ABSTRACT
Objective: To investigate the spatial distribution characteristics and correlation between the prevalence of dental fluorosis and the chemical elemental composition of drinking water sources in coal-fired fluorosis areas. Methods: Based on the survey data on the prevalence of dental fluorosis at CDC in Guizhou Province in 2022, 274 original surface drinking water sources were collected in typical coal-fired fluorosis areas, and fluoride (F), calcium (Ca), magnesium (Mg), aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), molybdenum (Mo), cadmium (Cd), barium (Ba), lead (Pb) 17 elements; apply Moran's I index, Getis-Ord Gi* hotspot analysis of the global spatial autocorrelation of chemical elements in drinking water and the degree of aggregation of each element on the local area, and correlation analysis with the prevalence of dental fluorosis in the region. Results: Except for Cu, Zn, and Cd, global spatial autocorrelation Moran's I was negative, and all other elements were positive. F, Ca, Al, Ti, As, Mo, Cd, and Cu elements showed high values of aggregation in the southeastern low-altitude area; Mg, Ba, Pb, Cr, Mn, and Fe elements were mainly aggregated in the central altitude terrain transition area, Zn and Se elements in water sources are significantly positively correlated with the prevalence of dental fluorosis (P<0.05). In contrast, F, Mg, Al, Ti, As, Mo, Cd, Ba, and Pb elements negatively correlate (P<0.05). Elements in the central region were high-high aggregation, as a hot spot aggregation area with high disease incidence, while F, Al, Mn, Mo, Cd, and Ba elements in the western region were low-low aggregation, as a cold spot aggregation area with a low incidence of fluorosis. Conclusions: The risk of population fluoride exposure in surface drinking water sources is shallow. However, the chemical element content of drinking water sources in coal-fired polluted endemic fluorosis areas has prominent spatial geographical distribution characteristics. There is a significant spatial aggregation effect with the prevalence of dental fluorosis, which may play a synergistic or antagonistic effect on the occurrence and prevalence of dental fluorosis.
Subject(s)
Humans , Drinking Water , Prevalence , Coal , Fluorides/adverse effects , Cadmium , Fluorosis, Dental/epidemiology , Lead , Selenium , ArsenicABSTRACT
Currently, the conventional empirical or semi-empirical dose calculation algorithms for radiation treatment planning system have been selected as dose engines. The accuracy of these dose calculation algorithms is limited. The main problem is that they fail to adequately consider the lateral transport of radiation or loss of electronic equilibrium near interface between two heterogeneous mediums. Monte Carlo method provides a kind of precise and general solution to photon and electron dose calculation problem, but the puzzle of the longer CPU time affects its clinical application finally. The Monte Carlo code system (EGSnrc) has been used to investigate the different voxel sizes effect on the accuracy of dose distributions and computing time in the present paper. Based on a patient head and neck CT data case studied, it may be concluded that less than 4mm voxels should be used for Monte Carlo dose calculations to insure the superior accuracy of dose distribution, higher image resolution and shorter CPU time.
ABSTRACT
The decrease of accuracy in patients' repeated positioning in radiotherapy due to body's transformation is considered and a positioning error measurement method using dynamic template matching technique is brought forward in this paper. This method is an improvement of the matching method to correct positioning error based on the CT digitally reconstructed radiograph(DRR), which uses the video reconstructed 3D surface model that can reflect the body's transformation as the matching template instead of DRR. This method can not only improve the positioning accuracy but also eliminate the adverse influence brought by body's transformation.
