Date of Award
Summer 2002
Document Type
Thesis - Restricted
Degree Name
Master of Science (MS)
Department
Biomedical Engineering
First Advisor
Jeutter, Dean
Second Advisor
Jevtic, Jovan
Third Advisor
Ropella, Kristina
Abstract
Several different protocols are used for estimating the SNR of an MR image. Since the SNR is an indicator of both coil performance and image quality, the field of MRJ would greatly benefit from a universal and practical standard protocol resulting in normalized SNR values [15]. However, a single, straightforward method has yet to be embraced. More specifically, a standard protocol for RF coils of any number of channels is needed. This study presents a simple, practical SNR evaluation method for coils of any number of channels. In addition, a mathematical formula is presented that both determines the noise levels in different regions of the phased-array image and describes the relationship between the noise levels and the number of RF coil channels. Phantoms were scanned using three different four-channel IGC Medical Advances, Inc. phased-array coils (on a 1.5 T GE MRI system). Multiple excited phantom scans and an unexcited background scan were performed. MATLAB was used to investigate regional noise levels within the MR images. Discrepancies among smoothing orders of the noise approximation technique, deviation of measured data from theoretical noise ratios, and accuracy of the single-scan method were determined in MATLAB. Statistical analysis of the data was used to determine possible statistical significance of MR scanning variables. Results indicate statistically significant differences in MR image quality as a function of several scanning variables and a reasonable agreement between theory and experimental regional noise levels. Additionally, experimental data validated the theory relating noise levels to the number of channels. First-order smoothing of image data in the signal area was determined to be an adequate approximation technique for signal area noise, and the single-scan method was proven to be satisfactory for noise level estimation.
Recommended Citation
Meisenheimer, Laura E., "An Investigation of Noise in Phased-Array Magnetic Resonance Images" (2002). Master's Theses (1922-2009) Access restricted to Marquette Campus. 4717.
https://epublications.marquette.edu/theses/4717