Optimized 3D ultrashort echo time pulmonary MRI

Authors

  • Kevin M. Johnson,

    Corresponding author
    1. Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA
    • Department of MR/CT Research, University of Wisconsin-Madison, 1122l Wisconsin Institutes Medical Research, 1111 Highland Ave., Madison, WI 53705-2275. E-mail: kmjohnson3@wisc.edu

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  • Sean B. Fain,

    1. Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA
    2. Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA
    3. Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, USA
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  • Mark L. Schiebler,

    1. Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA
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  • Scott Nagle

    1. Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA
    2. Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA
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Abstract

Purpose

To optimize 3D radial ultrashort echo time MRI for high resolution whole-lung imaging.

Methods

3D radial ultrashort echo time was implemented on a 3T scanner to investigate the effects of: (1) limited field-of-view excitation, (2) variable density readouts, and (3) radial oversampling. Improvements in noise performance and spatial resolution were assessed through simulation and phantom studies. Their effects on lung and airway visualization in five healthy male human subjects (mean age 32 years) were compared qualitatively through blinded ordinal scoring by two cardiothoracic radiologists using a nonparametric Friedman test (P < 0.05). Relative signal difference between endobronchial air and adjacent lung tissue, normalized to nearby vessel, was used as a surrogate for lung tissue signal. Quantitative measures were compared using the paired Student's t-test (P < 0.05). Finally, clinical feasibility was investigated in a patient with interstitial fibrosis.

Results

Simulation and phantom studies showed up to 67% improvement in SNR and reduced blurring for short T2* species using all three optimizations. In vivo images showed decreased artifacts and improved lung tissue and airway visualization both qualitatively and quantitatively.

Conclusion

The use of limited field-of-view excitation, variable readout gradients, and radial oversampling significantly improve the technical quality of 3D radial ultrashort echo time lung images. Magn Reson Med 70:1241–1250, 2013. © 2012 Wiley Periodicals, Inc.

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