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A new technology that has been used to construct virtual environments in the computer, where objects behave as if they were real ones, has been drawing attention. This paper studies virtual manipulation of elastic objects as a fundamental example of nonrigid materials. An elastic object modeled by a combination of material points and springs can be deformed with a rigid cylindrical manipulator controlled by a mouse in imitation of actual actions such as hitting or thrusting. The dynamic response of the elastic object in a collision with the manipulator is generated by a numerical method of solution based on physics and is displayed in real time. An improved spring model is presented in which the amplitude is restricted by elastic energy when the elastic object receives extensive external force. The results of implementation show the effectiveness of the spring model and interactivity of the system. © 1998 Scripta Technica. Electron Comm Jpn Pt 3, 81(4): 42–50, 1998 [ABSTRACT FROM AUTHOR]

This paper discusses the method of automatically extracting the intracranial region from the X-ray CT image and measuring its volume. In craniofacial surgery, the predicted increase of the intracranial volume after surgery is the important criterion to evaluate the effectiveness of the surgery. By applying the three-dimensional (3-D) image processing and the shape interpolation, a method is devised which almost automatically extracts the intracranial region and measures its volume. The processing method and the result of measurement are reported herein. The method can be applied to measure the intracranial volume before the surgery, after the surgery, and the intracranial volume simulated before the surgery for the postoperative skull. The feature of the method is that the intracranial volume can be determined for the post-surgical and planned skull, even if there exists a number of holes due to the surgery. [ABSTRACT FROM AUTHOR]