International Journal of PIXE

A precise target positioning system based on a laser position sensor was developed for a high-efficiency wavelength dispersive PIXE analysis. The absolute position and the target surface profile were clearly observed using this position sensor, which was rigidly connected to the target vacuum chamber. By using a thin proton beam (width = 2 mm) and a small target (width = 1 mm), the optimum target position for the measurement of chlorine (Cl) Kβ X-ray could be determined from X-ray detection yields measured at various target positions. We found that the relationship between the X-ray detection yield and the target position can be explained by the target size as well as the incident proton beam width. After precise adjustment of the target position using the above system, target samples with two different Cl compounds, NaCl and NH₄Cl, were successfully distinguished from the difference in the measured profiles of Kβ X-ray spectra.

A microbeam system was installed at Dynamitron laboratory at Tohoku University and is applicable to simultaneous in-air/in-vacuum PIXE, RBS, SE, and STIM analyses, and 3D µ-CT. Insufficient beam brightness of the source and field contamination of the microbeam line restricted spatial resolution. In order to improve the performance of Tohoku microbeam system, optimization and modification of the ion source and microbeam system were performed. By the modification of the system, the beam brightness of the system was increased to 1.0 pA·µm^-2·mrad^-2·MeV^-1 at the half divergence of 0.2 mrad. Considering the brightness and the magnification, obtainable target current will be 200 and 900 pA for beam spot sizes of 1.0 × 1.0 and 2.0 × 2.0 µm², respectively. The modification of the source meets both the lifetime and the performance. The parasitic field contamination of the system was reduced down to less than 0.5 % by replacing the beam scanner chamber and a part of beam duct. Both resolution and beam currents are sufficient for our applications of in-air/in-vacuum PIXE, RBS, SE, and STIM analyses and 3D PIXE-µ-CT.

For muti-elemental analysis, various standards are used to quantify the elements consists of environmental and biological samples. In this paper two different configuration standards, pressed powders and thin section standards, were assessed for their purpose as standards by conventional and micro-PIXE analysis. Homogeneity of manganese, iron, zinc (Zn), copper and yttrium added to pressed powder standard materials were validated and the relative standard deviation (RSD) of the X-ray intensity of the standards was <10% within the range, 62.5–250 µg/g. We established linear relationships between the metal concentration and the specific X-ray intensity of standards containing up to 250 µg/g of these metals. A homogenous distribution of Zn added to thin section standard materials was also confirmed by 10-µm-step scanning of the standard within the range, 50–250 µg/g (RSD ~ 10%). The calibration line between the X-ray intensity obtained from a 10-µm² area and the metal concentration was acceptable.

The radiation-induced releasing of the liquid-core of the microcapsules was improved using H₂O₂, which produced O₂ generation of H₂O₂ after irradiation. Further, we tested whether these microcapsules enhanced the antitumor effects and decreased the adverse effects in vivo in C3He/J mice. The capsules were produced by spraying a mixture of 3.0% hyaluronic acid, 2.0% alginate, 3.0% H₂O₂, and 0.3 mmol of carboplatin on a mixture of 0.3 molFeCl₂ and 0.15 molCaCl₂. The microcapsules were subcutaneously injected into MM46 tumors that had been inoculated in the left hind legs of C3He/J mice. The radiotherapy comprised tumor irradiation with 10 Gy or 20 Gy ⁶⁰Co. The antitumor effect of the microcapsules was tested by measuring tumor size and monitoring tumor growth. Three types of adverse effects were considered: fuzzy hair, loss of body weight, and death. The size of the capsule size was 23 ± 2.4 µmɸ and that of the liquid core, 20.2 ± 2.2 µmɸ. The injected microcapsules localized drugs around the tumor. The production of O₂ by radiation increased the release of carboplatin from the microcapsules. The antitumor effects of radiation, carboplatin, and released oxygen were synergistic. Localization of the carboplatin decreased its adverse effects. However, the H₂O₂ caused ulceration of the skin in the treated area. The use of our microcapsules enhanced the antitumor effects and decreased the adverse effects of carboplatin. However, the skin-ulceration caused by H₂O₂ must be considered before these microcapsules can be used clinically.

Highly functionalized drugs delivered via a drug delivery system are expected to have less side effects and higher accumulation rates compared to conventional anticancer drugs. An understanding of the kinetics of drugs contained within a delivery system is necessary to obtain the maximum therapeutic effect. We performed micro-elemental analysis of human pancreatic cancer cells treated with cis-diamminedichloroplatinum(II) (CDDP)-containing polymeric micelles. The results showed that the platinum signals were distributed inside the cellular nuclei and the cytoplasm indicating that CDDP was delivered into the cells. The results from this study will be useful for designing an optimum carrier for platinum-containing anticancer drugs.

In a biological body, trace elements including metallic elements play important roles. Knowing their spatial distribution and amounts, we can find out some relations among a physiological role of the trace element in vivo, the function, and the disease appearance. In this study, we investigated a method to obtain elemental distributions in whole brain slice taken from mental disease model mice and control mice using in-air submilli-PIXE camera at Tohoku University. We administered 5-BrdU that was the analogue of the thymidine as a marker to detect a new born cell in especially the dentate gyrus of the hippocampus. We obtained the elemental distributions of the whole brain of subject and control mice. From elemental distributions of the brain of a mental disease model mouse, a brain contained light elements, such as P, S, Cl and K, which were uniformly distributed over the brain. Fe was accumulated in the specific area of brain. Elemental concentration of Fe was more than 10 times higher than that in the other. However, the accumulation of iron in brain slices was not observed in those of control mice. Zn is accumulated in the vicinity in hippocampus. Br was uniformly distributed over the brain. The submilli-PIXE camera will provide a powerful tool for this research.

The early life environment has widespread consequences for later health and disease. To prevent the disease in later life, the assessment of fetal environment is very important. In Japan, birthweight has fallen rapidly during recent two decades. The reduction of birthweight represents reduced fetal nutrition. Deciduous tooth enamel contains pre- and postnatal enamel and its chemical composition reflects the status of metabolism of trace elements during formation period. Deciduous tooth enamel is considered to be a suitable indicator of trace elements exposure in utero. We applied micro-PIXE analysis to investigate the trace elemental content in deciduous tooth enamel. Two deciduous canines from one healthy Japanese boy were used for this study. The enamel section including pre-and postnatal enamel was prepared for micro-PIXE analysis. Five trace elements (Na, Mg, Cl, Zn, and Sr) were detected in the scanning area of tooth. The distribution profiles of 5 elements were obtained as X-ray maps. The distribution profiles of zinc and chlorine were specific, and showed higher concentration in surface enamel. No elements showed different profiles of X-ray maps between pre-and postnatal enamel in this sample. The results of this study suggested that micro-PIXE analysis would be able to estimate the trace elements in prenatal and postnatal enamel, respectively.

Consumption of coal is increasing as an alternative for petroleum. During the process, coal fly ash particles are produced and are disposed as an industrial waste. Coal ash contains toxic heavy metals, which leads to a concern about the possibility of leakage into environment. The spatial distribution and chemical form as well as elemental concentration of the toxic elements in the particles are important factors in assessing the leakage into the environment. In this study, we analyzed individual coal fly ash particles with 1 µm spatial resolution by using the simultaneous micro-PIXE/RBS/off-axis STIM system at Tohoku University. Eighty fly ash particles were analyzed. The particles are mainly composed of O, Si and Al and estimated as dioxide. Hydrogen and carbon are not observed in these particles. V, Zn, Sr, Cu, Ni, Mn, Cr and As are contained in the particles. The content of each element is quite different in each particle. These elements are distributed homogeneously. As an exception, Al, Ca, Fe, Zn, As and Zr are distributed on the surface of the particle which might be related to the combustion process.