Summary: Referenceless Interleaved Echo-Planar Imaging
Scott B. Reeder,1 Ergin Atalar,2* Anthony Z. Faranesh,1 and Elliot R. McVeigh1,2
Interleaved echo-planar imaging (EPI) is an ultrafast imaging
technique important for applications that require high time
resolution or short total acquisition times. Unfortunately, EPI is
prone to significant ghosting artifacts, resulting primarily from
system time delays that cause data matrix misregistration. In
this work, it is shown mathematically and experimentally that
system time delays are orientation dependent, resulting from
anisotropic physical gradient delays. This analysis character-
izes the behavior of time delays in oblique coordinates, and a
new ghosting artifact caused by anisotropic delays is de-
scribed. ``Compensation blips'' are proposed for time delay
correction. These blips are shown to remove the effects of
anisotropic gradient delays, eliminating the need for repeated
reference scans and postprocessing corrections. Examples of
phantom and in vivo images are shown. Magn Reson Med
41:87­94, 1999. 1999 Wiley-Liss, Inc.
Key words: MRI; EPI; reconstruction; calibration; reference
scans; compensation blips

Source: Atalar, Ergin - Department of Electrical and Electronics Engineering, Bilkent University

Collections: Engineering; Biology and Medicine