Comparison of air dose and operator exposure from portable X-ray units.

This study was aimed at investigating and comparing exposure dose of workers and the surrounding workers. In addition, worker's exposure was also measure about lens and finger. Four intraoral portable X-ray units were evaluated. The stray radiations were measured using Pitman 37D and ionization chamber (Pitman). MyDosemini (ALOKA) was used for measurement of the finger exposure dose. Without the shield became high in anterior 0.5 m. Comparing the air dose for the four models used in this study showed a high tendency for the two NOMAD models. And using the shields, the images could be taken 4.6 times of the baseline at a maximum and 3.6 times on average. The finger radiation exposure dose was low with both of the NOMAD models, with no significant difference found. By setting the baseline value without a shield, finger radiation exposure when using a shield was lower than the detection limit for the D3000, and was reduced by approximately 94-96% for other three models. All models can photograph around 100 bodies, so it is considered that it is not necessary to switch out the operator considering the operation limit. But even if it does not reach the operation limit, the stochastic effects of radiation exposure can be increased as well as the deterministic effects of the operation limit. The operator and the surrounding workers seek to protect themselves. It is important to perform exposure management that takes into account the stochastic effects to the operator and the surrounding workers.

Age estimation based on the volume change in the maxillary premolar crown using micro CT.

Age is often estimated using teeth because numerous external and internal changes appear due to aging. The purpose of this study was to investigate an age estimation method based on the volume ratio of the internal structure of the crown. 61 maxillary first premolars and 50 maxillary second premolars from subjects aged 20-79 years old were used. Micro CT, which can be used to analyze teeth in a non-destructive manner with high sensitivity, was employed in the present study. In consideration of individual differences among subjects, the volume ratio was calculated for the following four items: The pulp chamber was calculated separately based on the presence of enamel.In order to estimate age, regression analysis was conducted with the actual age as the dependent variable and each volume ratio as the independent variable. As a result, the highest correlation was found with PVR (E-) for each measurement item. Therefore, the regression equation using the volume change of the maxillary premolar crown as an index was as follows: Age = -12.43 × 4: PVR (E-) + 69.85. Age = -12.94 × 5: PVR (E-) + 72.54.