Abstract: This paper presents a volume representation format called BT Volumes, along with a technique to interactively render them and two methods to create useful data in BT Volume format, including high quality reconstruction filtering. Medical applications rely heavily on isosurface data to visualize anatomy, but current real-time iso-surface rendering techniques such as Marching Cubes are limited in flexibility and provide only low-order linear reconstruction filtering. As an alternative to creating triangular geometry to represent the surface, we ray trace an exact isosurface directly inside a pixel shader. We construct a set of Bézier Tetrahedra to approximate any reconstruction filter with arbitrary footprint. We then precompute the volume convolved with this filter as a tetrahedral grid with Bézier weights that can be ray traced in graphics hardware. Our technique is fast, renders any isosurface level without additional work, and performs high quality reconstruction filtering with arbitrary footprints and reconstruction kernels.