Thanks for the video link.

Look about 6 minutes into your video and about 2 minutes into the this one http://www.youtube.com/watch?v=eZS6DVGBx0k

This describes what fascinated me about the whole thing. I would see those leaves dynamically reshape constantly and it was the beam being shaped to hit the target in the manner specified in the planning system. The link I provided is from 10 years ago so there has been refinement for sure but the underlying principles still apply. One thing is the newer units are continuous sweeping and do not stop at all around or click so I suspect the dose is now able to be given all the time as it sweeps around. The processors are much faster now so they can keep up with all the real time calcs that previously was a go-stop-reposition-go-stop affair. Of course that is all a big guess on my part. lol