Multitracer Solution Research Articles

Simulation studies of a full-ring, CZT SPECT system for whole-body imaging of 99m Tc and 177 Lu.

Single photon emission computed tomography (SPECT) is an imaging modality that has demonstrated its utility in a number of clinical indications. Despite this progress, a high sensitivity, high spatial resolution, multi-tracer SPECT with a large field of view suitable for whole-body imaging of a broad range of radiotracers for theranostics is not available. With the goal of filling this technological gap, we have designed a cadmium zinc telluride (CZT) full-ring SPECT scanner instrumented with a broad-energy tungsten collimator. The final purpose is to provide a multi-tracer solution for brain and whole-body imaging. Our static SPECT does not rely on the dual- and the triple-head rotational SPECT standard paradigm, enabling a larger effective area in each scan to increase the sensitivity. We provide a demonstration of the performance of our design using a realistic model of our detector with simulated body-sized phantoms filled with 99m Tc and 177 Lu. We create a realistic model of our detector by using a combination of a Geant4 Application for Tomographic Emission (GATE) Monte Carlo simulation and a finite element model for the CZT response, accounting for low-energy tail effects in CZT that affects the sensitivity and the scatter correction. We implement a modified dual-energy-window scatter correction adapted for CZT. Other corrections for attenuation, detector and collimator response, and detector gaps and edges are also included. The images are reconstructed using the maximum-likelihood expectation-maximization. Detector and reconstruction performance are characterized with point sources, Derenzo phantoms, and a body-sized National Electrical Manufacturers Association (NEMA) Image Quality (IQ) phantom for both 99m Tc and 177 Lu. Our SPECT design can resolve 7.9mm rods for 99m Tc (140keV) and 9.5mm for 177 Lu (208keV) in a hot-rod Derenzo phantom with a 3-min exposure and reach an image contrast of 78% for 99m Tc and 57% for 177 Lu using the NEMA IQ phantom with a 6-min exposure. Our modified scatter correction shows an improved contrast-recovery ratio compared to a standard correction. In this paper, we demonstrate the good performance of our design for whole-body imaging purposes. This adds to our previous demonstration of improved qualitative and quantitative 99m Tc imaging of brain perfusion and 123 I imaging of dopamine transport with respect to state-of-the-art NaI dual-head cameras. We show that our design provides similar IQ and contrast to the commercial full-ring SPECT VERITON for 99m Tc. Regarding 177 Lu imaging of the 208keV emissions, our design provides similar contrast to that of other state-of-the-art SPECTs with a significant reduction in exposure. The high sensitivity and extended energy range up to 250keV makes our SPECT design a promising alternative for clinical imaging and theranostics of emerging radionuclides.

Characterizing land use impact on multi-tracer displacement and soil structure

Summary Leaching of solutes below the root zone has been identified as a main source of potential groundwater pollution. The occurrence of preferential flow paths in structured soils can enhance rapid leaching of solutes below the root zone. There is evidence that the actual land use can affect solute displacement by altering soil structure and the abundance of preferential flow paths. In the present study, a field experiment was conducted to assess the impacts of land use (grassland vs. no-till cropland) on profile-scale displacement of bromine (Br) and Brilliant Blue FCF. The objectives were (i) to study both solutes displacement patterns, (ii) to analyze the spatial variation and anisotropic variance structures of the solutes and controlling physical soil properties, and (iii) to analyze soil structure development as a result of the land use system and possible implications for solute displacement. Two ponding infiltration experiments with Potassiumbromide (KBr) and Brilliant Blue FCF were performed on a silt loam soil in Lexington, KY. A total of 30 mm multi-tracer solution was infiltrated on an area of 1.20 × 0.70 m. Eleven vertical profile sections (width: 1.10 m, depth: 0.80 m) were excavated in steps of 0.05 m and sampled. Dye stained areas were mapped based on digital image analysis. Small soil samples were taken for Br concentrations, soil texture, and volumetric soil water content at regular intervals along a vertical 0.10 × 0.10 m raster. Vane shear resistance was measured as a proxy for mechanical soil strength. X-ray fluorescence analysis was used to determine total Br contents and the relative SiO 2 signal intensity, the latter being used as proxy for soil particle size distribution. Although both experimental sites were under the same land use until some 10 years ago before the current land uses were established, solutes displacement differed between both land uses. The dye-stained patterns revealed a high proportion of non-equilibrium flow through vertically orientated macropores and a less permeable soil matrix at the grassland site. Continuous biological activity since transversion into grassland resulted in these macropores and the absence of any compaction in the subsoil. Large proportions of Br also infiltrated directly into the loose, densely rooted soil matrix close to the surface. Soil structure development at the no-till cropland site was mainly controlled by agricultural operations. The homogeneous Br distribution in the topsoil reflected a less dense soil matrix with a network of well-connected inter-aggregate pores. A residual plough pan restricted solute displacement to deeper soil layers or to groundwater bodies. Although ponding infiltration was applied in this study, the leaching risk for both applied solutes – Br and Brilliant Blue FCF – was rather small.

Development of an online preparation system for multitracer solutions

We have developed a new target-irradiation system for the online preparation of multitracer solutions, where the nuclear-reaction products recoiling out of the target are directly implanted in a solvent as a liquid catcher. A rapid online transportation of the solution has enabled highly efficient recovery of the multitracer solutions having even short-lived radioactive isotopes without any chemical treatments. It has been suggested that the collection efficiency depends on the chemical properties of the recoil elements.

Investigation of adsorption behaviour of fission products in soils using multitracer technique

The adsorption mechanism of fission products in soils has been investigated by using multitracer technique. The multitracer method used in this work contained fission products as carrier free isotopes which were prepared by neutron irradiation of 235U at Kyoto University Research Reactor. After the soil sample was mixed into the multitracer solution for two weeks, the solution was separated from soil sample. The gamma-ray spectrometry was carried out for the separated solution and the original multitracer solution which has not been mixed with soils. Distribution coefficients of fission products for soil samples were estimated by measured photoelectric peaks. In this work, distribution coefficients of ten elements for thirty typical Japanese soils were observed.

Multitracer Screening: Brain Delivery of Trace Elements by Eight Different Administration Methods

Trace elements are closely associated with the normal functioning of the brain. Therefore, it is important to determine how trace elements enter, accumulate, and are retained in the brain. Using the multitracer technique, which allows simultaneous tracing of many elements and comparison of their behavior under identical experimental conditions, we examined the influence of different administration methods, i.e., intravenous (IV), intraperitoneal (IP), intramuscular (IM), subcutaneous (SC), intracutaneous (IC), intranasal (IN), peroral (PO), and percutaneous (PC) administration, on the uptake of trace elements. A multitracer solution containing 16 radionuclides (i.e., 7Be, 46Sc, 48V, 51Cr, 54Mn, 59Fe, 56Co, 65Zn, 74As, 75Se, 83Rb, 85Sr, 88Y, 88Zr, 95mTc, and 103Ru) was used. The results indicated that the 83Rb brain uptake rate with intranasal administration was approximately twice those obtained with the other administration methods. This result indicated that a portion of Rb was delivered into the brain circumventing the blood circulation and that delivery could be accomplished mainly by olfactory transport. Multitracer screening of trace element delivery revealed differences in brain uptake pathways among administration methods.

Absorption behavior of technetium and rhenium through plant roots

The absorption behavior of technetium (Tc) and rhenium (Re) through plant roots was studied using nutrient solution culture. Radish samples, grown in culture solutions for 20-30 days in a greenhouse, were transferred into plastic vessels containing nutrient solutions contaminated with multitracer solutions including 95m Tc and 183 Re. The plant samples were grown individually for 1-7 days under laboratory conditions. The activities of radionuclides in nutrient solutions and oven-dried plant parts (roots, fleshy roots and leaves) were measured with Ge detecting systems. The concentrations of 95m Tc and 183 Re in the nutrient solutions after harvesting the plants were almost the same as those in the initial solution, though about 2 mL of the nutrient solution was lost per day per plant pot due to transpiration. Possibly, the radionuclides were taken up with water through the plant roots. The distributions of Tc and Re in the plants showed no differences, thus, soluble Tc and Re absorption mechanisms by plant samples were the same. It is suggested that Re could be used as a geochemical tracer for Tc in soil environments.

In Vivo Multitracer Analysis Technique: Screening of Radioactive Probes for Noninvasive Measurement of Physiological Functions in Experimental Animals

A novel screening experiment, to find radioactive probes for non-invasive measurements of physiological functions in experimental animals, was tested using the in vivo multitracer analysis technique. The details of the efficiency of the detector settings used in the in vivo multitracer analysis technique were examined by both computer simulations and practical measurements. Multiple radioactive isotopes, i.e. multitracer, were prepared by irradiating a silver foil target with a heavy ion beam at the RIKEN ring cyclotron. After chemical separation of the silver target, the multitracer was finally dissolved in isotonic citrate buffer. The multitracer solution was intravenously injected into rats. Using a gamma-ray detector equipped with a well-defined slit, the collimated gamma-rays from the upper abdomen of living rats were measured. After correction of detection efficiencies, it was possible to compare the distribution of radioactive elements between two groups of rats different in body weight. The in vivo measurement showed that the tissue substantial volume of the selenium-deficient (SeD) rat liver increased compared to normal rats. The possibility of a functional estimation of tissue/blood volume for living rats was proposed based on the characteristic in vivo distribution of 74As, 83Rb and 103Ru.

A multitracer study on the adsorption of 32 elements on a natural hematite (α-Fe2O3): effects of pH and fulvic acid

Abstract The distribution coefficients (K d ) of 32 elements from Na to Bi on a natural hematite (α-Fe 2 O 3 ) were determined at pH 4, 7, 9 and in the presence and absence of fulvic acid (FA) by using a multitracer technique and the batch method. The multitracer solution was prepared by irradiation of Th(NO 3 ) 4 with 40 Ar ion beam. The effects of pH and FA on the K d values of 32 elements on the natural hematite were studied. It was found that both the sequences of alkali elements and alkaline earth elements can be roughly explained in terms of chemical bond formation and ion hydration enthalpies. Though the various effects of pH and the positive and negative effects of FA on the K d values of 32 elements were found, the prevailing tendencies were the increase in K d value with increasing pH and the negative effect of FA on the adsorption of elements from Na to Bi at very low concentration and pH 7. The adsorption of lanthanides on the hematite against the atomic number exhibited approximately as a “W” figure, the peak was around the element Tb and the valley was around the elements Eu and Yb.

Preferential uptake of zinc, manganese, and rubidium in rat brain tumor

The search for radionuclides that can be an index of viability in proliferating cells is important for nuclear medicine diagnosis of brain tumors. On the basis of the finding that 65Zn is preferentially taken up in rat brain tumors, the uptake of various radionuclides was examined in rat brain tumor by using the multitracer technique. Male Fisher rats were intrahippocampally injected with C6 glioma cells. Fourteen days after implantation, the radioactive multitracer solution was injected into the tail vein of tumor-bearing rats. One hour after intravenous injection, the uptake of 65Zn, 83Rb and 54Mn was relatively high in C6 glioma of 15 radionuclides detected, and was much higher than in other brain regions and in the blood. It is likely that rubidium and manganese, in addition to zinc, are preferentially taken up by tumors in the brain.

Production of multitracers by 80 MeV/A 12C irradiation on thick gold foil

Multitracers were prepared by 80 MeV/A 12 C irradiation on thick gold foil at Heavy Ion Research Facility, Institute of Modern Physics, Lanzhou, China. The bulk gold was removed quantitatively from the multitracer solutions with a MIBK-HCl solution.

Uptakes of trace elements in Zn-deficient mice

A multitracer technique was used to obtain uptake rates of essential trace elements in various organs and tissues in Zn-deficient mice. A multitracer solution, containing more than 20 radioisotopes, was injected intraperitoneally into Zn-deficient state mice and control ones. Uptake rates of the radioisotopes were compared with concentrations of trace elements determined by instrumental neutron activation analysis (INAA) in order to study a specific metabolism of Zn and other essential trace elements, such as Mn, Co, Se, Rb, and Sr. The result suggests that Zn is supplied from bone to other organs and tissues and an increase in Co concentration in all organs and tissues depends on its chemical form, under the Z-deficient state.

Preparation of multitracer solution from silver target irradiated by 80 MeV/nucleon 20Ne ions

A convenient procedure for preparing a multitracer solution from irradiated silver foils by 80 MeV/nucleon 20Ne ions was developed. The carrier-free and salt-free solution containing 19 essential elements or trace elements for plant growth were prepared, and had been applied to study the regulation effect of metal ions on somatic embryogenesis of Lycium barbarum L.

A multitracer Study on the Adsorption of 36 Elements on a Silica: Effects of pH and Fulvic Acid

The distribution coefficients, Kd of 36 elements from Na to Bi on a silica were determined at pH 4, 7, 9 and in the absence and presence of fulvic acid (FA) using a multitracer technique. The multitracer solution was prepared by irradiation of Th(NO 3)4 with 40 Ar ion beam. The effects of pH and fulvic acid on the Kd values of 36 elements were studied. It was found that the sequences of the Kd values of alkali elements (Cs>Rb>K>Na) and of alkaline earth elements (Ba>Ca>Mg) in the absence of FA can be qualitatively explained in terms of chemical bond formati on and hydration. Various effects of pH and the negative or positive effect of FA on the adsorption of 36 elements were observed and a re probably related to the species of 36 elements in the aqueous solutions containing CO 3 2– , OH – , Cl – and FA. For most of the elements studied here the Kd values are increased with increasing pH and are decreased with adding FA.

Distribution of trace elements in normal and tumor-bearing mice using the multitracer technique.

A multitracer solution obtained from the nuclear reaction of selenium with 25-MeV/nucleon 40Ar ions was orally administered to normal and tumor-bearing Balb/c male mice. After 96 h, the mice were sacrificed and the elemental distribution was determined in various tissues, organs, and blood. The uptake of Na, Rb, Ga, Sc, V, Cr, Mn, Co, Fe, Zn, Y, Zr, Tc, Ru, Ag, and In in normal and, except for zinc, in tumor-bearing mice was simultaneously detected. Most elements were distributed in about the same manner in the skin and liver of animals in both groups. The distribution of Rb, Ga, V, Cr, Tc, and In showed little or no significant differences between the two study groups. The distribution of Na, Mn, Fe, Ag, Sc, and Co showed significant differences between normal and tumor-bearing mice. In the blood, spleen, and kidney of the normal mice, there was good absorption of Na, Mn, Fe, Ag, Co, and Zn. In the heart, these elements were well absorbed, except for Na and Mn.

The excretion of biotrace elements using the multitracer technique in tumour-bearing mice

A radioactive multitracer solution obtained from the nuclear reaction of selenium with 25 MeV/nucleon 40Ar ions was used for investigation of trace element excretion into the faeces and urine of cancerous mice. The excretion rates of 22 elements (Na, K, Rb, Mg, Ca, Sr, Ga, As, Sc, V, Cr, Mn, Co, Fe, Y, Zr, Mo, Nb, Tc, Ru, Ag and In) were simultaneously measured under strictly identical experimental conditions, in order to clarify the excretion behavior of these elements in cancerous mice. The faecal and urinary excretion rates of Mg, Sr, Ga, As, Sc, V, Cr, Mn, Co, Fe, Y, Zr, Nb, Ru and Mo in cancerous mice, showed the in highest value at 0–8 hours. The accumulative excretion of Ca, Mo, Y and Zr was decreased and Na, Fe, Mn and Co increased in tumour-bearing mice, when compared to normal mice.

Adsorption characteristics of 47 elements on a calcareous soil, a red earth and an alumina: a multitracer study

The distribution coefficients, K d of 47 elements from Na to Bi on a calcareous soil, a red earth and an alumina were, respectively, determined using a multitracer technique. The multitracer solution was prepared by irradiation of UO 2(NO 3) 2 with 40Ar ion beam. It was found that there is a common general trend of variation in K d for both soils and the alumina, i.e. all the shapes of plots of log K d versus electron binding energy ( I z ) are an ‘inverted V’, hence the important role of chemical interaction in the adsorption of trace inorganic cations, anions and neutral complexes on the soils and the oxides was demonstrated. For the alkali and alkaline earth elements, the common sequences of K d values on the three adsorbents were Na +<K +<Rb +<Cs + (except for Rb + on the alumina) and Mg 2+<Sr 2+<Ba 2+ and accord with the sequences of effective ionic radii or single ion hydration enthalpies.

Excretion of biotrace elements using the multitracer technique in mice

A radioactive multitracer solution obtained from the nuclear reaction of selenium with 25 MeV/nucleon40Ar ions was applied to the investigation of the trace elements behavior in feces and urine of mouse. The excretion rates of 23 elements, Na, K, Rb, Mg, Ca, Sr, Ga, As, Sc, V, Cr, Mn, Co, Fe, Zn, Y, Zr, Mo, Nb, Tc, Ru, Ag and In were simultaneously detected under strictly identical experimental conditions, in order to clarify the excretion behavior of the elements in mice. Fecal and urinary excretion rates of the elements in mice reached the highest value separately at 48 and 24 hours. The total excretion of Mo, Tc and Co within 96 hours were all larger, more than 60%. Accumulative excretion rates of Ca, Nb, Mg, Sr, V, Sc, Na, Cr, Fe, Ag, Mn and Zr were 60-30%. The total rates of Ru, K, As, Zn, Rb, Y, Ga and In were less than 30%, and low excretion. The main excretion pathway of Mo, Co, Mg, Fe and Ag was through urine, and Na, K, As and Rb were eliminated from the body also in urine. But fecal excretion of Tc, Nb, Sr, Y, Ru, and In were larger than urinary excretion, and Ca, Sc, Mn, Zr, Zn were eliminated from the body in feces.

Preparation of a radioactive multitracer solution from the reaction of selenium with 25 MeV nucleon40Ar ions

A radioactive multitracer solution was prepared from the reaction of selenium with 25 MeV/nucleon40Ar ions. Using off-line γ-ray spectrometry, the solution containing 47 radioactive isotopes of 24 elements was obtained. The nucleide with the longest half-life was22Na, and the shortest-lived one was81Rb8.

Adsorption Study of 47 Elements on Alumina and Bentonite Using a Multitracer Technique

Uranyl nitrate, UO2(NO3)2, was irradiated with a 25 MeV/nucleon 40Ar ion beam, and the target material removed by means of solvent extraction. A radioactive multitracer solution containing 47 elements and 83 nuclides free from carriers was thereby prepared. The multitracer solution was used in an adsorption study of 47 elements on alumina and bentonite. The distribution coefficients (Kd) of the 47 elements were simultaneously determined and correlated with the electron binding energy (Iz), and explained by the thermodynamic model for adsorption of James and Healy (1972).

The Excavation Project in the Grimsel Test Site: In Situ High-Resolution Gamma and Alpha Spectrometry of 60Co, 75Se, 113Sn, 152Eu, 235U, and 237Np/233Pa

ABSTRACTFull excavation of a water-conducting shear zone used for radionuclide migration experiments is part of a comprehensive study to physically determine the sites of in-situ radionuclide retardation. Prior to the excavation, multi-tracer solutions containing strongly sorbing y- and αemitting nuclides were injected into the shear zone and the water extracted was analyzed on-line using in situ, high-resolution y-spectrometry. In addition, water samples were collected to compare quantitatively the on-line data with subsequent laboratory measurements α- and γ- spectrometry) and also to analyze samples with activities below the detection limits of the in-situ analysis. The breakthrough curves indicate that Se had passed through the fracture with a velocity comparable to a conservatively behaving dye (uranine), but very strong retardation of Co. Eu and Sn was observed. The recoveries of these nuclides were found to be in the order of only a few percent when the dipole flow-field was interrupted about one month after radionuclide injection and the fracture was sealed off for excavation. Significant retardation was also obtained for the oxemitters U, Np and Pa. Almost identical breakthrough curves for these actinides were measured, suggesting a similar spatial distribution in the fracture at any given time.