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Measurement of the point spread function in MRI using constant time imaging
M D Robson1, J C Gore, R T Constable
1Yale University School of Medicine, Department of Diagnostic Radiology, New Haven, CT 06520-8042, USA.
Magnetic Resonance in Medicine
|November 14, 1997
Summary
This study introduces a novel method to precisely measure the point spread function (PSF) in magnetic resonance imaging. This technique enhances image quality assessment and correction for distortions in echo-planar imaging.
Area of Science:
- Medical Imaging
- Physics
- Biophysics
Background:
- The point spread function (PSF) is crucial for magnetic resonance imaging (MRI) quality and resolution.
- Precisely measuring PSF in MRI, especially for complex sequences like echo-planar imaging (EPI), is challenging.
- Existing methods struggle with accuracy and applicability to advanced imaging techniques.
Purpose of the Study:
- To develop and validate a high-resolution method for measuring the PSF at each pixel in MRI.
- To apply this method to EPI to analyze factors affecting image quality.
- To quantify and correct local distortions caused by susceptibility and chemical shift effects.
Main Methods:
- A novel technique employing additional phase encoding gradients before EPI acquisition.
- These gradients, varying in amplitude while constant in length, image individual voxel contents.
- The method enables rapid PSF assessment in EPI, including in vivo applications.
Main Results:
- Successfully measured the PSF with high spatial resolution across uniform intensity samples.
- Demonstrated the impact of k-space sampling, transverse relaxation, and motion on EPI PSF.
- Quantified and corrected local distortions using PSF displacement analysis.
Conclusions:
- The developed method offers a rapid and accurate way to assess PSF in EPI.
- This technique facilitates the understanding and correction of image artifacts in MRI.
- The approach is adaptable to other rapid imaging sequences with gradient modifications.