One of the main drivers influencing consumers in the purchasing of red meat is the level of visible fat, and this is particularly important in lamb, with lamb often being perceived as fatty. Consumer-driven preference for leaner meat, coupled with the meat processing industries preference for a reduction in carcass fat, increasing lean meat yield and reducing waste, have led to continued selection for lean growth and reduced fatness in several meat producing species The perception of lamb being fatty could be directly targeted in isolation by reducing overall fat levels, however there are related effects on meat (eating) quality, and the combined improvement and consistency of meat (eating) quality and the reduction of overall fatness is more complicated. It is apparent that fat content plays a significant role in meat (eating) quality. Generally four major fat depots are recognised in animal carcasses, these are: subcutaneous (under the skin); internal organ associated; intermuscular (between muscles and surrounding muscle groups); and intramuscular (marbling, between muscle fibres), the latter generally regarded as having the greatest association with meat (eating) quality. X-ray computed tomography (CT) can measure fat, muscle and bone in vivo in sheep and CT predictions of carcass composition have been used in commercial UK sheep breeding programmes over the last two decades. Together with ultrasound measures of fat and muscle depth in the loin region, CT measured carcass fat and muscle weights have contributed much to the success of breeding for leaner carcasses and increased lean meat yield. Recently it has also been considered that x-ray computed tomography provides the means to simultaneously estimate IMF and carcass fat in vivo. Thus the aim of this project is to investigate the use of two and three-dimensional x-ray computed tomography techniques in the estimation of meat (eating) quality traits in sheep, and to further investigate the genetic basis of these traits and the possibility of their inclusion into current breeding programmes. The primary approach was the use of two-dimensional x-ray computed tomography, determining the most accurate combination of variables to predict IMF and mechanical shear force in the loin. The prediction of mechanical shear force was poor with accuracies ranging from Adj R2 0.03 – 0.14, however the prediction of IMF in the loin was more promising. CT predicted carcass fat weight accounted for a moderate amount of variation in IMF (R2 =0.51). These accuracies were significantly improved upon by including other information from the CT scans (i.e. fat and muscle densities, Adj R2 >0.65). Average muscle density in a single or multiple scans accounted for a moderate amount of the variation in IMF (Adj R2 = 0.51-0.60), and again accuracies R2 >0.65 were achieved, independent of CT-measured fat areas or predicted fat weights. Similar results were achieved with the use of three-dimensional CT scanning techniques (Adj R2 0.51 – 0.71), however, there was a dramatically increased requirement for image analysis when compared to two-dimensional techniques, and the increase in accuracy was not significant. This suggests that the current method of two-dimensional image capture is sufficient in the estimation of IMF in vivo in sheep. The prediction equations developed as part of this work were applied across divergent breed types (Texel, Scottish Blackface and Texel cross mule), to investigate the transferability of the prediction equations directly across to other breeds of sheep. As part of this study, the IMF levels across the breed types and sexes were also compared and found that IMF was significantly affected by breed type (P<0.001) with Scottish Blackface lambs having higher levels of IMF when compared to Texel cross mule lambs, and the lowest levels of IMF were in the purebred Texel lambs at the same liveweight or similar levels of carcass fatness. Sex also had a significant effect on IMF across breeds (P<0.001) with females having higher levels of IMF at similar levels of both carcass fat and liveweight, and within breed, females had significantly higher levels of IMF in both the purebred Texel and Scottish Blackface lambs, when compared at similar levels of carcass fat and liveweight (P<0.05). Using the models previously developed in purebred Texel to predict IMF in the Scottish Blackface and Texel cross mule, accuracies were found to be R2 = 0.57 – 0.64 and R2 = 0.37 – 0.38 respectively. Providing evidence that the equations are transferable across to some breeds more successfully than others, however, given that there is currently no method of accurately estimating IMF in vivo, accuracies across to both breeds are acceptable. The genetic parameter estimation was unsuccessful using the same research-derived dataset as previously employed in the study. However the ambition was always to investigate the genetic relationships between traits in a large industry dataset, exploiting the wealth of commercial CT information available. These investigations were considerably more successful, and among the first to present genetic parameters of novel CT-derived IMF estimates. The results found moderate heritability estimates of h2 0.31 and 0.36 for the final selected prediction equations, with clear indications that one model not including CT predicted carcass fat or any other fat measures, was more independent of these measures and the two separate prediction methods were highly genetically correlated with each other (rg = 0.89). The results from this study show that not only is it possible to accurately estimate IMF levels in the loin of Texel sheep using CT scanning, but that, until breed specific predictions are developed, the methods developed in this study are transferable across some breed types. The results also show that CT predicted IMF is heritable, independent of overall fatness and has the potential to be included in current breeding programmes. These findings can now be used to develop breeding programmes which enable breeders to make the best use of CT scanning technology to improve carcass composition while maintaining or possibly improving aspects of meat (eating) quality.

Orientador: Francisco Antonio Bertoz / Banca: Eduardo Cesar Almada Santos / Banca: José Augusto Sproesser / Banca: Ney Soares de Araújo / Banca: Thomaz Wassal / Resumo: O objetivo nesta pesquisa foi analisar os resultados obtidos comparativamente entre as telerradiografias cefalométricas laterais convencional, digital e as geradas pela tomografia computadorizada por aquisição volumétrica Cone Beam (CBTC). Foram realizadas distintamente as três tomadas radiográficas em 35 pacientes que estavam compreendidos na faixa etária de 12 a 14 anos. Foram utilizados dois programas específicos para a realização das análises cefalométricas de Rickets, McNamara e Jarabak, sendo utilizadas medidas lineares e angulares dos traçados. Apenas no traçado de Jarabak, foram utilizadas duas medidas lineares, para todas as outras, foi usada somente uma mensuração. Quatro tipos de exames radiográficos associados aos programas de análise cefalométrica foram utilizados. Por considerar o melhor resultado nos valores obtidos, a variável de referência foi a aquisição volumétrica CBTC em norma ortogonal, sendo comparado com os outros métodos. Verificou-se que os resultados obtidos pelas medidas angulares apresentaram menor variabilidade, enquanto as medidas lineares somente no traçado cefalométrico de McNamara obteve-se similaridade das variáveis. Observou-se que as técnicas radiográficas cefalométricas laterais convencionais apresentaram as maiores discrepâncias em relação à variável de referência. As análises cefalométricas realizadas pelo mesmo programa obtiveram os melhores resultados. Concluiu-se que para a obtenção de análises cefalométricas mais fidedignas deve-se utilizar um mesmo programa de avaliação e a tecnologia digital, principalmente a aquisição volumétrica CBTC em norma ortogonal e a telerradiografia cefalométrica lateral digital. / Abstract: The aim of this research was to analyze the results obtained comparatively among digital and conventional lateral cephalometric teleradiographies and the ones generated by Cone Beam volume computerized tomography (CBCT). Three distinct radiographies were performed in 35 patients in a 12 to 14 year-old group. Two specific programs were used to perform the cephalometric analysis according to Ricketts, McNamara and Jarabak, using linear and angular measurements of tracings. Two linear measurements were used just for Jarabak's tracing, for all the others only one measurement was used. Four types of radiographic exams associated to the cephalometric analysis program were used. For considering the best result in the obtained values, the variable of reference was the volume acquisition (CBCT) being compared to the other methods. It was verified that the results obtained by angular measurements presented less variability, while the linear measurements only in McNamara's cephalometric tracing presented similarity of variables. It was observed that the conventional lateral cephalometric radiography techniques presented bigger discrepancies in relation to the variable of reference. The cephalometric analysis performed by the same evaluation program had the best results. It was concluded that in order to obtain more reliable cephalometric analysis, one should use the same evaluation program and digital technology, particularly the volume acquisition (CBCT) in octagonal norm and digital lateral cephalometric teleradiography. / Doutor

Orientador: Paulo Sergio Flores Campos / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-05T11:37:50Z (GMT). No. of bitstreams: 1 PenaNetoSegundo_Nilson_D.pdf: 2587191 bytes, checksum: 9144a7add2d477be411c0fce5a4d451f (MD5) Previous issue date: 2005 / Resumo: As fixações zigomáticas são uma alternativa aos enxertos ósseos na reabilitação de maxilas severamente atróficas. Os implantes zigomáticos possuem comprimento três a quatro vezes maior que os implantes convencionais e sua colocação requer muita habilidade e precisão cirúrgica, já que sua trajetória passa pelo interior do seio maxilar e seu ponto de travamento é no corpo do osso zigomático. Desvios do ângulo de inserção e erros de estimativa do comprimento do implante colocam em risco estruturas tão nobres quanto a órbita. O objetivo no presente estudo foi estabelecer e validar um protocolo de exame por tomografia computadorizada que permitisse ao radiologista estimar o comprimento do implante, tornando o procedimento cirúrgico mais previsível e seguro, com o mínimo de exposição do paciente à radiação. Foram utilizados dez crânios humanos secos com maxilas edêntulas e processos alveolares completamente reabsorvidos. Cortes tomográficos paracoronais foram executados e os comprimentos e ângulos horizontais de inserção foram estimados. Em seguida, os espécimes foram submetidos a um procedimento cirúrgico para colocação de implantes zigomáticos (n=20) e conseqüente determinação dos comprimentos real e clínico dos sítios de implante. As médias dos comprimentos tomográfico (CTC), clínico (CCLIN) e real (CREAL) foram: 45,73 ±4,82mm, 42,63 ±4,33mm e 44,73 ±4,53mm, respectivamente. O teste t de Student não revelou diferença estatisticamente significante entre as médias de CREAL e CTC (P=0,1532), ao passo que as médias de CREAL e CCLIN foram estatisticamente diferentes entre si (P<0,0001). O estudo de correlação (Coeficiente de Pearson) revelou que as variáveis analisadas correlacionavam-se significativamente entre si, de forma direta. O protocolo proposto mostrou-se preciso e eficaz na determinação do comprimento de implantes zigomáticos, o que garante ao paciente uma exposição à radiação relativamente baixa, em função da pequena quantidade de cortes tomográficos utilizada / Abstract: Zygomatic fixations offer an alternative to bone grafts in the rehabilitation of severely atrophic maxillas. Zygomatic implants are three to four times longer than conventional implants, and their positioning requires extreme surgical precision and skill, since they must be inserted in the maxillary sinus and their locking point is situated in the body of the zygomatic bone. Deviations in the angle of insertion and miscalculated estimates of the length of the implants may pose a risk to such important structures as the orbit. The present study aimed to establish and validate a testing protocol based on computed tomography that would allow radiologists to better estimate the length of the implants, making the surgical procedure more predictable and safer, and minimizing the patients¿ exposure to radiation. Ten dry edentulous human skulls with completely reabsorbed alveolar processes were used. Tomographic paracoronal images were obtained, and the lengths and horizontal angles of insertion were estimated. Next, the specimens underwent a surgical procedure for insertion of zygomatic implants (n=20) and determination of both actual and clinical lengths of the implants¿ locations. The tomographic, clinical and actual average lengths obtained were 45.73 ±4.82mm, 42.63 ±4.33mm, and 44.73 ±4.53mm, respectively. While Student¿s t-test did not reveal any statistically significant difference between the actual and the tomographic average lengths (P=0.1532), the actual and the clinical average lengths were statistically different (P<0.0001). The correlation study (Pearson¿s coefficient) revealed a significant and direct correlation among the analyzed variables. The proposed protocol proved to be not only precise but also efficient in determining the length of zygomatic implants, ensuring relatively low exposure of patients to radiation due to the small amount of tomographic scans needed. / Doutorado / Radiologia Odontologica / Doutor em Radiologia Odontológica

Radiography is a common radiologic investigation despite abundant evidence of its limited diagnostic value. On the other hand, computed tomography (CT) has a high diagnostic value and is widely considered to be among the most important advances in medicine. However, CT exposes patients to a higher radiation dose and it might therefore not be acceptable simply to replace radiography with CT, despite the powerful diagnostic value of this technique. At the expense of reduced CT image quality, which could be adjusted to the diagnostic needs, low-dose CT of abdomen and lumbar spine can be performed at similar dose to radiography. The aim of the current thesis project was to evaluate low-dose CT of the abdomen and lumbar spine and to compare it with radiography. The hypothesis was that CT would give better image quality and diagnostic information compared to radiography at similar dose levels. Firstly, the diagnostic accuracy of low-dose CT of the abdomen was evaluated. Results showed that low-dose CT of abdomen has a high sensitivity and specificity compared to radiography, i.e., it has higher diagnostic accuracy. Similar results were obtained from our systematic review. Secondly, in a phantom study, an ovine phantom was scanned at various CT settings. The image quality was evaluated to obtain a protocol for the optimal settings for low-dose CT of lumbar spine at 1 mSv. This new protocol was then used in a clinical study to assess the image quality of low-dose CT of the lumbar spine and compare it to radiography. Results showed that low-dose CT has significantly better image quality than radiography. Finally, the impact of Iterative reconstruction (IR) on image quality of lumbar spine CT was tested. Iterative reconstruction is a recent CT technique aimed to reduce radiation dose and/or improve image quality. The results showed that the use of medium strength IR levels in the reconstruction of CT image improves image quality compared to filtered back projection. In conclusion, low-dose CT of the abdomen and lumbar spine, at about 1 mSv, has better image quality and gives diagnostic information compared to radiography at similar dose levels and it could therefore replace radiography.

No description available.

In X-ray computed tomography, motion of the object (breathing, for example) while X-ray projections are acquired for tomographic reconstruction leads to mo- tion artifacts in the reconstructed image. Object motion (such as that of breathing lungs) during acquisition of a computed tomography scan causes artifacts in the reconstructed image due to the reason that the source and detectors require a finite amount of time to rotate around the object while acquiring measurements even as the object is changing with time. With traditional reconstruction algorithms, the object is assumed to be stationary while data is acquired. However, in the case of dynamic tomography, the projection data that is acquired is not consistent, as it is data measured from an object that is deformed at each view angle of measurement. In this work, we propose a method for estimation of general (non-rigid) small motion for dynamic tomography from motion-corrupted projection data. For a static object, the Helgason-Ludwig consistency conditions impose some structure on the moments of the projections. However in the case of dynamic object (result- ing in motion-corrupted projections) this is violated. In the proposed method, we estimate motion parameters of the general motion model from the moments of the dynamic projections. The dynamic object can be modeled as f (g(x, t)) where g is a time-dependent warping function. The non-linear problem of solving a system involving composition of functions is dealt with in the Fourier transform space where it simplifies into a problem involving multiplicatively separable functions. The system is then linearized to solve for object motion. We assume a general basis function in our model. For numerical simulations, we use polynomial and B-spline basis functions as special cases of the basis functions. Simulation is performed by applying known deformations to the Shepp-Logan phantom, to a head slice of the Visible Human phantom and a thorax slice of the Zubal phantom. Simulations are performed for projections generated by parallel- beam and fan-beam geometry. Simulation for fan-beam geometry are performed by rebinning the motion corrupted fan beam projections to parallel beam projections, followed by the proposed motion estimation method. Simulation for the Visible Human phantom and the thorax slice of the Zubal phantom are performed for fan- beam geometry. Poisson noise is also added to the generated dynamic projections before motion estimation is performed. To solve the ill-posed problem of motion estimation by the proposed method, we use a Tikhonov type regularization that involves minimizing an objective function that is the sum of a data discrepancy term, a term that penalizes temporal variation of motion, and another term to penalize large magnitudes of motion. Using the estimated motion, the original image has been reconstructed from the motion corrupted projection data, with the knowledge of the underlying motion which is estimated by the proposed algorithm, by an algebraic technique similar to the dynamic SART algorithm from the literature. Here, a SART-type coefficient matrix is computed using ray tracing with rays whose paths are warped according to the estimated motion. The dynamic image at t = 0 is then reconstructed with using the computed dynamic SART matrix.

Orientador: Alexandre Campane Vidal / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-24T11:53:39Z (GMT). No. of bitstreams: 1 Belila_AlineMariaPocas_M.pdf: 4962104 bytes, checksum: f61b885a8c2ed37b65751400d6efc90b (MD5) Previous issue date: 2014 / Resumo: A caracterização de reservatórios carbonáticos é um trabalho complexo devido a alta heterogeneidade dessas rochas. Com as recentes descobertas dos reservatórios barremianos/aptianos pertencentes a fase rifte da Bacia de Santos, observa-se a importância de novos estudos que auxiliem a interpretação e caracterização destes reservatórios. Com este propósito, foram estudadas sucessões carbonáticas aflorantes da Formação Morro do Chaves, Bacia de Sergipe-Alagoas, análogas aos reservatórios da Bacia de Santos. A caracterização destas rochas foi realizada através do estudo de afloramentos para avaliar aspectos de escala mais ampla e descrição petrográfica para identificação de características em micro-escala, visando a identificação das potenciais fácies reservatório com base nos dados petrofísicos. O espaço poroso foi caracterizado utilizando imagens de tomografia computadorizada de raios-x, determinando a heterogeneidade, anisotropia e volume elementar representativo das amostras. Para a utilização dos dados de tomografia, é proposto um novo método de segmentação de imagens tridimensionais baseado na rede neural de Self-Organizing Maps. A partir dos resultados, foram determinados o valor da porosidade absoluta e conectividade do espaço poroso, validando o método como uma ferramenta consistente para a análise quantitativa e qualitativa do espaço poroso em rochas heterogêneas / Abstract: The carbonate reservoir characterization is a complex activity due to the high heterogeneity of these rocks. The recent Barremian/Aptian reservoirs discoveries belonging to the rift phase of the Santos Basin, shows the importance of further studies to assist the reservoirs interpretation and characterization. For this purpose, outcropping carbonate successions of Morro do Chaves Formation in Sergipe-Alagoas Basin were studied, analogous to Santos Basin reservoirs. The rock characterization was developed through the study of outcrops to evaluate aspects of larger scale and petrographic description to assess micro-scale characteristics in order to identify of potential reservoir facies based on petrophysical data. The pore space was characterized using x-ray computed tomography images, determining the heterogeneity, anisotropy and representative elementary volume of the samples. For the tomography data, a new method is proposed for three-dimensional image segmentation based on neural network Self-Organizing Maps. From the results, we determined the absolute value of porosity and pore space connectivity, validating the method as a consistent tool for quantitative and qualitative analysis of the pore space in heterogeneous rocks / Mestrado / Geologia e Recursos Naturais / Mestra em Geociências

Introducción: La actual pandemia de COVID-19 es causada por el virus SARS-Cov-2, un betacoronavirus que puede provocar una gripe o desencadenar una tormenta de citoquinas, llegando a causar una neumonía severa o una falla multiorgánica. Desde el inicio de la pandemia se ha venido discutiendo sobre el valor diagnóstico de las pruebas de imagen para la COVID-19, resaltando el uso de la TC de tórax. Objetivo: Evaluar el uso de la TC de tórax como prueba diagnóstica en pacientes sospechosos de neumonía por COVID-19 en la clínica Anglo Americana de Lima, Perú en el año 2020. Material y métodos: Estudio de precisión diagnóstica retrospectivo, en el cual se incluirán mediante censo a 627 pacientes que hayan ingresado por Emergencia Respiratoria de la clínica y cuenten con resultado de RT-PCR para SARS-CoV-2 y TC de tórax, en esta última se clasificará como positiva para compromiso pulmonar por COVID-19 si cumple con los hallazgos de las categorías CO-RADS 4 y 5. Se evaluará la sensibilidad, especificidad, VPP y VPN de la TC de tórax en comparación con la RT-PCR para SARS-CoV-2 para el diagnóstico de COVID-19.

Rentgenová počítačová mikrotomografie (CT) je metoda pro trojrozměrné (3D) zobrazování vnitřní struktury objektů. Laboratoř rentgenové počítačové mikro a nanotomografie na CEITEC VUT (Středoevropský technologický institut, Vysoké učení technické v Brně) se zaměřuje zejména na nedestruktivní analýzu v průmyslovém odvětví. Ukázalo se ale, že tato metoda nachází široké uplatnění i v dalších vědeckých oblastech včetně vývojové biologie. Tato práce poskytuje propojení mezi materiálovými a živými vědami. Kompletní proces vedoucí k vytvoření 3D modelu různých anatomických struktur je detailně popsán. Tento postup zahrnuje kontrastování vzorků, samotné CT měření a analýzu dat. Právě zpracování dat je mnohdy považováno za nejdůležitější část v rentgenové počítačové tomografii a proto je této oblasti věnována v práci největší část. Úpravou měřicích parametrů byl dále optimalizován CT přístroj GE v|tome|x L 240 za účelem umožnění automatické segmentace. Navíc je diskutována možnost měření na synchrotronu za účelem zvýšení prostorového rozlišení a diferenciálního kontrastu. Předpokládá se, že v blízké budoucnosti získají průmyslové CT přístroje podobné zobrazovací vlastnosti, a to jak díky nedávnému vývoji v oblasti hardwaru, tak v oblasti zpracování dat.

This study is carried out to develop the workflow from image acquisition to numerical simulation for asphalt concrete (AC) microstructure. High resolution computed tomography (CT) images are acquired and the image quality is improved using digital image processing (DIP). Non-uniform illumination which results in inaccurate phase segmentation is corrected by applying an illumination profile to correct the background and flat-fields in the image. Distance map based watershed segmentation is used to accurately segment the phases and separate the aggregates. Quantitative analysis of the microstructure is used to determine the phase volumetric relationship and aggregates characteristics. The results of the phase reconstruction and internal structure quantification using this procedure shows a very high level of reliability. Numerical simulations are carried out in Two dimensions (2D) and Three dimensions (3D) on the processed AC microstructure. Finite element analysis (FEM) is used to capture the strength and deformation mechanisms of the AC microstructure. The micromechanical behaviour of the AC is investigated when it is considered as a continuum and when considered as a multi-phase model. The results show that the size and arrangement of aggregates determines the stress distribution pattern in the mix.