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Variable flip angle balanced steady‐state free precession for lower SAR or higher contrast cardiac cine imaging
Author(s) -
Srinivasan Subashini,
Ennis Daniel B.
Publication year - 2014
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.24764
Subject(s) - flip angle , biomedical engineering , cardiac imaging , magnetic resonance imaging , medicine , radiology
Purpose Cardiac cine balanced steady‐state free precession (bSSFP) imaging uses a high flip angle (FA) to obtain high blood‐myocardium signal‐to‐noise and contrast‐to‐noise ratios (CNR). Use of high FAs, however, results in substantially increased SAR. Our objective was to develop a variable FA bSSFP cardiac cine imaging technique with: (1) low SAR and blood‐myocardium CNR similar to conventional constant FA bSSFP (CFA‐bSSFP) or (2) increased blood‐myocardium CNR compared to CFA‐bSSFP with similar SAR. Methods Variable FA bSSFP cardiac cine imaging was achieved using an asynchronous k‐space acquisition, which is asynchronous to the cardiac cycle (aVFA‐bSSFP). Bloch simulations and phantom experiments were performed to compare the signal, resolution, and frequency response of the variable FA bSSFP and CFA‐bSSFP schemes. Ten volunteers were imaged with different aVFA‐bSSFP and asynchronous CFA‐bSSFP schemes and compared to conventional segmented CFA‐bSSFP. Results The SAR of aVFA‐bSSFP is significantly decreased by 36% compared to asynchronous CFA‐bSSFP (1.9 ± 0.2 vs. 3.0 ± 0.2 W/kg, P < 10 −10 ) for similar blood‐myocardium CNR (34 ± 6 vs. 35 ± 9, P = 0.5). Alternately, the CNR of the aVFA‐bSSFP is improved by 28% compared to asynchronous CFA‐bSSFP (49 ± 9 vs. 38 ± 8, P < 10 −4 ) with similar SAR (3.2 ± 0.5 vs. 3.3 ± 0.5 W/kg, P = 0.6). Conclusion aVFA‐bSSFP can be used for lower SAR or higher contrast cardiac cine imaging compared to the conventional segmented CFA‐bSSFP imaging. Magn Reson Med 71:1035–1043, 2014. © 2013 Wiley Periodicals, Inc.