Static and Gradient Field Inhomogeneity Compensation for Low-Cost MRI Machines

Abstract

The purpose of this research has been to develop technology necessary for Low-Cost Magnetic Resonance Imaging (LC-MRI) machines. This dissertation describes an overview of the tradeoffs necessary for LC-MRI machines and focuses on compensating for magnetic field inhomogeneity. The trade-offs for allowing inhomogeneous fields is examined. The equations describing inhomogeneity are derived for both one and two dimensions. Two methods of image compensation are compared, one from the literature and a new, proposed method. Both methods are demonstrated and analyzed on one-dimensional and two-dimensional images. The robustness of each method to uncompensated quantization errors and field mis-measurement is also examined. The computational complexity of each method is also investigated. The appendix of the dissertation covers background on MRI. The classical model of MRI is explained as well as the meaning of the time constants T1, T2, and T2*. Two fundamental pulse sequences (Field Echo and Spin Echo) are explained in detail, along with a description of k-space.