Extending slice coverage for breathhold fat-suppressed T2-weighted fast spin-echo of the liver at 3.0T: Application of Variable-Rate Selective-Excitation (VERSE) RF pulses

Purpose: To determine the benefits of variable-rate selective-excitation (VERSE) radio frequency (RF) pulses for increased slice coverage in breathhold (BH) fat-suppressed T2-weighted fast spin-echo (FS-T2W-FSE) liver imaging at 3.0T. Materials and Methods: A total of 12 healthy volunteers were imaged on 3.0T, using FS-T2W-FSE. Slice coverage and specific absorption rate (SAR) levels were monitored for VERSE-RF and standard-RF (sRF), respectively. BH time was 25 seconds; slice thickness 3.5 mm. Maximum coverage was recorded for interactive variation of repetition time (TR), bandwidth (BW), and echo-train length (ETL). Image quality was assessed qualitatively and quantitatively. Results: Total slice coverage was always higher using VERSE-RF, but varied depending on the selected parameters. For BW ≥ 62.5 kHz, slice coverage using VERSE increased between 38% (TR = 8200 msec) and 58% (TR = 2500 msec). Maximum coverage was obtained for TR = 5000 msec, ETL = 12, and BW ≥ 62.5 kHz; with a mean of 31.8 slices for VERSE-RF and 22.5 slices for sRF, respectively (P < 0.005, 41% increased coverage). SAR was lower for VERSE-RF using BW < 41.67 kHz (P < 0.05), and equal to sRF for higher BW. Image quality was best for TR ≤ 5000 msec (P < 0.05). FS was more homogeneous for lower ETL (P < 0.05). Blood suppression was best for TR ≤ 5000 msec (P < 0.05). Conclusion: VERSE-RF pulses can be applied for thin-slice BH FS-T2W liver imaging at 3.0T, with significantly improved slice coverage.