RESUMO

OBJECTIVES: To assess the effective and organ/tissue equivalent radiation doses of different scout projection protocols in four CBCT units. METHODS: Optically stimulated luminescence dosimeters (OSLD) were placed in reference anatomical locations in the head and neck segments of an anthropomorphic phantom representing an average adult male. Ten repeated exposures were obtained from each of the twelve scout projections studied, acquired from four maxillofacial cone beam computed tomography (CBCT) units (Midmark EIOS, 3D Accuitomo F170, Veraviewepocs 3D R100, and Veraview X800). The effective and organ/tissue equivalent doses were calculated for each protocol. RESULTS: Effective doses ranged from 0.7 µSv (Accuitomo F170 60 × 60 mm-anterior maxilla) to 6.9 µSv (Midmark 50 × 50 mm-anterior maxilla). The highest organ/tissue equivalent doses were recorded for the oral mucosa and salivary glands; however, the thyroid was the highest contributor to the effective dose, followed by the salivary glands. CONCLUSIONS: Despite some variability among CBCT machines and protocols, the acquisition of scout projections is a low-dose procedure. The use of scout projections to ensure an adequate position of the region of interest within the field of view is highly desirable as they contribute minimally to overall CBCT patient dose.

Assuntos

Tomografia Computadorizada de Feixe Cônico , Imagens de Fantasmas , Doses de Radiação , Tomografia Computadorizada de Feixe Cônico/métodos , Humanos , Masculino , Adulto , Dosimetria por Luminescência Estimulada Opticamente/métodos

RESUMO

OBJECTIVE: To compare the dosimetry between convex triangular fields of view (FOV) and similar dimension cylindrical FOVs of two cone-beam computed tomography (CBCT) models. METHODS: Optically stimulated luminescence dosimeters (OSLDs) were placed in fiducial anatomical locations in an anthropomorphic phantom representing an adult head male for dosimetry scans. Convex triangular FOVs (100 × 80 mm/maxilla-mandible; 100 × 50 mm mandible; 100 × 50 mm/maxilla) from Veraviewepocs 3D R100 (J. Morita, Kyoto, Japan) (R100) and Veraview® X800 (J. Morita, Kyoto, Japan) (X800) and cylindrical FOVs from R100 and X800 (80 × 80 mm/maxilla-mandible; 80 × 50 mm/mandible; 80 × 50 mm/maxilla) were obtained, resulting in 12 different scan protocols. Equivalent doses for each relevant organ/tissue and the effective dose for each protocol were calculated. Mean effective doses were compared by the two-way analysis of variance (ANOVA) with Tukey's post hoc test to evaluate the effect of the FOV and device (α = 0.05). RESULTS: The effective doses ranged between 69 and 324 µSv for the convex triangular FOVs and 76 and 332 µSv for the cylindrical FOVs. Convex triangular FOVs from the R100 device had effective doses 2.3 to 15.3% lower than their corresponding cylindrical FOVs with similar height (p < 0.05), and that difference ranged between 8.8 and 11.8% for the X800 device (p < 0.05). CONCLUSION: Convex triangular fields of view delivered slightly lower effective doses than the cylindrical fields of view of similar dimensions in the R100 and X800 CBCT devices. CLINICAL RELEVANCE: Understanding the influence of the image geometry formation in effective dose allows optimization to reduce patient dose.

Assuntos

Tomografia Computadorizada de Feixe Cônico , Radiometria , Adulto , Masculino , Humanos , Doses de Radiação , Tomografia Computadorizada de Feixe Cônico/métodos , Mandíbula/diagnóstico por imagem , Maxila , Imagens de Fantasmas

RESUMO

The quality of Cone Beam Computed Tomography (CBCT) images is directly influenced by scanning and visualization protocols. Evaluate the subjective quality of the Cone Beam Computed Tomography (CBCT) image of different devices and protocols for diagnosing periodontal structures and correlate the findings with the contrast-to-noise ratio (CNR). One dry dentate mandible was scanned by six CBCT devices: Accuitomo 3D 170, CS 9000, CS 9300, Eagle 3D, i-CAT Classic, and Orthophos XG 3D. All CBCT devices were adjusted to provide a spatial resolution closest to 0.2 mm, and a FOV height limited to less than 100 mm. Cross-sectional images were evaluated randomly. The buccal bone coverage, the periodontal ligament space and the amount of image noise were assessed. The statistics were calculated based on a logistic regression model with the significance level set at 5%. Protocols with large FOVs demonstrated significantly lower image quality. No statistical differences were found regarding buccal bone coverage between the CBCT devices. The CNR showed the highest value for the Accuitomo 60mm x 60mm HiFi 180°, followed by the Accuitomo 60mm x 60mm HiFi 360°, and lower values for the i-Cat Classic and Orthophos XG 3D devices. Most protocols studied presented good image quality in evaluating the buccal bone coverage and periodontal ligament space. However, the exam with the lowest FOV of the Accuitomo 60mm x 60mm HiFi 180° device showed superiority concerning the others.(AU)

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A qualidade das imagens de tomografia computadorizada de feixe cônico (CBCT) é diretamente influenciada pelos protocolos de digitalização e visualização. Avaliar a qualidade subjetiva da imagem da Tomografia Computadorizada de Feixe Cone (CBCT) de diferentes aparelhos e protocolos para o diagnóstico de estruturas periodontais e correlacionar os achados com a razão contraste-ruído (RCR). Uma mandíbula dentada seca foi digitalizada por seis dispositivos CBCT: Accuitomo 3D 170, CS 9000, CS 9300, Eagle 3D, i-CAT Classic e Orthophos XG 3D. Todos os dispositivos CBCT foram ajustados para fornecer uma resolução espacial próxima a 0,2 mm e uma altura de FOV limitada a menos de 100 mm. Imagens transversais foram avaliadas aleatoriamente. A cobertura óssea vestibular, o espaço do ligamento periodontal e a quantidade de ruído da imagem foram avaliados. As estatísticas foram calculadas com base em um modelo de regressão logística com nível de significância de 5%. Protocolos com grandes FOVs demonstraram qualidade de imagem significativamente inferior. Não foram encontradas diferenças estatísticas em relação à cobertura óssea vestibular entre os dispositivos CBCT. O CNR apresentou o maior valor para o Accuitomo 60mm x 60mm HiFi 180°, seguido pelo Accuitomo 60mm x 60mm HiFi 360°, e valores menores para os dispositivos i-Cat Classic e Orthophos XG 3D. A maioria dos protocolos estudados apresentou boa qualidade de imagem na avaliação da cobertura óssea vestibular e do espaço do ligamento periodontal. Entretanto, o exame com menor FOV do aparelho Accuitomo 60mm x 60mm HiFi 180° apresentou superioridade em relação aos demais. (AU)