Digital Autoradiography Research Articles

PD4-09 VASOACTIVE INTESTINAL PEPTIDE AND PITUITARY ADENYLATE CYCLASE ACTIVATING PEPTIDE RECEPTOR 1 (VPAC1) TARGETED IMAGING OF PROSTATE CANCER: A PILOT STUDY

INTRODUCTION AND OBJECTIVES: Prostate cancer (CaP) overexpresses VPAC1, representing a highly suitable target for imaging and treatment. VPAC1 is over-expressed at the onset of the malignancy, which may be prior to elevation of PSA, and before cell morphology is altered. We have successfully used VPAC1 receptor-specific peptide constructs to image breast cancer in experimental animal models, and in humans. We hypothesized that VPAC1 expressed in high density on PC can be targeted for detection of intraprostatic tumor foci on whole mount radical prostatectomy specimens, using TP3805, a VPAC1 specific biomolecule labeled with Cu-64 a PET imaging radionuclide. METHODS: As part of a PET imaging protocol targeting VPAC1, men (N1⁄425) with prostate cancer undergoing radical prostatectomy were imaged preoperatively, and compared to whole mount radical prostatectomy pathologic analysis. De-paraffinized slides from whole mount pathology from two patients who participated the protocol, as well as one malignant lymph node and one benign lymph node specimens and 3 BPH negative controls underwent digital autoradiography with Cu-64, and then were H&E stained. Autoradiography images were compared with prostate H&E staining in which tumor foci were delineated. RESULTS: Prostate cancer foci (n1⁄430/31) were identified by autoradiography imaging (Figure 1). Autoradiography missed one malignant lesion due to technical artifact. Additionally, 6 small cancerous lesions were identified by autoradiography that were not previously noted by histologic examinations. A total of 7 additional lesions seen by autoradiography corresponded with HGPIN. The positive lymph node and the benign lymph node were correctly identified by auto radiography (Fig.2). For the 3 BPH patients, no cancer foci were noted by autoradiography. CONCLUSIONS: VPAC1 peptide analog constructs accurately identified foci of prostate cancer on whole mount radical prostatectomy specimens. Several additional lesions were also identified. Detection of HGPIN is consistent with the early expression of VPAC1 prior to the modulations in cell morphology. The PPV (97%) and NPV(100%) were excellent, validating VPAC1 as a potential theragnostic target for prostate cancer imaging and treatment.

Photo- and digital-detectors for quantitative digital densitometry for distribution analysis of ores by means of gamma-activation

A method for photo processing of nuclear film detectors, which ensures higher reproducibility (about 2 %) of densitometry has been suggested. Application of the method allows for recovering fine mineralogical texture of a complex polymetallic ore of the Norilsk deposit with time series autoradiograms after computer processing. Some problems concerning interpretation of the results are discussed. It has been shown that application of digital imaging plates as a detector demonstrates high reproducibility suitable for precise quantitative autoradiography. The developed method of digital gamma-activation autoradiography via short-lived radionuclides may be successfully used for screening analysis of large area ore’s thin sections.

Characterization of a double‐sided silicon strip detector autoradiography system

The most commonly used technology currently used for autoradiography is storage phosphor screens, which has many benefits such as a large field of view but lacks particle-counting detection of the time and energy of each detected radionuclide decay. A number of alternative designs, using either solid state or scintillator detectors, have been developed to address these issues. The aim of this study is to characterize the imaging performance of one such instrument, a double-sided silicon strip detector (DSSD) system for digital autoradiography. A novel aspect of this work is that the instrument, in contrast to previous prototype systems using the same detector type, provides the ability for user accessible imaging with higher throughput. Studies were performed to compare its spatial resolution to that of storage phosphor screens and test the implementation of multiradionuclide ex vivo imaging in a mouse preclinical animal study. Detector background counts were determined by measuring a nonradioactive sample slide for 52 h. Energy spectra and detection efficiency were measured for seven commonly used radionuclides under representative conditions for tissue imaging. System dead time was measured by imaging (18)F samples of at least 5 kBq and studying the changes in count rate over time. A line source of (58)Co was manufactured by irradiating a 10 μm nickel wire with fast neutrons in a research reactor. Samples of this wire were imaged in both the DSSD and storage phosphor screen systems and the full width at half maximum (FWHM) measured for the line profiles. Multiradionuclide imaging was employed in a two animal study to examine the intratumoral distribution of a (125)I-labeled monoclonal antibody and a (131)I-labeled engineered fragment (diabody) injected in the same mouse, both targeting carcinoembryonic antigen. Detector background was 1.81 × 10(-6) counts per second per 50 × 50 μm pixel. Energy spectra and detection efficiency were successfully measured for seven radionuclides. The system dead time was measured to be 59 μs, and FWHM for a (58)Co line source was 154 ± 14 μm for the DSSD system and 343 ± 15 μm for the storage phosphor system. Separation of the contributions from (125)I and (131)I was performed on autoradiography images of tumor sections. This study has shown that a DSSD system can be beneficially applied for digital autoradiography with simultaneous multiradionuclide imaging capability. The system has a low background signal, ability to image both low and high activity samples, and a good energy resolution.

Calibration of digital autoradiograph technique for quantifying rock porosity using 14C-PMMA method

Digital autoradiography (DA) based on phosphor plate imaging was tested for porosity quantification using 14C-PMMA method, and was compared to the classical film autoradiography (FA) method. Validation was undertaken by characterizing porosity evolution of moraine deposits of Lamarck granodiorite (eastern Sierra Nevada, USA). The connected porosities obtained with FA and DA are comparable to density measurements. Using adapted exposure times, DA is more accurate than FA for analysing large variations of porosity within a given sample, and is faster than FA.

The iQID camera: An ionizing-radiation quantum imaging detector

We have developed and tested a novel, ionizing-radiation Quantum Imaging Detector (iQID). This scintillation-based detector was originally developed as a high-resolution gamma-ray imager, called BazookaSPECT, for use in single-photon emission computed tomography (SPECT). Recently, we have investigated the detector׳s response and imaging potential with other forms of ionizing radiation including alpha, neutron, beta, and fission fragment particles. The confirmed response to this broad range of ionizing radiation has prompted its new title. The principle operation of the iQID camera involves coupling a scintillator to an image intensifier. The scintillation light generated by particle interactions is optically amplified by the intensifier and then re-imaged onto a CCD/CMOS camera sensor. The intensifier provides sufficient optical gain that practically any CCD/CMOS camera can be used to image ionizing radiation. The spatial location and energy of individual particles are estimated on an event-by-event basis in real time using image analysis algorithms on high-performance graphics processing hardware. Distinguishing features of the iQID camera include portability, large active areas, excellent detection efficiency for charged particles, and high spatial resolution (tens of microns). Although modest, iQID has energy resolution that is sufficient to discriminate between particles. Additionally, spatial features of individual events can be used for particle discrimination. An important iQID imaging application that has recently been developed is real-time, single-particle digital autoradiography. We present the latest results and discuss potential applications.

Change in Cell Death Markers During 177Lu-mAb Radioimmunotherapy-Induced Rejection of Syngeneic Rat Colon Carcinoma

To monitor cell death in tumors during the rejection process after treatment with an antibody radiolabeled with a β-emitter. Tumors during rejection after treatment with (177)Lu-labeled antibody BR96 and after administration of unlabeled BR96 were compared with untreated tumors from the same immunocompetent syngeneic rat tumor model. Cell death was monitored with the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and immunohistochemical staining of activated caspase-3 and γH2AX. These data were evaluated together with histopathological morphology, BR96-binding antigen expression, and (177)Lu radioactivity distribution imaged by digital autoradiography. The untreated tumors showed staining for all the markers, mainly in and around the necrotic areas. One to 2 days p.i. large areas were stained with anti-γH2AX, followed by a slight decrease. Staining of activated caspase-3 was intense and extensive 1-2 days p.i., while found in and around necrotic areas 3-8 days p.i. TUNEL staining was similar to activated caspase-3 staining 1-2 days p.i. but more extensive than activated caspase-3 staining 3-4 days p.i. Digital autoradiography revealed activity concentration in granulation tissue from 1 day p.i. Following radioimmunotherapy in an immunocompetent syngeneic colon carcinoma model, tumor cells did not only die through caspase-3-dependent apoptosis, but also by other mechanisms.

A study of Cs-137 spatial distribution in soil thin sections by digital autoradiography and microscopy

Digital autoradiography with imaging plates and microprobe analysis was used to study 137Cs micro-distribution in thin sections of the podzolic sandy soil typical for the Chernobyl remote impact zone 25years after the accident. The zone is notable for contamination of the so-called condensation type where the contribution of the “hot” fuel particles was comparatively low. The initial 137Cs contamination level of the study plot located on the Iput river terrace ca. 20km to the east of the town of Novozybkov, Bryansk region, was approx. 40Ci/km2. According to the modern soil core data the main portion of cesium radioisotopes is still concentrated in the 10–20cm thick surface layer. Thin sections were prepared from the top 0–10cm layer of the soil profile located on the shoulder of the relatively steep northern slope of the forested hill. Autoradiography of the thin sections has clearly shown both cluster and dispersed patterns of 137Cs distribution presumably reflecting initial radiocesium accumulation in the surficial organic layer with mineral admixture and subsequent lateral and vertical propagation due to water movement and filtration. The propagation was accompanied by fixation of 137Cs ions on surfaces of soil particles. High sensitivity (0.03Bq/cm2) and resolution (ca 40μm) of the applied technique enable us to reveal concentration and dispersion zones in soil thin sections on microscale level. Soil micro-morphology and microprobe analysis have shown to be helpful in deciphering soil chemical and mineral composition assumed to be responsible for 137Cs retention in the soil top layer.

18F-Fluorodeoxyglucose Uptake and Tumor Hypoxia: Revisit 18F-Fluorodeoxyglucose in Oncology Application

This study revisited 18F-fluorodeoxyglucose (18F-FDG) uptake and its relationship to hypoxia in various tumor models. METHODS: We generated peritoneal carcinomatosis and subcutaneous xenografts of colorectal cancer HT29, breast cancer MDA-MB-231, and non–small cell lung cancer A549 cell lines in nude mice. The partial oxygen pressure (pO2) of ascites fluid was measured. 18F-FDG accumulation detected by digital autoradiography was related to tumor hypoxia visualized by pimonidazole binding and glucose transporter-1 (GLUT-1) in frozen tumor sections. RESULTS: Ascites pO2 was 0.90 ± 0.53 mm Hg. Single cancer cells and clusters suspended in ascites fluid as well as submillimeter serosal tumors stained positive for pimonidazole and GLUT-1 and had high 18F-FDG uptake. In contrast, 18F-FDG uptake was significantly lower in normoxic portion (little pimonidazole binding or GLUT-1 expression) of larger serosal tumors or subcutaneous xenografts, which was not statistically different from that in the liver. CONCLUSIONS: Glucose demand (18F-FDG uptake) in severely hypoxic ascites carcinomas and hypoxic portion of larger tumors is significantly higher than in normoxic cancer cells. Warburg effect originally obtained from Ehrlich ascites carcinoma may not apply to normoxic cancer cells. Our findings may benefit the better understanding of 18F-FDG PET in oncology application.

A Comparison of the Imaging Characteristics and Microregional Distribution of 4 Hypoxia PET Tracers

We compared the imaging characteristics and hypoxia selectivity of 4 hypoxia PET radiotracers ((18)F-fluoromisonidazole [(18)F-FMISO], (18)F-flortanidazole [(18)F-HX4], (18)F-fluoroazomycin arabinoside [(18)F-FAZA], and (64)Cu-diacetyl-bis(N4-methylsemicarbazone) [(64)Cu-ATSM]) in a single murine xenograft tumor model condition using small-animal PET imaging and combined ex vivo autoradiography and fluorescence immunohistochemistry. Nude mice bearing SQ20b xenograft tumors were administered 1 of 4 hypoxia PET tracers and images acquired 80-90 min after injection. Frozen sections from excised tumors were then evaluated for tracer distribution using digital autoradiography and compared with histologic markers of tumor hypoxia (pimonidazole, carbonic anydrase 9 [CA9]) and vascular perfusion (Hoechst 33342). The highest tumor uptake was observed with (64)Cu-ATSM (maximum standardized uptake values [SUV(max)], 1.26 ± 0.13) and the lowest with (18)F-FAZA (SUVmax, 0.41 ± 0.24). (18)F-FMISO and (18)F-HX4 had similar intermediate tumor uptake (SUV(max), 0.76 ± 0.38 and 0.65 ± 0.19, respectively). Digital autoradiographs of hypoxia tracer distribution were compared pixel by pixel with images of immunohistochemistry stains. The fluorinated nitroimidazoles all showed radiotracer uptake increasing with pimonidazole and CA9 staining. (64)Cu-ATSM showed the opposite pattern, with highest radiotracer uptake observed in regions with the lowest pimonidazole and CA9 staining. The fluorinated nitroimidazoles showed similar tumor distributions when compared with immunohistochemistry markers of hypoxia. Variations in tumor standardized uptake value and normal tissue distribution may determine the most appropriate clinical setting for each tracer. (64)Cu-ATSM showed the highest tumor accumulation and little renal clearance. However, the lack of correlation between (64)Cu-ATSM distribution and immunohistochemistry hypoxia markers casts some doubt on the hypoxia selectivity of (64)Cu-ATSM.

Radial diffusion of radiocaesium and radioiodide through cementitious backfill

The function of the backfill material in a geological disposal facility (GDF) is to chemically condition the environment of the near field and thereby chemically retard the transport of the radionuclides present in the waste. This function of the backfill material is usually referred to as chemical containment. Diffusion experiments are being carried out over periods up to four years to assess the diffusion of Cs, Ni, Eu, Th, U and I (as I−) through Nirex Reference Vault Backfill (NRVB). The method uses cylinders of NRVB (40mm diameter, 40–45mm height) which can be doped via a central well with the radionuclides of interest. Diffusion occurs radially into a surrounding solution already pre-equilibrated with the cement. This paper shows the results obtained during the first two years for experiments undertaken using 137Cs and 125I− tracers with and without carrier. Comparison is made to tritiated water under identical experimental conditions. Breakthrough of Cs and I− occurred within the first week of the experiments, reaching steady state in the surrounding solution after 20–50days. The maximum concentrations expected from the original inventories based on a simple dilution calculation have not been reached, indicating that retention in the matrix has occurred; ranging from 10% to 40% for Cs, and up to 50% for I−. Corresponding experiments using a solution containing cellulose degradation products (CDP) showed an increased diffusion for both Cs and I. Migration profiles have been obtained and the relative retention of each radionuclide has been confirmed using digital autoradiography. The results indicate that, for both isotopes, migration occurs through the cement matrix rather than through microfissures. However, whereas Cs is homogeneously distributed within the blocks, there is evidence of zones of preferential I− accumulation even where concentrations in solution have reached steady state. Transport modelling using GoldSim has replicated experimental observations, producing comparable partition ratios (Rd) to those reported in the literature.

Assessment of Global Cardiac Uptake of Radiolabeled Iron Oxide Nanoparticles in Apolipoprotein-E-Deficient Mice: Implications for Imaging Cardiovascular Inflammation

Atherosclerosis is a leading cause of death in industrialized countries and is characterized by the accumulation of lipids and inflammatory cells, including macrophages, in blood vessel walls. Therefore, the ability to image macrophages could help identify plaques that are precursors of acute thrombotic events. Previous research has shown that long-circulating nanoparticles could be used to detect macrophages within atherosclerotic plaques of the aorta. By conducting this study, we investigated whether global cardiac uptake of radiolabeled nanoparticles could allow assessment of total macrophage burden in the coronary arteries. Dextran-coated iron oxide nanoparticles (IONPs) were labeled with iodine-125 via Bolton-Hunter (sulfosuccinimidyl-3-[4-hydroxyphenyl]propionate) method. IONPs were characterized by means of dynamic light scattering and transmission electronic microscopy. Biodistribution studies were performed in healthy and atherosclerotic mice. Additionally, digital autoradiography of hearts from both healthy and atherosclerotic mice was performed to assess regional and global atherosclerotic burden. The [(125)I]IONPs exhibited high radiolabel stability and long blood circulation, which eventually led to high heart uptake in apoE -/- mice when compared with healthy controls. Furthermore, digital autoradiography showed substantially enhanced emission of signals from the hearts of atherosclerotic mice, while no or minimal cardiac signals were detected in healthy mice. This preparation showed adequate physical-chemical properties for in vivo studies, such as small size (∼30 nm), good radiolabel stability, and long circulation time. There was also significant accumulation in the heart of apoE-/- mice compared with that of healthy control animals. These findings suggest that radiolabeled dextran-coated iron oxide nanoparticles may have potential to become a useful tool to detect macrophages in the atherosclerosis plaques of coronary arteries; however, these preliminary findings should be confirmed by further studies in a larger scale in various atherosclerosis models.

Anti-CD45 Monoclonal Antibody (MAb) Dose Optimization For Astatine-211 (211At)-Radioimmunotherapy (RIT) Of Relapsed Non-Hodgkin Lymphoma (NHL) In a Canine Model

BackgroundDespite numerous new and improved therapies, a majority of NHL patients eventually succumb to relapse. An approach to increase survival and decrease normal tissue toxicity in hematopoietic cell transplantation (HCT) regimens has been to replace high-dose total body irradiation with targeted RIT. Although radiolabeled MAbs targeting CD20 as conditioning prior to HCT have proven feasible and may provide curative radiation doses for NHL, targeting CD45 may be superior because of increased antigen expression, longer anti-CD45 MAb retention at target sites, and potentially less impact from antigen blocking by prior anti-CD20 treatment. In addition, replacing commonly employed beta emitters with the more radiobiologically favorable alpha (α) emitter 211At may be more effective for anti-CD45 RIT and HCT conditioning. This study aims to investigate the MAb dose of 211At-anti-CD45 RIT that provides efficient pharmacokinetics and optimal targeting of hematopoietic cells, with minimal normal tissue toxicity, using a canine model of relapsed NHL that closely resembles human disease in terms of clinical presentation, histology, and biological behavior. MethodsFive normal dogs (7.7–12.8 kg) were injected i.v. with 211At-anti-CD45 MAb (B10-conjugated CA12.10C12) starting at a MAb dose of 0.75 mg/kg for dogs 1–4 (0.5 mg/kg was non-saturating in previous studies) and increasing to 1.0 mg/kg for dog 5. Blood was sampled from 5 min to 22 h post injection (p.i.) and measured for 211At activity. MAb clearance was assessed by ELISA. Dogs 1 and 2 were euthanized 22 and 19 h after 211At injection (0.395 and 0.745 mCi/kg) and tissues were harvested for comparing the % of injected radioactivity per gram (ID/g) in target organs and normal tissues. Dogs 3–5 received autologous HCT 3 days after 211At-anti-CD45 RIT (0.310–0.395 mCi/kg) and biopsies of lymph nodes and bone marrow were performed at 2 and/or 19 h p.i. Complete blood counts were obtained at baseline, daily for the first 2 months or until full hematopoietic recovery, then once a week until end of study. Electrolytes, BUN, creatinine, and liver enzymes were measured at baseline and then every other week for 3 months. Flow cytometry and immunohistochemistry (IHC) was used to assess CD45 binding and sub-organ MAb localization with saturation being determined by comparison of mean fluorescence intensity (MFI) of target cells stained with FITC-conjugated goat anti-mouse F(ab')2(FMF) or FITC-conjugated anti-CD45 (CD45F). In addition to IHC, localization of 211At-anti-CD45-MAb was evaluated using two novel digital autoradiography techniques: α-camera and iQID. Both systems enable quantitative ex vivo imaging of α-particles in tissue, allowing dosimetry and assessment of 211At distribution down to the cellular level. ResultsBiological half-lives for circulating 211At and anti-CD45 MAb were calculated using single-phase exponential fit to 2.8 ± 0.5 and 3.2 ± 1.3 h, respectively. CD45F staining of peripheral blood mononuclear cells showed that 0.75 mg/kg of MAb was saturating for blood lymphocytes, but gated on all cells the MFI was lower using 1.0 mg/kg, indicating a decrease in available CD45 sites at the higher dose. Lymph nodes remained sub-saturated at 1.0 mg/kg. A dramatic effect was seen on bone marrow lymphocytes with antigen saturation (low CD45F MFI) at 2 h p.i. and few cells (halved FMF MFI) remaining 19 h after treatment. Successful marrow targeting and ablation was supported by α-imaging of cryosectioned bone marrow, showing evenly distributed 211At in remaining cells. Lymph nodes showed efficient targeting of peripheral follicle-like structures at 19 and 22 h p.i., with lower activity seen in central areas (dogs 1–3). At 2 h p.i. (dog 4), the activity distribution was more homogeneous, indicating elimination of centrally located CD45-expressing cells between 2 and 19 h p.i. In dog 5, the 2-h lymph node biopsy displayed a heterogeneous 211At distribution as seen in dogs 1–3, hypothetically due to faster penetration and enhanced cell kill with increased 211At-MAb dose. ConclusionAdministration of 1.0 mg/kg of 211At-anti-CD45 MAb resulted in saturation of CD45 sites in bone marrow with ablation of marrow cells. While the lymph nodes were not saturated, there was highly effective targeting of the lymph node follicles. Further studies are needed to assess if targeting 211At to CD45 may be effective for therapy of NHL. Disclosures:No relevant conflicts of interest to declare.

Roles of Long-range Electrostatic Domain Interactions and K+ in Phosphoenzyme Transition of Ca2+-ATPase

Sarcoplasmic reticulum Ca(2+)-ATPase couples the motions and rearrangements of three cytoplasmic domains (A, P, and N) with Ca(2+) transport. We explored the role of electrostatic force in the domain dynamics in a rate-limiting phosphoenzyme (EP) transition by a systematic approach combining electrostatic screening with salts, computer analysis of electric fields in crystal structures, and mutations. Low KCl concentration activated and increasing salt above 0.1 m inhibited the EP transition. A plot of the logarithm of the transition rate versus the square of the mean activity coefficient of the protein gave a linear relationship allowing division of the activation energy into an electrostatic component and a non-electrostatic component in which the screenable electrostatic forces are shielded by salt. Results show that the structural change in the transition is sterically restricted, but that strong electrostatic forces, when K(+) is specifically bound at the P domain, come into play to accelerate the reaction. Electric field analysis revealed long-range electrostatic interactions between the N and P domains around their hinge. Mutations of the residues directly involved and other charged residues at the hinge disrupted in parallel the electric field and the structural transition. Favorable electrostatics evidently provides a low energy path for the critical N domain motion toward the P domain, overcoming steric restriction. The systematic approach employed here is, in general, a powerful tool for understanding the structural mechanisms of enzymes.

The Intratumoral Distribution of Radiolabeled 177Lu-BR96 Monoclonal Antibodies Changes in Relation to Tumor Histology over Time in a Syngeneic Rat Colon Carcinoma Model

The therapeutic effect of radioimmunotherapy depends on the distribution of the absorbed dose in relation to viable cancer cells within the tumor, which in turn is a function of the activity distribution. The aim of this study was to investigate the distribution of (177)Lu-DOTA-BR96 monoclonal antibodies targeting the Lewis Y antigen over 7 d using a syngeneic rat model of colon carcinoma. Thirty-eight tumor-bearing rats were intravenously given 25 or 50 MBq of (177)Lu-DOTA-BR96 per kilogram of body weight and were sacrificed 2, 8, 24, 48, 72, 96, 120, or 168 h after injection, with activity measured in blood and tumor samples. Adjacent cryosections of each tumor were analyzed in 3 ways: imaging using a silicon-strip detector for digital autoradiography, staining for histologic characterization, or staining to determine the distribution of the antigen, vasculature, and proliferating cells using immunohistochemistry. Absorbed-dose rate distribution images at the moment of sacrifice were calculated using the activity distribution and a point-dose kernel. The correlations between antigen expression and both activity uptake and absorbed-dose rate were calculated for several regions of interest in each tumor. Nine additional animals with tumors were given unlabeled antibody to evaluate possible immunologic effects. At 2-8 h after injection, activity was found in the tumor margins; at 24 h, in viable antigen-expressing areas within the tumor; and at 48 h and later, increasingly in antigen-negative areas of granulation tissue. The correlation between antigen expression and both the mean activity and the absorbed-dose rate in regions of interest changed from positive to negative after 24 h after injection. Antigen-negative areas also increased over time in animals injected with unlabeled BR96, compared with untreated tumors. The results indicate that viable Lewis Y-expressing tumor cells are most efficiently treated during the initial uptake period. The activity then seems to remain in these initial uptake regions after the elimination of tumor cells and formation of granulation tissue. Further studies using these techniques could aid in determining the effects of the intratumoral activity distribution on overall therapeutic efficacy.

Long-range tropospheric transport of uranium and plutonium weapons fallout from Semipalatinsk nuclear test site to Norway

A combination of state-of-the-art isotopic fingerprinting techniques and atmospheric transport modelling using real-time historical meteorological data has been used to demonstrate direct tropospheric transport of radioactive debris from specific nuclear detonations at the Semipalatinsk test site in Kazakhstan to Norway via large areas of Europe. A selection of archived air filters collected at ground level at 9 stations in Norway during the most intensive atmospheric nuclear weapon testing periods (1957–1958 and 1961–1962) has been screened for radioactive particles and analysed with respect to the concentrations and atom ratios of plutonium (Pu) and uranium (U) using accelerator mass spectrometry (AMS). Digital autoradiography screening demonstrated the presence of radioactive particles in the filters. Concentrations of 236U (0.17–23nBqm−3) and 239+240Pu (1.3–782μBqm−3) as well as the atom ratios 240Pu/239Pu (0.0517–0.237) and 236U/239Pu (0.0188–0.7) varied widely indicating several different sources. Filter samples from autumn and winter tended to have lower atom ratios than those sampled in spring and summer, and this likely reflects a tropospheric influence in months with little stratospheric fallout. Very high 236U, 239+240Pu and gross beta activity concentrations as well as low 240Pu/239Pu (0.0517–0.077), 241Pu/239Pu (0.00025–0.00062) and 236U/239Pu (0.0188–0.046) atom ratios, characteristic of close-in and tropospheric fallout, were observed in filters collected at all stations in Nov 1962, 7–12days after three low-yield detonations at Semipalatinsk (Kazakhstan). Atmospheric transport modelling (NOAA HYSPLIT_4) using real-time meteorological data confirmed that long range transport of radionuclides, and possibly radioactive particles, from Semipalatinsk to Norway during this period was plausible. The present work shows that direct tropospheric transport of fallout from atmospheric nuclear detonations periodically may have had much larger influence on radionuclide air concentrations and deposition than previously anticipated.

Digital autoradiography (DA) in quantification of trace level beta emitters on concrete

In the framework of dismantling of nuclear facilities, there is a strong need to obtain analytical results on residual radioactivity especially on concrete but also on metal surfaces. Since investigation of hundreds of m2 areas by the standard Wipe test method is difficult, a semi quantitative digital autoradiography (DA) technique was developed. The DA technique is sensitive to all types of radiation and therefore it is advantageous in dismantling investigations. Recent developments on the DA technique were investigated on concrete floor of an old laboratory in which research had been carried out using 3H and 14C beta emitters. The results showed that the DA technique was a powerful tool in localization and quantification of residual radioactivity on concrete floor.

Behaviour of radionuclides in the presence of superplasticiser

Superplasticisers improve the flow properties of fresh cement and offer undoubted benefits to the construction sector. There is concern in the nuclear industry, however, that the presence of a superplasticiser in grout or backfill cement may increase the solubility of radionuclides in the cementitious pore water and/or reduce their adsorption from solution. This paper describes the effect of a commercial, polycarboxylated, polyether comb type superplasticiser on the behaviour of selected metals in blended cements through a series of batch and monolith leach experiments. Results of batch experiments show that the presence of free superplasticiser in solution reduces uptake of nickel (63Ni) and europium (152Eu) by both blast-furnace-slag- and pulverised-fly-ash-modified ordinary Portland cement. Further, metal bound in the presence of free superplasticiser is readily remobilised on exposure to fresh cement solution. Conversely, metal uptake is almost complete and appears irreversible when exposed to hardened cements prepared with superplasticiser as part of the original mix. Monolithic slag cement samples prepared with superplasticiser suffer from bleed, with the surplus water containing a significant proportion of the metals added, including uranium and thorium. Digital autoradiography reveals heterogeneous distribution of radioactivity in the monoliths and demonstrates that the dissolved metals have not been effectively immobilised throughout the specimen. The mobility of thorium may indicate similar behaviour by other tetravalent actinide species, notably Pu(IV) and Np(IV).

Developing and evaluating di(2-ethylhexyl) orthophosphoric acid (HDEHP) based polymer ligand film (PLF) for plutonium extraction

A method was developed to produce a thin Polymer Ligand Film (PLF) using di(2-ethylhexyl) orthophosphoric acid (HDEHP) ligand for rapid extraction of plutonium. Ligands were incorporated into a polystyrene matrix to generate a smooth and durable surface for analyte extraction. PLFs were prepared with varying amount of ligands to find the optimimum ratio between the ligands and polymer structure to give best plutonium recovery. Also, the plutonium extraction is dependent on the concentration of nitric solution. This dependency was examined in the manuscript. The PLF samples were counted directly using alpha spectroscopy without any further chemical process to test the plutonium recovery. The alpha spectroscopy data shows that HDEHP based PLFs were effective in extracting plutonium from nitric acid solution. The surface characterization was performed with a scanning electron microscope (SEM) and digital autoradiography for defect examination of the PLF and plutonium distribution study, respectively.

Production technology and working parameters for serial 75Se based radiators

The main working characteristics of serial radioisotope sources of γ-radiation of the type GS75M11 based on 75Se to be used for flaw detection are analyzed and their manufacturing technology is examined. A method of digital autoradiography, adapted to the evaluation of the actual sizes of the radiating region of the active part of the source, is proposed and visualized estimates of the geometry of the activated cores of serial radiators are presented.

Enhancing the selectivity of digital gamma-activation autoradiography by computer processing of a series of autoradiography images

Computer processing of a series of autoradiography images obtained during sample storage (cooling) is first proposed to enhance the selectivity of gamma-activation autoradiography. To retain the spatial resolution of the method, the mathematical processing of the decay data is done for the selection of coaxially arranges pixels of a set of images. To visualize the results obtained, a method is proposed for generating a series of metaimages characterizing the spatial localization of pixels in the given range of half-lives. It was found that, for sample zones characterized by stable results in determining half-lives, the sample obeys the normal distribution, which provides a criterion for the differentiation of such zones from artifacts or background. Based on this discovery a new method is proposed for generating contrast metaimages, ensuring the separation of zones with half-lives differing by 1 h and more.