Automatic, localized in Vivo adjustment of all first‐and second‐order shim coils

Abstract

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 (Z², ZX, ZY, X²‐Y², 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 ¹³C, ³¹P, and ¹H spectroscopy of the human brain resulted in linewidths of ∼2 Hz for ¹³C (144‐ml volume), ∼2.5 Hz for ³¹P (36‐ml volume) and ∼4 Hz for ¹H (36‐ml volume) with symmetric and reproducible lineshapes.