Requirements for room temperature shimming of the human brain

Room temperature (RT) shims are used routinely in MRI to remove global and local B 0 field inhomogeneity introduced by the subject. Most clinical scanners use only second‐order spherical harmonic terms, but with the increasing availability of very high field systems, third‐ and fourth‐order terms are a serious consideration. However, choosing appropriate coil strengths is of critical importance in shim coil design since overspecification of the shim strengths can lead to a variety of problems, including shim coil self‐resonance. In this study B 0 field map data collected over a period of 6 months (over 400 brain volumes) were analyzed to find the characteristic B ‐fields required to shim these brains. These data can be used to specify the coil requirements to effectively shim the human brain. Magn Reson Med, 2006. © 2005 Wiley‐Liss, Inc.