I was of course talking specifically about WebGL for games...
But it seems like you'd run into many of the same hindrances. For example, how will you get around the 5MB local storage limit? It would be unwieldly to re-download the whole visualization dataset each time, no?
P.S. I have nothing but respect for the medical visualization community. A lot of game graphics techniques were derived directly from work done in medical research (for example, BSP rendering and voxel rendering).