A new filtering algorithm for medical magnetic resonance and computer tomography images

Automatic path searching for interactive navigation support within virtual medical 3-dimensional objects

RATIONALE AND OBJECTIVES

This article proposes the use of a disembodied autonomous actor for navigation support within complex virtual medical objects reconstructed from Computed Tomography or Magnetic Resonance Imaging. Such objects are often maze-like, and users risk getting lost within them during Virtual Reality sessions. Therefore, users need paths for guided fly-throughs when performing non-invasive diagnostic tasks.

MATERIALS AND METHODS

We present a synthetic vision-based actor capable of finding collision-free paths from a given position to a goal point in environments containing loops and impasses. When navigating, the actor voxelizes the virtual environment and searches for collision-free paths in voxel space by using a back tracking search algorithm. Automata and rules control its search behaviour. The resulting paths can be used in dedicated virtual endoscopy applications.

RESULTS

Our path search method has been tested within a variety of tubular virtual anatomical structures in 3D such as aortas, colons, or blood vessels of the brain. The actor finds paths within reasonable time limits, even when considering complex anatomical surface models.

CONCLUSION

The method may be used as a valuable tool for assisting virtual endoscopic diagnostic and screening activities in the near future.

Virtual endoscopy of the labyrinth, using a 3D-FastASE sequence

Virtual endoscopy (VE) of the labyrinth was performed using three-dimensional (3D)-fast asymmetric spin-echo MR imaging. The spatial resolution requirements and the usefulness of zero-fill interpolation (ZIP) were evaluated, and VE was used to examine three patients. The (0.6-mm) voxel data with ZIP satisfies the minimum requirements for VE for evaluation of the complex 3D anatomy and pathology of the labyrinth. J. Magn. Reson. Imaging 2001;13:792-796.

CT colonography: the next colon screening examination?

Computed tomographic (CT) colonography is a new-generation technique for detecting colorectal neoplasms by using volumetric CT data combined with specialized imaging software. Patient examinations require full colonic preparation, insufflation, and data acquisition with the patient in the supine and prone positions. Current CT technology allows a single image of the colon to be acquired in as little as 20 seconds with a minimum of patient discomfort. Specialized computer software for interpretation usually combines transverse, multiplanar reformation, and three-dimensional endoluminal images for the optimal visualization of the colon and rectum. As of the time this article was written, CT colonography was competitive as a full structural colonic examination for the detection of polyps and cancer. To the authors' knowledge, no study results have yet been reported in a screening population. The unique capabilities of CT colonography include the display of the proximal colon that is inaccessible at colonoscopy because of obstructing colonic lesions or because of incomplete endoscopic examinations and the assessment of extracolonic abdominal and pelvic organs. This abdominopelvic survey potential provides radiologists with an opportunity to discover other potentially life-threatening, asymptomatic conditions. Further technologic developments and validation studies are in progress. CT colonography is an exciting and promising technique with an enormous potential for colorectal screening in the future.