Myocardial Perfusion Imaging artifacts: centric h-EPI and its sensitivity to frequency errors
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BioMed Central
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Poster presentation
Myocardial Perfusion Imaging artifacts: centric h-EPI and its sensitivity to frequency errors Pedro Ferreira*, Peter Gatehouse and David Firmin Address: Imperial College London, London, UK * Corresponding author
from 13th Annual SCMR Scientific Sessions Phoenix, AZ, USA. 21-24 January 2010 Published: 21 January 2010 Journal of Cardiovascular Magnetic Resonance 2010, 12(Suppl 1):P219
doi:10.1186/1532-429X-12-S1-P219
Abstracts of the 13th Annual SCMR Scientific Sessions - 2010
Meeting abstracts - A single PDF containing all abstracts in this Supplement is available here. http://www.biomedcentral.com/content/files/pdf/1532-429X-11-S1-infoThis abstract is available from: http://jcmr-online.com/content/12/S1/P219 © 2010 Ferreira et al; licensee BioMed Central Ltd.
Introduction Clinical myocardial perfusion often uses Echo-PlanarImaging, in a multishot "hybrid" variety using centre-out phase-encode-order ("h-EPI") [S Ding, et al., MRM, 39:514, 1998] for robustness against susceptibility dephasing of signal within pixels, especially during firstpass of paramagnetic Contrast-Agent (CA). However, this sequence may be sensitive to frequency errors.
Purpose We examined the artifacts, specifically whether they could cause subendocardial Dark Rim Artifacts (DRA) mimicking perfusion defects in patients.
Methods Clinical h-EPI stress/rest perfusion studies were reviewed after phantom images drew our attention to the off-resonance sensitivity of the h-EPI technique. All work was done at 1.5 T (Avanto, Siemens); h-EPI (4 echoes); TR/TE 5.1/1.7 ms; pixel size 2.8 × 2.8 × 8 mm; flip angle 30 deg; bandwidth 1860 Hz/pixel; saturation-recovery (TI = 90 ms); TSENSE with R = 2; Gd-based CA 0.1 mmol/kg at 3.5 ml/s. The sequence was also used to image across a hollow diamagnetic gelatine cylinder containing 12.5 mmol/L Gd-DTPA solution, forming a magnetostatic and relaxation-time model of the LV during CA first-pass. Phantom images were acquired at two scanner reference frequencies, approximating the gelatine "myocardium" and LV "blood" frequencies. For comparison, the phantom was also imaged with a balanced-SSFP perfusion sequence. For one in-vivo perfusion study, accumulated phase-errors corresponding to scanner reference frequency offsets were
applied to the stored raw-data and images were repeatreconstructed to examine h-EPI's sensitivity to the frequency used for the patient.
Results When the reference frequency was set to myocardium (Figure 1 left), the LV blood "split" into two superimposed copies 5 mm above and below its true location (red-arrows) along the phase-encode direction. Conversely using the blood frequency (Figure 1 centre), the LV blood was imaged sharply, whereas the off-resonance myocardium split (green-arrows); explained by the opposite phase-encode directions of data collection of centreout h-EPI. Part of the myocardial splitting deepened the Gibbs DRA (yellow-arrows). BSSFP is also shown (Figure 1 right). Clinical examples of this effect occurred (
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