Sergios Gatidis1,2, Hansjörg Graf3, Jakob Weiß4, Alto Stemmer3, Berthold Kiefer3, Konstantin Nikolaou4, Mike Notohamiprodjo4, Petros Martirosian5. 1. Department of Radiology, Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany. sergios.gatidis@med.uni-tuebingen.de. 2. Department of Radiology, University Hospital Tübingen, Hoppe-Seyler-Str. 3, 72076, Tübingen, Germany. sergios.gatidis@med.uni-tuebingen.de. 3. Siemens Healthcare GmbH, Erlangen, Germany. 4. Department of Radiology, Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany. 5. Department of Radiology, Experimental Radiology, University of Tübingen, Tübingen, Germany.
Abstract
OBJECTIVE: Our objective was to compare available techniques reducing artifacts in echo planar imaging (EPI)-based diffusion-weighed magnetic resonance imaging MRI (DWI) of the neck at 3 Tesla caused by B0-field inhomogeneities. MATERIALS AND METHODS: A cylindrical fat-water phantom was equipped with a Maxwell coil allowing for additional linear B0-field variations in z-direction. The effect of increasing strength of this superimposed gradient on image quality was observed using a standard single-shot EPI-based DWI sequence (sEPI), a zoomed single-shot EPI sequence (zEPI), a readout-segmented EPI sequence (rsEPI), and an sEPI sequence with integrated dynamic shimming (intEPI) on a 3-Tesla system. Additionally, ten volunteers were examined over the neck region using these techniques. Image quality was assessed by two radiologists. Scan durations were recorded. RESULTS: With increasing strength of the external gradient, marked distortions, signal loss, and failure of fat suppression were observed using sEPI, zEPI, and rsEPI. These artifacts were markedly reduced using intEPI. Significantly better in vivo image quality was also observed using intEPI compared with the other techniques. Scan time of intEPI was similar to sEPI and zEPI and shorter than rsEPI. CONCLUSION: The use of integrated 2D shim and frequency adjustment for EPI-based DWI results in a significant improvement in image quality of the head/neck region at 3 Tesla. Combining integrated shimming with rsEPI or zEPI can be expected to provide additional improvements.
OBJECTIVE: Our objective was to compare available techniques reducing artifacts in echo planar imaging (EPI)-based diffusion-weighed magnetic resonance imaging MRI (DWI) of the neck at 3 Tesla caused by B0-field inhomogeneities. MATERIALS AND METHODS: A cylindrical fat-water phantom was equipped with a Maxwell coil allowing for additional linear B0-field variations in z-direction. The effect of increasing strength of this superimposed gradient on image quality was observed using a standard single-shot EPI-based DWI sequence (sEPI), a zoomed single-shot EPI sequence (zEPI), a readout-segmented EPI sequence (rsEPI), and an sEPI sequence with integrated dynamic shimming (intEPI) on a 3-Tesla system. Additionally, ten volunteers were examined over the neck region using these techniques. Image quality was assessed by two radiologists. Scan durations were recorded. RESULTS: With increasing strength of the external gradient, marked distortions, signal loss, and failure of fat suppression were observed using sEPI, zEPI, and rsEPI. These artifacts were markedly reduced using intEPI. Significantly better in vivo image quality was also observed using intEPI compared with the other techniques. Scan time of intEPI was similar to sEPI and zEPI and shorter than rsEPI. CONCLUSION: The use of integrated 2D shim and frequency adjustment for EPI-based DWI results in a significant improvement in image quality of the head/neck region at 3 Tesla. Combining integrated shimming with rsEPI or zEPI can be expected to provide additional improvements.
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