Application of PINS radiofrequency pulses to reduce power deposition in RARE/turbo spin echo imaging of the human head.
Norris DG., Boyacioğlu R., Schulz J., Barth M., Koopmans PJ.
PURPOSE: To explore the use of PINS radiofrequency (RF) pulses to reduce RF power deposition in multiband/simultaneous multislice imaging with the RARE/turbo spin echo (TSE) sequence at 3T and 7T. METHODS: A PINS-TSE sequence was implemented and combined with blipped CAIPI to improve the reconstruction of superposed slices. Whole brain imaging of healthy volunteers was performed at both 3T and 7T using a 32-channel coil for signal reception. RESULTS: A considerable reduction in power deposition was achieved compared with a standard sequence of the manufacturer. At 3T, the reduction in specific absorption rate (SAR) made short pulse repetition times (TRs) possible, however, in order to obtain a good T2 contrast, it is advisable to maintain TR while extending the echo train length. At 7T, whole brain coverage with a spatial resolution of 1 × 1 × 2 mm(3) was achieved in an acquisition time of 150 s. Furthermore, it could be shown that pulse sequences that use PINS pulses do not suffer from having additional magnetization transfer contrast. CONCLUSION: PINS RF pulses combined with multiband imaging reduce SAR sufficiently to enable routine TSE imaging at 7T within clinically acceptable acquisition times. In general, the combination of multiband imaging with PINS RF pulses represents a method to reduce total RF power deposition.