Elimination of Background and Kidney Depth Correction during Renal Uptake Rate Measurement with 99mTc-Dimercaptosuccinic Acid Using a Kinetic Modeling Approach.

Renal uptake rate measurement with 99mTc-dimercaptosuccinic acid (DMSA) requires accurate background and kidney depth correction as well as several hours for the examination. We developed a new method which required no correction and only 20 min for examination using the kinetic modeling approach. Our model consists of three compartments with the rate constants for the transport of DMSA from blood to renal tissue (k1), from tissue to blood (k2), and DMSA uptake in the tissue (k3) . In addition, we introduced a parameter indicating the blood pool fraction, rather than correcting for background. The parameters were calculated by fitting the model equation to the time-activity curve obtained by injection of 148 MBq of DMSA and sequential imaging for 20 min. The net uptake rate of DMSA by tubular cells (K) was also calculated from K=k1×k3/ (k2+k3) . The K values obtained without background and kidney depth correction were well correlated with the renal uptake rates measured two hours after DMSA administration (r=0.918, n=120), and with those obtained using background correction (r=0.989) or correction for attenuation due to kidney depth (r=0.982) . Our results indicate that this is a promising method of quantifying renal cortical function, as it requires no correction and only 20 min for image acquisition.