Stray radiation dose reduction using a backscatter shield and a rectangular collimator for a handheld intraoral X-ray unit

The objective of this study was to study the dose reduction effect on occupational exposure of operators and public exposure other than operators when a backscatter shield and a rectangular collimator are used in conjunction with a handheld intraoral X-ray unit. The occupational exposure was reduced to 40% when the backscatter shield was attached to the cone-tip, to 13% when the rectangular collimator was attached and to 7.7% when the backscatter shield and rectangular collimator were used together. On the other hand, the public exposure was reduced to 20% when the rectangular collimator was attached, but the backscatter shield was not effective in reducing the public exposure. Attaching a backscatter shield is effective in reducing the occupational exposure, and a rectangular aperture is effective in reducing the occupational exposure, as well as the public exposure.

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.

Reduction of operator exposure by rectangular collimation in portable intraoral radiography

Portable intraoral X-ray units are frequently used for home-visit dental treatment and personal dental identification. Therefore, the reduction of operator exposure is crucial. Rectangular collimation is effective at reducing patient exposure and operator exposure; however, its effects are not known. We investigated the reduction of operator exposure through rectangular collimation by measuring the backscattered dose in relation to the operator exposure dose. Using a portable intraoral X-ray unit, a head phantom for CT dose measurement as the object, a dosimeter, and stainless-steel rectangular collimator, a 1-cm ambient dose equivalent was measured in intervals of 15° in horizontal and vertical planes with the radii of 50 and 100 cm. The backscattered dose decreased to approximately one-third when a rectangular collimator was attached to the cone tip. This may have been due to the reduction of the volume of scattered X-rays generated in the phantom by rectangular collimation. We clarified that rectangular collimation is effective at reducing the operator exposure and is useful for protecting the operators of portable intraoral X-ray units during home-visit dental treatment and personal dental identification.