Clearance and distribution parameters of 99mTc-EHIDA, -DTPA and -MAG-3 by dynamic liver/kidney scintigraphy

The radiopharmaceuticals (RF) EHIDA, DTPA and MAG-3 (labeled by 99mTc), commonly used in dynamic liver/kidney scintigraphy, are distributed in intravascular (i.v.) and extravascular (e.v.) spaces, as they are simultaneously cleared from the blood passing through their target organ (liver/kidney). The drop in concentration of these RF in blood is therefore determined by distribution as well as by clearance up to the time of equilibrium. From that time only the rate of decrease of RF in blood expresses the "true" (liver/kidney) clearance and this clearance parameter is a clinically reliable index of the function of the target organ. (A) The method of analysis of the clearance curve obtained from the heart region has been reported; the method is based on a physiological approach with respect to the distribution processes of the RF in the organism. Apart from the main important parameter, T (clear) (half-time of the "pure" clearance of the resp. RF from its distribution space), two further parameters are obtained: T (distr.) (half-time of the e.v. distribution of the RF) and END (distr.) (end of this distribution). (B) The results of 218 patients examined using 99mTc-EHIDA, 192 using DTPA and 65 using MAG-3 have been statistically processed. The mutual correlation of all parameters [T (distr.), END (distr.), T (clear)] within each group of patients as well as the differences of corresponding parameters between the groups of patients are studied. The main purpose of the work was to obtain the reliable clearance parameters of the RF with extravascular distribution for routine clinical practice.(ABSTRACT TRUNCATED AT 250 WORDS)