Abstract:
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Purpose: A major problem of free breathing CMRA with respiratory navigator gating is low navigator efficiency and prolonged scan time due to irregular breathing patterns. 3D MAG is a new navigator technique, which adapts in realtime to changes of the endexpiratory position of diaphragm. The aim of this study was to evaluate the influence of 3D MAG on Navigator efficiency and scan time, image quality and diagnostic accuracy in CMRA.
Methods and Materials: 3D MAG uses two additional gating windows grouped around the conventional one. Each gating window is divided into three bands which are assigned to different portions of k—space. The scan is terminated when three consecutive bands — which represent the optimized 5 mm navigator window over the entire scan — are filled and one complete image dataset is collected. 48 patients with suspected coronary artery disease underwent free breathing navigator gated CMRA (Intera, 1.5 T, Philips). An ECG gated, 3D segmented—k—space gradient echo sequence (in plane resolution 0.70 ´ 0.79 mm) was used. Scans of the coronary arteries (CA) using 3D MAG and conventional navigator technique (5 mm gating window for both techniques) were performed in random order in each patient. The following parameters were evaluated for both navigator techniques: 1. navigator efficiency, 2. scan time, 3. visualized CA length, 4. qualitative assessment of image quality (from 1 (excellent) to 4 (poor) and 5. detection of stenoses ³ 50% in correlation to catheter angiography.
Results: The average navigator efficiencies of the LCA scan and the RCA scan were 51% The average navigator efficiencies of the LCA scan and the RCA scan were 51% ± 14 and 50% ± 15 in the scans with and 42% ± 16 and 41% ± 17 in the scans without 3D MAG (p<0.05). 3D MAG resulted in a significant reduction of scan time (mean: 18% ± 4, p<0.05) for CMRA compared to conventional navigator technique. There were no significant differences in the average contiguously visualized vessel lengths and in the assessment of CA visualization between the scans with and without 3D MAG (p>0.05). There was also no significant differences in the sensitivity (89% (24/27) vs. 85% (23/27); p>0.05) and specificity (86% (18/21) vs. 81% (17/21); p>0.05) in the detection of coronary artery stenosis between scans with and without 3D MAG.
Conclusion: 3D MAG improves navigator efficiency and reduces scan time significantly (p<0.05) in navigator gated CMRA while maintaining image quality and diagnostic accuracy. This new navigator technique might be especially useful in patients with irregular breathing patterns.
Questions about this event email: Matthias.Hackenbroch@ukb.uni-bonn.de
Hackenbroch MD, M,
3D Motion Adapted-gating (3D MAG): A New Navigator Technique for Accelerated Acquisition of Free Breathing Navigator-gated 3D Coronary MR Angiography (MRA). Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3101583.html
