Measuring and shimming the magnetic field of a 4 Tesla MRI magnet
Date
1993
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Texas A&M University
Abstract
The Biomedical Magnetic Resonance Laboratory (BMRL) of the University of Illinois at Urbana-Champaign (UIUC) has ordered from the Texas Accelerator Center (TAC) a superconducting, self-shielded, solenoidal magnet with a maximum field of 4 Tesla and a bore diameter of 1.05 in. The magnet is going to be used for research on full-body MRI which is targeted to functional imaging of the human brain. This is a completely new and promising approach to MRI. The critical specification is that the magnetic field must be homogeneous within a 25 cm. radius around the center and within 10 ppm (parts per million). The whole design is very challenging, since not many superconducting magnets of such a big diameter and, at the same time, high field exist. Even more challenging is the fact that this is the first self-shielded magnet working at such a field, which poses many design problems. Additionally, the magnet is expected to operate with the same degree of homogeneity from 1.5 to 4 Tesla. Therefore, a system had to be implemented that would map the magnetic field and calculate the necessary adjustments to be made, so that changes from one field intensity to another would be fast. Needless to say, the field homogeneity of a magnet used for MRI is of crucial importance. In this thesis, first the design of the magnet in question is described, then the theory of measuring the magnetic field of such a magnet is presented. Consequently, the device and the program which were used are explained. Last, the measurement data taken on the MAGNEX magnet are presented.
Description
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Includes bibliographical references.
Includes bibliographical references.
Keywords
physics., Major physics.