Alejandro Santos-Díaz1,2, Sergei I Obruchkov3, Rolf F Schulte4, Michael D Noseworthy5,6,7. 1. School of Biomedical Engineering, McMaster University, Hamilton, ON, Canada. 2. Imaging Research Center, St. Joseph's Healthcare, Hamilton, ON, Canada. 3. Robinson Research Institute, Victoria University of Wellington, Wellington, New Zealand. 4. GE Healthcare, Munich, Germany. 5. School of Biomedical Engineering, McMaster University, Hamilton, ON, Canada. nosewor@mcmaster.ca. 6. Imaging Research Center, St. Joseph's Healthcare, Hamilton, ON, Canada. nosewor@mcmaster.ca. 7. Department of Electrical and Computer Engineering, McMaster University, Engineering Technology Building, ETB-406, 1280 Main St. West, Hamilton, ON, L8S 4K1, Canada. nosewor@mcmaster.ca.
Abstract
OBJECT: To present and evaluate a fast phosphorus magnetic resonance spectroscopic imaging (MRSI) sequence using echo planar spectroscopic imaging with flyback readout gradient trajectories. MATERIALS AND METHODS: Waveforms were designed and implemented using a 3 Tesla MRI system. 31P spectra were acquired with 2 × 2 cm2 and 3 × 3 cm2 resolution over a 20- and 21-cm field of view and spectral bandwidths up to 1923 Hz. The sequence was first tested using a 20-cm-diameter phosphate phantom, and subsequent in vivo tests were performed on healthy human calf muscles and brains from five volunteers. RESULTS: Flyback EPSI achieved 10× and 7× reductions in acquisition time, with 68.0 ± 1.2 and 69.8 ± 2.2% signal-to-noise ratio (SNR) per unit of time efficiency (theoretical SNR efficiency was 74.5 and 76.4%) for the in vivo experiments, compared to conventional phase-encoded MRSI for the 2 × 2 cm2 and 3 × 3 cm2 resolution waveforms, respectively. Statistical analysis showed no difference in the quantification of most metabolites. Time savings and SNR comparisons were consistent across phantom, leg and brain experiments. CONCLUSION: EPSI using flyback readout trajectories was found to be a reliable alternative for acquiring 31P-MRSI data in a shorter acquisition time.
OBJECT: To present and evaluate a fast phosphorus magnetic resonance spectroscopic imaging (MRSI) sequence using echo planar spectroscopic imaging with flyback readout gradient trajectories. MATERIALS AND METHODS: Waveforms were designed and implemented using a 3 Tesla MRI system. 31P spectra were acquired with 2 × 2 cm2 and 3 × 3 cm2 resolution over a 20- and 21-cm field of view and spectral bandwidths up to 1923 Hz. The sequence was first tested using a 20-cm-diameter phosphate phantom, and subsequent in vivo tests were performed on healthy humancalf muscles and brains from five volunteers. RESULTS: Flyback EPSI achieved 10× and 7× reductions in acquisition time, with 68.0 ± 1.2 and 69.8 ± 2.2% signal-to-noise ratio (SNR) per unit of time efficiency (theoretical SNR efficiency was 74.5 and 76.4%) for the in vivo experiments, compared to conventional phase-encoded MRSI for the 2 × 2 cm2 and 3 × 3 cm2 resolution waveforms, respectively. Statistical analysis showed no difference in the quantification of most metabolites. Time savings and SNR comparisons were consistent across phantom, leg and brain experiments. CONCLUSION: EPSI using flyback readout trajectories was found to be a reliable alternative for acquiring 31P-MRSI data in a shorter acquisition time.
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