[Production of a leaf electroscope having separators and proposal of an experiment using the diagnostic X-ray equipment].

In order to use the practical training for beginners by means of a diagnostic X-ray, a leaf electroscope (which has a function to explain the ionization) was newly produced. The X-ray was introduced to the air in the electroscope having the electric charged leaf (the leaf was open at this time). The air irradiated by the X-ray was ionized, and then the produced ions or electrons were combined with charges on the leaf. As a result, the leaf was closed. In this way, experimenters can know the production and/or movement of charges by observing the conditions of the leaf. For the developed leaf electroscope, we added separators to divide the inner space into two regions; one is the irradiation area and the other is the space including the leaf. The separators have through-holes and/or a metallic mesh in order to create various conditions. In this paper, we described that different experimental results based on uses of the different separators were reflected in the ionization of the irradiated air and in the interaction of the charged particles. We summarized that the practical training by means of the developed leaf electroscope was valuable to educate beginners.

[Proposal of a cloud chamber experiment using diagnostic X-ray apparatus and an analysis assisted by a simulation code].

A cloud chamber is a radiation detector that can visualize the tracks of charged particles. In this study, we developed a middle-type cloud chamber for use in practical training using a diagnostic X-ray apparatus. Because our cloud chamber has a heater to vaporize ethanol and features antifogging glass, it is possible to observe the vapor trails for a long time without the need for fine adjustments. X-rays with a tube voltage of 40 kV or of 120 kV (with a 21-mm aluminum filter) were irradiated at the chamber and the various phenomena were observed. We explain these phenomena in terms of the range of electrons and/or interactions between X-rays and matter and conclude that our analysis is consistent with analysis using the Monte Carlo simulation code EGS5.

[Basic research for development of pinhole camera using a Geiger Mueller counter].

To visualize the scattered X-ray distribution in the diagnosis domain, we examined whether a Geiger Mueller (GM) counter could be applied to a pinhole camera as an X-ray detector. The GM counter detects radiation at certain detection points. To obtain two-dimensional images using the GM counter, the detector needs to be moved two-dimensionally. We constructed an apparatus using industrial actuators to move the detector. To investigate the usability of the developed apparatus, the scattered X-rays from the phantom were measured using the GM counter. The images obtained were then compared with those measured using the phosphor plate. Our results demonstrated that the GM counter can detect low count-rate radiation, but further research will be needed to obtain clear two-dimensional images. In this paper, we propose that the GM counter can be used as a complementary detector to a phosphor plate.

[Fabrication of a visualization equipment for scattered X-rays in the diagnosis domain and proposal of a practical training].

We have built equipment that can visualize the angle distributions of scattered X-rays. The main body of the equipment is made of a lead-shielded box 340 mm long, 300 mm wide and 270 mm high. The collimated X-rays are introduced into the equipment from the front face, then scattered by the sample located in the center of the equipment. The X-rays scattering toward the upper side are detected by the phosphor plate. To verify the usability of the equipment, an experiment using diagnostic X-rays was carried out. X-rays with a tube voltage of 100 kV were narrowed down to 6 mm(phi) and a 2 mm-thick acrylic sample was irradiated. The experimental conditions with a tube current-time product of 300 mAs to 1500 mAs proved appropriate for obtaining suitable images on a 10 inch x 12 inch phosphor plate. The obtained images were analyzed using ImageJ. The experimental values were in good agreement with the theoretical distribution calculated by Klein and Nishina. Because the distribution of the scattered X-rays can be visualized in relatively simple experiments using the developed equipment, it is hoped that it will be of use for the practical training of beginners.

[An experiment to estimate locations of radioisotopes producing black spots on medical images].

Caused by the accident of nuclear power plants in the Fukushima at 2011, many radioisotopes (RI) were diffused to the environment. As a result, X-ray detectors were stained with RIs and black spots appeared on the medical images. Using the RI of (134)Cs and (137)Cs, black spots which appeared on the photostimulable phosphor plate (X-ray detector) were reproduced experimentally. The aim of this study is the following two points; firstly, to clarify the relationship between long-time irradiations of RI and fading effect, and secondly, to clarify the positional relationship between the RI sources and the X-ray detector based on irradiation times of RI. For the latter experiment, the samples were made by spraying water (containing the RI) in order to reproduce small point sources. Then, the sources were placed on the photostimulable phosphor plate or on the cassette, and corresponding images with different irradiation times were taken. The black spots could be reproduced with the condition, in which sources were directly adhered to the photostimulable phosphor plate. We observed the black spots when sources were placed on the cassette for one week. Based on the result, we summarized that the RI which are directly adhered on the photostimulable phosphor plate may produce the black spots.

[Estimation of activities caused by black spots in digital radiography systems: analysis of black spots by the low concentrate radioisotopes adhered directly to the surface of the phosphor plate].

Because of an accident of the nuclear power plants in the Fukushima, many radioisotopes (RI) have been diffused to the environment. As a result, black spots were appearing on the medical images which were taken by the phosphor plate. The aim of this study is to evaluate the activity (Bq) of radioactive contaminated IP based on the experiment using RI. The radioactive material ((134)Cs and/or (137)Cs) in the form of liquid was dropped on filter paper (25 mm(2)), and radioactive sources having 40-240 Bq activities were made. These sources were closely attached to the IP with irradiation times of 2-22 h. Then, we obtained the relationship between pixel values and products of activities and irradiation times. Using these relationships, we evaluated the activity in the contaminated IP. The evaluated value of approximately 7 Bq was in good agreement with a value which was inhered in a chemical wiper used for the decontamination of the IP. Based on the results, we summarized that almost all black spots were created by the RI adhered directly to the IP.