Rapid magnetic resonance imaging (MRI) was used to characterize properties of a single central gas jet injected into a 3D gas fluidized bed under incipient fluidization conditions. Snapshots of both particle concentration and particle velocity are provided. The average jet height, oscillations in jet height and the size of bubbles breaking off from the jet increased with increasing jet velocity. The frequency of bubble breakoff from the jet decreased with increasing jet velocity. The jet height measurements are compared with various correlations in the literature, and the quantitative data provided here can be compared directly with that from numerical simulations and theoretical predictions for validation purposes. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.