Single‐shot RARE with Dixon: Application to robust abdominal imaging with uniform fat and water separation at 3T

Abstract

Purpose To develop a true single shot turbo spin echo (SShTSE) acquisition with Dixon for robust T2‐weighted abdominal imaging with uniform fat and water separation at 3T. Methods The in‐phase (IP) and out‐of‐phase (OP) echoes for Dixon processing were acquired in the same repetition time of a SShTSE using partial echoes. A phase‐preserved bi‐directional homodyne reconstruction was developed to compensate the partial echo and the partial phase encoding of SShTSE. With IRB approval, the SShTSE‐Dixon was compared against standard SShTSE, without and with fat suppression using spectral adiabatic inversion recovery (SPAIR) in 5 healthy volunteers and 5 patients. The SNR and contrast ratio (CR) of spleen to liver were compared among different acquisitions. Results The bi‐directional homodyne reconstruction successfully minimized ringing artifacts because of partial acquisitions. SShTSE‐Dixon achieved uniform fat suppression compared to SShTSE‐SPAIR with fat suppression failures of 1/10 versus 10/10 in the axial plane and 0/5 versus 5/5 in the coronal plane, respectively. The SNRs of the liver (12.2 ± 4.9 vs. 11.7 ± 5.2; P = .76) and spleen (25.9 ± 11.6 vs. 23.7 ± 9.7; P = .14) were equivalent between fat‐suppressed images (SShTSE‐Dixon water‐only and SShTSE‐SPAIR). The SNRs of liver (14.4 ± 5.7 vs. 13.4 ± 5.0; P = .60) and spleen (26.5 ± 10.1 vs. 25.7 ± 8.5; P = .56) were equivalent between non‐fat‐suppressed images (SShTSE‐Dixon IP and SShTSE). The CRs of spleen to liver were also similar between fat‐suppressed images (2.6 ± 0.4 vs. 2.5 ± 0.5; P =.92) and non‐fat‐suppressed images (2.3 ± 0.6 vs. 2.2 ± 0.4; P =.84). Conclusion SShTSE‐Dixon generates robust abdominal T2‐weighted images at 3T with and without uniform fat suppression, along with perfectly co‐registered fat‐only images in a single acquisition.

Ultrafast water–fat separation using deep learning–based single‐shot MRI

“…Currently, most of the water–fat separation techniques need to acquire multiple images with different parameters, and the outcomes may be susceptible to physiological motions, such as respiratory or cardiac pulsation, or the physical movement by the patient 11 . Many efforts have been made to reduce the total scan time by either accelerating the imaging speed or reducing the required shot numbers 12–14 …”

“…11 Many efforts have been made to reduce the total scan time by either accelerating the imaging speed or reducing the required shot numbers. [12][13][14] EPI, as a classic ultrafast imaging technique, has been adopted for improving the speed of water−fat separation. [15][16][17][18][19] However, the performance of EPI-based water− fat separation is challenged by B 0 field inhomogeneity and large fat shift along the phase-encoding (PE) dimension.…”