Magnetic field strength dependence of chemical shift artifacts.
The dependence of proton MRI chemical shift artifacts on main magnetic field strength was investigated using three MR whole body systems from 0.3 to 1.5 T with both permanent and superconducting magnet designs. The magnetic field gradients varied from 0.09 to 1.0 gauss/cm. The image bandwidth varied from 8.54 to 32 kHz. Both phantoms and normal volunteers were studied. The chemical shift misregistration error in hertz was determined by the main magnetic field strength of the system which was proportional to the Larmor frequency. The actual image error in millimeters was determined by a combination of the shift in hertz as well as by the amplitude of the magnetic field gradients applied to form the image. Steeper gradients mapped a given shift in hertz onto a smaller millimeter displacement. The higher field strength systems tended to use steeper magnetic field gradients, but this increase was not enough to offset the higher absolute shift in hertz due to the higher Larmor frequencies. In general, the chemical shift in millimeters tended to increase with the increasing field strength despite the steeper imaging gradients. Based on these findings, strategies for minimizing the chemical shift artifact may be developed.
Lufkin
R
R
Department of Radiological Sciences, UCLA School of Medicine 90024.
Anselmo
M
M
Crues
J
J
Smoker
W
W
Hanafee
W
W
D000273:Adipose Tissue; D001834:Body Water; D005583:Fourier Analysis; D008279:Magnetic Resonance Imaging; D008961:Models, Structural; D010938:Plant Oils; D014867:Water
D010938:Plant Oils; D014867:Water