Evaluation of Obstructed Kidneys by Discriminant Analysis of ^99mTc-MAG₃ Renograms

Summary

This study sought to develop a method of improving the differential diagnostic between healthy and obstructed kidneys using only parameters derived from the ^99mTc-MAG₃ renogram. The analysis included data from 46 healthy and 36 obstructed kidney units. The parameters calculated were: mean transit time (MTT), time at 20% of the initial height of the renal retention function (T20) and time to peak of the renogram (TP). A discriminant analysis was carried out to obtain a discriminant function in order to differentiate between the two groups. The best results were obtained using the function: (2.5629 lnT20) +(2.1280 In TP) -27.1224 which correctly classified 97.56% of the cases, giving a sensitivity of 94.44% and a specificity of 99.99%.

Zusammenfassung

Zweck dieser Arbeit war die Differentialdiagnose von gesunden (46) und abflußbehinderten Nieren (36) aus verschiedenen Werten des ^99mTc-MAG₃ Radio-isotopennephrogramms (RIN) und seiner Dekonvolution. Es wurden folgende Parameter berücksichtigt: mittlere Transitzeit (MTT), Zeit bis zum Abfall der maximalen Aktivität der Impulsreaktionsfunktion auf 20% (T20) und Zeit bis zum Erreichen des Kulminationspunktes (sog. Sekretionsmaximum) des RIN (TP). Mittels der Diskriminanzanalyse wurde folgende Funktion als die beste gefunden: (2,5629 lnT20) + (2,1280 In TP) - 27,1224 mit 94,44% Sensitivität, 99,99% Spezifität und 97,56% Genauigkeit.

Key words

Discriminant analysis - obstructed kidneys - renographic parameters - deconvolution - isotope renography

Schlüsselwörter

Diskriminanzanalyse - abflußbehinderte Nieren - renographische Parameter - Dekonvolution - Isotopen-Renographie

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