Cartesian echo planar hybrid scanning with two to eight echoes

Abstract

A method of fast nuclear magnetic resonance (NMR) imaging which uses only square wave gradient shapes and also collects data on Cartesian coordinates in a way similar to the blipped echo planar imaging method (BEPI) is described. The method is a heuristic attempt at finding an optimal data collection strategy for NMR imaging. Its advantages and disadvantages compared to other methods are carefully analyzed. Clinical size anatomical (head and body) images are shown. It is found that the interecho phase-angle discrepancies that are caused bv the B(0) inhomogeneity and by the gradient wave form distortion can largely be eliminated by using the half Fourier method with full Fourier phase map correction, but one phase map is required for each echo. GRASS/FLASH spoiling techniques are incorporated into the method in order to allow multiecho speed increases for scans which would run under 10 s using a single-echo method. The technique can be applied directly to GRASS/FLASH itself, as is demonstrated by a two-echo GRASS scan. The fastest image was 1.9 s.

Βελτιωση Αναλυση Σχεδιασμος Και Αναπτυξη Νεων Τεχνικων Γρηγορης Εικονογραφησης Στη Μαγνητικη Τομογραφια

“…Η τροχιά αυτή συχνά θεωρείται σα μια προσέγγιση της πολικής γεωμετρίας σάρωσης. Τέλος, έχει προταθεί και μια εκδοχή "υβριδικής" γεωμετρίας σάρωσης, ένα είδος "στραμμένης καρτεσιανής γεωμετρίας" [KAS91]. Η τροχιά αυτή είναι η πιο γρήγορη δυνατή σάρωση του κ-χώρου.…”