title: Multiecho sequence for velocity imaging in inhomogeneous rf fields.
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.
authors.affiliation: Institut für Technische Chemie und Makromolekulare Chemie, RWTH Aachen, D-52056, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Ahola
authors.forename: J
authors.initials: J
authors.lastname: Perlo
authors.forename: F
authors.initials: F
authors.lastname: Casanova
authors.forename: S
authors.initials: S
authors.lastname: Stapf
authors.forename: B
authors.initials: B
authors.lastname: Blümich