3D-imaging of the Liver by Free-Breath SPACE with a 3.0T MRI system

Multi-slice 2D turbo spin echo (TSE) sequences are widely used for T2-weighted MR imaging of the liver. On the other hand, there is a demand for 3D imaging to enable the observation of thinner slices, though 3D TSE has often been associated with a high SAR (specific absorption rate) which is caused by repeated 180-degree refocusing pulses. The high SAR has been a limiting factor for 3D TSE, especially with 3.0 Tesla scanners. We carried out free-breath 3D SPACE T2-weighted MR imaging of the liver to yield TSE contrast. This is a variant of 3D TSE that employs specially-designed refocusing pulses to reduce the SAR. The PACE (prospective acquisition correction) technique was used to eliminate motion artifacts that appear conspicuously at 3 Tesla as compared with 1.5 Tesla. The 3D SPACE parameters were as follows; FOV=384mm and base matrix size=320, effective slice thickness=1.2mm. Five volunteers were examined with this sequence on a 3.0-Tesla whole-body scanner. The acquired isotropic 3D image data set was processed with both multi-planar reconstruction (MPR) and volume rendering technique (VRT) to yield images with high quality and very distinct continuity. Such processing was possible due to the isotropic 1.2-mm resolution made feasible by the 3D SPACE sequence. 3D T2-weighted imaging of the liver was performed successfully and safely by combining 3D SPACE and PACE, and the high-resolution isotropic image data assured the continuity of blood vessels and the cystic duct of the liver. I.