van der Zwet P M, Reiber J H
Department of Diagnostic Radiology, University Hospital Leiden, The Netherlands.
Int J Card Imaging. 1995 Dec;11(4):211-21. doi: 10.1007/BF01145189.
In the coming years, cinefilm will gradually be replaced by some digital medium for the archiving of angiographic images. However, not only the question which digital archiving medium will be used in the future is important, but also which images are to be stored. Options are to either archive the raw, unprocessed images, or the enhanced images as they are displayed on the viewing monitor in the catheterization laboratory. In the first case, an off-line workstation will need additional hardware to display the images with the same image quality as they were acquired; in the second case, the question remains whether quantitative analysis programs still provide reliable results. Goal of this study was to investigate the possible effects of image enhancement and reconstruction on the results from quantitative coronary arteriographic (QCA) measurements with the Philips ACA-package (Automated Coronary Analysis). Image enhancement was achieved by an unsharp masking approach; the reconstruction of the original image from the enhanced image was attempted by an iterative deconvolution approach. The evaluation study consisted of two parts; a technical evaluation on eleven phantom tubes with known dimensions, and a clinical evaluation study on 48 coronary lesions. The results of the technical evaluation demonstrate that the measurement errors increase for the smaller vessel sizes (< 1.2 mm) when QCA is applied to reconstructed images. The systematic difference on the smallest phantom tube (0.687 mm) on unprocessed images was limited to 0.050 mm, while it increased to 0.089 mm for the reconstructed images. Moreover, the random differences for the smaller vessel sizes increased for all processed images: for 0.159 mm for the unprocessed image to 0.189 mm for the enhanced and 0.204 mm for the reconstructed image (p < 0.01). For the larger vessels, in general, no significant differences could be observed between the results of the unprocessed and processed images. The results of the clinical evaluation study demonstrate that especially the obstruction diameter is overestimated when QCA is applied to reconstructed images (0.113 mm). Although the measurements on the enhanced images did not show a significant overestimation of the obstruction diameter, the intra-observer random difference was much higher (0.199 mm for the enhanced images versus 0.140 mm for the unprocessed images, p < 0.01). In more general terms, applying QCA on enhanced images increases the random difference values, while reconstructing the original image from the enhanced images increases the systematic errors in the measured diameters. This study has clearly demonstrated that especially the smaller diameter values (< 1.2 mm) are influenced by image enhancement. Therefore, to obtain quantitative results with the desired small values for systematic and random differences, requires that the raw, unprocessed image data be archived.
在未来几年，电影胶片将逐渐被某种数字媒介所取代，用于血管造影图像的存档。然而，不仅未来将使用哪种数字存档媒介这一问题很重要，而且要存储哪些图像也很关键。选择要么存档原始的、未处理的图像，要么存档在导管实验室的观察监视器上显示的增强图像。在第一种情况下，离线工作站将需要额外的硬件来以与采集时相同的图像质量显示图像；在第二种情况下，定量分析程序是否仍能提供可靠结果仍是个问题。本研究的目的是调查图像增强和重建对使用飞利浦ACA软件包（自动冠状动脉分析）进行的定量冠状动脉造影（QCA）测量结果可能产生的影响。通过锐化掩膜方法实现图像增强；尝试通过迭代反卷积方法从增强图像重建原始图像。评估研究包括两部分：对11根已知尺寸的模拟血管进行技术评估，以及对48个冠状动脉病变进行临床评估研究。技术评估结果表明，当将QCA应用于重建图像时，较小血管尺寸（<1.2毫米）的测量误差会增加。未处理图像上最小模拟血管（0.687毫米）的系统差异限制在0.050毫米，而重建图像的系统差异增加到0.089毫米。此外，所有处理图像中较小血管尺寸的随机差异都增加了：未处理图像为0.159毫米，增强图像为0.189毫米，重建图像为0.204毫米（p<0.01）。对于较大血管，一般来说，未处理图像和处理后图像的结果之间未观察到显著差异。临床评估研究结果表明，当将QCA应用于重建图像时，尤其是阻塞直径被高估（0.113毫米）。尽管增强图像上的测量未显示阻塞直径有显著高估，但观察者内随机差异要高得多（增强图像为0.199毫米，未处理图像为0.140毫米，p<0.01）。更一般地说，对增强图像应用QCA会增加随机差异值，而从增强图像重建原始图像会增加测量直径的系统误差。这项研究清楚地表明，尤其是较小的直径值（<1.2毫米）会受到图像增强的影响。因此，为了获得具有所需小系统和随机差异值的定量结果，需要存档原始的、未处理的图像数据。
