Single-shot velocity mapping by rewinding of velocity encoding with Echo-Planar Imaging

SERIAL, MARÍA R.; SILLETTA, EMILIA V.; PERLO, JOSEFINA; GIOVACCHINI, JUAN P.; VELASCO, MANUEL I.; BLÜMICH, BERNHARD; DANIELI, ERNESTO D.; CASANOVA, FEDERICO; ACOSTA, RODOLFO H.

JOURNAL OF MAGNETIC RESONANCE

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2019 vol. 307

1090-7807

The ability of single-shot NMR imaging methods to follow the time evolution of a velocity distributionwithin an object is strongly limited by the phase errors accumulated as velocity maps are acquired. Inthe particular case of Carr-Purcell based sequences combined with Echo Planar Imaging acquisition,phase accumulates through subsequent images, hampering the possibility to acquire several velocitymaps, which would be useful to determine transient behavior. In this work, we propose the use of arewinding velocity encoding module applied after the acquisition of each image during the CPMG echotrain. In this way, the first velocity module imparts a velocity dependent phase prior to the image acquisitionand the second pair cancels this phase out before the next refocusing radiofrequency pulse isapplied. The performance and limits of this method are studied by acquiring 100 images of a corotatingCouette cell over a period of 1.6 s as a function of the rotation speed. The method is appliedto determine the kinematic viscosity of a water/alcohol mixture, which is a relevant topic in many physical,chemical and biological processes.