Browsing by Author "Unan, Mahmut 1986-"
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Item 3D Reconstruction of Tubular Structures Using MRI Projection Images(2018-05) Unan, Mahmut 1986-; Tsekos, Nikolaos V.; Shah, Dipan J.; Leiss, Ernst L.; Shi, WeidongAfter imaging information became available in digital form, techniques for acquiring volumetric data evolved. 3D reconstruction is mostly performed using multislice stack images. The objective of this dissertation is to introduce a simple magnetic resonance technique for imaging tubular structures, such as blood vessels and catheters, and 3D reconstruction of these structures. This study includes three major chapters: one on simulation and two on experiments with MRI projection images. First, a MATLAB simulation was created to analyze the reconstruction process; it was tested with different shapes of the structures and different numbers of projections. Second, triplanar projection imaging was evaluated on a phantom filled with a T1-shortening, Gd-based contrast agent embedded into a lipid matrix. The object is reconstructed from three mutually orthogonal projections of the volume that contain the structure of interest. The projected structures of the object were segmented out on each projection, back-projected to generate the segmented tubular object, and mesh-rendered in 3D. The accuracy of this approach was investigated by comparing the mesh-rendered tubular structure generated from projections with the mesh rendered from a multislice set of images of the same volume. Third, Inverse Radon Transform was implemented for 3D reconstruction of complex helical tubular structure from multiple radially deployed (oblique) projections. To compute the correctness of the 3D reconstruction processes, we compared the resulting meshes with the multislice-rendered meshes. Hausdorff distance and Point Cloud Comparison methods were used to evaluate the reconstruction error. The average error was less than 1 pixel for the triplanar projection images, and it was less than 2 pixels for the oblique orientation projection images. With further optimization and reduction of acquisition time, this method can be used for 3D fast imaging of interventional tools or segments of blood vessels with applications in interventional MRI.Item MODELING OF DUAL MODALITY PROBE FOR CONCURRENTLY COLLECTING MR AND OPTICAL SPECTRA(2013-12) Unan, Mahmut 1986-; Tsekos, Nikolaos V.; Garbey, Marc; Sonmez, Ahmet E.Magnetic Resonance Spectroscopy and Optical Spectroscopy are both the most common modalities for molecular and near-cellular imaging, and they offer a new chance for evaluating tissue characteristic in situ. Nowadays, combining multimodality sensors on a single probe is an emerging and promising trend in multimodality approach. The aim of this study is to create simulations for both MR Spectroscopy and Optical Spectroscopy in order to find out the effective areas of the sensors. Due to having MR Spectroscopy and Optical Spectroscopy on the same dual probe, this work presents two separate simulations. The first simulation was created to determine the powerful region of the miniature RF coils of the MRS, and the second simulation was programmed to detect the visible field of the tissue by using Optical Spectroscopy. The coil simulation was created by using the Biot Savart Law in the C++ environment. Additionally, two more programs were developed to test the results and display the images. In order to test the accuracy of the simulation and to figure out the optimum values for the simulation parameters, the test software was coded. With the help of optimum values, the effective area can be spotted for four different geometrical shapes of the coils. Furthermore, the software may easily be converted to evaluate any kind of coils. vi Light-induced fluorescence simulation was formed by modifying the Monte Carlo light simulation for Multi Layer tissues (MCML) code by using the Standard C programming language. The MCML code was converted to compute photon transportation in one layer and to detect the fluorescence on light propagation for different probe geometries. Moreover, a GUI was built to create input file more easily and effectively, and a Matlab program was coded to display output file as a 3-D image. The logic behind the simulations was explained comprehensively by introducing the related equations. The resulting output figures and data were presented in detail and the benefits and limitations of the simulations were discussed.