Field-of-view zoom during a single-shot short-axis image for cardiac contraction correction
© Gatehouse and Firmin; licensee BioMed Central Ltd. 2012
Published: 1 February 2012
Evaluate a new method correcting for cardiac contraction during each single-shot image.
Cardiac motion during a single-shot image causes blurring along the phase-encode axis and dark rim artefact (1). We attempt to correct for myocardial contraction during short-axis single-shot acquisition, to optimise subendocardial myocardium.
A myocardial perfusion sequence (balanced SSFP) was modified to vary field-of-view and in-plane offsets during each single-shot rawdata acquisition to “zoom” in [or out] following myocardial contraction [filling]. FOV-zoom varied linearly during raw data acquisition, and for each phase-encode line p scaled the FOV and in-plane offsets by factor Sc(p) = 1 + ((Db - De)/De) x (p-N/2)/N where Db and De were LV short-axis diameter at the begin and end of the single-shot scan, and N was the total phase encode lines (96) for each single-shot. The diameters Db and De were measured using a short-axis cine pre-scan in the same slice. The sequence acquired 300x225mm FOV (2.3x2.3x6mm). For in-vitro tests, a conical cup of fluid was imaged in circular cross-section. The slice was shifted along the cone during acquisition, so that the apparently changing diameter modelled contraction of a short-axis LV. In healthy volunteers without contrast agent, T2-preparation was used for endocardial image contrast (1). Each 200ms perfusion image was acquired during ventricular contraction, starting 80ms after the R-wave, repeated with and without FOV-zoom.
Some local improvement of subendocardial clarity by FOV-zoom was seen, and ghosting from other tissues was not problematic. However, reliable implementation of this idea remains a challenge.
NIHR Cardiovascular Biomedical Research Unit.
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