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Sato, Tatsuhiko; Yokoya, Ritsuko; Niita, Koji*
Radiation Protection Dosimetry, 122(1-4), p.41 - 45, 2006/12
Times Cited Count：66 Percentile：96.81(Environmental Sciences)Estimation of biological effects due to exposure of HZE particles is one of the key issues in the planning of long-term space missions and heavy ion cancer therapies. Detailed information on the specific energy distributions around their tracks is indispensable in the issue. We therefore calculated the specific energy distributions in liquid water around the tracks of protons and several kinds of heavy ions with energies from 1 MeV/n to 100 GeV/n. The calculations were performed by a Monte Carlo electron track structure simulation code coupled with the Katz's delta-ray production model. An analytical function to reproduce the simulation results has been developed in order to predict the distribution for all kinds of heavy ions with wide energy ranges. By incorporated into the Particle and Heavy Ion Transport code System PHITS, the function enables us to calculate the specific energy distribution in macroscopic matters such as specified organs of astronauts or tumor of patients within a short computational time.
Yokoya, Akinari; Fujii, Kentaro; Ushigome, Takeshi; Shikazono, Naoya; Urushibara, Ayumi; Watanabe, Ritsuko
Radiation Protection Dosimetry, 122(1-4), p.86 - 88, 2006/12
Times Cited Count：11 Percentile：60.11(Environmental Sciences)We have studied yields of DNA damages induced by soft X-rays obtained from a conventional soft X-ray machine in a LET region between 
-rays and ultrasoft X-rays. Practically soft X-rays with a broad energy spectrum emitted from a target of heavy metal, such as tungsten, have been widely used not only for radiobiological experiments but also for medical application such as mammography. Radiation weighting factors for these soft X-rays have been assigned to be 1 by ICRP. However, the fraction of a large number of low energy photons in the spectrum (below several tens keV) provided by bremsstrahlung is expected to be more effective for DNA damage induction than -rays since low energy photo- and Auger electrons predominantly ejected in consequence of a photoelectric effect can produce dense clusters of ionization/excitation on DNA molecules. We have examined the yield of DNA strand breaks induced by white soft X-rays (150 kVp, tungsten target). Yields of base lesions revealed by base excision repair enzymes will be also presented.
Urushibara, Ayumi; Shikazono, Naoya; Watanabe, Ritsuko; Fujii, Kentaro; O'Neill, P.*; Yokoya, Akinari
Radiation Protection Dosimetry, 122(1-4), p.163 - 165, 2006/12
Times Cited Count：4 Percentile：30.64(Environmental Sciences)no abstracts in English
Watanabe, Ritsuko; Nikjoo, H.*
no journal, ,
no abstracts in English
