Method for preparing an exact-size model using helical volume scan computed tomography.

Helical volume scan computed tomography is a recently developed technology by means of which detailed data for most facial bone areas can be accumulated in a very short period, i.e., about 30 seconds, a much shorter time than required with conventional computed tomography. From a clinical standpoint, this is extremely important. In this report we discuss the principles of a method for preparing actual-size models by laser lithographic procedures based on data obtained by helical volume scan computed tomography. With these procedures, it is possible to obtain a good reproduction with high accuracy, on the order of 0.5 mm, not only of the outer morphologic structure of the cranial and maxillofacial bones but also of portions of the inner structure of cavities such as the cranium and paranasal sinuses. The difference between the original and model was under 3 percent, as confirmed by constructing a model of the dry skull with helical volume scan computed tomography. Therefore, production of exact-size models using helical volume scan computed tomography data represents an important technological development, breaking through previous limits imposed by conventional simulations prepared with three-dimensional images using CRT. With the combined use of laser lithographics and helical volume scan computed tomography, operative methods for craniomaxillofacial surgery should improve significantly in the near future.