Stoll E, Stern C, Stucki P, Wildermuth S
Physics Institute, University of Zurich, Switzerland.
J Digit Imaging. 1999 Feb;12(1):23-8. doi: 10.1007/BF03168623.
Inner views of tubular structures based on computer tomography (CT) and magnetic resonance (MR) data sets may be created by virtual endoscopy. After a preliminary segmentation procedure for selecting the organ to be represented, the virtual endoscopy is a new postprocessing technique using surface or volume rendering of the data sets. In the case of surface rendering, the segmentation is based on a grey level thresholding technique. To avoid artifacts owing to the noise created in the imaging process, and to restore spurious resolution degradations, a robust Wiener filter was applied. This filter working in Fourier space approximates the noise spectrum by a simple function that is proportional to the square root of the signal amplitude. Thus, only points with tiny amplitudes consisting mostly of noise are suppressed. 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 fluctuations and medically significant structures.
基于计算机断层扫描（CT）和磁共振（MR）数据集的管状结构内部视图可通过虚拟内窥镜检查生成。在进行用于选择要呈现的器官的初步分割程序之后，虚拟内窥镜检查是一种使用数据集的表面或体绘制的新后处理技术。在表面绘制的情况下，分割基于灰度阈值技术。为了避免由于成像过程中产生的噪声而导致的伪影，并恢复虚假的分辨率下降，应用了一种稳健的维纳滤波器。该滤波器在傅里叶空间中工作，通过一个与信号幅度平方根成比例的简单函数来近似噪声频谱。因此，只有主要由噪声组成的小幅度点被抑制。通过正确选择阈值范围可避免进一步的伪影。之后，管状结构的管腔和内壁得到很好的呈现，并且能够区分无害波动和具有医学意义的结构。
