"FUR"--one size suits all

This work used amalgamated data from previous projects in order to test the concept that when organ function is expressed in terms of tracer kinetics, the results are independent of patient size or gender. Dynamic gamma camera studies were analysed by measuring the rate of movement of tracers from the blood into various organs. These rates were expressed as a "fractional uptake rate" (FUR), which is the fraction of tracer in the blood taken up by the organ per unit time. As these values were small, it was convenient to express the FUR per million seconds. The FUR was calculated using the expression FUR = SLOPE (of Rutland-Patlak plot), multiplied by B(0) (the blood curve value back-extrapolated to time zero), and divided by the TOTAL amount of tracer injected. Data were used from adult patients between the ages of 20 and 49 years who had normal organ function. Organ/tracer groups studied were the skeletal uptake of 99mTc-MDP, the renal uptake of 99mTc-MAG3, the renal uptake of 99mTc-MDP, the renal uptake of 99mTc-DTPA, the hepatic uptake of 99mTc-colloid, the splenic uptake of 99mTc-colloid, and the hepatic uptake of 99mTc-DISIDA. Each organ/tracer group was divided into three subgroups according to patient size (smallest, middle and largest), and also into subgroups according to gender. Comparison of these subgroups did not show any significant size- or gender-related differences in FUR values. It is concluded that for patients with normally functioning organs the FUR is independent of patient size or gender. Thus, the FUR is a valuable way of expressing organ function, particularly in patients with unusual or rapidly changing body size, such as children.