Influência do voxel e da miliamperagem na qualidade da imagem e dose de radiação em tomografia computadorizada por feixe cônico
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2022-02-25
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Universidade Federal de Goiás
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The diagnostic accuracy in cone beam computed tomography (CBCT) must be maintained with the lowest possible radiation dose, therefore, the protocol must be optimized according to the clinical indication, in terms of technical parameters, following the acronym ALADA, as low as diagnostically acceptable. This study aimed to evaluate the influence of technical parameters - voxel, tube current, exposure time and number of base images - in the Ortopantomograph™ OP300 equipment (Instrumentarium Dental™, Charlotte, NC, USA) on image quality and radiation dose in CBCT from nine image acquisition protocols. For this, 19 thermoluminescent dosimeters were used, for each of the protocols, located in radiosensitive regions, according to the recommendations of the International Commission on Radiological Protection (ICRP), positioned in an Alderson RANDO® anthropomorphic phantom for later calculation of the equivalent and effective doses. The subjective assessment of image quality was performed through the analysis of CBCT exams by 3 specialists in Dental Radiology and Imaging, independent from each other, who identified anatomical structures, for each protocol, in a macerated mandible. Descriptive analysis of radiation dose and multiple linear regression were performed to assess the influence of parameters on radiation dose [F (2,6) = 17,294; p = 0,003; R² = 0,852] with emphasis on milliamperage and number of base images, described in the equation: y = - 114,382 + 17,910 (milliamperage) + 0,196 (base images). Intra- and inter-observer reliability of subjective assessments were calculated as a kappa agreement analysis. Fisher's exact test showed no association between image quality and acquisition protocols (x²(8) = 6.685; p = 0.622). The chi-square test of independence showed that there is no association between the examiners' confidence and the acquisition protocols (x²(8) = 13.767; p = 0.090). A statistical significance level of p<0.05 was used. With the manipulation of the technical parameters for the evaluated protocols, a variation of up to 225.6% in the effective dose was observed. Protocol 1 (FOV 6x8 cm, 90 kV, voxel 0.3 mm, 8 mA, 4.9 s and 486 base images) was considered superior to the others in terms of subjective assessment of image quality and radiation dose.
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NUNES, F. F. Influência do voxel e da miliamperagem na qualidade da imagem e dose de radiação em tomografia computadorizada por feixe cônico. 2022. 68 f. Dissertação (Mestrado em Odontologia) - Universidade Federal de Goiás, Goiânia, 2022.