Manyetik parçacık görüntülemede relaksasyon haritalama

Cataloged from PDF version of article.Thesis (M.S.): Bilkent University, Department of Electrical and Electronics Engineering, İhsan Doğramacı Bilkent University, 2018.Includes bibliographical references (leaves 45-51).Magnetic Particle Imaging (MPI) is a novel biomedical imaging modality that shows great potential in terms of sensitivity, resolution, and contrast. Since its first introduction in 2005, several applications of MPI have already been demonstrated such as angiography, stem cell tracking, and cancer imaging. Recently, multi-color MPI techniques have been proposed to increase the functionality of MPI, where different nanoparticles are distinguished according to the differences in their responses to oscillating magnetic fields. These methods can also be extended to probe environmental factors such as viscosity and temperature, provided that the responses of different nanoparticles or nanoparticles in different environments are pre-calibrated. This thesis proposes a new multi-color MPI technique that does not require a calibration phase. This new technique directly estimates the relaxation time constants of nanoparticles to distinguish nanoparticle types and environmental factors from the MPI signal, and generates a multi-color relaxation map. The validity of the proposed technique is confirmed through an extensive experimental work with an in-house Magnetic Particle Spectrometer (MPS) at 10.8 kHz and an in-house MPI scanner at 9.7 kHz drive field frequencies, successfully distinguishing different nanoparticle types. The proposed calibration-free multi-color MPI technique is a promising method for future functional imaging applications of MPI.by Yavuz Muslu.M.S

Blind Source Separation for Multi-Color MPI

In magnetic particle imaging (MPI), different magnetic nanoparticles (MNPs) in the same field-of-view can be distinguished via color-MPI techniques. Existing system-function-based techniques require extensive calibration scans, whereas x-space-based approaches require either multiple scans at different drive field parameters, or rely on the underlying mirror symmetry of the adiabatic MPI signal. In this work, we propose a novel blind source separation technique for multi-color MPI, exploiting the distinct signal delays of different MNPs. The proposed technique blindly decomposes the MPI signals from different MNPs, which can then be individually reconstructed and assigned to separate color channels to form a multi-color MPI image.   Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009058, DOI: 10.18416/IJMPI.2020.200905

Rapid Relaxation-Based Color MPI

Color magnetic particle imaging (MPI) techniques have recently gained popularity, with the purposes of distinguishing different nanoparticle types or nanoparticles in different environments. In this work, we extend a relaxation-based color MPI technique that we recently proposed, and make it applicable to rapid trajectories that distort the underlying mirror symmetry of the adiabatic MPI signal. We propose a method to recover the mirror symmetry, with delay and signal amplitude compensations. The proposed technique rapidly produces a relaxation map of the scanned region, without any prior information about the nanoparticles.    Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009040, DOI: 10.18416/IJMPI.2020.200904

Does altitude affect blood gases in hemodialysis patients?

Introduction This study aimed to determine whether predialysis blood gases is affected by altitude differences in hemodialysis patients with arteriovenous fistulas living in Turkey at three different altitudes. Methods Patients' predialysis blood gases were compared by standardizing both arterial blood gases collections and working methods for patients undergoing hemodialysis using a dialysate with the same properties at altitudes of 30 m (sea level), 1020 m (moderate altitude), and 1951 m (high altitude). Findings Blood gases disorders were detected in 32 (82.1%) high altitude group patients, whereas 49 (74.2%) sea level group patients had no blood gases disorders (P < 0.001). pH values in the high altitude group were significantly lower than those in the other groups, and the pH increased as altitude decreased (P < 0.001). The partial pressure of carbon dioxide (PaCO2) values was higher in the sea level group than in the other groups and increased at lower sea levels (P < 0.001). Bicarbonate values were significantly higher in the sea level group than in the other groups and increased at lower sea levels, similar to PaCO(2)values (P < 0.001). The partial pressure of oxygen (PaO2) values in the high altitude and sea level groups were significantly higher and increased at lower sea levels (P < 0.001). The oxygen saturation (SaO(2)) values were significantly lower in the high altitude group than in the other groups and increased gradually at lower sea levels (P < 0.001). Discussion Predialysis metabolic acidosis was more pronounced in patients undergoing hemodialysis at high altitudes, whereas PaCO2, PaO2, and SaO(2)values were lower