What does vlFC ROI stand for?

According to the article, vlFC obviously stands for ventrolateral frontal cortex. But ROI?

Context:

(A) The right vlFC ROI. Dorsally it included the inferior frontal sulcus and, more posteriorly, it included PMv; anteriorly it was bound by the ... paracingulate sulcus and ventrally by the lateral orbital sulcus and the border between the dorsal insula and the opercular cortex. (B) A schematic depiction of the result of the 12 cluster parcellation solution using an iterative parcellation approach. We subdivided PMv into ventral and dorsal regions (6v and 6r, purple and black). We delineated the IFJ area (blue) and areas 44d (gray) and 44v (red) in lateral pars opercularis. More anteriorly, we delineated areas 45 (orange) in the pars triangularis and adjacent operculum and IFS (green) in the inferior frontal sulcus and dorsal pars triangularis. We found area 12/47 in the pars orbitalis (light blue) and area Op (bright yellow) in the deep frontal operculum. We also identified area 46 (yellow), and lateral and medial frontal pole regions (FPl and FPm, ruby colored and pink).
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Credit: Neuron, Neubert et al.

More:
http://www.sciencedaily.com/releases/2014/01/140128124649.htm