Local variation of soil contamination with radioactive cesium at a farm in Fukushima

Radioactive cesium concentration in soil was measured at 27 sections with 5 points per section, and surface dose of ground was measured at 10 sections with 13 points per section at a farm in Fukushima to assess local variation of soil contamination with radioactive cesium. As for the cesium in soil, averages of the coefficient of variance (CV) and the maximum/minimum ratio in each section were 49% and 4.9, respectively. As for the surface dose, average of its CV in each section was 20% and the maximum/minimum ratio reached a maximum of 3.0. These findings suggest that exact evaluation of soil contamination with cesium is difficult. Small changes or differences in soil contamination may not be detected in studies of the environmental radioactivity

Quantitative Measurement of Electron Density in Method of Dual-Energy X-Ray CT

The electron density is indispensable to the treatment planning for heavy-ion radiotherapy, so that the precise measurement of that is important for advancing radiotherapy. Usually the electron density for the radiotherapy is derived from an image based on CT number by conventional CT. CT number include ambiguilty due to the beam hardening. In a method of dual-energy x-ray CT, the information on an electron density can be obtained directly using monochromatic x-rays. The precision of the electron density was experimentally proved to be about 1%.The 8th Conference on Biology and Synchrotron Radiatio

Study on Dual-Energy X-ray Computed Tomography using Synchrotron Radiation

The electron density is one of the most important element for thetreatment planning in the radiotherapy, because this information isused for the range estimation of the heavy-ion beam. Although theelectron density has been converted from CT number obtained byconventional x-ray computed tomography(CT) at present, it is notenough for the more detailed planning due to uncertainties that arisefrom the beam hardening effect and the conversion process. In order totake more accurate electron density, we have developed the dual-energyx-ray CT system using the synchrotron radiation. The dual-energy x-rayCT has no influence of the beam hardening because of scanning usingmonochromatic x-rays. The experiments were carried out using twomonochromatic x-rays at the monochromatic beam-lines in KEK-AR andSPring-8. As the result, it was succeeded that the electron densitiesby the dual-energy x-ray CT were agreement with the theoretical valueswith the accuracy less than 1% for some materials. In addition, as theapplication for more practical use in diagnostics, the CT using themixture of main and harmonics x-rays produced by the monochromator hasbeen investigated. From the preliminary experiments, it was found thatthe accuracy was as same as that by dual-energy x-ray CT. We willdescribe the dual-energy x-ray CT system and discuss thequantitativity and the image characteristic for this system.Eighth International Conference on Synchrotron Radiation Instrumentatio

Predicting Metastatic Potential of Gastrointestinal Stromal Tumors in Dog by Ultrasonography

Gastrointestinal stromal tumor (GIST), a mesenchymal neoplasm affecting the gastrointestinal tract, shows a variety of clinical behaviors from inactive benign to aggressive malignant in dogs. In this study, the feasibility of using clinically significant ultrasonographic features to predict the metastatic potential of canine GIST was investigated through comparison with actual metastatic incidence and findings of malignancy obtained by postoperative pathological examination. Ultrasonographic features, including large tumor size, irregular margin and heterogeneous internal echogenicity with large hypoechoic areas, related closely with the presence of metastasis as well as a high-risk ranking by the human classification system according to pathological findings. Based on these ultrasonographic features, the potential of metastasis in canine GIST could be preoperatively predicted

L-Band Electron Paramagnetic Resonance Tooth Dosimetry Applied to Affected Cattle Teeth in Fukushima

We applied a non-destructive tooth dosimetry technique using L-band electron paramagnetic resonance (EPR) to assess radiation doses in cattle due to the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, which occurred 10 years ago. The radiation exposure of cattle in the area affected by the FDNPS accident was estimated retrospectively with X-band and L-band EPR devices. Characteristic radiation-induced EPR signals were obtained from the teeth of the cattle in Fukushima, confirming their exposure. The estimated doses to the teeth were found to be consistent with the dose trends estimated for individual cows, while considerable uncertainties were seen in the doses of some tooth samples. This variation might be due to errors in the accuracy of the method but also might reflect the actual exposure because the cattle may have been exposed to higher areas of radioactivity in their quest for food and/or due to irradiation from absorption of the isotopes with localization in or near the teeth. However, at a minimum, these results confirm that L-band EPR can be used for non-destructive qualitative assessment of radiation exposure to animals using their teeth, which could be very valuable. Possible causes of the uncertainties should be investigated to enhance the value of the use of this technique