A METHOD FOR IMPROVING THE EFFICIENCY OF BREATH-HELD MULTI-SLICE 2D FIESTA IMAGING OF HEART
Publication Date: 2005-Mar-29
The IP.com Prior Art Database
In an embodiment, the method includes using ECG trigger to simultaneously signal the end of imaging for one slice and the beginning of imaging for the next. A short steady-state preparation sequence is used for consecutive slices in a multi-slice 2D scan. The use of a small portion of one cardiac cycle per slice for this preparation sequence, the missing data of which is interpolated during reconstruction in a similar manner as the normally acquired data.
FIELD OF THE INVENTION
 This invention relates generally, to breath-held multi-slice 2D FIESTA imaging of heart, and more particularly to, a method for improving the efficiency of breath-held multi-slice 2D fast cine imaging of heart in medical imaging.
BACKGROUND OF THE INVENTION
 FIESTA cine imaging sequences are typically employed in clinical magnetic resonance imaging (MRI) of the heart to characterize ventricular function. Evaluation can be qualitative (by visually assessing the motion of the ventricular myocardium) or quantitative (by measuring ventricular volumes and calculating ejection fractions, for example. Imaging of the whole heart (10-12 slices) is typically achieved using multi-slice 2D FIESTA, where each slice requires a 12 to 16-second breath-hold. While repeated breath holding can be time consuming and exhausting for the patient, it also increases the likelihood of slice mis-registration especially, due to different breath-hold positions, which can negatively impact quantitative ventricular volume measurements.
 Accordingly, research has been directed at reducing the acquisition time for covering the entire heart to a single breath-hold using a 3D acquisition. Such an approach, however, suffers from very low spatial and/or temporal resolution and very long breath-holds. The advantages of 3D acquisitions include higher SNR, thinner slices, and the need to achieve steady state only once at the beginning of the scan. The first two benefits are less compelling for functional FIESTA imaging, because steady-state sequences already offer high SNR, and the use of thin slices would make the requisite number of slices prohibitive.
 The main disadvantages of 3D for single-breath-hold functional imaging of the heart include: 1) the need to discard several slices from the ends of the slab due to aliasing in the slice-encoding direction and 2) the effect on the whole slab resulting from any motion during the entire breath-hold time due to the two directions of phase encoding. For example, if the patient moves or loses the breath-hold during a 3D scan, the resulting artifacts can corrupt the entire slab. In a 2D scan, on the other hand, only one slice would be affected. These problems are not present with 2D scans. However, multi-slice 2D imaging requires setting each slice to steady state individually for example, often with 1 or 2 dummy heartbeats prior to data acquisition. This, too, can be prohibitive as it can increase breath-hold time by 25-50% (up to an additional 12 heartbeats) for a 6-slice scan.
 In a typical implementation of multi-slice steady-state (FIESTA) imaging, when the scan button is pushed, imaging begins asynchronously with the cardiac cycle. The pulse sequence then waits for the next ECG trigger, whereupon the next full heartbeat is used to set the spins in slice 1 to stea...