Phase unwrapping with a rapid opensource minimum spanning tree algorithm (ROMEO)

Purpose To develop a rapid and accurate MRI phase‐unwrapping technique for challenging phase topographies encountered at high magnetic fields, around metal implants, or postoperative cavities, which is sufficiently fast to be applied to large‐group studies including Quantitative Susceptibility Mappi...

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Bibliographic Details
Published in:Magnetic resonance in medicine Vol. 85; no. 4; pp. 2294 - 2308
Main Authors: Dymerska, Barbara, Eckstein, Korbinian, Bachrata, Beata, Siow, Bernard, Trattnig, Siegfried, Shmueli, Karin, Robinson, Simon Daniel
Format: Journal Article
Language:English
Published: United States Wiley Subscription Services, Inc 01.04.2021
John Wiley and Sons Inc
Subjects:
Algorithms
Animals
Brain - diagnostic imaging
Datasets
distortion correction
Echoes
fMRI
Full Papers—Computer Processing and Modeling
Functional magnetic resonance imaging
Graph theory
Head
Image acquisition
Magnetic fields
Magnetic permeability
Magnetic Resonance Imaging
MRI phase
multi‐echo
Phase unwrapping
QSM
Rats
Surgical implants
fMRI
QSM
distortion correction
MRI phase
multi-echo
phase unwrapping
ISSN:0740-3194, 1522-2594, 1522-2594
Online Access:Get full text
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Summary:Purpose To develop a rapid and accurate MRI phase‐unwrapping technique for challenging phase topographies encountered at high magnetic fields, around metal implants, or postoperative cavities, which is sufficiently fast to be applied to large‐group studies including Quantitative Susceptibility Mapping and functional MRI (with phase‐based distortion correction). Methods The proposed path‐following phase‐unwrapping algorithm, ROMEO, estimates the coherence of the signal both in space—using MRI magnitude and phase information—and over time, assuming approximately linear temporal phase evolution. This information is combined to form a quality map that guides the unwrapping along a 3D path through the object using a computationally efficient minimum spanning tree algorithm. ROMEO was tested against the two most commonly used exact phase‐unwrapping methods, PRELUDE and BEST PATH, in simulated topographies and at several field strengths: in 3T and 7T in vivo human head images and 9.4T ex vivo rat head images. Results ROMEO was more reliable than PRELUDE and BEST PATH, yielding unwrapping results with excellent temporal stability for multi‐echo or multi‐time‐point data. It does not require image masking and delivers results within seconds, even in large, highly wrapped multi‐echo data sets (eg, 9 seconds for a 7T head data set with 31 echoes and a 208 × 208 × 96 matrix size). Conclusion Overall, ROMEO was both faster and more accurate than PRELUDE and BEST PATH, delivering exact results within seconds, which is well below typical image acquisition times, enabling potential on‐console application.
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Funding informationAustrian Science Fund project (FWF31452); Marie Skłodowska‐Curie Actions (MRI COMIQSUM 798119 and MS‐fMRI‐QSM 794298); European Research Council Consolidator Grant (DiSCo MRI SFN 770939); and the Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology, and Development
Barbara Dymerska and Korbinian Eckstein contributed equally to this work.
ISSN:0740-3194
1522-2594
1522-2594
DOI:10.1002/mrm.28563