3D single point imaging with compressed sensing provides high temporal resolution R 2* mapping for in vivo preclinical applications
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Purely phase-encoded techniques such as single point imaging (SPI) are generally unsuitable for in vivo imaging due to lengthy acquisition times. Reconstruction of highly undersampled data using compressed sensing allows SPI data to be quickly obtained from animal models, enabling applications in preclinical cellular and molecular imaging.
Materials and methods
TurboSPI is a multi-echo single point technique that acquires hundreds of images with microsecond spacing, enabling high temporal resolution relaxometry of large-R 2* systems such as iron-loaded cells. TurboSPI acquisitions can be pseudo-randomly undersampled in all three dimensions to increase artifact incoherence, and can provide prior information to improve reconstruction. We evaluated the performance of CS-TurboSPI in phantoms, a rat ex vivo, and a mouse in vivo.
An algorithm for iterative reconstruction of TurboSPI relaxometry time courses does not affect image quality or R 2* mapping in vitro at acceleration factors up to 10. Imaging ex vivo is possible at similar acceleration factors, and in vivo imaging is demonstrated at an acceleration factor of 8, such that acquisition time is under 1 h.
Accelerated TurboSPI enables preclinical R 2* mapping without loss of data quality, and may show increased specificity to iron oxide compared to other sequences.
KeywordsMagnetic resonance imaging Image reconstruction Three-dimensional imaging
JAR acknowledges funding from the Natural Sciences and Engineering Research Council (NSERC) Vanier Canada Graduate Scholarship program and the Killam Foundation. CVB and SDB acknowledge funding from the NSERC Discovery Grant program. Some research support during the preparation of this manuscript was provided by an investigator-sponsored research grant from GE Healthcare. Thanks to Kim Brewer, Erin Mazerolle, Christa Davis and Iulia Dude for assistance with the animal imaging experiments.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted, with protocols approved by the Dalhousie University Care for Laboratory Animals committee. This article does not contain any studies with human participants performed by any of the authors.
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