[en] Microdosimetric spectra were measured at a new therapy facility to obtain the microdosimetric parameters, our result indicates they were rapidly changed by the filtration with heavy water. (author)

[en] Single event spectra of a clinical carbon beam have been measured by an ultra-miniature tissue-equivalent proportional counter (UMC). In order to cover the energy range of the Bragg peak, the incident energy of the carbon beam was degraded by aluminium plates. Single event spectra for carbon-events incident to the UMC were analysed and selected at several carbon energies using thin scintillation counters. It was found that the dose weighted lineal energy distributions have a doublet peak structure due to incident carbon beam and fragment contributions. (author)

[en] We have measured the microdosimetric spectra of a Senographe 600T mammography machine employing an Mo target with 0.8 mm Be inherent filtration and 0.03 mm Mo added filtration, giving a half-value layer of 0.35 mm Al at 28 kVp. In all of our measurements a large collimator producing a 24cmx30cm field at 65 cm was used. Two different phantom compositions differing in the ratio of adipose to fibroglandular tissue were compared, using simulated breast material from Nuclear Associates. Spectra were taken at various depths and locations in simulated breasts of 3, 4 and 5 cm thickness. The detector used was a miniature proportional counter having outer dimensions of 5cmx1.8cm diameter, with a sensitive volume 0.5mmx0.5mm. The small dimensions of the counter and the cavity allowed total embedding in the breast material with minimal disturbance of the photon and secondary electron spectrum. Our results show that there can be changes in the radiation quality amounting to as much as 17% (as measured by the dose mean lineal energy, y_D) between breasts of different thickness, at the same relative position within the breast. There is little difference due to breast composition. (author)

[en] Microdosimetric spectra were measured in order to gain the microdosimetric parameters of some epithermal neutron fields. Changes in dose mean lineal energy Y_D as a function of depth of heavy water showed a trend of softening with heavy water of the beam. The neutron absorbed dose was obtained by using the frequency of mean lineal energy. Results show good agreement with measurements with the activation method using gold foil. This study demonstrated how microdosimetric parameters change in radiation quality as a function of heavy water depth. (author)

[en] A heavy water installation at the Kyoto University Reactor (KUR) is used for the boron neutron capture therapy. The contributions of boron neutron capture reaction to the dose are required for the evaluation of the boron neutron capture therapy in relation to the biological effectiveness. The radiation therapy fields are measured by a technique of micro-dosimetry. Three types of tissue equivalent-proportional counter are used for measurement of the radiation therapy fields; a LET counter with wall containing boron for thermal neutrons, a LET counter with wall containing no boron for epithermal neutrons, and a helical wire proportional counter with carbon wall for gamma rays. Irradiations of the counters are carried out in the neutron capture therapy fields with two modes, a thermal neutron mode and an epithermal neutron mode. An acrylic plate is used for human body phantom. Each energy spectrum in the counters is measured at depth 6.7 mm in the phantom by multi-channel analyzer. The energy spectra in three types of the counters show that most of neutron energy transfers to the effects of ⁴He(1.49 MeV) and ⁷Li(0.85 MeV) following to thermal neutron capture reactions of ¹⁰B in the wall. (M. Suetake)

[en] High-spin states in ⁸³Zr have been studied via the ⁵⁸Ni(²⁸Si,2pn)⁸³Zr reaction using in-beam gamma-ray spectroscopy techniques. Measurements of multiple (charged-particle)γ-coincidence, nγγ-coincidence, gamma-ray excitation function and gamma-ray angular distribution were performed. These experimental results established a positive-parity band based on the g_9/2 neutron shell and two negative-partity bands built on the 1/2^- and 5/2^- states. The existence of the two low-lying isomeric states with the half-lives of 1.8 → 0.1 and 0.50 → 0.25 μs was also revealed. It was found that each band exhibits a rotational-lie character and the structures are similar to those of neighboring N = 43 isotones, whereas change of neutron number leads to abrupt change at N = 43 ≅ 45 with regard to the level structure of odd-Zr isotopes. (orig.)

[en] New neutron-deficient isotopes of ^83,85Nb were identified with the aid of results of the in-beam spectroscopic studies of ^83,85Zr. The activities were generated by the ⁵⁸Ni(²⁸Si, p2n)⁸³Nb, ⁶⁰Ni(²⁸Si, p2n)⁸⁵Nb and ⁵⁸Ni(³²S, αp)⁸⁵Nb, reactions, and the radiations were measured by means of βγ-coincidence. Then the half-lives of ⁸³Nb and ⁸⁵Nb were found to be 4.1±0.3 and 20.9±0.7 sec, and the Q_EC values were determined to be 7.5±0.3 and 6.0±0.2 MeV for ⁸³Nb and ⁸⁵Nb, respectively, which are noticeably lower than predicted values from mass formulae. (orig.)

[en] The specific heat of two-dimensional spin gap system SrCu₂(BO₃)₂ realizing the Shastry-Sutherland model was measured between 1.3 K and 25 K under various magnetic fields up to 12 T. The analysis based on an isolated dimer model in a low temperature region revealed that the value of the spin gap at zero field is Δ = 34.4 K. It turned out that Δ decreases in proportion with H due to the Zeeman splitting of the excited triplet levels. This simplest model, however, fails to reproduce the result in a high temperature region, suggesting rather strong spin-spin correlation of the system

[en] In this study, microdosimetric energy distributions of secondary charged particles from the ¹⁰B(n,α)⁷Li reaction in boron neutron capture therapy (BNCT) field were calculated using the Particle and Heavy Ion Transport code System (PHITS). The PHITS simulation was performed to reproduce the geometrical set-up of an experiment that measured the microdosimetric energy distributions at the Kyoto Univ. Reactor where two types of tissue-equivalent proportional counters were used, one with A-150 wall alone and another with a 50-ppm-boron-loaded A-150 wall. It was found that the PHITS code is a useful tool for the simulation of the energy deposited in tissue in BNCT based on the comparisons with experimental results. (authors)

[en] The purpose of this study was to develop a computerized method for estimation of the location of a lung tumor in cine images on an electronic portal imaging device (EPID) without implanted markers during stereotactic body radiotherapy (SBRT). Each tumor region was segmented in the first EPID cine image, i.e., reference portal image, based on a multiple-gray level thresholding technique and a region growing technique, and then the image including the tumor region was cropped as a 'tumor template' image. The tumor location was determined as the position in which the tumor template image took the maximum cross-correlation value within each consecutive portal image, which was acquired in cine mode on the EPID in treatment. EPID images with 512 x 384 pixels (pixel size: 0.56 mm) were acquired at a sampling rate of 0.5 frame s^-1 by using energies of 4, 6 or 10 MV on linear accelerators. We applied our proposed method to EPID cine images (226 frames) of 12 clinical cases (ages: 51-83, mean: 72) with a non-small cell lung cancer. As a result, the average location error between tumor points obtained by our method and the manual method was 1.47 ± 0.60 mm. This preliminary study suggests that our method based on the tumor template matching technique might be feasible for tracking the location of a lung tumor without implanted markers in SBRT.