Quantification of amplitude images of gated radionuclide heart studies: a new universal method

Absolute quantification in nuclear medicine is difficult because of the individual shape, size, and position of human organs. In this study, a general data processing procedure is presented that allows inter-individual comparison and definition of normal count density pattern of unevenly shaped scintigraphic structures. This new method is demonstrated on Fourier amplitude images of gated heart studies. The information contained in the original irregularly shaped left ventricular amplitude scans was transformed into a standard sized circle by interpolating the radiant profiles of varying length from the original left ventricular ROI into the radii of the standard circle using 720, 360, 180, and 72 sampling angles. Retransformation of the individual left ventricular amplitude image from the standard circle area is feasible with only approximately 1% error with the 180, 360, or 720 sampling steps. As a first application of this new method 20 normal amplitude studies were transferred into the standard circle, which allowed the definition of a statistically normal reference image against which individual left ventricular amplitude images may be compared for documenting areas of significantly depressed amplitudes quantitatively. This simple and unique approach may be applied to most organ-related scans such as brain, kidneys, lung, and liver both in planar and tomographic studies to first create a normal reference image and second, to quantify the significance of locally increased or decreased activity in routine scans automatically.