MRI of the Gastrointestinal Tract 2 at High - Field Strength

High-fi eld imaging of the GI tract at 3 T can be very attractive in terms of signal to noise ratio (SNR) when compared with 1.5 T imaging. However, several issues need to be addressed and a direct transition of sequences used at 1.5–3 T is not possible. The main constraints in 3 T imaging are related to changes in tissue T1 and T2 relaxation parameters, susceptibility artifacts, changes in effi ciency of contrast agents, chemical shift artifacts, B1-inhomogeneity artifacts, specifi c absorption rate (SAR) limitations, and steady-state free precession (SSFP) banding artifacts. In general, a careful adjustment of sequence parameters is needed to avoid these artifacts. The use of parallel imaging techniques is more benefi cial at 3 T when compared with 1.5 T because by reducing scan time SAR problems often present at 3 T can be avoided. For reducing B1-inhomogeneity, hardware adjustments are needed. Banding artifacts generated in SSFP-sequences pose a severe limitation to the clinical use of these sequences. Though methods exist to overcome this problem, a satisfactory solution has not been proposed so far.