K-t-GRAPPA accelerated flow measurements
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POSTER PRESENTATION
Open Access
K-t-GRAPPA accelerated flow measurements Bernd A Jung1*, Simon Bauer1, Jelena Bock1, Michael Markl2 From 15th Annual SCMR Scientific Sessions Orlando, FL, USA. 2-5 February 2012 Background Parallel imaging can reduce scan time with typical reduction factors of ~2, often not sufficient to reduce scan time to breath hold duration. Spatiotemporal parallel imaging such as k-t-GRAPPA allows for a significantly higher speed-up in data acquisition, but previous studies mostly acquired full k-space data while removing data retrospectively. Here, aortic flow scans were acquired during breath-hold using kt-GRAPPA based reconstruction [1,2] and compared to conventional protocols using GRAPPA and navigator respiration gating.
Results Images in Fig.1a clearly demonstrate improved image quality of the breath-hold scans compared to freebreathing. The mean velocity time courses in Fig.1b show good agreement between kt-GRAPPA and conventional 2D-PC. A slight underestimation of peak velocities by conventional GRAPPA data can be seen whereas both kt-GRAPPA scans demonstrated an excellent agreement and less low pass filtering, corroborated by
Methods PC imaging in the ascending aorta (venc 1.5m/s) was performed on a 3T system (Trio, Siemens) using a 12channel thorax coil with three different scans in 10 healthy volunteers: 1) Breath-hold using kt-GRAPPA (R=5/Rnet=4.0); 2) Free-breathing using conventional GRAPPA (R=2/ Rnet=1.7); 3) Free-breathing using kt-GRAPPA (R=5/ Rnet=4.0). Scan parameters were: thickness 8mm, matrix 256x160 (1.3x1.5mm), temporal resolution 28ms, 6mm navigator gating window for free-breathing scans, scan time 12s for breath-hold scan (R=5) and 55s for freebreathing scan (R=2) assuming a 50% navigator efficiency and an RR-interval of 0.9s. The reconstruction was directly implemented into the Siemens image reconstruction environment. Velocity time courses and peak velocities in the ascending aorta were determined. Further, 4D flow scans were acquired with GRAPPA (R=2/Rnet=1.6), and kt-GRAPPA (R=5/Rnet=4.4 and R=8/Rnet=6.2) in a healthy volunteer using acquisition patterns for R=5 and 8 according to [3]. Streamline visualization and velocity time courses were evaluated and compared. 1 Dept. of Radiology, Medical Physics, University Medical Center, Freiburg, Germany Full list of author information is available at the end of the article
Figure 1
© 2012 Jung et al; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Jung et al. Journal of Cardiovascular Magnetic Resonance 2012, 14(Suppl 1):P257 http://www.jcmr-online.com/content/14/S1/P257
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References 1. Jung : MRM. 2008, 60:1169. 2. Huang : MRM. 2005, 54:1172. 3. Jung : MRM. 2011, Epub. doi:10.1186/1532-429X-14-S1-P257 Cite this article as: Jung et al.: K-t-GRAPPA accele
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