Free breathing 1H MRI of the human lung with an improved radial turbo spin-echo
To optimize a radial turbo spin-echo sequence for motion-robust morphological lung magnetic resonance imaging (MRI) in free respiration.
Materials and methods
A versatile multi-shot radial turbo spin-echo (rTSE) sequence is presented, using a modified golden ratio-based reordering designed to prevent coherent streaking due to data inconsistencies from physiological motion and the decaying signal. The point spread function for a moving object was simulated using a model for joint respiratory and cardiac motion with a concomitant T2 signal decay and with rTSE acquisition using four different reordering techniques. The reordering strategies were compared in vivo using healthy volunteers and the sequence was tested for feasibility in two patients with lung cancer and pneumonia.
Simulations and in vivo measurements showed very weak artifacts, aside from motion blur, using the proposed reordering. Due to the opportunity for longer scan times in free respiration, a high signal-to-noise ratio (SNR) was achieved, facilitating identification of the disease as compared to standard half-Fourier-acquisition single-shot turbo spin-echo (HASTE) scans. Additionally, post-processing allowed modifying the T2 contrast retrospectively, further improving the diagnostic fidelity.
The proposed radial TSE sequence allowed for high-resolution imaging with limited obscuring artifacts. The radial k-space traversal allowed for versatile post-processing that may help to improve the diagnosis of subtle diseases.
KeywordsLung Magnetic resonance imaging Radial sampling Turbo spin-echo
The authors wish to acknowledge funding from the German Research Foundation (DFG), Grant numbers DFG JA 827/8-1 and DFG JA 827/8-2.
Conflict of interest
The authors declare that they have no conflict of interest.
All human studies were approved by the ethics committee at the medical facility of Heidelberg University and written informed consent was obtained from all subjects. All studies have, therefore, been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and amendments.
- 1.Mugler JP, Driehuys B, Brookeman JR, Cates GD, Berr SS, Bryant RG, Daniel TM, De Lange EE, Downs JH, Erickson CJ, Happer W, Hinton DP, Kassel NF, Maier T, Phillips CD, Saam BT, Sauer KL, Wagshul ME (1997) MR imaging and spectroscopy using hyperpolarized 129Xe gas: preliminary human results. Magn Reson Med 37(6):809–815CrossRefPubMedGoogle Scholar
- 3.Kaushik SS, Cleveland ZI, Cofer GP, Metz G, Beaver D, Nouls J, Kraft M, Auffermann W, Wolber J, McAdams HP, Driehuys B (2011) Diffusion-weighted hyperpolarized 129Xe MRI in healthy volunteers and subjects with chronic obstructive pulmonary disease. Magn Reson Med 65(4):1154–1165CrossRefPubMedCentralPubMedGoogle Scholar
- 12.Kiefer B, Grassner J, Hausman R (1994) Image acquisition in a second with half Fourier acquisition single shot turbo spin echo. J Magn Reson Imaging 4:86–87Google Scholar
- 13.Haacke E, Lindskogj E, Lin W (1969) A fast, iterative, partial-fourier technique capable of local phase recovery. J Magn Reson 92(1):126–145Google Scholar
- 31.Speier P, Trautwein F (2006) Robust radial imaging with predetermined isotropic gradient delay correction. In: Proc ISMRM 2006 #2379. http://cds.ismrm.org/ismrm-2006/files/02379.pdf
- 42.Hennig J, Weigel M, Scheffler K (2003) Multiecho sequences with variable refocusing flip angles: optimization of signal behavior using smooth transitions between pseudo steady states (TRAPS). Magn Reson Med 49(3):527–535Google Scholar