Premium
Automatic, localized in Vivo adjustment of all first‐and second‐order shim coils
Author(s) -
Gruetter Rolf
Publication year - 1993
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910290613
Subject(s) - shim (computing) , nuclear magnetic resonance , volume (thermodynamics) , residual , noise (video) , physics , signal to noise ratio (imaging) , spectroscopy , chemistry , optics , mathematics , computer science , algorithm , artificial intelligence , medicine , quantum mechanics , erectile dysfunction , image (mathematics)
The implementation of a “fast, automatic shimming technique by mapping along projections” (FASTMAP) on a 2.1‐Tesla whole‐body system is described. The method provides a localized adjustment of all first‐ (X, Y, Z) and second‐order (Z 2 , ZX, ZY, X 2 ‐Y 2 , 2XY) coils in 2 min. The time savings are achieved by mapping the magnetic field along six projections rather than from whole‐imaging data sets. An analysis of noise error propagation suggests that in 64‐ml volumes the residual linewidths obtained with the method are negligible when the signal‐to‐rms‐noise ratio is above 30. The initial application of the method to localized 13 C, 31 P, and 1 H spectroscopy of the human brain resulted in linewidths of ∼2 Hz for 13 C (144‐ml volume), ∼2.5 Hz for 31 P (36‐ml volume) and ∼4 Hz for 1 H (36‐ml volume) with symmetric and reproducible lineshapes.