Selective in vivo bone imaging with long-T2 suppressed PETRA MRI

Cheng Li, Jeremy F. Magland, Xia Zhao, Alan C. Seifert, Felix W. Wehrli

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


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.

Original languageEnglish
Pages (from-to)989-997
Number of pages9
JournalMagnetic Resonance in Medicine
Issue number3
StatePublished - 1 Mar 2017
Externally publishedYes


  • image reconstruction
  • inversion recovery
  • long-T suppression
  • phase-modulated RF excitation
  • short T
  • ultrashort echo time
  • zero echo time


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