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Automated monitoring of diaphragm end‐expiratory position for real‐time navigator echo MR coronary angiography
Author(s) -
Taylor Andrew M.,
Jhooti Permi,
Firmin David N.,
Pennell Dudley J.
Publication year - 1999
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/(sici)1522-2586(199903)9:3<395::aid-jmri6>3.0.co;2-y
Subject(s) - diaphragm (acoustics) , medicine , position (finance) , angiography , magnetic resonance imaging , nuclear medicine , computer science , radiology , physics , acoustics , finance , loudspeaker , economics
Real‐time navigator echo (NE)‐gated magnetic resonance coronary angiography (MRCA) during free respiration is now possible. However, the mean diaphragm end‐expiratory position (DEEP) drifts over time, and this results in a reduction in scanning efficiency and increased artifacts due to the acquisition of data during periods of high diaphragm velocity. To address these problems, a diaphragm monitoring program that follows the mean DEEP over time has been developed. Fifteen subjects with ischemic heart disease underwent continuous NE monitoring of their diaphragm for 30 minutes. Using these diaphragm traces, theoretical MRCA scans were performed. Several diaphragm monitoring algorithms were developed and compared with the simplest case (a stationary 5 mm NE acceptance window placed around the mean DEEP, as measured by NE monitoring at the outset of the scan). An overall scan efficiency was calculated, and the number of completed scans where the mean DEEP lay within the NE acceptance window was recorded. Of the six algorithms considered, the most effective one monitored the mean DEEP and prospectively placed the upper limit of the NE acceptance window on this position for the subsequent acquisition. Using this algorithm in comparison with the simplest stationary scenario, both scan efficiency (47.9% vs. 38.5%, P = 0.01) and the number of completed scans where the mean DEEP lay within the NE acceptance window (71.2 vs. 30.3, P < 0.001) were improved. The implementation of such a monitoring algorithm, in combination with adaptive motion correction techniques, should improve overall scan efficiency while maintaining the end‐expiratory position at the top end of the NE acceptance window, to reduce image artifacts.J. Magn. Reson. Imaging 1999;9:395–401. © 1999 Wiley‐Liss, Inc.