An elongated, tubular-shaped balloon for a balloon catheter includes three regions along its length, in sequence: a proximal region, an intermediate region, and a distal region. The intermediate region is defined by a curved outer surface that is established by a radius of curvature r1. Similarly, a curved inner surface for the intermediate region is established by a radius of curvature r2, wherein r1≧r2. Balloon thickness at the center of the intermediate region is tc, while balloon thickness in both the proximal and distal regions is t (t>；tc). The stretchability and bendability of the balloon material is directly proportional to the thickness of the balloon, to thereby shape the balloon as a prolate spheroid when inflated.
