Interleaved flow-sensitive dephasing (iFSD): Toward enhanced blood flow suppression and preserved T weighting and overall signals in 3D TSE-based neuroimaging.

PURPOSE

To develop and validate a 3D turbo spin-echo (TSE)-compatible approach to enhancing black-blood (BB) effects while preserving T weighting and overall SNR.

METHODS

Following the excitation RF pulse, a 180° RF pulse sandwiched by a pair of flow-sensitive dephasing (FSD) gradient pulses in the phase- (y) and partition-encoding (z) directions, respectively, is added. The polarity of FSD gradients in z direction is toggled every TR, achieving an interleaved FSD (iFSD) configuration in y-z plane. The technique was optimized and evaluated in 18 healthy volunteers and 32 patients with neurovascular disease or brain metastases. Comparisons were made among TSE with and without one of BB preparations: iFSD, delay alternating with nutation for tailored excitation, and motion-sensitized driven equilibrium.

RESULTS

iFSD-TSE achieved the best blood flow suppression indicated by venous sinus SNR and parenchyma-to-sinus contrast-to-noise ratio (CNR). iFSD-TSE yielded slightly lower white matter SNR (106.6 ± 32.9) and white-to-gray matter CNR (27.3 ± 8.1) compared to TSE (111.4 ± 31.5 and 28.6 ± 8.8), which were significantly higher than those of delay alternating with nutation for tailored excitation-prepared TSE (84.3 ± 25.0 and 16.8 ± 4.8) and motion-sensitized driven equilibrium-prepared TSE (77.3 ± 26.6 and 15.9 ± 5.3). At the neurovascular wall lesions, iFSD-TSE yielded the highest wall-to-lumen CNR among the three sequences with a BB preparation, all of which significantly outperformed TSE. iFSD-TSE effectively suppressed slow-flow artifacts that otherwise mimicked an atherosclerotic lesion or strongly contrast-enhancing vessel wall. In diagnosing brain metastases, iFSD allowed for highest inter-reader agreement (κ 0.75) and shortest reading time.

CONCLUSION

iFSD is a promising approach compatible with 3D TSE for robust blood flow suppression and preserved T weighting and overall SNR.