FIG. 2.

A sketch of the ray tracing process used to determine free-path access to the prostate. Bones are rendered from high X-ray density locations in a CT dataset. Rays emanate from a target location within the prostate (pink). Those striking bone are considered to be blocked (red lines), whereas those passing through only soft tissue are part of the accessible path (green lines). Blue and red squares below represent the clear and blocked regions of a hypothetical curved transducer surface. For clarity, only a fraction of the 1001 simulated rays are shown.