Computer-derived regions of interest for the determination of renal parenchymal transit time

Renal parenchymal transit time measurements are used in the diagnosis of obstructive nephropathy but parenchymal regions are usually drawn by hand with or without the aid of a functional image. This paper describes three computerized methods for derivation of parenchymal regions from a mean time functional image and compares them with the manual method by processing renogram data from 82 normal, 19 obstructed and 11 dilated nonobstructed kidneys using all four techniques. Receiver-operator characteristic analysis demonstrated the computer methods to be superior to manually drawn regions. The optimum computer method had a sensitivity of 95% and specificity 95% for distinguishing obstructed kidneys from dilated nonobstructed kidneys. The computer method could be readily incorporated into routine renogram analysis programs.