By means of ultrasound waves, images can be formed of structures in the human body. In a certain frequency band, the higher the frequency used, the more shallow the image will be formed. This offers the opportunity to investigate the dimensions of both superficial as well as more deep lying structures in the body. Thus heart, brain circulation and superficial blood vessels are examined.
In response to gravitational stress and exercise, the blood vessel diameters change. After spaceflight it seems that vessels that normally should contract to maintain the blood pressure do that less well than before the flight. Onboard, gravitational pull can be created artificially by exposing the lower body to negative air pressure, thus testing in microgravity, to which extent these reflexes are changed.
The effectiveness of the Lower Body Negative Pressure exposure, that is used as a countermeasure against the negative effects of Space, is likewise tested in this manner.