International Journal of PIXE

This paper reviews the work carried out in a wide variety of scientific programmes with particular reference to broad beam PIXE and elemental mapping. The paper is illustrated with results from studies in Biomonitoring, Environmental Health and Human Diseases. In mammals and especially in humans, pollutants can be inhaled, ingested or contact mucosa and skin and be internalized, eventually entering the circulation and accumulating in tissues. Persistent exposure to environmental contaminants is known to cause pathologies that become chronic and debilitating. Human diseases often influence the amount of essential trace element in tissues and organs. Thus, organic fluids, organs and tissues, when accessible, may give significant data on the individual physiological status. Relating clinical, functional and morphological changes with variations in the elemental contents and other biochemical indicators, can significantly contribute to a better understanding of the mechanisms of disease and toxicity risks of certain pollutants.

The soil bacterium Cupriavidus metallidurans CH34 resist selenite by reducing it into the insoluble and less toxic elemental selenium. Two mechanisms of reduction of selenium oxides in C. metallidurans CH34 were highlighted: assimilation leading to organic species and detoxification leading to precipitation of selenite in nanoparticules of elemental selenium. The alkyl selenide detected as an intermediate product during assimilation of selenite or as the major accumulated chemical form during assimilation of selenate was identified as selenomethionine.

Soluble and membrane proteins were extracted from C. metallidurans CH34 submitted to selenium oxides challenge. After separation by SDS-PAGE, µPIXE analyses were used for Se identification and quantification at a micrometer scale. The profiles of Se distribution in the different samples suggest a non-specific incorporation of selenium probably reflecting the incorporation of selenomethionin in place of the naturally occurring methionin.

We report two medical applications of particle-induced X-ray emission (PIXE) as described below (1) Observation of biological events: The kinetics of trace elements during the initiation of radiation-induced apoptosis (RIA) was observed using a micro-PIXE and PIXE. RIA is a process in which irradiated cells commit suicide; it results in the removal of severely damaged and harmful cells. During RIA, cytochrome c is released from the mitochondria and reaches the nucleus, where it activates a Ca- or Mg-dependent endonuclease. We examined this phenomenon by using a micro-PIXE and PIXE. A high concentration of Fe was detected in the stroma of cells in the early apoptotic phase. We also observed accumulation of large amounts of Ca and Mg in the nucleus.

(2) Development of liquid-core microcapsules for novel cancer chemoradiotherapy: Currently, we are developing liquid-core (containing an anticancer drug) microcapsules that release their core content upon irradiation. These microcapsules will localize the anticancer drug within the irradiated field. The outer shell of these microcapsules is prepared from alginate and hyaluronic acid and polymerized by Fe, while the anticancer drug Paraplatin^® (carboplatin) containing Pt is the liquid core. The micro-PIXE revealed that these microcapsules released their core content after irradiation, and the amount of carboplatin released was measured by PIXE. More than 83.1% ± 8.3% of the microcapsules were ruptured, and the amount of carboplatin released was more than 81.2% ± 2.3%. Thus, the combination of radiotherapy and chemotherapy showed improved antitumor effects and a decrease in adverse effects because of drug localization.

A standard-free method for small lymph node and spleen samples taken from rats, and lymph node, esophagus, colon etc. taken from real patients has been developed in order to take measure to meet increasing demands for quantitative analyses of small amount of organs. It becomes possible to quantitatively analyze organ samples of less than 1 mg collected from small experimental animals and also from patients by biopsy, and accuracy and sensitivity of the method were examined by comparing the results with those obtained by a powdered-internal-standard method and a chemical-ashing method. It is found that the method is quite effective for estimating therapeutic effect of CDDP (Cisplatin) since it allows us to quantitatively evaluate uptake of CDDP into organs by analyzing small quantity of samples taken from actual patients by biopsy. It is expected that the method will become a powerful tool for studies not only in fundamental and clinical medicines but also on practical diagnosis and treatment.

Biomineralization has two types, biologically induced mineralization (BIM) and biologically controlled mineralization (BCM). Shark teeth is a typical representative of BCM. We have measured concentrations of fluorine and multi elements in shark teeth collected in the south of Japan. As a result, it was confirmed that the sample preparation method, which was established for the biological samples, is applicable to the shark teeth samples and the elemental concentration was obtained in good accuracy and reproducibility. Moreover, we clarified that the shark teeth is composed of Fluorapatite by the combination with X-ray Diffraction. Fluorine concentration is found to be 5500 µg/g in the shark teeth. We have 100 samples of Shark teeth and are planning on reporting the findings of a study with larger samples in the near future.

Otoliths are small structures in fish ears made of calcium carbonate which carry a record of the environment in which the fish live. Traditionally, in order to study their microchemistry by a scanning technique such as PIXE the otoliths have been either ground down by hand or thin sectioned to expose the otolith core. However this technique is subject to human error in judging the core position. In this study we have scanned successive layers of otoliths 50 and 100 µm apart by removing the otolith material in a lapping machine which can be set to a few µm precision. In one study by comparing data from otoliths from the two ears of a freshwater species we found that polishing by hand could miss the core and thus give misleading results as to the life cycle of the fish. In another example we showed detail in a marine species which could be used to build a three dimensional picture of the Sr distribution.

The level and change in concentration of trace elements in the fluids of a body may be the result and an evidence of alterations in life functions. In the search for trace element alterations in the human body it is necessary to know referenced values for as many elements as possible. In this work, Proton Induced X-ray Emission (PIXE) was used to study elemental concentrations in human blood serum of 30 healthy donors. The serum samples were obtained by centrifugation and were micro-pipetted on 10µm thick Nuclepore film for PIXE analysis. The elemental concentrations were calculated relative to an internal yttrium standard added during sample preparation. A total of 9 elements were measured (P, S, Cl, K, Ca, Fe, Cu, Zn and Br) in good agreement with literature data. The accuracy of the method was verified analysing reference serum samples from the NIPH-Québec (ICP04S-06 and ICP02S-05). A preliminary statistical analysis indicated a log-normal distribution only for Fe and Cu, while concentration data for the other elements followed the normal distributions. This result indicates the need for stronger statistical data set since the distribution of the elemental concentrations may be a criterion to access their role in biological functions.

An Artificial Neural System, ANS, has been designed to operate in the analysis of spectra obtained from a PIXE (Proton Induced X-ray Emissions) application. The special designed ANS was used in the calculation of the concentrations of the major elements in the samples. Neural systems using several feed-forward ANN of similar topology working in parallel were trained with error back propagation algorithm using sets of spectra of known elemental concentrations. Following the training phase of the neural networks, other PIXE spectra were analyzed with this methodology providing unknown elemental concentrations. ANS results were compared with results obtained by traditional computer codes like AXIL and GUPIX, obtaining correlations factors close to one. The rather short time required to process each spectrum, of the order of microseconds, allows fast analysis of a large number of samples. Here we present applications of ANS in the PIXE analyses of samples of organic nature like liver, gills and muscle from fishes. ANS results were compared with elemental concentrations obtained in a previous application where a single ANN was used for each analyzed element. PIXE analyses were performed at the Nuclear Physics Laboratory of the University of Chile, using 2.2 MeV proton beams provided by a Van de Graaff accelerator.

Recently, Nutrition Support Teams (NSTs) has been spreading throughout Japan. Nutritional assessment is important as an initial step among NST activities, since the patients can be identified based on this assessment whether they needs supports by NST or not. Serum trace element is one of the most useful and convenient nutritional indices. The aim of this study is to analyze the relationships between serum trace element values and clinical backgrounds in NST patients by data mining. The subjects of this study consisted of 29 NST patients who were admitted to our hospital between January 2005 and October 2006. Serum trace elements in patients were analyzed by PIXE method. The data were analyzed by a data mining software, i.e. "ICONS Miner" (Koden Industry Co., Ltd.). The significant "if-then rules" were extracted from the decision trees. The target variable of the decision trees is whether nutritional conditions of the patients are improved or not (Yes/No). The explanatory variables of the decision trees are the values in serum trace elements (Fe, Cu, Zn, Se, Mn) and TTR (transthyretin). The analyses demonstrated that the first node of the decision tree was Zn. Therefore, serum Zn value might be the most significant factor among these trace elements in estimating the improvement of nutritional conditions of the patients. In the decision, the second branch was the Fe value, and the Cu the third. The following significant "If-then rules" were extracted from the decision trees.

If-then rule 1: If serum Zn value >758.6 µg/l, then improvement of nutritional condition = Y. (1.00 = 9/9)

If-then rule 2: If serum Zn value ≤758.6 µg/l and Fe ≤653.2 µg/l and Cu ≤682.5 µg/l, then improvement of nutritional condition = Y. (1.00 = 5/5)

If-then rule 3: If serum Zn value ≤758.6 µg/l and Fe ≤653.2 µg/l and Cu >682.5 µg/l and Se >119.8 µg/l, then improvement of nutritional condition = Y. (1.00 = 3/3)

In conclusion, data mining analysis of serum trace elements was found to be an effective method in assessing the nutritional conditions in NST patients.

We are developing a µ-CT (micro computed tomography) which enables to observe the interior of living small insects. In this study, we applied the µ-CT to get CT images of the egg of drosophila, since the drosophila is applied to various basic studies, such as gene research. The interior of the living egg was observed and it was uniform. In the case of the dried egg, the shell and the interior structure were confirmed. This result comes from the growth of the living egg.

In order to shed light on the problem of atmospheric particulate matter (PM) pollution of roadside atmosphere in the Tokyo metropolitan area, we carried out high time-resolution and size-resolved sampling of PM at the Ikegami-Shincho crossing in Kawasaki City, Kanagawa Prefecture, Japan. Elemental and ionic composition analysis of those samples was then conducted. The research results are important for the physicochemical characterization of nano- to micrometer-size particles in roadside atmosphere, enabling detailed analysis of the various roadside emission sources and atmospheric processes.

Fine airborne particulate matter (FAPM) samples were collected at an urban site (19° 17' 33.47" N, 99° 38' 50.55" W and 2670 m asl) in Toluca, the capital city of the State of Mexico. The samples, a total of 143, were collected every third day from March 2006 to April 2007 on Teflon^® filters, with 24 h time resolution, using an U.S. EPA designation BGI PQ200 air sampler. The PIXE elemental analysis revealed the presence and the mass concentrations of 18 elements (S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Rb, Sr and Pb), thirteen of which (S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As) were consistently detected in most of the samples, and five of them (Se, Br, Rb, Sr and Pb) appeared occasionally. So, only those consistently detected were considered significant for the analysis. In order to verify whether the fine particulate concentrations complied with the FAPM Mexican Official Standard of 65 µg/m³, the filters were weighed before and after the sampling using a Cahn™ 33 microbalance with a 0.1 µg resolution, following the EPA procedures. The one year study was divided into three parts in accordance with the three climatic seasons identified in the city: dry-cold, dry-hot and rainy seasons. Results on the elemental and mass concentrations, as well as seasonal and time variations are presented. Correlations between concentrations of pairs of elements were also calculated, and the results obtained were found in good agreement with the enrichment factors determined for each season. Some pollution sources are suggested based on the analysis performed on the database and also from information obtained in a wide survey of the area. This paper presents the results of the first assessment of atmospheric pollution in this size of particle in this important city.

Indoor aerosols are directly affecting human lives. Especially aerosols in workshops, factories, and laboratories, where many chemical substances are used in treatment and production processes, might contain toxic elements: special care must be taken to alleviate air pollution and assure a clean breathing environment for the workers. For this study, size segregated aerosol particle sampling with a cascade impactor was performed in the machine workshop of Jožef Stefan Institute. The samples, collected during weekdays and weekend were analyzed with a microbeam facility at Tohoku University. Bulk PIXE analysis with scanning over the whole sample area was conducted along with multimodal microanalysis with microscopic scanning. Using bulk analysis, high concentrations of Pb and Ba were detected on weekend days, which was related to the removal of an old white paint from the furniture. On weekdays, concentrations of W and of soil origin elements increased, probably because of the machine operations and worker movements. At the same time high concentration of sulfur was detected. A microscopic multimodal analysis shows that it stems from a lubricant oil vapor. The combination of bulk and microanalysis of the size selected samples is an effective approach to aerosol characterization in the working environment.

Accurate quantifications of aerosol components are crucial to predict global atmospheric transport models. Recently developed International Monitoring System (IMS) network represents an opportunity to enhance comprehensive systematic aerosol observations on a global scale because it provides a global infrastructure. As such, a local pilot study utilizing several state-of-the-art instruments has been conducted at the peak of the Rattlesnake Mountain, Washington, USA, during three month periods (June-August) in 2003 to explore this opportunity. In this study, routine aerosol samples were collected using a 3-stage Cascade Impactor Beam Analyzer (0.07 to 2.5 µm) with time resolution about 6 hours on long Teflon strips while radionuclide aerosols were collected using Radionuclide aerosol sampler/analyzer (RASA) developed at Pacific Northwest National Laboratory. The elemental composition and hydrogen concentration were measured using proton induced x-ray emission (PIXE) and proton elastic scattering analysis (PESA), respectively. In addition, short and long-lived radionuclides that exist in nature were measured with same time resolution (6 hours) using RASA. In this method, high-resolution gamma-ray spectra were analyzed for radionuclide concentration. Combination of trace radioactive and non-radioactive element analysis in aerosols makes this investigation unique.

A large amount of yellow sand dust from Asian continent transported to Japan by air, affecting traffic, climate and human health. The yellow sand is known as a natural phenomenon, but it is mixed with anthropogenic aerosols over the industrial area in East Asia and causes environmental pollution. In addition, atmospheric turbid phenomena are occasionally observed in spring of recent years over western part of Japan. This phenomenon is caused by the increase in the amounts of fine particles. For a better comprehension of such turbid phenomena, we collected aerosols at Nagasaki. At the same time, particle number concentrations were observed by OPC. The samples were analyzed by an in-air PIXE system at Tohoku University. Time series of elemental concentrations and particle number concentration were obtained. It found that the yellow sand dust phenomenon occurred when coarse particles reached high concentrations, and elemental concentrations of Si, Ca, Fe, Pb and Hg showed similar variations along with that of coarse particles. On the other hand, when fumes or mists were observed, concentrations of fine particles were also correlated with concentrations of S and Zn.

The aim of this project is to apply particle induced X-ray emission analysis for the assessment of elemental variations in sediment samples collected after the 2004 Boxing Day tsunami event in Thailand. Samples were collected in June 2007 at two near-shore locations (C-1 and C-2) along the east coast of Phuket Island. The C-1 and C-2 sites received moderate and low impacts from the tsunami, respectively. For each location, sediment cores of 0.75m were collected. Sediment samples extracted from the cores were dried to constant weight at 60°C. All samples were prepared as a fine homogeneous powder by grinding and passing through a 125 µm sieve. Pellets were pressed from these samples. It was found by comparison with a suite of standard soils and sediments that the Si, Al and K contents of these moderate and low-impact Tsunami effected sediment samples are low by a factor of about two. Chlorine was detected at up to about 20000 ppm in both series with suggestions of a decrease at greater depth in the cores. Iron was detected in all samples, and was found at higher concentration in the samples from the C-1 site with a trend to higher concentration at greater depth. By contrast the two shallow C-2 samples showed a higher concentration than the deeper samples. Titanium was detected at the 1000–2000 ppm level in both series with no discernable depth trends.

Pytoremediation using an arsenic hyperaccumulator, Petris vittata L., has generated an increasing interest worldwide due to both environmentally sound and cost effectiveness. However the mechanism of arsenic accumulation by this fern is not clear at this time. This study examined the uptake of arsenate (As(V)) and arsenite (As(III)) by a hydroponic culture of Pteris vittata using both in-air submilli-PIXE for different parts of the fern and in-air micro-PIXE for the tissue cells. These PIXE analysis systems used 3 MeV proton beams from a 4.5-MV single-ended Dynamitron accelerator at Tohoku University, Japan. The fern took up both arsenate and arsenite from hydroponic solutions which were spiked with 50 mg of arsenic per litter. Final amount of arsenic accumulation in the fern is 1,500 mg per kg (wet weight) of the plant biomass in arsenite treatment and 1,100 mg per kg in arsenate treatment. Arsenic accumulation was not observed at the root parts of the ferns. The in-vivo mapping of elements by submilli-PIXE analyses on the fern laminas showed the arsenic accumulation in the edges of a pinna. The micro-PIXE analyses revealed arsenic maps homogeneously distributed in cells of the lamina, stem and rhizome of the fern. These results indicate that arsenic, both arsenate and arsenite in a contaminated medium are translocated quickly from roots to fronds of Pteris vittata, and distributes homogeneously into tissue cells of the fern laminas.

Elemental concentrations in Chinese peanuts have been analyzed and compared with those in Japanese peanuts by means of a PIXE (Particle Induced X-ray Emission) technique with an internal standard method to investigate traces of residual agricultural chemicals or toxic elements in them because frequent detection of excessive agrochemical residues in food imported from China has posed serious health concerns to Japanese people. We prepared the samples by separating the peanut seed into two cotyledons (seed leaves) and an embryo. Significant differences in elemental concentrations between Chinese and Japanese peanuts have not been observed as far as the peanut seeds used in the present measurement are concerned. The concentrations of the several elements in the embryo are higher than those in the cotyledon.

PIXE is used for the elemental analysis of CCA treated timber samples, because of the simplicity of sample preparation, in-situ measurement of metal distribution, high sensitivity and the large number of samples which can be measured in a short time (typically less than 15 min per sample). The concentrations of Cr, Cu and As in the thin sections of treated poles from a vineyard were measured at 2 cm intervals from the centre of the pole. PIXE analysis indicated that in the case of fresh CCA treated timber the concentrations of Cu, Cr and As varied little with depth. In aged timber, the concentrations increased from the centre of the pole to the surface, indicating horizontal migration of these elements. The increase was greater for aged poles than for freshly treated poles, indicating surface migration of the CCA chemical with weathering. This was supported by data obtained in leaching experiments that indicated elevated concentrations of these metals in the extractants.

In recent years, the self-sufficiency ratio of food in Japan has gradually decreased and 60% of foods are now imported from abroad. Japanese people rely strongly upon imported food and should take care of their safety, but what is happening now is that soil pollution in country of origin grows into a serious problem and can affect imported food. Umeboshi is one of the traditional pickled food in Japan and very popular. In the case of umeboshi, more than 65% of it is imported. We analyzed imported umeboshi and domestic ones by using in-air PIXE system and submili-PIXE camera at Tohoku University. In this experiment, the concentrations of toxic heavy metals such as As, Cd, Hg and Pb were lower than standard values given by a food hygiene law. Concentrations of elements heavier than Ca show similar trend among each sample. On the other hand, lighter elements than Ca show large differences, which is related to food coloring or processing technique.

The contamination of heavy metals in food becomes a serious problem. We analyzed oolong tea from different production areas by PIXE using very simple sample preparation and examined trace elements contained in these samples. From the results of this experiment, we could know oolong tea which analyzed in this experiment contains various minerals such as K, Ca, P, S, Cl, Fe, Mn, Cu and Cr but not toxic element of As which detection limit of PIXE was lower than the standard values given by the food hygiene law in Japan.

For years, scientists have developed several new techniques to read texts of Herculaneum scrolls without destroying them. Recently, the use of a custom built high-resolution CT scanner was proposed to scan and then virtually unroll the scrolls for reading. Identification of any unique chemical signatures in the ancient ink would allow better calibration of the CT scanner to improve the chances of resolving the ink from the burned papyrus background. To support this effort, we carried out one pilot study to see whether the composition of the ink can be obtained from an ancient scroll sample using PIXE technique. PIXE data were collected and analyzed in two different regions of the ancient scroll sample (ink and blank regions). This preliminary work shows that elemental distributions from the ink used in this scroll mainly contained Al, Fe and Ti as well as minor trace amounts of Cr, Cu and Zn.