The reduction of renogram deconvolution to a direct method of transit time determination

It is known that the intrarenal mean transit time (MTT) can be determined using renography by first deconvolving the kidney retention function from the obtained time-activity curve and then integrating the retention function. A direct and approximate calculational method, based on an integral mathematical model, has also been employed to estimate the MTT. It is shown that the direct approximate method is equivalent to the standard deconvolution method applied with the assumption of a time independent retention function. Potential errors incurred using the direct method are thus quantified and assessed over a range of representative decay parameters. (author)