- Meeting abstract
- Open Access
107 Small field of view black-blood imaging of the human heart using local excitation
© Abd-Elmoniem et al; licensee BioMed Central Ltd. 2008
- Published: 22 October 2008
- Local Excitation
- Echo Train Length
- Move Chest Wall
- Alias Artifact
- Signal Intensity Profile
Black-blood-prepared fast spin-echo (FSE) imaging is a widely used technique for cardiovascular imaging. To avoid fold-over artifacts, a sufficiently large field of view (FOV) in fold-over direction has to be selected. Nevertheless, respiratory artifacts originating from the moving chest wall are commonly observed. While enlarging the FOV leads to an increase in scanning time, motion artifacts have a detrimental impact on image quality. To address these issues, limiting the FOV in fold-over direction using pre-pulses has been proposed [1, 2]. While promising results have been obtained, additional pre-pulses are required and the quality of the suppression outside of the desired FOV is T1-dependent.
To develop, implement and test an MRI method that integrates local excitation for small-FOV imaging into the imaging part of an FSE sequence.
In conventional FSE imaging, a slice-selective 90° pulse is typically followed by a train of slice-selective 180° refocusing pulses. If the initial slice selective 90° pulse is replaced by a 2D-selective cylindrical excitation perpendicular to the imaging plane, the resultant signal will originate from a 'disc' located at the intersection between the 90° cylindrical pulse and the slice selective 180° pulses. Such local excitation enables small-FOV imaging without fold-over artifacts and avoids motion artifacts originating from structures outside of the 2D-selective pulse.
In vivo experiments
An axial slice in a healthy adult subject was acquired using free-breathing dual-inversion 2D FSE imaging with large and small FOV, and with/without local excitation (slice thickness = 3 mm, FOV = 350 × 350 mm, matrix = 352 × 350, and small FOV = 160 × 160 mm with a matrix of 160 × 150, ETL = 15, TE = 12 ms, interecho spacing = 6 ms, local excitation diameter = 140 mm). Total SNR and total scan time were kept constant by doubling the number of signal averages during the small-FOV acquisitions.
Local excitation is an effective method for small-FOV TSE imaging without the need of extra pre-pulses while the drawback of aliasing artifacts can be avoided. Since the surrounding tissue is suppressed, motion artifacts may be reduced as well. Two-dimensionally-selective excitation pulses are inherently self refocused and therefore no compromises in FSE imaging are necessary and no modifications of TE or interecho spacing are required.