Ahola S, Perlo J, Casanova F, Stapf S, Blümich B. Multiecho sequence for velocity imaging in inhomogeneous rf fields.
JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2006;
182:143-51. [PMID:
16843023 DOI:
10.1016/j.jmr.2006.06.017]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Revised: 06/14/2006] [Accepted: 06/14/2006] [Indexed: 05/10/2023]
Abstract
The unambiguous determination of velocities with spatial resolution in a multiecho PFG NMR sequence strongly depends on the homogeneity of the B1 field. This affects, in particular, the use of surface coils that bear considerable potential for on-line flow monitoring where a fast-imaging sequence can become vital. However, even with most rf coils dedicated for imaging applications, B1 inhomogeneities are sufficiently large to generate severe problems in performing velocity-imaging experiments. In this paper, the use of a combination of different phase cycles in Carr-Purcell sequences is discussed. The suggested phase cycling scheme tolerates large flip angle imperfections arising in inhomogeneous B1 fields, and thus allows acquisition of a maximum number of echoes within a pulse train. The performance of the velocity-imaging sequence is proven by using phantom samples developing known laminar flow patterns.
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