International Journal of PIXE

In order to investigate the validity of the cancer development, the presence of active oxygen need to be taken into account since active oxygen participates in the initiation and promotion of cancer. However, it is impossible to measure the amount of active oxygen in vivo directly. Therefore, the levels of trace elements such as Zn, Cu and Mn in enzyme which eliminates active oxygen were measured at each stage of cancer development by PIXE. The large differences between the normal mucosa and colonic adenoma in the amount of Zn, Cu and Mn within the enzyme eliminating free radicals were observed. There was a significant relationship among trace element levels, active oxygen and the development of tumor in connection with the levels of Zinc and Copper.

Trace elements present in bottled mineral water have been studied by PIXE and ICP-MS. Samples from ten different brands of bottled mineral water were prepared by preconcentration techniques. Measurements were carried out using the 2 MeV proton beam obtained from 3 MV Tandem pelletron accelerator at the Institute of Physics, Bhubaneswar. Our results are compared with Indian standard packaged natural mineral water specifications, World Health Organisation (WHO) and European guidelines for drinking water standards. Concentration of aluminium was found to be more in one of the brands. In general, our results are comparable to the above standards.

A Standard-free method, which has been developed by ourselves, was applied to powdered biomedical samples to which a conventional method of quantitative analysis, such as an internal standard method, can not be successfully applied. First, NIST-Bovine liver and NIES-rice targets, which are powdered as they are, were analyzed by the standard-free method and correct quantitative values of potassium and manganese concentration, which are consistent with those obtained by the conventional internal standard method, were obtained. Furthermore, for relative values of concentration of various elements, almost the best results we have ever had were obtained. Next, the present method has been successfully applied to a hard tissue sample (mouse bone), which is quite difficult to be accurately analyzed by the internal standard method. In order to solve the problem of falling off of powdered samples from a backing film, a carbon tape with an adhesive agent has been examined and found to be quite effective.

PIXE (Particle Induced X-ray Emission), mainly Proton Induced X-ray Emission, has been developed into a well established technique for elemental analysis, especially for trace elemental analysis down to ppm or even ppb level. Nuclear Microprobe is a quickly developing technique around the world for 2 dimensional or even 3 dimensional element analysis if several nuclear analytical techniques, such as Rutherford backscattering spectrometry (RBS) can be available at the same time. The present resolution of NMP can be down to less than 1μm.

To thick target analysis, i.e., the energy loss effect and the consequent X-ray cross section Change with the depth can not be neglected, therefore we have to consider the process of particle interactions with atoms in detail. In this article, NMP (Nuclear Micro-Probe) and micro-PIXE analysis of thick target, which are mainly involved into the process of ions interaction with atoms, are reviewed on the basis of work what we have done at Fudan University. The software package TSPIXE (PIXE analysis of Thick Sample), which includes different versions for different applications, developed at Fudan University for quantitative analysis of thick target and simulation of PIXE and micro-PIXE spectra are described and its performance is demonstrated too. The TSPIXE package, which includes TSPIXE version I, version II, version III and TSμPIXE, was written in FORTRAN and C computer language and can be run at PC computer under MSDOS or WINDOWS environment. From the different demonstrations and applications we can see the package is very useful to quantitative analysis of thick samples and to understand the relationships between elemental X-ray intensity distributions and concentration distributions, sample structure, beam size and etc.

A position-sensitive proportional counter (PSPC) for a wavelength-dispersive crystal spectrometer system has been constructed for high-resolution PIKE experiments in atmospheric air. This PSPC has seven resistive wire anodes. Each anode operates as one PSPC. Pulses from the anodes are converted into digital signals with a 512 × 7 channel charge-division analyzer. We can simultaneously obtain seven spectra. A computer software converts this 2D data set into one spectrum after adjusting the offset channels and conversion factors. The spatial resolution of this detector is somewhat larger than that of our single PSPC system previously developed, while its counting efficiency is seven times higher than that of the single one.

PIXE technique has been applied to quantitative analysis of thorium and uranium ions in drainage from a radioisotope laboratory of Tohoku University. Two kinds of targets were prepared and analyzed with an in-air vertical PIXE system of 3 MeV protons. The concentrations of thorium and uranium higher than 40 ppb were easily determined by 3-μC irradiation on targets which are made from a 0.12-ml solution containing Ga-internal standard evaporated on a hand-made polycarbonate film. Uranium(VI) ions in a 25-ml sample were preconcentrated into a thin uniform target containing Zr or Pd as an internal standard by means of dibenzyldithiocarbamate complexation with subsequent condensation into dibenzylidene-D-sorbitol gels, and low concentration of 10 ppb was precisely determined by PIXE measurement. This method does not work for concentrating thorium ions. The PIXE analysis for these two kinds of targets has good sensitivity and precision enough to determine concentrations of thorium and uranium lower than their permissible concentration limits in drainage from a radioisotope laboratory.

Silicon levels in dialysis patients are markedly increased. Using PIXE we determined the relationship between silicon concentration and creatinine clearance in 30 samples. Urine silicon concentration were significantly correlated to creatinine clearance (p<0.001). And also serum silicon concentration were significantly correlated to creatinine clearance (p<0.0001).

Elemental concentrations of human gallstones were determined by PIXE method. Gallstone samples analyzed in this report are classified into cholesterol gallstone (pure cholesterol stone and mixed stone) and pigment gallstone (black stone and calcium bilirubinate stone). The targets were prepared by paste spreading method previously reported, which enable us to determine also volatile elements, such as halogen atoms, Hg and so on, under acidic condition. Concentrations of 17 kinds of elements were determined and characteristic distributions are presented for each type of gallstone. Ca values are the highest among of them in all types of gallstones. Pigment gallstones contain significantly higher concentrations of 9 kinds of elements (Na, Mg, S, Cl, Ca, Mn, Fe, Cu, Zn) than cholesterol gallstones. Concentrations of S, Fe, and Zn in black stones are significantly higher than those in calcium bilirubinate stones. Almost all elements contained in the samples can be determined by PIXE method, and it is supposed that the elements or some of them affect formation of gallstones and their pigment. Some samples of the pigment gallstones include I, Hg, and Pb.