Echo-Planar Imaging: Magnetic Resonance Imaging in a Fraction of a Second

Abstract

Progress has recently been made in implementing magnetic resonance imaging (MRI) techniques that can be used to obtain images in a fraction of a second rather than in minutes. Echo-planar imaging (EPI) uses only one nuclear spin excitation per image and lends itself to a variety of critical medical and scientific applications. Among these are evaluation of cardiac function in real time, mapping of water diffusion and temperature in tissue, mapping of organ blood pool and perfusion, functional imaging of the central nervous system, depiction of blood and cerebrospinal fluid flow dynamics, and movie imaging of the mobile fetus in utero. Through shortened patient examination times, higher patient throughput, and lower cost per MRI examination, EPI may become a powerful tool for early diagnosis of some common and potentially treatable diseases such as ischemic heart disease, stroke, and cancer.

Improving resolution in single-scan 2D spectroscopy

“…Traditional twodimensional experiments are intrinsically time consuming, since many t 1 increments have to be acquired in order to obtain 2D spectra with adequate digital resolution in the indirect x 1 dimension [2,3], even when samples with sufficient concentration or suitably enhanced nuclear polarization are available. Frydman and co-workers [4,5] have introduced a scheme inspired by echo planar imaging (EPI) [6], enabling the acquisition of a complete 2D NMR spectrum in a single scan, i.e., in less than a second. Thus, the time required to acquire multi-dimensional NMR experiments can be reduced by orders of magnitude.…”

Functional Differentiation in the Human Auditory and Language Areas Revealed by a Dichotic Listening Task

“…We scanned over four horizontal slices of 8-mm thickness, covering between 0 and 32 mm from the AC-PC line, with a gradient echo echoplanar imaging (EPI) sequence (TR ϭ 2 s, TE ϭ 22 ms, half scanning, flip angle ϭ 90°, field of view ϭ 384 ϫ 384 mm 2 , resolution ϭ 3 ϫ 3 mm 2 ) (Stehling et al, 1991;Sakai et al, 1995aSakai et al, , 1995b. The distance from AC-PC line to the top of the cerebral cortex was 71.2 Ϯ 4.2 mm (mean Ϯ SD) in tested subjects.…”

Diffusion-weighted magnetic resonance imaging for assessment after neoadjuvant chemotherapy in breast cancer, based on morphological concepts

“…Multiple nodular and/or unlocalized dendritic tumors usually demonstrate dendritic or multicentric shrinking and remain extensively in the original tumor beds (15,16). In the two cases of pCR, the conventional MRI and DWI findings may represent so-called pseudotumors corresponding to xanthomatous change (20).…”