A QUANTITATIVE COMPARISON OF SOME FADS METHODS IN RENAL DYNAMIC STUDIES USING SIMULATED AND PHANTOM DATA

Simulated and phantom data were used to determine if factor analysis o f dynamic structures (FADS) methods can be used quantitatively. FADS m ethods tested included variants of apex seeking, the intersection meth od, cluster analysis and spatial constraints. These were compared with a region-of-interest (ROI) approach. Simulated renal studies were pre pared using from three to six homogeneous structures. These correspond ed to two blood background structures; two structures (one pathologica l) for parenchyma; and two structures (one pathological) for the colle cting system. Time-activity curves for background, parenchyma and coll ecting system were obtained for each method and compared with the true curve. A kidney phantom was modelled using a tunnelled vessel filled with chelating material. A variable dow was controlled by a peristalti c pump representing the renal filtration of fluid. The glomerular filt ration rate (GFR) was estimated using FADS and ROI-based methods and c ompared with the values measured experimentally. Most FADS methods per form well in the absence of pathology, but less well than the ROI-base d method when pathology is present. Some FADS methods perform better t han the ROI-based method when background estimation is a problem as in the GFR experiment. For quantitative analysis, the success of FADS de pends on the validity of the underlying assumptions and on the appropr iate nature of the constraints.