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Published on: February 12, 2014
k-space undersampling in PROPELLER imaging
Konstantinos Arfanakis1, Ashish A Tamhane, James G Pipe
1Department of Biomedical Engineering, Illinois Institute of Technology, 10 West 32nd Street, E1-116, Chicago, IL 60616, USA. arfanakis@iit.edu
Abstract:
PROPELLER MRI (periodically rotated overlapping parallel lines with enhanced reconstruction) provides images with significantly fewer B(0)-related artifacts than echo-planar imaging (EPI), as well as reduced sensitivity to motion compared to conventional multiple-shot fast spin-echo (FSE). However, the minimum imaging time in PROPELLER is markedly longer than in EPI and 50% longer than in conventional multiple-shot FSE. Often in MRI, imaging time is reduced by undersampling k-space. In the present study, the effects of undersampling on PROPELLER images were evaluated using simulated and in vivo data sets. Undersampling using PROPELLER patterns with reduced number of samples per line, number of lines per blade, or number of blades per acquisition, while maintaining the same k-space field of view (FOV(k)) and uniform sampling at the edges of FOV(k), reduced imaging time but led to severe image artifacts. In contrast, undersampling by means of removing whole blades from a PROPELLER sampling pattern that sufficiently samples k-space produced only minimal image artifacts, mainly manifested as blurring in directions parallel to the blades removed, even when reducing imaging time by as much as 50%. Finally, undersampling using asymmetric blades and taking advantage of Hermitian symmetries to fill-in the missing data significantly reduced imaging time without causing image artifacts.
Insights
Undersampling PROPELLER MRI (periodically rotated overlapping parallel lines with enhanced reconstruction) can reduce scan times. Removing whole blades or using asymmetric blades with Hermitian symmetries minimizes artifacts, making MRI faster and clearer.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Medical Imaging Physics
Background:
- PROPELLER MRI offers superior artifact reduction compared to EPI and FSE.
- However, PROPELLER MRI has longer minimum imaging times than EPI and FSE.
- Reducing MRI scan time is often achieved by undersampling k-space.
Purpose of the Study:
- To evaluate the impact of k-space undersampling on PROPELLER MRI image quality.
- To identify effective undersampling strategies for reducing PROPELLER MRI scan time without significant artifact induction.
Main Methods:
- Simulated and in vivo PROPELLER MRI datasets were used.
- Evaluated undersampling by reducing samples per line, lines per blade, or blades per acquisition.
- Investigated undersampling via whole blade removal and asymmetric blade acquisition utilizing Hermitian symmetries.
Main Results:
- Reducing samples per line, lines per blade, or blades per acquisition led to severe artifacts.
- Removing whole blades reduced imaging time by up to 50% with minimal artifacts (slight blurring).
- Asymmetric blades with Hermitian symmetry significantly reduced imaging time without artifacts.
Conclusions:
- PROPELLER MRI undersampling strategies vary in their impact on image quality and scan time.
- Whole blade removal and asymmetric blade acquisition with Hermitian symmetry are effective methods for accelerating PROPELLER MRI.
- These optimized undersampling techniques enhance the clinical utility of PROPELLER MRI by reducing scan duration while maintaining image fidelity.
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