Fig. 4: Ultrasound localization microscopy imaging (ULM) reveals the strong density and high speed of blood flow in the rat trigeminal ganglion in vivo.

Following intravenous injection of bio-compatible microbubbles, known as conventional ultrasonic contrast agent (a), allows the determination of bubble velocity in both the vertical (b, c, f), or horizontal directions (d, g) through the analysis of single bubble trajectories (b–h). Pictures illustrate ULM imaging on a sagittal plane at lateral = 4.2 mm. a Doppler image of all bubbles in both the brain and the TG. The TG is surrounded by a white square. b ULM imaging of the whole brain and TG depicting velocity in the vertical direction. Panels c, d are a higher power magnification of the area delimited in b, c, and d show major blood vessels approaching the TG, which contain two descending veins and one ascending artery. Panels f, g are higher power magnification of c and d, respectively. Panels e, h are the field vectors in these blood vessels (e) and the TG (h). These field vectors illustrate not only the dense vascular network detected in the TG and the high blood speed in these vessels (9–20 mm/sec), but also the multiple directions of blood flow within the TG’s sub-parts imaged. e, h The size of the arrows is proportional to the local speed. Scale bars = a, b: 2 mm, c–d: 250 μm, e: 150 µm, f, g: 100 μm, h: 77 μm. The color bar (g right) applies for panels b–d and f, g.