Dose assessment of medical exposure of radiographic dental studies

The purpose of the study is to evaluate the effective doses of patients for the most common radiographic dental studies, comparing the obtained data with the literature and reference values given in the guidelines “Filling in the forms of the federal state statistical observation No. 3-DOZ” and are still often used for form filling instead of measured values. In the framework of this work in 2016-2018, 44 X-ray units were examined at 37 dental medical facilities in St. Petersburg and the Leningrad Region. Seven radiographic studies were included: radiographs of three groups of teeth (incisors, premolars, and molars) for the upper and lower jaw and bite radiography. Physical-technical and geometrical parameters were collected for selected types of the standard patient studies: X-ray tube voltages, total filtration, radiation output, combination of the time and the current of exposure or the exposure, area of the study, size of the irradiation field; the focal length. Further, the input (surface) dose was calculated from the radiation output of the device. Then, based on the initial information about the parameters of the procedures and the input dose, the absorbed doses and the effective dose were calculated using the PCXMC program. For most devices, the dose values are in the range of 0.5 to 10.7 µSv, which is significantly lower than the values used to fill in the 3-DOS form. The results of evaluating the effective dose for these devices are fairly homogeneous, but on one device, there were doses exceeding not only the values of doses on other devices, but also the values from the recommendations for 3-DOS for devices with digital receivers, as well as those approaching similar values for film devices. An almost linear dependence of the effective dose on the exposure time was established, while a similar dependence on the voltage on the X-ray tube was not found. The median value of the effective dose for the units with films detectors was 3.2 µSv for the maxillary incisors, 3.8 µSv for the maxillary premolars, 6.8 µSv for the maxillary molars, and for the mandibular incisors, premolars and molars – 3.2, 3.4 and 5.8 µSv, and for bitewing – 6.7 µSv. For the unit with digital detectors, effective doses were 1 µSv, 1,2 µSv, 2,2 µSv for maxilla, 1 µSv, 1,3 µSv, 2 µSv for mandibula and 2,8 µSv for bitewing. Attention is drawn to the substantial width of the ranges without emissions for the examination of premolars of the upper jaw, molars of both jaws and occlusion, which is the reason for the possible enhancement of optimization measures in these studies. When comparing with published data, it was found that the effective doses in St. Petersburg and the regional institutions are lower than the values obtained using standard round collimator and medium and high sensitivity films (class D and F, respectively), as well as lower dose levels in the European Commission Guidelines. In addition, the dose values deduced in this study are significantly lower than the values given in the guidelines “Filling in the forms of federal state statistical observation No. 3-DOZ” and which are still often used to fill in the form instead of the measured values. This indicates an overestimation of estimates of patient doses when using reference values from the 3-DOZ manual and the need to use individual patient doses, obtained on the basis of measurements. However, the effective doses in St. Petersburg and the Leningrad Region are higher than those obtained using a square collimator and high-sensitivity films. The above results suggest that it is necessary and possible to carry out optimization in X-ray dental studies in St. Petersburg and the Leningrad Region. Analysis of similar studies on other X-ray diagnostic techniques allows to extrapolate this statement to other regions of Russia.

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