# Comparison of the Operator and Surrounding Dose When Using Portable Intraoral X-ray Devices
## 4 Discussion
Exposure can be effectively controlled using recent advances in radiologic equipment to stay below the thresholds for these effects. Instead, the critical concerns lie in stochastic effects, such as cancer and genetic impacts. These effects, occurring later, have required considerable time to fully understand, quantify, and contextualize. Even now, there is great uncertainty about the biological effects of low-dose radiation (less than 100 mGy). Currently, the radiological protection systems and recommendations operate under the assumption that the risk of radiation-related stochastic effects is directly proportional to the dose received. Importantly, this model does not incorporate a dose threshold below which there is no risk. Thus, it is commonly known as the linear no-threshold model. The linear no-threshold model has been a topic of extensive scientific debate and controversy. Some researchers propose that it may overestimate the actual risk and suggest the existence of a dose threshold below which no risk exists or even the possibility of health benefits of lower doses of radiation (hormesis effects). Other critics argue that the linear no-threshold model underestimates the true risk at low doses of ionizing radiation. They propose that the relationship between the received dose and undesirable effects is supra-linear, meaning the risk increases more significantly than predicted by the linear no-threshold model [23]. In the absence of definitive supportive evidence, the regulatory organizations, such as the ICRP and the NCRP, still use the linear no-threshold model as the basis for recommending public and occupational dose limits. Mobile and portable X-ray devices, as well as X-ray devices used during surgery, must be operated at a distance of 2 m or more from the X-ray tube [8,15]. It has to be considered that in several settings where the use of portable dental radiographic devices is indicated, setting up the equipment in a radiation-controlled area becomes challenging, and operators and surrounding workers may unavoidably acquire images within the 2 m range from the X-ray tube. Therefore, it is important to study the exposure doses in distances less than 2 m from the radiation source. In the present study, the 0.5 and 1 m distances were applied for measurements of scattered dose of different portable dental radiographic units. NCRP and ICRP guidelines provide whole-body occupational dose limits of 50 mSv and 20 mSv (averaged over 5 consecutive years), respectively [21]. The presumption for this study was that one operator is in charge of all of these exposures. In real situations, more than one individual is usually in charge of exposures, thus the number of permitted daily radiographs is even higher than the calculations in this study. On the other hand, some patients may require several radiographs and the number of permitted daily radiographs must not be mistaken for the number of patients. However, the NCRP reports that the annual dose for dental radiology operators does not seem to exceed 1 mSv in each year. Protective measures devised in portable dental radiographic devices include a plastic shield providing a safe zone for the operator behind the device when the device is held horizontally. Also, internal shielding material reduces the leakage of radiation from the radiographic system [24]. [PERSON] et al. presented approaches for radiation protection while using portable devices such as protective tube shields, protective gloves, and longer collimators [24,25]. The present study has some limitations. In vivo experiment was not possible due to ethical concerns. However, efforts were made in order to replicate the clinical situation for radiographic exposures. Additionally, although all the portable dental units were operated at the same voltages and exposure times, EZRay Air used 2.5 mA (the lowest mA setting in the device) while iRay D3 and Epix used 2 mA tube currents.