Mean transit times without deconvolution...reconsidered

A new deconvolution technique is described. It is based on an earlier method which used a graphical technique to analyse the early stages of organ data and blood curves to obtain the background subtraction factor and the uptake constant for tracer uptake by the organ. In that initial application, those variables were then applied to a later point on the organ and blood curves to calculate a mean transit time without first producing a retention function. This new deconvolution technique performs that later step on all points of the organ data curve to produce a function showing how the mean transit time varies with time. This considered to be the area under the retention function (i.e. the integral of the retention function), and the retention function itself is then obtained by differentiation. Modelling techniques were used to create renogram shapes by convoluting known (input) retention functions with a calculated blood curve. The new deconvolution method was then used to recover the retention function from each artificial data curve. The recovery of that input data implies that the new deconvolution technique is sufficiently successful to justify further consideration. In addition, as a demonstration, iterative deconvolution and the new method were both used on renograms from an obstructed kidney and a kidney with normal outflow. Both methods produced similar shaped retention functions.