Biomedical subjects

Ayako Tonari

Publications and source records attributed to Ayako Tonari.

2 recordsLinked to original sources

PubMed2005

Radiation-induced apoptosis of oligodendrocytes in the adult rat optic chiasm.

OBJECTIVES: The present study characterized glial cell injury provoked in adult rat chiasm within 24 hours after a single, high-dose irradiation of 20 Gy. METHODS: All chiasmal glial cells in a section were counted, and the percentage of TUNEL-positive glial cells exhibiting apoptotic morphology was defined as the apoptotic rate. RESULTS: Numbers of apoptotic cells increased significantly (p<0.0001) from 3 to 8 hours after exposure, but returned to baseline levels by 24 hours. Little evidence of apoptosis was observed in non-irradiated chiasms. Similar patterns of increase in apoptotic rate were observed in the genu of the corpus callosum, but the extent was significantly lower (p=0.047) in the optic chiasm, with a maximal rate of 1.9%. Immunohistochemically, apoptotic cells were positive for CNP, a marker for oligodendrocytes. DISCUSSION: These data indicate that chiasmal irradiation induces limited, but significant apoptotic depletion of the oligodendroglial population, and may participate in the development of radiation-induced optic neuropathy.

Analysis of Variance↗

PubMed2002

Dose evaluation and effective dose estimation from multi detector CT.

Computed tomography (CT) has evolved remarkably through device improvement and advancement of peripherals, including computers. In 1999, multi detector-row CT (MDCT) appeared and rapid high-speed scanning became possible. However, usefulness of MDCT in actual clinical application cannot be assessed until the exposure doses are assessed appropriately. Since CT examinations need a comparatively high dose, it is necessary to evaluate patient exposure for introduction of MDCT. Patient doses by three types of MDCTs were evaluated for cases of scanning of the chest and abdomen-pelvis. The examination conditions were the same as those in actual clinical examinations. The obtained effective doses were 9.4-28 mSv for the chest examination and 13-28 mSv for the abdomen-pelvis. The average surface doses varied between 16-43 mGy for the chest examination and 20-37 mGy for the abdomen-pelvis. The highest surface dose was 57 mGy for the abdomen-pelvis examination. The exposed doses differed according to scanning method and imaging conditions such as tube current, slice thickness and so on. It seemed that there is room for dose reduction by proper adjustment of scan conditions in MDCT examinations.

Humans↗