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Increased speed and image quality in single‐shot fast spin echo imaging via variable refocusing flip angles
Author(s) -
Loening Andreas M.,
Saranathan Manojkumar,
Ruangwattanapaisarn Nichanan,
Litwiller Daniel V.,
Shimakawa Ann,
Vasanawala Shreyas S.
Publication year - 2015
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/jmri.24941
Subject(s) - flip angle , image quality , medicine , fast spin echo , nuclear medicine , magnetic resonance imaging , fourier transform , pulse sequence , radiology , physics , computer science , artificial intelligence , image (mathematics) , quantum mechanics
Purpose To develop and validate clinically a single‐shot fast spin echo (SSFSE) sequence utilizing variable flip angle refocusing pulses to shorten acquisition times via reductions in specific absorption rate (SAR) and improve image quality. Materials and Methods A variable refocusing flip angle SSFSE sequence (vrfSSFSE) was designed and implemented, with simulations and volunteer scans performed to determine suitable flip angle modulation parameters. With Institutional Review Board (IRB) approval/informed consent, patients referred for 3T abdominal magnetic resonance imaging (MRI) were scanned with conventional SSFSE and either half‐Fourier ( n = 25) or full‐Fourier vrfSSFSE ( n = 50). Two blinded radiologists semiquantitatively scored images on a scale from −2 to 2 for contrast, noise, sharpness, artifacts, cardiac motion‐related signal loss, and the ability to evaluate the pancreas and kidneys. Results vrfSSFSE demonstrated significantly increased speed (∼2‐fold, P < 0.0001). Significant improvements in image quality parameters with full‐Fourier vrfSSFSE included increased contrast, sharpness, and visualization of pancreatic and renal structures with higher bandwidth technique (mean scores 0.37, 0.83, 0.62, and 0.31, respectively, P ≤ 0.001), and decreased image noise and improved visualization of renal structures when used with an equal bandwidth technique (mean scores 0.96 and 0.35, respectively, P < 0.001). Increased cardiac motion‐related signal loss with full‐Fourier vrfSSFSE was seen in the pancreas but not the kidney. Conclusion vrfSSFSE increases speed at 3T over conventional SSFSE via reduced SAR, and when combined with full‐Fourier acquisition can improve image quality, although with some increased sensitivity to cardiac motion‐related signal loss. J. MAGN. RESON. IMAGING 2015;42:1747–1758.