RESUMO
A curvature-adaptive implicit surface reconstruction for noisy and irregularly spaced points in 3D is introduced. The reconstructed surface traces the zero crossings of a signed field obtained from the sum of first-derivative anisotropic Gaussians centered at the points. The standard deviations of the anisotropic Gaussians are adapted to surface curvatures estimated from local data. A key characteristic of the formulation is its ability to smooth more along edges than across them, thereby preserving shape details while smoothing noise. The behavior of the proposed method under various density and organization of points is investigated and surface reconstruction results are compared with those obtained by well-known methods in the literature.
RESUMO
To separate object motion from camera motion in an aerial video, consecutive frames are registered at their planar background. Feature points are selected in consecutive frames and those that belong to the background are identified using the projective constraint. Corresponding background feature points are then used to register and align the frames. By aligning video frames at the background and knowing that objects move against the background, a means to detect and track moving objects is provided. Only scenes with planar background are considered in this study. Experimental results show improvement in registration accuracy when using the projective constraint to determine the registration parameters as opposed to finding the registration parameters without the projective constraint.
RESUMO
BACKGROUND: Real-time intraoperative image guidance has been successfully applied to malignancies of the head, neck and central nervous system. Few attempts have been made to apply this technology to gastrointestinal cancers. Our purpose was to determine if a computer-assisted navigation system could be accurately used at the time of abdominal exploration. METHODS: Fourteen patients with resectable recurrent colorectal cancer underwent computer tomography (CT) imaging of the abdomen and pelvis. The CT images were uploaded to a StealthStation (Medtronic, Inc., Minneapolis, MN), a device that tracks the motion of a handheld probe in the operating field and displays its position, in real time, on the uploaded images. Various anatomic points were utilized to match, or register, the patient to the images in the navigation system. After four or more anatomic points were registered, the accuracy of the registration process was computed by the navigation system and reported as the global error. RESULTS: A total of 23 different anatomic structures were used for registration. The median number of points used for registration per patient was 6.5 (range 5-9). The anatomic sites most commonly used were the anterior superior iliac spines, aortic bifurcation, sacral promontory, symphysis pubis, and iliac artery bifurcation. The median global error was 10.0 mm (range 6.7 mm-27.0 mm). CONCLUSION: Computer-assisted navigation systems can be used to accurately deliver image guidance at the time of abdominal exploration. Future work will be directed at determining the value of this technology in the localization and resection of tumors.
