In the past 5 years, the number of layer-fMRI applications with VASO has multiplied faster than any other layer-fMRI acquisition methodology (Fig. 10A). Since the advent of human layer-fMRI VASO in 2014–2015, layer-fMRI has become the sole driver of VASO-fMRI in humans. While the number of layer-fMRI VASO studies is still building up, there are 25 published peer-reviewed journal articles on layer-fMRI VASO until today (see Fig 10A). This is a significant portion of the entire field of layer-fMRI (Fig. 10B). While most of the VASO sequence development has been conducted in a handful of research labs only (Johns Hopkins, Max-Planck Leipzig, SFIM at NIH, MBIC in Maastricht, and DZNE in Bonn), the layer-fMRI user-base has significantly extended beyond these sites. Fig. 10C depicts that there are currently more than 30 labs around the globe that are using layer-fMRI VASO (effective January 2020). Most of these layer-fMRI VASO labs are in Europe, followed by Asia. Despite the high 7T scanner density in North America, the number of layer-fMRI VASO labs in USA is still emerging.
