on chemical and biological properties of 99mTc(III) complexes [99mTc(L)(CDO)(CDOH)2BMe] (L = Cl,F, SCN and N3; CDOH2 = cyclohexanedione dioxime)

Introduction^99mTc-Teboroxime ([^99mTcCl(CDO)(CDOH)₂BMe]) is a member of the BATO (boronic acid adducts of technetium dioximes) class of ^99mTc(III) complexes. This study sought to explore the impact of co-ligands on solution stability, heart uptake and myocardial retention of [^99mTc(L)(CDO)(CDOH)₂BMe] (^99mTc-Teboroxime: L = Cl; ^99mTc-Teboroxime(F): L = F; ^99mTc-Teboroxime(SCN): L = SCN; and ^99mTc-Teboroxime(N₃): L = N₃).MethodsRadiotracers ^99mTc-Teboroxime(L) (L = F, SCN and N₃) were prepared by reacting ^99mTc-Teboroxime with NaF, NaSCN and NaN₃, respectively. Biodistribution and imaging studies were carried out in Sprague–Dawley rats. Image quantification was performed to compare their heart retention and liver clearance kinetics.ResultsComplexes ^99mTc-Teboroxime(L) (L = F, SCN and N₃) were prepared in high yield with high radiochemical purity. All new radiotracers were stable for > 6 h in the kit matrix. In its HPLC chromatogram, ^99mTc-Teboroxime showed one peak at ~ 15.5 min, which was shorter than that of ^99mTc-Teboroxime(F) (~ 16.4 min). There were two peaks for ^99mTc-Teboroxime(SCN) at 16.5 and 18.3 min. ^99mTc-Teboroxime(N₃) appeared as a single peak at 18.4 min. Their heart retention and liver clearance curves were best fitted to the bi-exponential decay function. The half-times of fast/slow components were 1.6 ± 0.4/60.7 ± 8.9 min for ^99mTc-Teboroxime, 0.8 ± 0.2/101.7 ± 20.7 min for ^99mTc-Teboroxime(F), 1.2 ± 0.3/84.8 ± 16.6 min for ^99mTc-Teboroxime(SCN), and 2.9 ± 0.9/51.6 ± 5.0 min for ^99mTc-Teboroxime(N₃). The 2-min heart uptake followed the order of ^99mTc-Teboroxime (3.00 ± 0.37%ID/g) > ^99mTc-Teboroxime(N₃) (2.66 ± 0.01 %ID/g) ≈ ^99mTc-Sestamibi (2.55 ± 0.46 %ID/g) > ^99mTcN-MPO (2.38 ± 0.15 %ID/g). ^99mTc-Teboroxime remains the best in first-pass extraction. The best image acquisition window is 0–5 min for ^99mTc-Teboroximine and 0–15 min for ^99mTc-Teboroximine(N₃).ConclusionCo-ligands had significant impact on the heart uptake and myocardial retention of complexes [^99mTc(L)(CDO)(CDOH)₂BMe] (L = Cl, F, SCN and N₃). Future studies should be directed towards minimizing the liver uptake and radioactivity accumulation in the blood vessels while maintaining their high heart uptake.     

Spectral interference corrections for the measurement of 238U in materials rich in thorium by a high resolution γ-ray spectrometry

In this study, the spectral interferences are investigated for the analytical peaks at 63.3 keV of ²³⁴Th and 1001.0 keV of ^234mPa, which are often used in the measurement of ²³⁸U activity by the γ-ray spectrometry. The correction methods are suggested to estimate the net peak areas of the γ-rays overlapping the analytical peaks, due to the contribution of ²³²Th that may not be negligible in materials rich in natural thorium. The activity results for the certified reference materials (CRMs) containing U and Th were measured with a well type Ge detector. The self-absorption and true coincidence-summing (TCS) effects were also taken into account in the measurements. It is found that ignoring the contributions of the interference γ-rays of ²³²Th and ²³⁵U to the mixed peak at 63.3 keV of ²³⁴Th (²³⁸U) leads to the remarkably large systematic influence of 0.8–122% in the measured ²³⁸U activity, but in case of ignoring the contribution of ²³²Th via the interference γ-ray at 1000.7 keV of ²²⁸Ac to the mixed peak at 1001 keV of ^234mPa (²³⁸U) results in relatively smaller systematic influence of 0.05–3%, depending on thorium contents in the samples. The present results showed that the necessary correction for the spectral interferences besides self-absorption and TCS effects is also very important to obtain more accurate ²³⁸U activity results. Additionally, if one ignores the contribution of ²³²Th to both ²³⁸U and ⁴⁰K activities in materials, the maximum systematic influence on the effective radiation dose is estimated to be ~6% and ~1% via the analytical peaks at 63.3 and 1001 keV for measurement of the ²³⁸U activity, respectively.     

Fukushima radionuclides in Vilnius/Lithuania aerosols: Modelling of aerosol transport

Measurements of activity concentrations of ¹³¹I; ^129mTe, ¹³²Te, ¹³⁴Cs and; ¹³⁶Cs, ¹³⁷Cs in aerosol were carried out in daily samples after the Fukushima accident during the period of March–April, 2011 in Vilnius. The maximum activity concentrations of ¹³¹I and ¹³⁷Cs were found to be 3700 μBq m⁻³ and 1040 μBq m⁻³, respectively. Variations in activity ratios of ¹³²Te/^129mTe and ¹³⁷Cs/¹³⁶Cs observed after the accident were explained by the decay of the short-lived isotopes, while those in ¹³⁴Cs/¹³⁷Cs by the dilution effect of the Chernobyl-derived ¹³⁷Cs. It was found that different behaviours of highly volatile ¹³¹I and ¹³⁷Cs resulted in enrichment of ground level aerosol particles by ¹³¹I with respect to ¹³⁷Cs. Simulated activity concentrations of ¹³⁷Cs attached to aerosol particles for the Vilnius site reasonably agreed with measured activities in aerosol samples during the Fukushima accident.     

National comparison of activity measurements of 131I, 60Co,and 133Ba in Indonesia

National comparisons of radioactivity measurements of ¹³¹I and ⁶⁰Co (in 2010) and of ¹³³Ba (in 2011) were carried out within the framework of the National Radiation Metrology Laboratory Program of Indonesia, coordinated by PTKMR-BATAN. Eleven laboratories took part in the comparison, and all measurements were made using gamma spectrometry, on point sources with an activity between 2000 Bq and 6000 Bq. Several laboratories reported values which were more than 10% different from the reference value for ¹³¹I and ¹³³Ba. Possible reasons for these differences are discussed. This program will be continued with other radionuclides to maintain and control quality assurance for the local laboratories.     

Low-level γ-ray spectrometry at the underground laboratory Garching

Two low-background setups for material screening based on HPGe detectors were built in the Garching Underground Laboratory with an overburden of ~10 m.w.e. They include several layers of passive shielding as well as an active muon veto. The first setup (GEM) comprises a 150% efficiency HPGe detector which can optionally be surrounded by a NaI(Tl) scintillation detector that serves as anti-Compton veto. The second setup (LoAx) consists of two smaller HPGe detectors which are arranged face-to-face to cover a larger solid angle around the sample and to allow coincidence measurements.For a 5.6 kg piece of copper after 11 days of measurement we have reached a sensitivity for ²²⁶Ra and ²²⁸Ra/²²⁸Th of ~5 mBq kg⁻¹ with the GEM setup. In the LoAx setup we have achieved limits of less than 100 mBq kg⁻¹ for ²³⁴Th and ²¹⁰Pb with a 156 g sample of PPO wavelength shifter after 18 days of measurement.     

Radiochemical determination of cross sections of α-particle induced reactions on 192Os for the production of the therapeutic radionuclide 193mPt

For determination of cross sections of α-particle induced reactions on 99.65% enriched ¹⁹²Os, the methods for electrolytic preparation of thin samples and radiochemical separation of radioplatinum were optimized. The excitation functions of the ¹⁹²Os(α,n)^195mPt and ¹⁹²Os(α,3n) ^193mPt reactions were measured from 20 to 39 MeV. The cross section of the latter reaction reaches a maximum value of about 1.5 b at an energy around 36 MeV. The results of nuclear model calculations using the codes TALYS and STAPRE agreed well with the measured data. The optimum energy range for the production of no-carrier-added ^193mPt (T_1/2=4.33 d) was found to be E_α=40→30 MeV. The thick target yield amounts to 10 MBq/μA h and a possible batch yield of 2 GBq should be sufficient for Auger electron therapy on a wide scale.     

Synthesis and characterization of coordination polymer nanoparticles as radioisotope tracers

Coordination polymer nanoparticles (NPs) with gamma-emitting nuclide (Au-198), 411 keV, 675 keV, 822 keV and 1087 keV were prepared by coordination polymerization of the radioisotope Au³⁺ ions and 1,4-bis(imidazole-1-ylmethyl)benzene in an aqueous solution at room temperature for 3 h. Here, the radioisotope Au³⁺ ions were prepared by dissolution of Au-198 foil, which was prepared by neutron irradiation from the HANARO reactor, in KCN aqueous solution. The successful synthesis of the radioisotope coordination polymer NPs with 5±0.5 nm was confirmed via UV–vis spectroscopy, Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectrometry (EDXS), Thermogravimetric analysis (TGA), and Gamma spectroscopy analysis. The synthesized radioisotope coordination polymer NPs can be used as radiotracers in science, engineering, and industrial fields.     

Adjuvant Liposomal Doxorubicin Markedly Affects Radiofrequency Ablation–induced Effects on Periablational Microvasculature

PurposeTo evaluate the effects of radiofrequency (RF) ablation without and with adjuvant intravenous (IV) liposomal doxorubicin (Doxil) on microvessel morphology and patency and intratumoral drug delivery and retention.Materials and MethodsThere were 133 tumors/animals used in this experiment. First, single subcutaneous tumors (R3230 in Fischer rats and 786-0 in nude mice) were randomly assigned to receive RF ablation alone or no treatment and sacrificed 0–72 hours after treatment. Next, combined RF ablation and liposomal doxorubicin (1 mg given 15 min after RF ablation) was studied in R3230 tumors at 0–72 hours after treatment. Histopathologic assessment, including immunohistochemical staining for cleaved caspase-3, heat-shock protein 70, and CD34, was performed to assess morphologic vessel appearance, vessel diameter, and microvascular density. Subsequently, tumors were randomly assigned to receive RF ablation alone, RF ablation and liposomal doxorubicin, or no treatment (control tumors), followed by IV fluorescent-labeled liposomes (a surrogate marker) given 0–24 hours after RF ablation to permit qualitative assessment.ResultsRF ablation alone resulted in enlarged and dysmorphic vessels from 0–4 hours, peaking at 12–24 hours after RF ablation, occurring preferentially closer to the electrode. The addition of doxorubicin resulted in earlier vessel contraction (mean vessel area, 47,539 μm²±9,544 vs 1,854 μm²±458 for RF ablation alone at 15 min; P<.05). Combined RF ablation and liposomal doxorubicin produced similar fluorescence 1 hour after treatment (40.88 AU/μm²±33.53 vs 22.1 AU/μm²±13.19; P = .14) but significantly less fluorescence at 4 hours (24.3 AU/μm²±3.65 vs 2.8 AU/μm²±3.14; P<.002) compared with RF ablation alone denoting earlier reduction in microvascular patency.ConclusionsRF ablation induces morphologic changes to vessels within the ablation zone lasting 12–24 hours after treatment. The addition of liposomal doxorubicin causes early vessel contraction and a reduction in periablational microvascular patency. Such changes would likely need to be considered when determining optimal drug administration and imaging paradigms.     

Targeting breast carcinoma with radioiodinated anti-HER2 Nanobody

IntroductionWith a molecular weight an order of magnitude lower than antibodies but possessing comparable affinities, Nanobodies (Nbs) are attractive as targeting agents for cancer diagnosis and therapy. An anti-HER2 Nb could be utilized to determine HER2 status in breast cancer patients prior to trastuzumab treatment. This provided motivation for the generation of HER2-specific 5F7GGC Nb, its radioiodination and evaluation for targeting HER2 expressing tumors.Methods5F7GGC Nb was radioiodinated with ¹²⁵I using Iodogen and with ¹³¹I using the residualizing agent N^?-(3-[¹³¹I]iodobenzoyl)-Lys⁵-N^α-maleimido-Gly¹-GEEEK ([¹³¹I]IB-Mal-d-GEEEK) used previously successfully with intact antibodies. Paired-label internalization assays using BT474M1 cells and tissue distribution experiments in athymic mice bearing BT474M1 xenografts were performed to compare the two labeled Nb preparations.ResultsThe radiochemical yields for Iodogen and [¹³¹I]IB-Mal-d-GEEEK labeling were 83.6 ± 5.0% (n = 10) and 59.6 ± 9.4% (n = 15), respectively. The immunoreactivity of labeled proteins was preserved as confirmed by in vitro and in vivo binding to tumor cells. Biodistribution studies showed that Nb radiolabeled using [¹³¹I]IB-Mal-d-GEEEK, compared with the directly labeled Nb, had a higher tumor uptake (4.65 ± 0.61% ID/g vs. 2.92 ± 0.24% ID/g at 8 h), faster blood clearance, lower accumulation in non-target organs except kidneys, and as a result, higher concomitant tumor-to-blood and tumor-to-tissue ratios.ConclusionsTaken together, these results demonstrate that 5F7GGC anti-HER2 Nb labeled with residualizing [¹³¹I]IB-Mal-d-GEEEK had better tumor targeting properties compared to the directly labeled Nb suggesting the potential utility of this Nb conjugate for SPECT (¹²⁹I) and PET imaging (¹²⁴I) of patients with HER2-expressing tumors.