Rehm K, Strother S C, Anderson J R, Schaper K A, Rottenberg D A
Health Computer Sciences, University of Minnesota, Minneapolis.
J Nucl Med. 1994 Nov;35(11):1815-21.
This article reviews common methods for two-dimensional display of registered multimodality brain images and describes a software package for presentation of merged MRI and PET images that runs on a workstation with an eight-bit color display. The software package displays merged brain images from multiple modalities in a way that is readily manipulated, visually pleasing and easy to interpret. The display method used, i.e., interleaving of alternate pixels with independent color scales, is effective in producing merged images with high contrast-detail for each volume. Interleaving images from different volumes creates unusual perceptual effects, one of which is the apparent camouflage of low-contrast signals by high values in the paired volume.
The camouflage effect was thought to arise from perceptual merging of adjacent pixels. An observer experiment was conducted to investigate this tendency of high-activity PET data to obscure low-contrast detail in interleaved MRI data in spite of the digital independence of neighboring pixels. Four observers were presented with 20 combinations of signal plus background targets with uniform mask images, using a two-alternative forced-choice experimental design with 50 trials per combination.
The psychophysical evaluation of the ability of human observers to detect the simple test objects in an interleaved image presentation indicated a statistically significant camouflage effect of one volume on the other for some combinations of target and mask. The concept of perceptual merging of adjacent pixels was able to predict which combinations caused the greatest degradations in performance.
The image interleaving approach to the display of two-dimensional slices from registered image volumes makes efficient use of an eight-bit color display. Contrast resolution of both individual volumes is high compared with that in other techniques and the volumes are presented in familiar color scales. However, the method yields an unexpected camouflage effect that tends to obscure low-contrast signals. The practical effect of such camouflage on the interpretation of clinical images remains to be investigated.
本文回顾了已配准的多模态脑图像二维显示的常用方法，并介绍了一个用于在具有八位彩色显示器的工作站上显示融合的MRI和PET图像的软件包。该软件包以易于操作、视觉上令人愉悦且易于解释的方式显示来自多种模态的融合脑图像。所使用的显示方法，即具有独立颜色刻度的交替像素交织，对于每个容积有效地产生具有高对比度细节的融合图像。来自不同容积的交织图像会产生不寻常的感知效果，其中之一是配对容积中的高值对低对比度信号的明显掩盖。
这种掩盖效应被认为是由相邻像素的感知融合引起的。进行了一项观察者实验，以研究尽管相邻像素在数字上是独立的，但高活性PET数据在交织的MRI数据中掩盖低对比度细节的这种趋势。使用双选强制选择实验设计，为四位观察者呈现20种信号加背景目标与均匀掩模图像的组合，每种组合进行50次试验。
对人类观察者在交织图像呈现中检测简单测试对象能力的心理物理学评估表明，对于某些目标和掩模的组合，一个容积对另一个容积具有统计学上显著的掩盖效应。相邻像素感知融合的概念能够预测哪些组合会导致性能下降最大。
从已配准的图像容积显示二维切片的图像交织方法有效地利用了八位彩色显示器。与其他技术相比，单个容积的对比度分辨率都很高，并且容积以熟悉的颜色刻度呈现。然而，该方法会产生意想不到的掩盖效应，往往会掩盖低对比度信号。这种掩盖对临床图像解释的实际影响仍有待研究。
