PURPOSE: To design and evaluate an optimized PETRA (point-wise encoding time reduction with radial acquisition) sequence with long-T2 suppression at 3 Tesla. METHODS: An adiabatic inversion recovery-based scheme was used to null the long-T2 signal. To minimize scan time, the signal was sampled multiple times after each inversion with variable excitation flip angles designed to yield constant short-T2 signal amplitude. The excitation pulses were phase-modulated, allowing for increased flip angle and higher signal-to-noise ratio (SNR). A fast, noniterative image reconstruction algorithm was designed to minimize image artifacts due to nonuniform excitation profile. RESULTS: Phase-modulated pulse excitation, along with the noniterative reconstruction algorithm, allows the use of larger radiofrequency pulse flip angles, resulting in effective suppression of long-T2 protons and improved image SNR without causing image artifacts. Midtibia images representative of collagen-bound water yielded SNR of 15 at 1-mm isotropic resolution in 6.5 minutes with a standard extremity coil. Further, the technology is shown to be suited for generating multi-angle projection images of bone akin to X-ray images displaying subtle anatomic detail. CONCLUSION: Optimized long-T2 suppressed PETRA allows imaging of bone matrix water unencumbered by long-T2 soft tissue and pore water protons, opening up new possibilities for anatomic bone imaging at isotropic resolution and quantification in clinically practical scan times. Magn Reson Med 77:989-997, 2017.
PURPOSE: To design and evaluate an optimized PETRA (point-wise encoding time reduction with radial acquisition) sequence with long-T2 suppression at 3 Tesla. METHODS: An adiabatic inversion recovery-based scheme was used to null the long-T2 signal. To minimize scan time, the signal was sampled multiple times after each inversion with variable excitation flip angles designed to yield constant short-T2 signal amplitude. The excitation pulses were phase-modulated, allowing for increased flip angle and higher signal-to-noise ratio (SNR). A fast, noniterative image reconstruction algorithm was designed to minimize image artifacts due to nonuniform excitation profile. RESULTS: Phase-modulated pulse excitation, along with the noniterative reconstruction algorithm, allows the use of larger radiofrequency pulse flip angles, resulting in effective suppression of long-T2 protons and improved image SNR without causing image artifacts. Midtibia images representative of collagen-bound water yielded SNR of 15 at 1-mm isotropic resolution in 6.5 minutes with a standard extremity coil. Further, the technology is shown to be suited for generating multi-angle projection images of bone akin to X-ray images displaying subtle anatomic detail. CONCLUSION: Optimized long-T2 suppressed PETRA allows imaging of bone matrix water unencumbered by long-T2 soft tissue and pore water protons, opening up new possibilities for anatomic bone imaging at isotropic resolution and quantification in clinically practical scan times. Magn Reson Med 77:989-997, 2017.
Authors: Hyunyeol Lee; Xia Zhao; Hee Kwon Song; Rosaline Zhang; Scott P Bartlett; Felix W Wehrli Journal: Magn Reson Med Date: 2018-12-18 Impact factor: 4.668
Authors: Hyungseok Jang; Yajun Ma; Adam C Searleman; Michael Carl; Jody Corey-Bloom; Eric Y Chang; Jiang Du Journal: Magn Reson Med Date: 2019-09-18 Impact factor: 4.668
Authors: Dengrong Jiang; Hanzhang Lu; Charlamaine Parkinson; Pan Su; Zhiliang Wei; Li Pan; Aylin Tekes; Thierry A G M Huisman; W Christopher Golden; Peiying Liu Journal: Magn Reson Med Date: 2019-05-07 Impact factor: 4.668