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PURPOSE: To evaluate the effect of reconstruction and noise removal algorithms on the accuracy and precision of iodine concentration (CI) quantified with subtracted micro-computed tomography (micro-CT). PROCEDURES: Two reconstruction algorithms were evaluated: a filtered backprojection (FBP) algorithm and a simultaneous iterative reconstruction technique (SIRT) algorithm. A 3D bilateral filter (BF) was used for noise removal. A phantom study evaluated and compared the image quality, and the accuracy and precision of CI in four scenarios: filtered FBP, filtered SIRT, non-filtered FBP, and non-filtered SIRT. In vivo experiments were performed in an animal model of chemically-induced mammary cancer. RESULTS: Linear relationships between the measured and nominal CI values were found for all the scenarios in the phantom study (R2 > 0.95). SIRT significantly improved the accuracy and precision of CI compared to FBP, as given by their lower bias (adj. p-value = 0.0308) and repeatability coefficient (adj. p-value < 0.0001). Noise removal enabled a significant decrease in bias in filtered SIRT images only; non-significant differences were found for the repeatability coefficient. The phantom and in vivo studies showed that CI is a reproducible imaging parameter for all the scenarios (Pearson r > 0.99, p-value < 0.001). The contrast-to-noise ratio showed non-significant differences among the evaluated scenarios in the phantom study, while a significant improvement was found in the in vivo study when SIRT and BF algorithms were used. CONCLUSIONS: SIRT and BF algorithms improved the accuracy and precision of CI compared to FBP and non-filtered images, which encourages their use in subtracted micro-CT imaging.

Asunto(s)

Yodo , Animales , Microtomografía por Rayos X , Algoritmos , Fantasmas de Imagen , Dosis de Radiación , Interpretación de Imagen Radiográfica Asistida por Computador/métodos

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Abstract Objective To evaluate the feasibility of using ultra-low-dose computed tomography of the chest with iterative reconstruction without anesthesia for assessment of pulmonary diseases in children. Methods This prospective study enrolled 86 consecutive pediatric patients (ranging from 1 month to 18 years) that underwent ultra-low-dose computed tomography due to suspicion of pulmonary diseases, without anesthesia and contrast. Parameters used were: 80 kVp; 15-30 mA; acquisition time, 0.5 s; and pitch, 1.375. The adaptive statistical iterative reconstruction technique was used. Subjective visual evaluation and quantitative assessment of image quality were done using a 5-point scale in 12 different structures of the chest. Results Mean age was 66 months (interquartile range, 16-147). Final diagnosis was performed in all exams, and 44 (51.2%) were diagnosed with cystic fibrosis, 27 (31.4%) with bronchiolitis obliterans, and 15 (17.4%) with congenital pulmonary airways malformations. Diagnostic quality was achieved in 98.9%, of which 82.6% were considered excellent and 16.3% were slightly blurred but did not interfere with image evaluation. Only one case (1.2%) presented moderate blurring that slightly compromised the image, and previous examinations demonstrated findings compatible with bronchiolitis obliterans. Mean effective radiation dose was 0.39 ± 0.15 mSv. Percentages of images with motion artifacts were 0.3% for cystic fibrosis, 1.3% for bronchiolitis obliterans, and 1.1% for congenital pulmonary airways malformations. Conclusion Chest ultra-low-dose computed tomography without sedation or anesthesia delivering a sub-millisievert dose can provide image quality to allow identification of common pulmonary anatomy and diseases.

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Resumo Objetivo Avaliar a viabilidade do uso de tomografia computadorizada com ultrabaixa dose com reconstrução iterativa sem anestesia para avaliação de doenças pulmonares em crianças. Métodos Este estudo prospectivo envolveu 86 pacientes pediátricos consecutivos (um mês a 18 anos) submetidos à tomografia computadorizada com ultrabaixa dose por suspeita de doenças pulmonares, sem anestesia e contraste. Os parâmetros utilizados foram: 80 kVp; 15-30 mA; tempo de aquisição, 0,5 s; e pitch de 1,375. Foi utilizada a técnica de reconstrução estatística adaptativa iterativa. A avaliação visual subjetiva e a avaliação quantitativa da qualidade da imagem foram feitas com uma escala de 5 pontos em 12 estruturas do tórax. Resultados A média de idade foi de 66 meses (intervalo interquartil, 16-147). O diagnóstico final foi feito em todos os exames e 44 (51,2%) foram diagnosticados com fibrose cística, 27 (31,4%) com bronquiolite obliterante e 15 (17,4%) com malformação congênita pulmonar das vias aéreas. A qualidade diagnóstica foi alcançada em 98,9% dos casos, dos quais 82,6% foram considerados excelentes e 16,3% alteração leve na definição, mas isso não interferiu na avaliação da imagem. Apenas um caso (1,2%) apresentou alteração moderada na definição, comprometeu discretamente a imagem, e exames prévios demonstraram achados compatíveis com bronquiolite obliterante. A dose de radiação média efetiva foi de 0,39 ± 0,15 mSv. As porcentagens de imagens com artefatos de movimento foram de 0,3% para fibrose cística, 1,3% para bronquiolite obliterante e 1,1% para malformação congênita pulmonar das vias aéreas. Conclusão É possível realizar a tomografia computadorizada com ultrabaixa dose torácica sem sedação ou anestesia, administrando uma dose de submilisievert, com qualidade de imagem suficiente para a identificação pulmonar anatômica e de doenças pulmonares comuns.

Asunto(s)

Humanos , Lactante , Preescolar , Niño , Adolescente , Anestesia , Dosis de Radiación , Tomografía Computarizada por Rayos X , Estudios Prospectivos

RESUMEN

OBJECTIVE: To evaluate the feasibility of using ultra-low-dose computed tomography of the chest with iterative reconstruction without anesthesia for assessment of pulmonary diseases in children. METHODS: This prospective study enrolled 86 consecutive pediatric patients (ranging from 1 month to 18 years) that underwent ultra-low-dose computed tomography due to suspicion of pulmonary diseases, without anesthesia and contrast. Parameters used were: 80kVp; 15-30mA; acquisition time, 0.5s; and pitch, 1.375. The adaptive statistical iterative reconstruction technique was used. Subjective visual evaluation and quantitative assessment of image quality were done using a 5-point scale in 12 different structures of the chest. RESULTS: Mean age was 66 months (interquartile range, 16-147). Final diagnosis was performed in all exams, and 44 (51.2%) were diagnosed with cystic fibrosis, 27 (31.4%) with bronchiolitis obliterans, and 15 (17.4%) with congenital pulmonary airways malformations. Diagnostic quality was achieved in 98.9%, of which 82.6% were considered excellent and 16.3% were slightly blurred but did not interfere with image evaluation. Only one case (1.2%) presented moderate blurring that slightly compromised the image, and previous examinations demonstrated findings compatible with bronchiolitis obliterans. Mean effective radiation dose was 0.39±0.15mSv. Percentages of images with motion artifacts were 0.3% for cystic fibrosis, 1.3% for bronchiolitis obliterans, and 1.1% for congenital pulmonary airways malformations. CONCLUSION: Chest ultra-low-dose computed tomography without sedation or anesthesia delivering a sub-millisievert dose can provide image quality to allow identification of common pulmonary anatomy and diseases.

Asunto(s)

Anestesia , Adolescente , Niño , Preescolar , Humanos , Lactante , Estudios Prospectivos , Dosis de Radiación , Tomografía Computarizada por Rayos X

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OBJECTIVE: The purpose of this study is to compare radiation dose and image quality of abdominopelvic CT studies reconstructed with iterative and conventional techniques. MATERIALS AND METHODS: This retrospective study enrolled 99 patients who underwent abdominopelvic CT examinations with the portal venous phase images reconstructed with both filtered back projection and Adaptive Iterative Dose Reduction 3D (AIDR 3D) at different time points. Subjective assessment of image quality was performed by two radiologists who scored axial images for overall quality, sharpness, noise, and acceptability in a blinded fashion. The SD of the mean attenuation of the liver, aorta, and paraspinal muscle (as a measurement of image noise) and contrast-to-noise and signal-to-noise ratios for liver and aorta were used as objective parameters of image quality. Radiation dose parameters included CT dose index volume (CTDIvol), dose-length product, effective dose (ED), and size-specific dose estimate (SSDE). Results were compared for different body mass index (BMI; weight in kilograms divided by the square of height in meters) categories. Paired t test and McNemar paired tests for noninferiority were used, with p < 0.05 considered statistically significant. RESULTS: We obtained a 62.5% mean reduction in CTDIvol, a 58% mean reduction in ED, and a 63% mean reduction in SSDE when AIDR 3D was used (p < 0.001). Subjective parameters of image quality were considered noninferior for AIDR 3D studies compared with filtered back projection (p < 0.001), except for the sharpness of images of patients with BMI 20-24.9. Variable results were found regarding objective assessment of image quality. CONCLUSION: AIDR 3D allowed a significant reduction in radiation dose of abdominopelvic CT examinations without a loss of image quality in general.

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Abdomen/diagnóstico por imagen , Imagenología Tridimensional , Pelvis/diagnóstico por imagen , Dosis de Radiación , Tomografía Computarizada por Rayos X , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Reproducibilidad de los Resultados , Estudios Retrospectivos , Relación Señal-Ruido , Adulto Joven

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AIM: To explore whether computer tomography coronary angiography (CTCA) using iterative reconstruction (IR) leads to significant radiation dose reduction without a significant loss in image interpretability compared to conventional filtered back projection (FBP). METHODS: A consecutive series of 200 patients referred to our institution to undergo CTCA constituted the study population. Patients were sequentially assigned to FBP or IR. All studies were acquired with a 256-slice CT scanner. A coronary segment was considered interpretable if image quality was adequate for evaluation of coronary lesions in all segments ≥ 1.5 mm. RESULTS: The mean age was 56.3 ± 9.6 years and 165 (83%) were male, with no significant differences between groups. Most scans were acquired using prospective ECG triggering, without differences between groups (FBP 84% vs IR 82%; P = 0.71). A total of 3198 (94%) coronary segments were deemed of diagnostic quality. The percent assessable coronary segments was similar between groups (FBP 91.7% ± 4.0% vs IR 92.5% ± 2.8%; P = 0.12). Radiation dose was significantly lower in the IR group (2.8 ± 1.4 mSv vs 4.6 ± 3.0 mSv; P < 0.0001). Image noise (37.8 ± 1.4 HU vs 38.2 ± 2.4 HU; P = 0.20) and signal density (461.7 ± 51.9 HU vs 462.2 ± 51.2 HU; P = 0.54) levels did not differ between FBP and IR groups, respectively. The IR group was associated to significant effective dose reductions, irrespective of the acquisition mode. CONCLUSION: Application of IR in CTCA preserves image interpretability despite a significant reduction in radiation dose.