Apparently, an industrial design degree won't give you much insight into basic physics; otherwise, Alexander Broeman would've realized that 3-D already means an object has length, width, and depth. Adding one more dimension won't make sense, unless you meant that 4th dimension is time. Still, a hands-free ultrasound scanner that provides a constant 3-D view of internal organs is useful, especially during surgery.
The echoCHOLE is a gurney-mounted ultrasound scanner that automates the usual side-to-side action needed to get a full 3-D view of internal organs, like a dysfunctional kidney or a baby. The hands-free nature of the device assures that you don't need to have a nurse constantly rubbing the patient's belly with a plastic device just to get a bead on the situation.
A pity it really can't see into the 4th dimension; I'm pretty sure any surgeon worth his malpractice premiums would love to know if the operation's going to go belly up in the end.
[source: Yanko Design]