The major activities of this division are research and development in four fields such as medical imaging, radiation dosimetry, radiation protection and applied radiation physics.
Activities in this field are research and development of methodology and instrumentation on medical imaging such as positron emission tomography (PET) and single photon emission computed tomography (SPECT), which play an important role in nuclear medicine. Studies are carried out with a great interest on three-dimensional data acquisition and image reconstruction methods. Another activity is research and development of methodology for automated image recognition of aberrations in blood cell nuclei. Highly automated microscopic imaging analyzers for chromosome aberrations and micronuclei in blood cells have been developed. Scanning probe microscopic imaging and analysis of the effects by heavy ion beams are new subjects.
![[Fig. 1]](/ENG/Resource/f019.jpg)
[Fig.1] Automated MICRONUCLEUS ANALYZER and an image showing a micronucleus in the central erythrocyte cell.
The analyzer counts automatically the numbers of micronuclei and cells.The ratio of the numbers depends on dose of radiations or mutagenic chemicals.
The main research is carried out on the determination of an absorbed dose in tissue irradiated by radiation using ionization chambers, calorimeters, Fricke dosemeter and solid state dosemeters. Dose distributions in phantom are also investigated for radiation therapy in terms of percentage depth dose, TAR, TPR, SAR and SPR. Standard measuring methods and a traceability are investigated to establish practical dosimetry protocols for the estimation of an absorbed dose in tissue exposed to photons, electrons, neutrons and protons. Studies are also carried out on energy spectra, W-values, stopping powers and LET distributions for various radiations, especially for neutron, proton and heavy charged particle beams.
![[Fig. 2]](/ENG/Resource/f020.jpg)
[Fig.2] An NMR T1 dependent image and dose distributions in a dialogical plane parallel to the incident 15 MeV electron beams in a gel phamtom.
Researches are carried out on dosimetry and instrumentation for radiation protection. Determination of organ and tissue doses irradiated by ionizing radiations are theoretically and experimentally studied in which dosemeters such as ionization chambers, thermoluminescent and glass dosemeters are used. Quantities used in the radiation protection are reexamined. Age-dependent nominal probability coefficients are calculated. Retrospective dose estimations in accidents are carried out with quartz in bricks and tiles. Circuits for the linear energy transfer measurement and apparatus for the electrochemical etching of polycarbonates irradiated by alpha and heavier charged particles are developed. A neutron shielding measurement is performed by activation analysis and boron-plastic combination. The dose equivalent in the space mission in future is to be studied.
Research activities cover 1) application of stable and radioactive heavy ion beams to medicine and 2) basic research on the mechanisms that link primary ionization and excitation processes to the biological radiation damages. The current activity of the former research is the application of the positron emitting radioisotope beams to the verification of dose distribution in heavy ion therapy with the aid of positron emission tomographic techniques. The latter interdisciplinary research program covers such fields as microdosimetry, nanodosimetry, radiation chemistry of liquid water, modeling of the biological dose response curves and molecular dynamic approach to the study on the conformational changes in DNA induced by OH radicals.
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