Method of radiating ultrasound beam to accelerate lymphatic circulation

A method of activating a lymphatic system in a brain, the method comprising:

• radiating a focused ultrasound beam toward a boundary portion between a skull and brain parenchyma;
• allowing the focused ultrasound beam to enter the boundary portion at a specific angle to a normal direction that is perpendicular to a surface of the boundary portion to convert longitudinal waves into transverse waves inside the boundary portion, wherein the transverse waves generate a directional acoustic radiation force;
• moving the focused ultrasound beam along a predefined pathway corresponding to a lymphatic drainage route;
• and
• activating a lymphatic system in the brain by inducing an anisotropic fluid movement along the lymphatic drainage route.