A comparison of deconvolution and the Patlak-Rutland plot in renography analysis

Deconvolution and the Patlak-Rutland plot are two of the most commonly used methods for analyzing dynamic radionuclide renography. Both methods allow estimation of absolute and relative renal uptake of radiopharmaceutical and of its rate of transit through the kidney.

A theoretical comparison of uptake assessment by both techniques is made and a mathematical derivation of the relationship between mean transit time (MTT) and renal outflow efficiency (ROE) is presented. The validity of these theoretical findings was tested in a series of 120 renograms obtained using 99mTc-mercaptoacetyltriglycine (MAG3).

The estimates of renal uptake obtained are theoretically equivalent. The renogram measurements confirmed this, because there was no significant systematic difference in relative counts obtained by the two methods. Absolute counts were significantly higher for the deconvolution measurements, but only by 2.0%. The SDs of the differences between the two techniques, expressed as a percentage of the mean, were 1.7% and 5.4% for relative and absolute counts, respectively. There was an inverse monotonic relationship between MTT and ROE. ROE evaluated at a particular time was shown to depend on absolute renal function. Measured values of MTT and ROE were consistent with the theoretical prediction.

The two approaches to renogram analysis provide consistent parameters for both uptake and transit evaluation.