Download Mitigation of Artifacts in T1-weighted Spiral Projection Imaging

School of Electrical, Computer and Energy Engineering
PhD Final Oral Defense
Mitigation of Artifacts in T1-weighted Spiral Projection Imaging
by
Ryan K. Robison
April 15, 2010
9:00 a.m.
GWC 409
Committee:
Dr. James G. Pipe (co-chair)
Dr. Lina Karam (co-chair)
Dr. David Frakes
Dr. David Allee
Abstract
Magnetic Resonance Imaging (MRI) is a proven method of obtaining high resolution,
high contrast images of soft tissue. Among the various applications of MRI, T1-weighted
contrast imaging is a staple in the diagnosis of many different diseases. Threedimensional (3D) T1-weighted MRI provides additional information in many cases but
also requires significantly longer scan times. This work introduces Spiral Projection
Imaging (SPI) as a 3D T1-weighted MRI acquisition capable of providing high quality
images in a reduced total scan time.
The majority of MRI acquisition methods utilize a rectilinear sampling of k-space. Many
alternative approaches have emerged over the history of MRI. One such approach
samples k-space while spiraling outward from the origin and is known as spiral MRI.
Spiral MRI serves as the basis of SPI. It provides greater sampling and signal-to-noise
ratio (SNR) efficiency than the standard Cartesian acquisitions. Unfortunately, spiral
MRI also suffers from many degradations introduced by off-resonant signal and gradient
field distortions among other effects.
Several approaches of mitigating the effects of gradient field errors and lipid offresonant signal are presented. They are shown to significantly improve the quality of T1weighted SPI data acquired in a spoiled gradient echo acquisition. The quality of SPI data
is compared to the standard 3D Cartesian acquisition. The quality of SPI is found to be
comparable to that of the Cartesian acquisition. However, the proposed reduction in scan
time and improvement in SNR efficiency is not achieved in this work due to limitations
imposed by off-resonance blurring.
Rigid body motion of the patient’s head is another source of artifact in T1-weighted
imaging of the brain. It is shown that SPI can track rigid body patient motion directly
from the acquired data. The SPI data can then be reconstructed in a manner that accounts
for the motion and produces a significant reduction in motion related artifact.