Effect of data binning and frame averaging for micro-CT image acquisition on the morphometric outcome of bone repair assessment.

Despite the current advances in micro-CT analysis, the influence of some image acquisition parameters on the morphometric assessment outcome have not been fully elucidated. The aim of this study was to determine whether data binning and frame averaging affect the morphometric outcome of bone repair assessment using micro-CT. Four Wistar rats' tibiae with a surgically created bone defect were imaged with micro-CT six times each, frame averaging set to 1 and 2, and data binning set to 1, 2 and 4, for each of the averaging values. Two-way ANOVA followed by Bonferroni tests assessed the significance of frame averaging and data binning on a set of morphometric parameters assessed in the image volumes (p < 0.01). The effect of frame averaging was not significant for any of the assessed parameters. Increased data binning led to larger trabecular thickness. In contrast, smaller bone volume fraction and bone volume were found as data binning increased. Trabeculae number and trabecular separation were not influenced by any of the parameters. In conclusion, the morphometric outcome of bone repair assessment in micro-CT demonstrated dependency upon data binning, but not frame averaging. Therefore, image acquisition of small anatomical structures (e.g., rat trabeculae) should be performed without data binning.

Three-dimensional imaging of mitochondrial cristae complexity using cryo-soft X-ray tomography.

Mitochondria are dynamic organelles that change morphology to adapt to cellular energetic demands under both physiological and stress conditions. Cardiomyopathies and neuronal disorders are associated with structure-related dysfunction in mitochondria, but three-dimensional characterizations of the organelles are still lacking. In this study, we combined high-resolution imaging and 3D electron density information provided by cryo-soft X-ray tomography to characterize mitochondria cristae morphology isolated from murine. Using the linear attenuation coefficient, the mitochondria were identified (0.247 ± 0.04 µm-1) presenting average dimensions of 0.90 ± 0.20 µm in length and 0.63 ± 0.12 µm in width. The internal mitochondria structure was successfully identified by reaching up the limit of spatial resolution of 35 nm. The internal mitochondrial membranes invagination (cristae) complexity was calculated by the mitochondrial complexity index (MCI) providing quantitative and morphological information of mitochondria larger than 0.90 mm in length. The segmentation to visualize the cristae invaginations into the mitochondrial matrix was possible in mitochondria with MCI ≥ 7. Altogether, we demonstrated that the MCI is a valuable quantitative morphological parameter to evaluate cristae modelling and can be applied to compare healthy and disease state associated to mitochondria morphology.

Avaliação por microtomografia computadorizada da remoção de smear layer e debris em molares inferiores após utilização de diferentes agentes desmineralizantes / Computerized microtomography evaluation of smear layer removal and debris in lower molars after use of different demineralizing agents

O objetivo do estudo foi avaliar, por microtomografia computadorizada, a eficiência da solução de ácido fosfórico 37% e do EDTA 17% na remoção de smear layer e debris de tecidos mineralizados acumulados (DTMA) após o preparo químico-mecânico. Métodos: Vinte e seis raízes mesiais de molares inferiores foram microtomografadas em três momentos distintos: exame inicial, após preparo-químico mecânico e após remoção de smear layer pelo emprego do microtomógrafo Skyscan 1173 utilizando resolução de 14,97 µm. Os canais foram preparados utilizando limas Reciproc R40, NaOCl 6% e o Sistema EndoVac para irrigação/aspiração. Após preparo, os espécimes foram divididos aleatoriamente em dois grupos, de acordo com a solução desmineralizante utilizada: solução de ácido fosfórico 37% ou EDTA 17%. O software CTan foi utilizado para análise volumétrica e o software Seg3D para reconstruções tridimensionais. Os dados foram analisados através do teste Mann-Whitney utilizando α=0.05 como nível de significância estatística. Resultados: A diferença entre os volumes após remoção de smear layer e após o preparo químico-mecânico demonstrou que o ácido fosfórico 37% foi significativamente mais eficiente na remoção de smear layer e DTMA que o EDTA 17% (p<0,05). Conclusões: Demonstrou-se que ambos, ácido fosfórico 37% e EDTA 17%, são agentes eficazes na remoção de smear layer e debris, porém melhores resultados foram obtidos com o uso do ácido fosfórico 37%. (AU)

Introduction: The aim of this study was to evaluate, by micro­computed tomography, the efficiency of 37% phosphoric acid solution with that of 17% EDTA in the removal of smear layer and accumulated hard tissue debris (AHTD) after canal preparation. Methods: Twenty-six mesial roots of mandibular molars were subjected to three microtomographic scannings: initial scanning, after instrumentation and after smear layer removal using the SkyScan 1173 X-ray microtomograph at a resolution of 14,97 µm. The canals were prepared using R40 Reciproc instruments, 6% NaOCl and EndoVac System to irrigation/aspiration. After instrumentation, the specimens were randomly divided into two groups according to the demineralizing solution used: 37% phosphoric acid solution or 17% EDTA. CTAn software was used for volumetric analysis and Seg3D software was used for 3D model reconstructions. Data were analyzed using Mann-Whitney test using α=0.05 as level of statistical significance. Results: The difference between the volumes after removal of smear layer and after chemical-mechanical preparation demonstrated that 37% phosphoric acid was significantly more effective in removing smear layer and AHTD than EDTA 17% (p <0.05). Conclusions: It was shown that both 37% phosphoric acid and 17% EDTA are effective agents in the removal of smear layer and debris, but better results were obtained with the use of 37% phosphoric acid. (AU)

Acurácia de um sistema de diagnóstico de cárie visual e da estereofotografia de superfícies oclusais comparado à um padrão ouro em micro-CT / Acuracy of a carie diagnosis visual system and stereophotography of surface occlusal compared to a gold standard in micro-CT

O objetivo do presente estudo foi verificar a acurácia in vitro do ICDAS visual e baseado em imagens digitais no diagnóstico de cárie oclusal incipiente em molares permanentes e compará-los com um padrão ouro em micro-CT. Para este fim, foram utilizados 40 molares permanentes, obtidos através de um biorrepositório, onde três avaliadores calibrados atribuíram escores ICDAS. Primeiramente os escores foram atribuídos através de exame visual e este foi repetido após uma semana. Em seguida, passado um mês da primeira avaliação visual, os mesmos avaliadores receberam imagens digitais dos espécimes utilizados anteriormente para nova atribuição de scores ICDAS, sendo repetido também após uma semana. Os dentes foram então escaneados através de micro-CT que foi definido como método padrão-ouro para comparação. O coeficiente de correlação de Spearman foi utilizado para comparar as pontuações de consenso com o padrão-ouro. Os métodos de detecção foram comparados por meio de sensibilidade, especificidade, área sob a curva (AUC), valores preditivos positivos e negativos e precisão para dois limiares diferentes (dentes hígidos versus dentes cariados e dentes que necessitam de tratamento operatório versus tratamento não ­ operatório). Os valores médios de kappa para o intra-examinador foram 0,68 e 0,74 para inspeção visual e método baseado em imagens, respectivamente. Os valores de sensibilidade para o limiar de "presença de cárie" no método ICDAS visual e ICDAS fotográfico foram elevados quando comparados com micro-CT (0,93 e 0,97, respectivamente), mesmo com valores de precisão (0,83 e 0,85). Já a especificidade foi mais expressiva para o limiar de "cárie com necessidade de tratamento operatório" com 0,77 e 0,82 para os mesmos métodos. O coeficiente de correlação de Spearman foi de 0,53 e 0,43 (p <0,05). Em vista disso, conclui-se que o ICDAS visual e o baseado em imagens digitais foram semelhantes quanto à exatidão diagnóstica em comparação com um padrão - ouro em micro-CT, podendoe ser uma prosposta para estudos epidemiológicos. (AU)

The aim of the present study was to verify the in vitro accuracy of visual and digital-based ICDAS in the diagnosis of incipient occlusal caries in permanent molars compared to a micro-CT gold standard. For this purpose, 40 permanent molars were obtained from a pool of extracted teeth, cleaned and mounted in gypsum bases where three calibrated examiners assigned ICDAS scores. The scores were attributed by means of visual examination and were repeated after one week. One month after the first visual evaluation, the same examiners received digital images of the previously used specimens for re-assignment of ICDAS scores, which were also repeated after one week. The teeth were then scanned through a micro-CT device which was defined as gold standard method for comparison. The Spearman correlation coefficient was used to compare the consensus scores with the gold standard. The detection methods were compared by means of sensitivity, specificity, area under the curve (AUC), positive and negative predictive values and precision for two different thresholds (healthy teeth X decayed teeth and teeth requiring operative treatment X non - operative treatment). Mean kappa values for the intra-examiner agreement were 0.68 and 0.74 for visual inspection and image-based method, respectively. Sensitivity values for the "decayed teeth" threshold in the visual ICDAS method and the photographic ICDAS were high compared with the micro-CT golden standard (0.93 and 0.97, respectively), even with precision values (0.83 and 0.85). The specificity was more significant for the "caries in need for operative treatment" threshold, with 0.77 and 0.82 for the same methods. The Spearman correlation coefficient was 0.53 and 0.43 (p <0.05). It can be concluded that the visual and digital-based ICDAS were similar in terms of diagnostic accuracy compared to a gold standard in micro-CT, and may be advocated for epidemiological studies. (AU)