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

Inner views of tubular structures based on computer tomography (CT) and mag netic resonance (MR) data sets may be created by virtual endoscopy, After a preliminary segmentation procedure for selecting the organ to be represent ed, the virtual endoscopy is a new postprocessing technique using surface o r volume rendering of the data sets. In the case of surface rendering, the segmentation is based on a grey level thresholding technique. To avoid arti facts owing to the noise created in the imaging process, and to restore spu rious resolution degradations, a robust Wiener filter was applied. This fil ter working in Fourier space approximates the noise spectrum by a simple fu nction that is proportional to the square root of the signal amplitude. Thu s, only points with tiny amplitudes consisting mostly of noise are suppress ed, Further artifacts are avoided by the correct selection of the threshold range. Afterwards, the lumen and the inner walls of the tubular structures are well represented and allow one to distinguish between harmless fluctua tions and medically significant structures. Copyright (C) 1999 by W.B. Saun ders Company.