981 resultados para Radiography, panoramic
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Anterior cruciate ligament (ACL) tear is a common sports injury of the knee. Arthroscopic reconstruction using autogenous graft material is widely used for patients with ACL instability. The grafts most commonly used are the patellar and the hamstring tendons, by various fixation techniques. Although clinical evaluation and conventional radiography are routinely used in follow-up after ACL surgery, magnetic resonance imaging (MRI) plays an important role in the diagnosis of complications after ACL surgery. The aim of this thesis was to study the clinical outcome of patellar and hamstring tendon ACL reconstruction techniques. In addition, the postoperative appearance of the ACL graft was evaluated using several MRI sequences. Of the 175 patients who underwent an arthroscopically assisted ACL reconstruction, 99 patients were randomized into patellar tendon (n=51) or hamstring tendon (n=48) groups. In addition, 62 patients with hamstring graft ACL reconstruction were randomized into either cross-pin (n=31) or interference screw (n=31) fixation groups. Follow-up evaluation determined knee laxity, isokinetic muscle performance and several knee scores. Lateral and anteroposterior view radiographs were obtained. Several MRI sequences were obtained with a 1.5-T imager. The appearance and enhancement pattern of the graft and periligamentous tissue, and the location of bone tunnels were evaluated. After MRI, arthroscopy was performed on 14 symptomatic knees. The results revealed no significant differences in the 2-year outcome between the groups. In the hamstring tendon group, the average femoral and tibial bone tunnel diameter increased during 2 years follow-up by 33% and 23%, respectively. In the asymptomatic knees, the graft showed homogeneous and low signal intensity with periligamentous streaks of intermediate signal intensity on T2-weighted MR images. In the symptomatic knees, arthroscopy revealed 12 abnormal grafts and two meniscal tears, each with an intact graft. Among 3 lax grafts visible on arthroscopy, MRI showed an intact graft and improper bone tunnel placement. For diagnosing graft failure, all MRI findings combined gave a specificity of 90% and a sensitivity of 81%. In conclusion, all techniques appeared to improve patients' performance, and were therefore considered as good choices for ACL reconstruction. In follow-up, MRI permits direct evaluation of the ACL graft, the bone tunnels, and additional disorders of the knee. Bone tunnel enlargement and periligamentous tissue showing contrast enhancement were non-specific MRI findings that did not signify ACL deficiency. With an intact graft and optimal femoral bone tunnel placement, graft deficiency is unlikely, and the MRI examination should be carefully scrutinized for possible other causes for the patients symptoms.
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Bone stress injuries of the foot have been known for more than 150 years. For a century, their primary diagnostic imaging tool has been radiography. However, currently the golden standard for establishing the diagnosis of stress injuries is magnetic resonance imaging (MRI). Although the injury type has been fairly well documented in the earlier literature, little information is available on the healing of stress injuries located in e.g. the talus and calcaneus. The current study retrospectively evaluated the stress injuries of the foot and ankle treated at the Central Military Hospital over a period of eight years in patients who underwent MRI for stress injury of the foot. The imaging studies of the patients were reevaluated to determine the exact nature of the stress injury. Moreover, the hospital records of the patients were reviewed to determine the healing of stress injuries of the talus and calcaneus. Patients with a stress fracture in the talus were recalled for a follow-up examination and MRI scan one to six years after the initial injury to determine if the fracture had completely healed, clinically and radiologically. The bone stress injuries of the foot were found to affect more than one bone in a majority of the cases. The talus and the calcaneus were the bones most commonly affected. In the talus, the most common site for the injuries was the head of the bone, and in the calcaneus, the posterior part of the bone. The injuries in these bones were associated with injuries in the surrounding bones. Stress injuries in the calcaneus seemed to heal well. No complications were seen in the primary healing process. The patients were, however, sometimes compelled to refrain from physical training for up to months. In the talus, minor degenerative findings of the articular surface were seen in half of the patients who participated in a follow-up MRI scan and radiographs taken one to six years after the initial injury. Half of the patients also reported minor exercise related symptoms in the follow-up. The symptoms were, however, not noticeable in everyday life.
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Acute knee injury is a common event throughout life, and it is usually the result of a traffic accident, simple fall, or twisting injury. Over 90% of patients with acute knee injury undergo radiography. An overlooked fracture or delayed diagnosis can lead to poor patient outcome. The major aim of this thesis was retrospectively to study imaging of knee injury with a special focus on tibial plateau fractures in patients referred to a level-one trauma center. Multi-detector computed tomography (MDCT) findings of acute knee trauma were studied and compared to radiography, as well as whether non-contrast MDCT can detect cruciate ligaments with reasonable accuracy. The prevalence, type, and location of meniscal injuries in magnetic resonance imaging (MRI) were evaluated, particularly in order to assess the prevalence of unstable meniscal tears in acute knee trauma with tibial plateau fractures. The possibility to analyze with conventional MRI the signal appearance of menisci repaired with bioabsorbable arrows was also studied. The postoperative use of MDCT was studied in surgically treated tibial plateau fractures: to establish the frequency and indications of MDCT and to assess the common findings and their clinical impact in a level-one trauma hospital. This thesis focused on MDCT and MRI of knee injuries, and radiographs were analyzed when applica-ble. Radiography constitutes the basis for imaging acute knee injury, but MDCT can yield information beyond the capabilities of radiography. Especially in severely injured patients , sufficient radiographs are often difficult to obtain, and in those patients, radiography is unreliable to rule out fractures. MDCT detected intact cruciate ligaments with good specificity, accuracy, and negative predictive value, but the assessment of torn ligaments was unreliable. A total of 36% (14/39) patients with tibial plateau fracture had an unstable meniscal tear in MRI. When a meniscal tear is properly detected preoperatively, treatment can be combined with primary fracture fixation, thus avoiding another operation. The number of meniscal contusions was high. Awareness of the imaging features of this meniscal abnormality can help radiologists increase specificity by avoiding false-positive findings in meniscal tears. Postoperative menisci treated with bioabsorbable arrows showed no difference, among different signal intensities in MRI, among menisci between patients with operated or intact ACL. The highest incidence of menisci with an increased signal intensity extending to the meniscal surface was in patients whose surgery was within the previous 18 months. The results may indicate that a rather long time is necessary for menisci to heal completely after arrow repair. Whether the menisci with an increased signal intensity extending to the meniscal surface represent improper healing or re-tear, or whether this is just the earlier healing feature in the natural process remains unclear, and further prospective studies are needed to clarify this. Postoperative use of MDCT in tibial plateau fractures was rather infrequent even in this large trauma center, but when performed, it revealed clinically significant information, thus benefitting patients in regard to treatment.
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The structure and operation of CdTe, CdZnTe and Si pixel detectors based on crystalline semiconductors, bump bonding and CMOS technology and developed mainly at Oy Simage Ltd. And Oy Ajat Ltd., Finland for X- and gamma ray imaging are presented. This detector technology evolved from the development of Si strip detectors at the Finnish Research Institute for High Energy Physics (SEFT) which later merged with other physics research units to form the Helsinki Institute of Physics (HIP). General issues of X-ray imaging such as the benefits of the method of direct conversion of X-rays to signal charge in comparison to the indirect method and the pros and cons of photon counting vs. charge integration are discussed. A novel design of Si and CdTe pixel detectors and the analysis of their imaging performance in terms of SNR, MTF, DQE and dynamic range are presented in detail. The analysis shows that directly converting crystalline semiconductor pixel detectors operated in the charge integration mode can be used in X-ray imaging very close to the theoretical performance limits in terms of efficiency and resolution. Examples of the application of the developed imaging technology to dental intra oral and panoramic and to real time X-ray imaging are given. A CdTe photon counting gamma imager is introduced. A physical model to calculate the photo peak efficiency of photon counting CdTe pixel detectors is developed and described in detail. Simulation results indicates that the charge sharing phenomenon due to diffusion of signal charge carriers limits the pixel size of photon counting detectors to about 250 μm. Radiation hardness issues related to gamma and X-ray imaging detectors are discussed.
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This thesis is a study of the x-ray scattering properties of tissues and tumours of the breast. Clinical radiography is based on the absorption of the x-rays when passing right through the human body and gives information about the densities of the tissues. Besides being absorbed, x-rays may change their direction within the tissues due to elastic scattering or even to refraction. The phenomenon of scattering is a nuisance to radiography in general, and to mammography in particular, because it reduces the quality of the images. However, scattered x-rays bear very useful information about the structure of the tissues at the supra-molecular level. Some pathologies, like breast cancer, produce alterations to the structures of the tissues, being especially evident in collagen-rich tissues. On the other hand, the change of direction due to refraction of the x-rays on the tissue boundaries can be mapped. The diffraction enhanced imaging (DEI) technique uses a perfect crystal to convert the angular deviations of the x-rays into intensity variations, which can be recorded as images. This technique is of especial interest in the cases were the densities of the tissues are very similar (like in mammography) and the absorption images do not offer enough contrast. This thesis explores the structural differences existing in healthy and pathological collagen in breast tissue samples by the small-angle x-ray scattering (SAXS) technique and compares these differences with the morphological information found in the DEI images and the histo-pathology of the same samples. Several breast tissue samples were studied by SAXS technique in the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Scattering patterns of the different tissues of the breast were acquired and compared with the histology of the samples. The scattering signals from adipose tissue (fat), connective tissue (collagen) and necrotic tissue were identified. Moreover, a clear distinction could be done between the scattering signals from healthy collagen and from collagen from an invasive tumour. Scattering from collagen is very characteristic. It includes several scattering peaks and scattering features that carry information about the size and the spacing of the collagen fibrils in the tissues. It was found that the collagen fibrils in invaded tumours were thinner and had a d-spacing length 0,7% longer that fibrils from healthy tumours. The scattering signals from the breast tissues were compared with the histology by building colour-coded maps across the samples. They were also imaged with the DEI technique. There was a total agreement between the scattering maps, the morphological features seen in the images and the information of the histo- pathological examination. The thesis demonstrates that the x-ray scattering signal can be used to characterize tissues and that it carries important information about the pathological state of the breast tissues, thus showing the potential of the SAXS technique as a possible diagnostic tool for breast cancer.
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Differentiation of various types of soft tissues is of high importance in medical imaging, because changes in soft tissue structure are often associated with pathologies, such as cancer. However, the densities of different soft tissues may be very similar, making it difficult to distinguish them in absorption images. This is especially true when the consideration of patient dose limits the available signal-to-noise ratio. Refraction is more sensitive than absorption to changes in the density, and small angle x-ray scattering on the other hand contains information about the macromolecular structure of the tissues. Both of these can be used as potential sources of contrast when soft tissues are imaged, but little is known about the visibility of the signals in realistic imaging situations. In this work the visibility of small-angle scattering and refraction in the context of medical imaging has been studied using computational methods. The work focuses on the study of analyzer based imaging, where the information about the sample is recorded in the rocking curve of the analyzer crystal. Computational phantoms based on simple geometrical shapes with differing material properties are used. The objects have realistic dimensions and attenuation properties that could be encountered in real imaging situations. The scattering properties mimic various features of measured small-angle scattering curves. Ray-tracing methods are used to calculate the refraction and attenuation of the beam, and a scattering halo is accumulated, including the effect of multiple scattering. The changes in the shape of the rocking curve are analyzed with different methods, including diffraction enhanced imaging (DEI), extended DEI (E-DEI) and multiple image radiography (MIR). A wide angle DEI, called W-DEI, is introduced and its performance is compared with that of the established methods. The results indicate that the differences in scattered intensities from healthy and malignant breast tissues are distinguishable to some extent with reasonable dose. Especially the fraction of total scattering has large enough differences that it can serve as a useful source of contrast. The peaks related to the macromolecular structure come to angles that are rather large, and have intensities that are only a small fraction of the total scattered intensity. It is found that such peaks seem to have only limited usefulness in medical imaging. It is also found that W-DEI performs rather well when most of the intensity remains in the direct beam, indicating that dark field imaging methods may produce the best results when scattering is weak. Altogether, it is found that the analysis of scattered intensity is a viable option even in medical imaging where the patient dose is the limiting factor.
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Hormone therapy (HT) is widely used to relieve climacteric symptoms in order to increase the well-being of the women. The benefits as well as side-effects of HT are well documented. The principal menopausal oral symptoms are dry mouth (DM) and sensation of painful mouth (PM) due to various causes. Profile studies have indicated that HT users are more health-conscious than non-users. The hypothesis of the present study was that there are differences in oral health between woman using HT and those not using HT. A questionnaire study of 3173 women of menopausal age (50-58 years old) was done to investigate the prevalence of self-assessed sensations of PM and DM. Of those women participating in the questionnaire study, a random sample of 400 (200 using, 200 not using HT) was examined clinically in a 2-year follow-up study. Oral status was recorded according to WHO methods using DMFT and CPITN indices. The saliva flows were measured, salivary total protein, albumin and immunoglobulin concentrations and selected periodontal micro-organisms were analysed, and panoramic tomography of the jaws was taken. The patients filled in a structured questionnaire on their systemic health, medication and health habits. According to our questionnaire study there was no significant difference in the occurrence of self- assessed PM or DM between the HT users and non-users. According to logistic regression analyses, climacteric complaints significantly correlated with the occurrence of PM (p=0.000) and DM (p=0.000) irrespective of the use of HT, indicating that PM and DM are associated with climacteric symptoms in general. There was no difference between the groups in DMFT index values at follow up. The number of filled teeth (FT) showed a significant (p<0.05) increase in the HT group at follow-up. Periodontitis was diagnosed in 79% of HT users at baseline and in 71% at the follow-up. The values for non-HT users were 80% vs. 76%, respectively (Ns.). The mean numbers of ≥ 6 mm deep periodontal pockets were 0.9 ± 1.7 at baseline vs. 1.1 ± 2.1 two years later in the HT group, and 1.0 ± 1.7 vs. 1.2 ± 1.9, respectively, in the non-HT group. In a large Finnish national health survey, the prevalence of peridontitis of women of this age group was lower, but the prevalence of severe periodontitis seemed to be higher than in our study. Salivary albumin, IgG and IgM concentrations decreased in the HT group during the 2-year follow up (p<0.05), possibly indicating an improvement in epithelial integrity. No difference was found in any other salivary parameters or in the prevalence of the periodontal bacteria between or within the groups. In conclusion, the present findings showed that 50 to 58 year old women living in Helsinki have fairly good oral and dental health. The occurrence of PM and DM seemed to be associated with climacteric symptoms in general, and the use of HT did not affect the oral symptoms studied.
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Because of the wide variety of projected applications of ultrapure nitrides in advanced technologies, there is interest in developing new cost-effective methods of synthesis. Explored in this study is the use of ammonia and hydrazine for the synthesis of nitrides from oxides, sulfides and chlorides. Even when the standard Gibbs energy change for the nitridation reactions involved are moderately positive, the reaction can be made to proceed by lowering the partial pressure of the product gas below its equilibrium value. Use of a metastable form of precursor in the nanometric size range is an alternative method to facilitate nitridation. Ellingham-Richardson-Jeffes diagrams are used for a panoramic presentation of the driving force for each set of reactions as a function of temperature. Oxides are the least promising precursors for nitride synthesis; sulfides offer a larger synthetic window for many useful nitrides such as BN, AlN, InN, VN, TiN, ThN and Si3N4. The standard Gibbs free energy changes for reactions involving chlorides with either ammonia or hydrazine are much more negative. Hydrazine is a more powerful nitriding agent than ammonia. The metastability of hydrazine requires that it be introduced into a reactor through a water-cooled lance. The use of volatile halides with ammonia or hydrazine offers the potential for synthesis of pure and doped nanocrystalline nitrides. Nitride thin films can also be prepared by suitable adaptations of the chloride route. (C) 2002 Kluwer Academic Publishers.
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It is important to know and to quantify the liquid holdups both dynamic and static at local levels as it will lead to understand various blast furnace phenomena properly such as slag/metal.gas.solid reactions, gas flow behaviour and interfacial area between the gas/solid/liquid. In the present study, considering the importance of local liquid holdup and non-availability of holdup data in these systems, an attempt has been made to quantify the local holdups in the dropping and around raceway zones in a cold model study using a non-wetting packing for liquid. In order to quantify the liquid holdups at microscopic level, a previously developed technique, X-ray radiography, has been used. It is observed that the liquid flows in preferred paths or channels which carry droplets/rivulets. It has been found that local holdup in some regions of the packed bed is much higher than average at a particular flow rate and this can have important consequences for the correct modelling of such systems.
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The mechanical behaviour of composite materials differs from that of conventional structural materials owing to their heterogeneous and anisotropic nature. Different types of defects and anomalies get induced in these materials during the fabrication process. Further, during their service life, the components made of composite materials develop different types of damage. The performance and life of such components is governed by the combined effect of all these defects and damage. While porosity, voids, inclusions etc., are some defects those can get induced during the fabrication of composites, matrix cracks, interface debonds, delaminations and fiber breakage are major types of service induced damage which are of concern. During the service life of components made of composites, one type of damage can grow and initiate another type of damage. For example, matrix cracks can gradually grow to the interface and initiate debonds. Interface debonds in a particular plane can lead to delaminations. Consequently, the combined effect of different types of distributed damage causes the failure of the component. A set of non-destructive evaluation (NDE) methods is well established for testing conventional metallic materials. Some of them can also be utilized for composite materials as they are, and in some cases with a little different approach or modification. Ultrasonics, Radiography, Thermography, Fiber Optics, Acoustic Emision Techniques etc., to name a few. Detection, evaluation and characterization of different types of defects and damage encountered in composite materials and structures using different NDE tools is discussed briefly in this paper.
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[ES] China ha irrumpido como actor principal del escenario global al haber protagonizado, durante las tres últimas décadas, un proceso de transformación económica y social de gran magnitud. Ahora bien, vender productos –sobre todo, del sector de alimentación– de origen occidental en China es, con diferencia, el reto más complicado al que deben enfrentarse las compañías de deciden entrar a operar en este mercado.
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[ES] Los siguientes enlaces proporcionan información adicional sobre este texto:
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Wide field-of-view (FOV) microscopy is of high importance to biological research and clinical diagnosis where a high-throughput screening of samples is needed. This thesis presents the development of several novel wide FOV imaging technologies and demonstrates their capabilities in longitudinal imaging of living organisms, on the scale of viral plaques to live cells and tissues.
The ePetri Dish is a wide FOV on-chip bright-field microscope. Here we applied an ePetri platform for plaque analysis of murine norovirus 1 (MNV-1). The ePetri offers the ability to dynamically track plaques at the individual cell death event level over a wide FOV of 6 mm × 4 mm at 30 min intervals. A density-based clustering algorithm is used to analyze the spatial-temporal distribution of cell death events to identify plaques at their earliest stages. We also demonstrate the capabilities of the ePetri in viral titer count and dynamically monitoring plaque formation, growth, and the influence of antiviral drugs.
We developed another wide FOV imaging technique, the Talbot microscope, for the fluorescence imaging of live cells. The Talbot microscope takes advantage of the Talbot effect and can generate a focal spot array to scan the fluorescence samples directly on-chip. It has a resolution of 1.2 μm and a FOV of ~13 mm2. We further upgraded the Talbot microscope for the long-term time-lapse fluorescence imaging of live cell cultures, and analyzed the cells’ dynamic response to an anticancer drug.
We present two wide FOV endoscopes for tissue imaging, named the AnCam and the PanCam. The AnCam is based on the contact image sensor (CIS) technology, and can scan the whole anal canal within 10 seconds with a resolution of 89 μm, a maximum FOV of 100 mm × 120 mm, and a depth-of-field (DOF) of 0.65 mm. We also demonstrate the performance of the AnCam in whole anal canal imaging in both animal models and real patients. In addition to this, the PanCam is based on a smartphone platform integrated with a panoramic annular lens (PAL), and can capture a FOV of 18 mm × 120 mm in a single shot with a resolution of 100─140 μm. In this work we demonstrate the PanCam’s performance in imaging a stained tissue sample.
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O estudo epidemiológico transversal randomizado objetivou avaliar condições de saúde bucal nos competidores dos XV Jogos Pan-Americanos (JPA) e III Jogos Parapan-Americanos (JPPA), 2007. Foram enviados convites para 5.662 atletas (JPA) e 1.300 (JPPA). Radiografias panorâmicas digitais (RPD) foram utilizadas para o exame de triagem nos 2 eventos, e nos JPPA, os atletas também foram submetidos à avaliação do sangramento gengival interdental (SI) através de uma versão modificada do Índice de Sangramento Interdental de Eastman (EIBI). Foram obtidas RPDs de 410 atletas dos JPA, média de idade 24,38 (dp5,35), 55% homens; e de 118 dos atletas dos JPPA, média de idade de 32,3 (dp9,53), 77,97% homens. 121 competidores (JPPA) foram avaliados para SI: 78,51% homens, média de idade 32,6(dp9,6), e foram separados em grupos (G), conforme sua deficiência física: GI c/ deficiência visual (DV), com 2 subgrupos: GI-a: DV tardia e GI-c-: DV congênita/precoce; GII- deficiência de membro superior; com 1 subgrupo: GII-t: deficiência/ausência bilateral; GIII- deficiência de membro inferior (grupo controle). As RPDs foram examinadas por 1 examinador com o Kodak Dental Imaging(v6.7). A frequência e a distribuição do SI foram calculadas, e os grupos foram comparados. Resultados da triagem com RPDs, representados por número de observações(média por atleta) JPA//número de observações(média por atleta JPPA: Dentes erupcionados/ hígidos: 9097(22,19)//2451(20,77); Ausentes: 803(1,96 //405(3,43); Não erupcionados ou impactados: 330(0,80)//52(0,44); Parcialmente erupcionados e/ou hígidos: 109(0,27)//20(0,17); Cárie extensa: 261(0,64)//62(0,53); Cárie extensa e lesão periapical: 96(0,23)//50(0,42); Tratamento endodôntico e lesão periapical: 24(0,06)//13(0,11); Restaurados: 2298(5,60)//670(5,68); Imagens radiolúcidas patológicas circunscritas: 23(0,06)//0; Raízes-residuais: 27(0,07)//22(0,19); Implantes:6(0,01)//5(0,04); Dentes anteriores fraturados: 13 (0,03)//3(0,03); Molares bandados: 26(0,06)//11(0,09); Dentes anômalos: 7(0,02)//12(0,10). Resultados para SI: G-I>G-III (p=0.0002);GI-c>GI-a (p=0,042). Homens exibiram > freqüência de SI (3,6%+1,7) que mulheres (0,8%+0,5), p<0,01. Conclusões: Os dados das 2 populações de atletas mostraram que há uma grande variação na saúde bucal entre os indivíduos avaliados. Diversas condições com potencial de influenciar o desempenho esportivo dos atletas foram detectadas através de radiografias panorâmicas digitais, sugerindo que um programa de saúde bucal deve ser incluído como parte da preparação destes indivíduos.A avaliação da frequência e distribuição de sangramento gengival interdental em uma população de atletas que competiu nos III Jogos Parapan-Americanos, revelou que o tipo de deficiência ou limitação física dos competidores é um fator que influencia na saúde gengival desses indivíduos. O planejamento de um programa de saúde bucal para esta população deve ser adaptado às diferentes limitações de cada atleta.
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Phosphate glasses 60P