Parametric imaging in salivary gland scintigraphy

Salivary gland scintigraphy (SGS) is an imaging technique to evaluate functional aspects of the salivary glands. First described in 1965, visual analyses of summed images and of time-activity curves generated through regions of interest (ROI) are still the main evaluation tools used in clinical practice. An alternative to ROI-based analysis is the use of parametric images, which are images generated through pixel-by-pixel calculation of parameters from the original frames. In this article, we would like to present some parametric images for SGS studies and how to create and use them. Two images, vascular flow and uptake velocity, were created using the intercept and slope of a linear model of the frames from after the first to fifth minute of acquisition. And two others, excretion fraction and absolute excretion, by subtraction and division methods of the frames before and after sialogogue stimulation. These images allow the visualization of the spatial distribution and heterogeneity of these quantitative parameters, favoring different forms of analysis and helping with image segmentation. After more than a year of using these images in daily routine, our general impression is that they have been very helpful. This article, however, still represents only our early experiences with this technique, and clinical studies are yet needed to better evaluate this method.