  The role of brain hemodynamics in neurodegenerative diseases cannot be fully
assessed using existing imaging technologies. Recently, 2D Dynamic Ultrasound
Localization Microscopy (DULM) has allowed for the quantitative mapping of the
pulsatile flow at sub-wavelength resolution. However, to obtain accurate
velocity estimates, 3D imaging is more adapted, especially for complex
vascularized organs like the brain. 3D+t DULM is achievable using matrix array
probes, but suffers from limitations in terms of cost, device complexity
associated with the high channel count, and operating frequencies.
Alternatively, Row Column Arrays (RCA) can reduce the number of elements while
maintaining a large field of view and high frame rate. Herein, we demonstrate
the feasibility of performing 3D+t blood flow measurements in the mouse brain
using an RCA and a DULM sequence with a high spatiotemporal resolution.
Transcranial images of anesthetized mice (n=7) were acquired at a volume rate
of 750 Hz using 42 tilted plane waves. After microbubbles localization and
tracking, super-resolved dynamic density and velocity maps of the 3D brain
vascular network were obtained. Cortical vessels were segmented and pulsatility
in the arteries was significantly higher than in veins for all mice, in
accordance with the literature. Our results demonstrate the feasibility and
reproducibility of achieving high spatiotemporal resolution volumes of the
mouse brain vasculature with DULM using a RCA.
