Effects of constant frequency noise in magnetic resonance imaging with nonuniform k‐space sampling
Abstract
Magnetic resonance images can be compromised by constant frequency (CF) noise, such as radio frequency (RF) noise. We investigate the effects of CF noise in four imaging methods with nonuniform k‐space sampling: single‐shot echo‐planar imaging (EPI) with sinusoidal readout gradients, phase‐encoded echo‐planar spectroscopic imaging (EPSI) with sinusoidal readout gradients, projection–reconstruction imaging, and single‐shot spiral imaging. The characteristics of the CF artifacts in each imaging method are studied with numerical simulations. CF noise is found to cause artifacts of nonclassic forms in the reconstructed images. Specifically, dashed‐line, streak, and spiral patterns of CF noise appear in EPI/EPSI with sinusoidal readout gradients, projection–reconstruction imaging, and spiral imaging, respectively. The analytical expression for dashed‐line artifacts is found to be a weighted sum of Bessel functions and is verified with in vivo experiments. The CF artifacts can be removed during post‐processing by eliminating the noise spikes in the Fourier domain of the raw data.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jul 24, 2002
- Source ID
- 10.1118/1.1496096
Entities
People
- Gregory S. Karczmar
- Weiliang Du
- Xiaochuan Pan
Organizations
- National Institutes of Health
- United States Department of Defense