الفهرس 
Chapter 1 IntroductionOnly 14 pages are availabe for public view
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Abstract
An urgent need for early detection and diagnosis of diseases continuously pushes the advancements of imaging modalities and contrast agents. Current challenges include fast and detailed imaging of tissue’s microstructures and lesion’s characterization. Such requirements that could be achieved via the development of nontoxic contrast agents with longer circulation time to keeping nanoparticles in blood for sufficiently long times so as to allow them to reach their target. Nanoparticles are free from bleaching, the cross-section is much larger, and the plasmonic resonance band is broadly tunable with particle shape and size, making it an ideal and robust contrast agent for long-term observation. This thesis reports application of the plasmonic gold nanostructures in medical imaging based on scattering, photothermal, and photoacoustic techniques. Subsequently, it studies plasmonic nanoparticles and particularly gold nanostars as signal enhancers, and contrast agents for bioimaging based scattering applications. In this thesis, the optical properties of the nanoparticles of different sizes and morphology were compared. The results illustrated that by studying the different shapes of nanoparticles, the best results in terms of light scattering efficiency then quality, and resolution of medical images were the nanostars. The nanoparticles of the gold stars and the effect of changing the number of spikes of the stars were investigated in detail. It was found that by increasing the number of spikes of the gold nanostars, the scattering of light increases. This leads to a great improvement in the quality of the medical images. In addition, increasing the length of the spikes of the nanostar increases the scattering of light thus improvement in resolution and clear images. The effect of the number of stars as well as the distance between them was also studied. As the number of gold nsnostars increases, the scattering of light increases, and as the distance between stars decreases, the scattering increases. In summary, all of these factors can be controlled and changed to obtain the best results for light scattering contrast agents and thus increase the quality of medical imaging based on scattering modalities includes darkfield microscopy, optical coherent tomography, reflectance confocal microscopy, and Diffuse reflectance spectroscopy.