Matsubara Hiroaki

<title>Abstract</title> Cardiac implantable electronic devices (CIEDs) were believed to have a tolerance dose and that direct irradiation has to be avoided. Thus, no clinical guidelines have mentioned the feasibility of total body irradiation (TBI) with a CIED directly. The purpose of this work was to study a feasible and safe condition for TBI using a CIED. Eighteen CIEDs were directly irradiated by a 6-MV X-ray beam, where a non-neutron producible beam was employed for the removal of any neutron contribution to CIED malfunction. Irradiation up to 10 Gy in accumulated dose was conducted with a 100-cGy/min dose rate, followed by up to 20 Gy at 200 cGy/min. An irradiation test of whether inappropriate ventricular shock therapy was triggered or not was also performed by using a 6-MV beam of 5, 10, 20 and 40 cGy/min to two CIEDs. No malfunction was observed during irradiation up to 20 Gy at 100 and 200 cGy/min without activation of shock therapy. These results were compared with typical TBI, suggesting that a CIED in TBI will not encounter malfunction because the prescribed dose and the dose rate required for TBI are much safer than those used in this experiment. Several inappropriate shock therapies were, however, observed even at 10 cGy/min if activated. The present result suggested that TBI was feasible and safe if a non-neutron producible beam was employed at low dose-rate without activation of shock therapy, where it was not inconsistent with clinical and non-clinical data in the literature. The feasibility of TBI while using a CIED was discussed for the first time.

Spin-<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"><mml:mrow><mml:mi>M</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:math></inline-formula> excitations of nuclei are important for describing neutrino reactions in supernovae or in neutrino detectors since they are allowed transitions mediated by neutral current neutrino interactions. The spin-<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"><mml:mrow><mml:mi>M</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:math></inline-formula> excitation strength distributions in self-conjugate <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m3"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mi>Z</mml:mi></mml:mrow></mml:math></inline-formula> nuclei were studied by proton inelastic scattering at forward angles for each of isovector and isoscalar excitations as reported in H. Matsubara et al., Phys. Rev. Lett. <bold>115</bold>, 102501 (2015). The experiment was carried out at the Research Center for Nuclear Physics, Osaka University, employing a proton beam at 295 MeV and the high-resolution spectrometer Grand Raiden. The measured cross-section of each excited state was converted to the squared nuclear matrix elements of spin-<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m4"><mml:mrow><mml:mi>M</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:math></inline-formula> transitions by applying a unit cross-section method. Comparison with predictions by a shell-model has revealed that isoscalar spin-<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m5"><mml:mrow><mml:mi>M</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:math></inline-formula> strengths are not quenched from the prediction although isovector spin-<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m6"><mml:mrow><mml:mi>M</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:math></inline-formula> strengths are quenched similarly with Gamow-Teller strengths in charged-current reactions. This finding hints at an important origin of the quenching of the strength relevant to neutrino scattering, that is, the proton-neutron spin-spin correlation in the ground state of the target nucleus. In this manuscript we present the details of the unit cross-section method used in the data analysis and discuss the consistency between the quenching of the isoscalar magnetic moments and that of the isoscalar spin-M1 strengths.

PURPOSE: Cardiac implantable electronic devices (CIEDs) were believed to possess a tolerance dose to malfunction during radiotherapy. Although recent studies have qualitatively suggested neutrons as a cause of malfunction, numerical understanding has not been reached. The purpose of this work is to quantitatively clarify the contribution of secondary neutrons from out-of-field irradiation to the malfunction of CIEDs as well as to deduce the frequency of malfunctions until completion of prostate cancer treatment as a typical case. MATERIALS AND METHODS: Measured data were gathered from the literature and were re-analyzed. Firstly, linear relationship for a number of malfunctions to the neutron dose was suggested by theoretical consideration. Secondly, the accumulated number of malfunctions of CIEDs gathered from the literature was compared with the prescribed dose, scattered photon dose, and secondary neutron dose for analysis of their correlation. Thirdly, the number of malfunctions during a course of prostate treatment with high-energy X-ray, passive proton and passive carbon-ion beams was calculated while assuming the same response to malfunctions, where X-rays consisted of 6-MV, 10-MV, 15-MV, and 18-MV beams. Monte Carlo simulation assuming simple geometry was performed for the distribution of neutron dose from X-ray beams, where normalization factors were applied to the distribution so as to reproduce the empirical values. RESULTS: Linearity between risk and neutron dose was clearly found from the measured data, as suggested by theoretical consideration. The predicted number of malfunctions until treatment completion was 0, 0.02±0.01, 0.30±0.08, 0.65±0.17, 0.88±0.50, and 0.14±0.04 when 6-MV, 10-MV, 15-MV, 18-MV, passive proton, and passive carbon-ion beams, respectively, were employed, where the single model response to a malfunction of 8.6±2.1 Sv-1 was applied. CONCLUSIONS: Numerical understanding of the malfunction of CIEDs has been attained for the first time. It has been clarified that neutron dose is a good scale for the risk of CIEDs in radiotherapy. Prediction of the frequency of malfunction as well as discussion of the risk to CIEDs in radiotherapy among the multiple modalities have become possible. Because the present study quantitatively clarifies the neutron contribution to malfunction, revision of clinical guidelines is suggested.

The dose distribution of passive and scanning irradiation for carbon-ion radiotherapy for breast cancer was compared in order to determine the preferred treatment method. Eleven Japanese patients who received carbon-ion radiotherapy for breast cancer were retrospectively analyzed. The original clinical plans were used for the passive irradiation method, while the plans for the scanning irradiation method were more recently made. Statistical analysis suggested that there was no significant difference in superiority in terms of dose distribution between the passive and scanning irradiation methods. The present study found that the scanning irradiation method was not always superior to the passive method, despite a previous study having reported the superiority of scanning irradiation. The present result is considered to arise from characteristics of breast cancer treatment, such as the simplicity of the organ at risk and the shallow depth point of the target from the skin. It is noteworthy that the present study suggests that the passive irradiation method can provide better dose distribution, depending on the case.

Differential cross sections of isoscalar and isovector spin-M1 (0(+) -&gt; 1(+)) transitions are measured using high-energy-resolution proton inelastic scattering at E-p = 295 MeV on Mg-24, Si-28, S-32, and Ar-36 at 0 degrees-14 degrees. The squared spin-M1 nuclear transition matrix elements are deduced from the measured differential cross sections by applying empirically determined unit cross sections based on the assumption of isospin symmetry. The ratios of the squared nuclear matrix elements accumulated up to E-x = 16 MeV compared to a shell-model prediction are 1.01(9) for isoscalar and 0.61(6) for isovector spin-M1 transitions, respectively. Thus, no quenching is observed for isoscalar spin-M1 transitions, while the matrix elements for isovector spin-M1 transitions are quenched by an amount comparable with the analogous GamowTeller transitions on those target nuclei.

Purpose: Skin toxicity caused by radiotherapy has been visually classified into discrete grades. The present study proposes an objective and continuous assessment method of skin erythema in digital images taken under arbitrary lighting conditions, which is the case for most clinical environments. The purpose of this paper is to show the feasibility of the proposed method. Methods: Clinical data were gathered from six patients who received carbon beam therapy for lung cancer. Skin condition was recorded using an ordinary compact digital camera under unfixed lighting conditions; a laser Doppler flowmeter was used to measure blood flow in the skin. The photos and measurements were taken at 3 h, 30, and 90 days after irradiation. Images were decomposed into hemoglobin and melanin colors using independent component analysis. Pixel values in hemoglobin color images were compared with skin dose and skin blood flow. The uncertainty of the practical photographic method was also studied in nonclinical experiments. Results: The clinical data showed good linearity between skin dose, skin blood flow, and pixel value in the hemoglobin color images; their correlation coefficients were larger than 0.7. It was deduced from the nonclinical that the uncertainty due to the proposed method with photography was 15%; such an uncertainty was not critical for assessment of skin erythema in practical use. Conclusions: Feasibility of the proposed method for assessment of skin erythema using digital images was demonstrated. The numerical relationship obtained helped to predict skin erythema by artificial processing of skin images. Although the proposed method using photographs taken under unfixed lighting conditions increased the uncertainty of skin information in the images, it was shown to be powerful for the assessment of skin conditions because of its flexibility and adaptability. (C) 2015 American Association of Physicists in Medicine.

Spectroscopy for neutron-rich nuclei He-9 and Be-12 has been performed by means of heavy-ion double charge exchange (HIDCX) (O-18, Ne-18) reaction on stable target nuclei Be-9 and C-12, respectively. Several clear peaks in Be-12 at low excitation energy region even above neutron separation energy have been observed in one-shot measurement, whereas no prominent signals of He-9 have been observed owing to the small cross section. It is shown that the HIDCX reaction is a new powerful spectroscopic tool for study of unstable neutron-rich nuclei.

A gas target system has been developed for nuclear scattering experiments with a highly dispersive spectrometer at small scattering angles including 0 degrees. The system is equipped with a gas cell that has a wide beam window of 44 mm in width and 14 mm in height. The size is sufficient to pass a dispersed beam, which is essential for high energy-resolution measurement. A gas handling system allows target gas that is often limited in quantity, to be collected for reuse. Typical areal density is 1 mg/cm(2) for Ne-20 or Ar-36 gas. The target can be operated either at room temperature or at the liquid nitrogen temperature. The gas target has been employed in a proton inelastic-scattering experiment at 295 MeV with the Grand Raiden spectrometer at the Research Center for Nuclear Physics. A good energy resolution of 20 keV (FWHM) has been achieved at scattering angles of 0-4.5 degrees. (C) 2012 Elsevier B.V. All rights reserved.

A self-supporting target made of elemental sulfur has been developed for use in vacuum in high energy-resolution measurements at 0° using charged particle beams. The sulfur target is placed on a target ladder that is cooled by liquid nitrogen to minimize its sublimation due to heating by the energy loss of the beam in the target. Sulfur sheets with areal densities of 6-60 mg/cm2 and size of 2 × 2 cm2 are prepared. An energy resolution of 29 keV (FWHM) in the 32 S (p, p′) experiment at 0° is achieved using a 295 MeV proton beam. The target thickness is stable within ±5% during irradiation with a beam energy loss of 0.2 mW in the target. A windowless sulfur target was used successfully for the first time. © 2009 Elsevier B.V. All rights reserved.