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MRI receiver frequency response as a contributor to Nyquist ghosting in echo planar imaging
Ioannis Delakis1, Krystallia Petala, Janet P De Wilde
1Department of Bioengineering, Imperial College London, Exhibition Road, South Kensington, London SW7 2AZ, United Kingdom. i.delakis@imperial.ac.uk
Journal of Magnetic Resonance Imaging : JMRI
|July 20, 2005
Summary
The frequency response of MRI signal receivers directly impacts Nyquist ghosting in echo-planar imaging (EPI). Adjusting receiver characteristics can help reduce ghosting artifacts, especially in low-coil-loading scenarios like pediatric scans.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Biomedical Engineering
Background:
- Nyquist ghosting is a common artifact in echo-planar imaging (EPI).
- The signal receiver system's frequency response characteristic is a potential contributor to EPI artifacts.
Purpose of the Study:
- To investigate the role of MRI signal receiver frequency response in Nyquist ghosting formation during EPI.
- To understand how receiver characteristics influence ghosting artifacts.
Main Methods:
- Experiments were conducted on a 1.5 T MRI system using a water-filled phantom.
- Image acquisition involved axial EPI sequences with varying water conductivity and receiver bandwidths.
- Computer simulations were employed to model the impact of receiver frequency response variations on ghosting.
Main Results:
- Nyquist ghosting intensified as the receiver system's frequency response varied within the image bandwidth.
- Increased ghosting was observed with steeper frequency response variations (lower coil loading) or wider bandwidths.
- Simulation results corroborated experimental findings on the relationship between frequency response and ghosting.
Conclusions:
- The study demonstrates that receiver frequency response is a key factor in EPI Nyquist ghosting.
- Findings suggest strategies to mitigate ghosting in EPI, particularly in situations with reduced coil loading, such as pediatric and phantom imaging.