Single-shot half-Fourier RARE sequence with ultra short inter-echo spacing for lung imaging

Purpose: To improve the image quality of pulmonary magnetic resonance (MR) imaging using an ultra-short interecho spacing half-Fourier single shot rapid acquisition with relaxation enhancement (USHA-RARE) sequence. Materials and Methods: Pulmonary MR images were acquired by USHA-RARE sequence with various inter-echo spacings. The sequence parameters were as follows: repetition time (TR)/effective TE: infinite/39-41 msec; section thickness: 10 mm; acquisition matrix: 128 × 128; field of view: 450 × 450 mm. Inter-echo spacing varied (2.5 msec, 3.0 msec, 3.5 msec, 4.0 msec, 4.5 msec, 5.0 msec), and the respective phase-encoding steps were 80, 77, 75, 74, 73, and 72. Signal-to-noise ratios (SNRs), the signal ratios between lung and fat (lung-to-fat ratio: LFRs), and the signal ratios between the lung and the serratus anterior muscle (lung-to-muscle ratio: LMRs) of each inter-echo spacing were calculated, and statistically evaluated. Results: The SNRs at inter-echo spacings of ≤ 3.0 msec were significantly higher than those ≥ 4.0 msec (P < 0.05). The LFRs and LMRs at inter-echo spacing ≤ 3.0 msec were significantly higher than those ≥ 4.0 msec (P < 0.05). Conclusion: USHA-RARE sequence does improve signal intensity from the lung.