Thyroid autoimmunity and thyroid nodule elasticity - relation to thyroid nodule biological nature.

Tyreoidální uzly představují velmi častou patologii. S využitím moderních ultrazvukových přístrojů jejich prevalence dosahuje až 68 %. Nejzásadnějším úkolem je včasná detekce tyreoidálního karcinomu, který sice tvoří asi 5-15 % klinicky signifikantních uzlů, ale jeho incidence stále stoupá. Ani s využitím aspirační biopsie tenkou jehlou není vždy možné rozhodnout o biologické povaze uzlu. Velká část těchto pacientů je pak nucena podstoupit diagnostickou operaci štítné žlázy, která je spojena s riziky pro pacienta a zároveň s finančními náklady pro zdravotní systém. V posledních desetiletích je snaha o zlepšení neinvazivní diagnostiky biologické povahy tyreoidálních uzlů. Elasticita tyreoidálních uzlů stanovená pomocí elastografického vyšetření a přítomnost tyreoidální autoimunity patří mezi zkoumané rizikové parametry. S využitím strain elastografie jsme v naší práci prokázali, že tyreoidální karcinomy mají signifikantně sníženou elasticitu v porovnání s benigními tyreoidálními uzly. Elastografie tyreoidálních uzlů může být využita jako vhodný doplněk konvenčního sonografického vyšetření. Kombinace obou vyšetření zvyšovala negativní prediktivní hodnotu v porovnání s konvenčním přístupem. Výsledky naší práce dále naznačují, že pro potřebu semikvantitativní analýzy elastografie tyreoidálních uzlů...Thyroid nodules represent a very common pathology. Using modern high-resolution ultrasound, nodules could be found in up to 68 % of patients. The most important task is the diagnosis of thyroid cancer which represents only about 5-15 % of nodules, however the incidence is still growing. Even with the use of a fine needle aspiration biopsy, it is not always possible to decide on the biological nature of the nodule. A significant proportion of such patients have to undergo thyroid surgery for diagnostic reason. Thyroid surgery is associated with risks to the patient and financial costs to the health-care system. In recent decades, the efforts to improve non-invasive diagnostics of thyroid nodules have been made. The thyroid elastography and thyroid autoimmunity are among the examined risk parameters. Using real-time strain elastography, thyroid carcinomas elasticity has been significantly reduced compared to benign thyroid nodules in our group of patients. The elastography of thyroid nodules can be used as a suitable complement to conventional sonographic examination. In our work, the combination of both methods (conventional ultrasound and elastography) increased the negative predictive value compared to both methods individually. The results of our work further indicate that, in case of absence of...3rd Medical Department - Clinical Department of Endocrinology and MetabolismIII. interní klinika - klinika endokrinologie a metabolismu 1. LF UK a VFN1. lékařská fakultaFirst Faculty of Medicin

The role of hydrodynamic interactions in the dynamics and viscoelasticity of actin networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 143-146).Actin, the primary component of the cytoskeleton, is the most studied semi-flexible filament, yet its dynamics remains elusive. We show that hydrodynamic interactions (HIs) significantly alter the time scale of actin deformation by 2-20 fold at different levels of network structure. For a single fiber, HIs between the mesh-sized segments can change the net force by up to 7 fold. Relaxation times are underestimated, if HIs are ignored, but mode shapes are not affected. HIs can explain deviation of the relaxation times from standard worm like chain models, speculated to be due to internal viscosity of the filament. HIs affect filament alignment, a necessary step for bundle formation. Ignoring HIs can result in up to 20-fold overestimation of shear loss modulus in the 2 ym range investigated. Even for a 1 mg/ml F-actin (0.1% volume fraction), HIs cannot be neglected whether the network is discretized into beads or rods. A shear loss modulus, slightly dependent on system-size, can be defined consistent with (intrinsic) viscoelasticity. However, axial loss modulus follows a quadratic system-size dependency consistent with poroelasticity. Our results suggest that including HIs is critical for consistency in theoretical models or analyzing experimental observation in cytoskeleton mechanics and dynamics. We also propose a new rod method to incorporate the HIs accurately and effectively. This method includes HIs in the larger systems, the same way as typical bead models, but it can decrease the computational cost by up to 100,000 fold. The primary part of this thesis deals with the viscous properties of the cytoskeletal actin networks investigated via theoretical bottom-up approaches in the nm to pm ranges. However, initially we focus on elastic properties of arterial tissue in the pm to mm ranges via an experimental top-down approach. We develop a combined robust registration and inverse elasticity method to investigate the mechanical properties of arterial tissue. We quantify the accuracy of this method with simulated problems and in vitro gels. This method can identify lipid pools via OCT (optical coherence tomography) and assess plaque rupture risk for cardiovascular diagnosis. The method can also be used as a model-based registration technique.Key words: Actin, Hydrodynamic Interactions, Relaxation Time, Cytoskeleton, Rod Model, Brownian Dynamics, Viscoelasticity, Poroelasticity, Length-Scale Dependent, Inverse Elasticity Problem, Registration, Optical Coherence Tomography (OCT), Atherosclerotic Plaque, Cardiovascular Mechanics.by Reza Karimi.Ph.D