Nagylak O. The reconstruction of spatial characteristics of the object in inverse task of Magnetic Resonance Imaging and reconstructive tomography while local echo signal distortion.

Dissertation is devoted to the investigation of tomographic methods of data reconstruction received by MR and emission projection tomography methods. Proposed methods of MR reconstruction gives the possibility to obtain more accurate diagnostic data with less impact of artifacts and without additional volume data and time reconstruction demands. The obtained properties of X-Ray radiation and biological tissues interaction in CT and calculated parameters of radiative receiving system gives us possibility to build the tomography hardware with needed characteristics to obtain tomograms of needed quality. The method of reconstruction based on pseudo-inversion matrix was proposed for reconstruction of tomograms in MR tomography when data lose. The reconstructed tomograms for different level of data lose obtained and compared with the one without data lose. The result shows that the proposed method of reconstruction can be used for correct reconstruction of tomograms when the data lose up to 30%. The reconstruction of tomograms can be performed by this method when data lose while classical reconstruction methods don't work. The method of reconstruction of tomograms that considers the interaction of magnetic moments in objects smaller then the size of voxel in traditional MRI has been used for obtaining more accurate diagnostic information.The method can be used for such type of reconstruction while the classical methods don't consider the magnetic moments interaction. For calculation of optimal parameters of CT system the method of back projection reconstruction was modified according of characteristics of energy spectrum of radiation interaction with biological tissues. The limit values of of spectrum frecuency deviation and biological tissue absorbtion coefficient were obtained. The deviation of 11,7% for bone tissues and 21,6% for soft tissues and corresponding value of biological tissue absorbtion coefficient 77% were obtained like limit values for correct tomograms reconstruction.