A New Image Display and Analysis System (IDA) for Radionuclide Imaging

In diagnostic procedures utilizing radionuclide imaging, the distribution of administered radioactivity within the body is usually displayed as a tonal image in various shades of gray, and the spatial distribution of the administered radioactivity is portrayed as a two-dimensional image. A three-dimensional image is then perceived by viewing multiple images, such as lateral, anterior, posterior, or other views. The interpretation of the study is based on characteristics of the image, such as the size, shape, and relative density of various regions. Any abnormalities are noted, followed by characterization of their size, shape, and position with respect to anatomical landmarks. In most cases, the lesions are seen as regional defects in specific functions. For example, a tumor in the liver decreases reticuloendothelial function in the space occupied by the tumor. In some studies, the spatial distribution of the radiopharmaceutical within the body changes as a function of time after the administration of the dose, and the rate of change as well as the spatial distribution is the desired information. There are numerous advantages in looking quantitatively at the basic data on which the analog image is based. The value of the procedures can be enhanced if we combine the analog image of the distribution of activity with the ability to obtain quantitative data in the analysis of single and serial images. Quantitative measurements are useful for relating radionuclide distributions depicted in various regions of an image or in serial images. The analog image of the distribution is useful for selecting areas of interest prior to quantification. The image display is an interface between the detection system and the observer, whose performance depends on optical characteristics of the display system. Thus, brightness, contrast, image size, and color all contribute to the subjective effect of the display on the observer. Hence, it is helpful if the observer can vary and optimize the characteristics of the display while viewing the image and can then get quantitative answers to questions suggested by the image. For example, the precise size of lesions or their changes over a period of time may be the quantitative information desired by the observer as he views the image. In other cases, the relative function between paired organs, such as the lungs or kidneys, or between various parts of an organ may be the desired quantitative information. It is also useful to be able to construct a composite image that relates the changes that occur with time in an original series of images. For example, if a series of images are obtained of the kidney after the administration of chlormerodrin, which accumulates in the various regions of the kidney as an exponential function of time, it is quite useful to be able to construct an image that presents the spatial distribution of the regional rate constants.