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Conventional three-dimensional imaging uses thresholding, or surface rendering technique, which limits accuracy and detail, and hinders soft tissue definition. Volumetric image rendering preserves all CT data, not just surface boundaries, and therefore overcomes these limitations. Three-dimensional images thus generated can be used for muscular and vascular anatomy as well as skeletal structures, with preservation of subtle detail. Representative cases are used to illustrate this technique and its implications for therapy and plastic and reconstructive surgery.

Volumetric image processing is a new approach to generating simulated three-dimensional images from transaxial CT data. The major advantages compared to conventional surface-rendering 3D technique include: preservation of every pixel of CT data for increased accuracy of rendered image; tissue layer translucency allowing appreciation of multiple tissue layers on each image; simulation of real-time rotation in varying axes for optimal appreciation of abnormalities; and a high-speed, high-capacity computer setup which generates high-quality images rapidly, giving the system sufficient flexibility for these complicated functions while remaining user friendly and fast.

Simulated femoral neck fractures with varying amounts of distraction were studied using four modifications in a volumetric, three-dimensional CT reconstruction program to allow an objective comparison of volumetric versus surface (thresholded) rendering. Binary classification caused spurious fusion of gaps less than 2.0 mm or, at settings preserving these gaps, produced false holes in adjacent bone. Fracture gaps were visible to 0.0 mm using volumetric CT image rendering technique.