The true three-dimensional reconstruction (TTR) algorithm previously proposed by the authors is extended to an algorithm with which full utilization of all the oblique rays is possible. Through this extended TTR (ETTR) algorithm, it is now possible not only to reconstruct an image of a larger object but also possible to obtain images which have substantially better signal-to-noise ratio. The basic TTR algorithm, as well as its extended version, will be discussed together with computer simulation results. In the appendixes, a new two-dimensional Fourier domain weighting function necessary for the implementation of the TTR and ETTR algorithms as well as the generality of the proposed TTR algorithm are discussed.

Objective: Biopsy with an inserted needle is an important procedure for lesion detection in the spine, but is difficult to perform due to the presence of many critical organs near the spine. This article presents a spine needle biopsy simulator, based on visual and force feedback, which can be used to plan the optimal path of a needle and to practice the procedure without risk.Materials and Methods: The simulator is composed of a 3D human model, a visual-feedback component, a force-feedback component, and an evaluation module. The human model is based on 3D CT data. The visual-feedback component provides an oblique section, multiplanar reformatting images, and a volume-rendered image. Of these, the oblique section display is very useful for planning a 3D path for the needle. During simulation, the force-feedback component generates and provides realistic forces acting on the biopsy needle in real time by synchronizing them to visual feedback. After each simulation, the evaluation module provides a performance analysis for the trainee.Results: For an XCT abdomen volume data set of 256 X 256 x 256, the update rate of image rendering due to needle movement is over 25 Hz, with a force-feedback rate of 1 kHz. This performance proved to be good enough for the trainee to learn the relationship between visual and force feedback. Conclusions: The simulator is useful for the planning of and training in complicated 3D spine needle biopsy procedures. It may be used as an educational tool for beginners, a practice tool to increase expertise, or a test bed for new procedures. Comp Aid Surg 7:353-363 (2002). 02003 WiIey-tiss, h C .

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