Selective 3D ultrashort TE imaging: comparison of “dual-echo” acquisition and magnetization preparation for improving short-T2 contrast
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The objective of this study was to compare two different schemes for long-T2 component suppression in ultrashort echo-time (UTE) imaging. The aim was to increase conspicuity of short-T2 components accessible by the UTE technique.
Materials and methods
A “dual-echo” and a magnetization-preparation approach for long-T2 and fat suppression were implemented on clinical scanners. Both techniques were compared in 3D UTE exams on healthy volunteers regarding short-T2 Signal-to-noise ratio (SNR), long-T2 suppression quality, and scan efficiency. A quantitative SNR evaluation was performed using ankle scans of six volunteers. T2 suppression profiles were simulated for both approaches to facilitate interpretation of the observations.
At 1.5 T, both techniques perform equally well in suppressing long-T2 components and fat. Magnetization preparation requires more shimming effort due to the use of narrow-band pulses, while the “dual-echo” technique requires a post-processing step to form a subtraction image. For scans with a short repetition time (TR), the “dual-echo” approach is much faster than the magnetization preparation, which depends on slow T1 recovery between preparation steps. The SNR comparison shows slightly higher short-T2 SNR for the “dual-echo” approach. At 3.0 T, magnetization preparation becomes more challenging due to stronger off-resonance effects.
Both techniques are well suited for long-T2 suppression and offer comparable short-T2 SNR. However, the “dual-echo” approach has strong advantages in terms of scan efficiency and off-resonance behavior.
KeywordsMR imaging Ultrashort TE imaging 3D imaging Long-T2 suppression Musculoskeletal imaging
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