A segmented T2-prepared SSFP sequence for T2-weighted imaging and T2-mapping of the myocardium
https://doi.org/10.1186/1532-429X-12-S1-P221
© Stainsby et al; licensee BioMed Central Ltd. 2010
Published: 21 January 2010
Keywords
Introduction
Recent studies demonstrate that hyperintense regions in T2-weighted images in acute myocardial infarction (AMI) reflect the presence of edema [1] and area at risk. Single-shot T2-prepared SSFP methods have been presented for T2-weighted imaging in AMI [2]. Here a segmented SSFP approach suitable for multi-slice, multi-echo imaging of the myocardium is presented.
Methods
Sequence schematic. Following a T2 preparation, a multi-slice segmented acquisition is acquired.
To maximize T2 contrast while minimizing eddy current effects [3], an even-odd, centric phase encode ordering scheme was implemented.
To preserve the prepared T2 contrast across multiple slices an RF chopping scheme [4] consisting of two averages with an inversion pulse following the T2-preparation on even averages was implemented. This enables subtraction of contaminant signal that recovers with time constant T1.
To preserve in-slice signal integrity, in-slice signal is catalyzed prior to, and spoiled following, data acquisition to minimize cross-slice contamination.
Finally, fat saturation was integrated into the preparation interval [5] to reduce contributions of recovering fat signal.
T2 values are estimated using a 2-parameter exponential fit or a 3-parameter fit including baseline offset.
Results
Images obtained as part of a multi-slice, multi-echo acquisition in a single breath hold. Images at a single slice at different T E times from left to right TE = 20, 40, 80, 120 ms
T2 maps from a healthy volunteer generated from a 4-echo, 3 slice acquisition acquired in a 16 heart-beat breath hold.
Quantitative T2 mapping results from a T2 phantom with actual T2 = 62 ms. Without RF chopping (o's0, recovering signal contaimates consecutive slice acquisition resulting in elevated T2 estimates. Estimating this recovery term via a T2-fit with baseline offset yields uniform, but erroneous values across slices. With RF chopping (x's) the T2-contrast is better preserved across slices and a simple 2-parameter fit yields the correct T2 values. A 3-parameter fit gives resonable estimates but suffers error from the reduced degrees-of-freedom in the fit, sub-optimal TE times to estimate the baseline and sensitivity to nois.
Discussion/cnclusion
A segmented, T2-prepared, multi-slice, multi-echo imaging sequence is presented that can be applied to edema identification in AMI patients.
Authors’ Affiliations
References
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Copyright
This article is published under license to BioMed Central Ltd.