A valvuloplasty system comprises a balloon adapted to be placed adjacent leaflets of a valve. The diffusing optical fiber tip has an outer diameter which is no greater than that of the optical fiber, and appears as a point source of illumination, having substantially the same output pattern when immersed in water as it does in air. A plastic body embeds the measurement and transmission electronics unit and also the power source. The dopant can convert the crystal structure of the hafnium oxide or zirconium oxide to a tetragonal structure and increase the dielectric constant of the metal oxide.