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Journal Articles

Ratio of aerosol and gases of radioactive chlorine and particle size distribution of aerosol formed by high-energy proton irradiation

Yokoyama, Sumi; Sato, Kaoru; Manabe, Kentaro; Noguchi, Hiroshi; Kaneko, Hirohisa; Oki, Yuichi*; Iida, Takao*; Tanaka, Susumu*

Radiation Protection Dosimetry, 127(1-4), p.392 - 397, 2007/11

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

To estimate internal doses due to the inhalation of radionuclides produced by the nuclear spallation of the air nuclei in high-energy proton accelerator facilities, the physicochemical properties of radionuclides are very important. However, there is not enough information of the properties for airborne radioactive chlorine formed from argon gas in the air of a high-energy proton irradiation field. Thus we have measured the ratio of aerosol and gases of radioactive chlorine which are formed by irradiating argon gas-added air with a 48 MeV proton beam. In addition, the particle size distribution and chemical form of non-radioactive aerosol were examined. It was found that Cl-38 and Cl-39 exist as aerosol, acidic and non-acidic gases. The percentages of Cl-38 and Cl-39 aerosols are more than 70%. In total radioactive chlorine gas, about 30% and 70% are acidic and non-acidic gases, respectively. The concentration of non-radioactive aerosol had a peak at an aerodynamic diameter of 20-30 nm in the early irradiation period. The particle size of non-radioactive aerosol shifted to larger with time. After 10 min, the aerosols grew very slowly and many of the non-radioactive aerosols were distributed widely under 200 nm. This suggests that the diameter of the radioactive chlorine aerosol formed by the attachment of the radioactive chlorine to the non-radioactive aerosol around a beam line of the accelerator is much smaller than the default value adopted in ICRP Publication 66.

Journal Articles

Development of a voxel phantom of Japanese adult male in upright posture

Sato, Kaoru; Noguchi, Hiroshi; Endo, Akira; Emoto, Yutaka*; Koga, Sukehiko*; Saito, Kimiaki

Radiation Protection Dosimetry, 127(1-4), p.205 - 208, 2007/11

 Times Cited Count:12 Percentile:65.48(Environmental Sciences)

Calculation of specific absorbed fractions (SAFs) used in internal dosimetry requires a human phantom. However, radiation exposure occurs under various postures, which may affect the shape and location of organs. Therefore, it is important to clarify the effect of posture on SAFs. In the present study, a voxel phantom was developed on the basis of CT images in upright posture, and the difference of SAFs between supine and upright postures was investigated. The authors developed the voxel phantom of Japanese adult in supine posture named JM for the evaluation of SAFs of Japanese adult male. The subject, who was employed for the construction of JM, was selected as a volunteer again to obtain the CT images. The developed voxel phantom in upright posture was named JM2. The voxel size of JM2 is 0.98mm$$times$$0.98mm$$times$$1mm, which is the same as that of JM. The fine voxels reproduce the shape and location of organs in the body realistically. It is possible to compare directly the change in the shape and location of organs due to the postures between JM and JM2, since the CT images for construction of the both phantoms were obtained from the identical person. This paper describes the physical characteristics of JM and JM2 and discusses the impact of posture on SAFs for photons in selected organs.

Journal Articles

Practical action levels for chelation therapy in plutonium inhalation using nose swab

Kurihara, Osamu; Takada, Chie; Takasaki, Koji; Ito, Kimio; Momose, Takumaro; Miyabe, Kenjiro

Radiation Protection Dosimetry, 127(1-4), p.411 - 414, 2007/11

 Times Cited Count:7 Percentile:48.98(Environmental Sciences)

Practical action levels for beginning chelation therapy to remove plutonium in the body are now under discussion in Japan since there has been no experience in administrating agents to a subject in accidental intake in Japan although a first commercial reprocessing plant is about to start operation. Recently, International Commission on Radiological Protection (ICRP) proposed some medical intervention levels for chelation therapy on ICRP Publication 96. These levels are determined based on internal dose however common monitoring methods such as lung counting or excreta analysis are not necessarily suitable in terms of both sensitivity and promptness. As an alternative, the authors paid attention to nose swabs and introduced the practical action levels.

Journal Articles

Evaluation of self-dose $$S$$ values for positron emitters in voxel phantoms

Kinase, Sakae; Saito, Kimiaki

Radiation Protection Dosimetry, 127(1-4), p.197 - 200, 2007/11

 Times Cited Count:2 Percentile:19.35(Environmental Sciences)

In the present study, Monte Carlo simulations have been carried out to evaluate $$S$$ values - the mean absorbed dose to the target region per unit cumulated activity in the source region - for positron emitters in the brain, the heart and the urinary bladder contents. The positron emitters of interest were four radionuclides that were used for PET imaging: $$^{11}$$C, $$^{13}$$N, $$^{15}$$O and $$^{18}$$F. The $$S$$ values were evaluated on the Medical Internal Radiation Dose (MIRD) Committee of the Society of Nuclear Medicine Pamphlet No.5 type phantom (MIRD 5 type phantom) and the adult voxel phantoms developed at the Japan Atomic Energy Research Institute (JAERI). Consequently, Monte Carlo simulation and voxel phantoms were found to be useful in the evaluation of the beta dose to organs, in particular to hollow organs such as the urinary bladder. It was also demonstrated that the self-dose $$S$$ values largely depend on the beta-ray energy and the mass of each target region.

Journal Articles

Development and assessment of new radioactive decay database used for dosimetry calculation

Endo, Akira; Yamaguchi, Yasuhiro; Eckerman, K. F.*

Radiation Protection Dosimetry, 105(1-4), p.565 - 569, 2003/09

 Times Cited Count:11 Percentile:60.77(Environmental Sciences)

The present paper discusses a strategy for the development of a new radioactive decay database, which will succeed ICRP Publ.38 used for dosimetry calculations. The development of the database requires 1) Consistency checking of the ENSDF used for compilation of the decay data, 2) Improvement of the computer code EDISTR for processing the ENSDF, and 3) Comparison with other decay data prepared from the different computer codes and libraries for the verification of the compiled data. This paper identifies several technical issues that need to be addressed for the development of the new radioactive decay database.

Journal Articles

Evaluation of specific absorption fractions in voxel phantoms using Monte Carlo simulation

Kinase, Sakae; Zankl, M.*; Kuwabara, Jun; Sato, Kaoru; Noguchi, Hiroshi; Funabiki, Jun*; Saito, Kimiaki

Radiation Protection Dosimetry, 105(1-4), p.557 - 563, 2003/09

 Times Cited Count:26 Percentile:84.61(Environmental Sciences)

There exists a need to calculate specific absorbed fractions (SAFs) in voxel phantoms for internal dosimetry. For this purpose, an EGS4 user code for calculating SAFs using voxel phantoms was developed on the basis of an existing EGS4 user code for external dosimetry (UCPIXEL). In the developed code, the transport of photons, electrons and positrons in voxel phantoms can be simulated, particularly the transport simulations of secondary electrons in voxel phantoms can be made. The evaluated SAFs for the GSF Child voxel phantom using the developed code were found to be in good agreement with the GSF evaluated data. In addition, SAFs in adult voxel phantoms developed at JAERI were evaluated using the developed code and were compared with several published data. It was found that SAFs for organ self-absorption depend on the organ masses and would be affected by differences in the structure of the human body.

Journal Articles

Application of a Ge semi-conductor detector to whole-body counter

Kinase, Sakae; Noguchi, Hiroshi; Nakamura, Takashi*

Radiation Protection Dosimetry, 105(1-4), p.467 - 472, 2003/09

 Times Cited Count:4 Percentile:32.21(Environmental Sciences)

To calibrate a whole-body counter, it is necessary to find a determination method for peak efficiencies of detectors that the whole-body counter has. For the purpose, peak efficiencies of a Ge semi-conductor detector for point sources and volume sources were evaluated in the photon energy range of 60-1,836 keV by Monte Carlo simulation and experiment. It was found that the calculated peak efficiency curves as a function of energy without modeling the actual sensitive region of the detector are similar in shape to those measured. The calculated peak efficiencies of the detector that has an apparent dead layer (1mm) were also found to agree with the experimental values. Consequently, the simulation method for peak efficiencies was validated. In addition, an optimum design for a whole-body counter with Ge semi-conductor detectors was examined by simulation. This simulation enables to provide a method to determine an optimum arrangement of detectors in a whole-body counter offering a uniform response to various Cs-137 distributions in a human body.

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